# 2011 specialized crank set issue



## flymosquera (Feb 25, 2011)

Hey everyone, 

I bought a 2011 specialized tarmac sl3 s-works about 2 month ago. That bike came with the specialized fact carbon crank set. I have been having an issue that the chain fall to the out side of the crank when I get up and sprint or just accelerate quickly. I want to know if anyone out there is having this same issue with the specialized crank set. 

If you could post your comments I will greatly appreciated. 

Thanks :thumbsup:


----------



## PJ352 (Dec 5, 2007)

You might get some feedback here, but IMO it would be better to post this in the Manufacturers (Specialized) forum.


----------



## rx-79g (Sep 14, 2010)

Normally, the front derailleur keeps the chain on. What does your dealer say?


----------



## TomH (Oct 6, 2008)

Bent rings will do this.. the added load of a sprint makes the chain jump off the bent section.


----------



## Lelandjt (Sep 11, 2008)

rx-79g said:


> Normally, the front derailleur keeps the chain on.


+1 on that. You can usually set the low limit screw so that the chain doesn't rub in 1st gear and it consistently shifts down from the big ring but the cage is close enough that the chain gets guided onto the ring and usually prevents derailment. However, I'm aware that some people have this problem because chain catchers have been invented to prevent it. If you can't get your derailleur to stop the chain from falling to the inside get the "K-edge" or another chain catcher.

On a side note, I heard the 2011 Specialized cranks have a slight redesign around the BB axle to prevent the chain from jamming in there so a lot of users must have had derailments that resulted in a jammed chain.


----------



## flymosquera (Feb 25, 2011)

I have taken in the bike several times and the front derailleur is at the lowest possible point. The chain is falling to the out side of the crank. I have heard that specialized have had this same issue in the past, and I thought they had fix the problem but I am having the same issue. I heard that the problem is that the chain rings flex when you put a lot of force into the pedal stoke so it kicks the chain out. 

Thanks for all the responds


----------



## PJ352 (Dec 5, 2007)

flymosquera said:


> I have taken in the bike several times and the front derailleur is at the lowest possible point. The chain is falling to the out side of the crank. I have heard that specialized have had this same issue in the past, and I thought they had fix the problem but I am having the same issue. I heard that the problem is that the chain rings flex when you put a lot of force into the pedal stoke so it kicks the chain out.
> 
> Thanks for all the responds


Someone with firsthand experiences with this may post, but try a search in this forum. IIRC, there have been similar posts and Spec has subsequently made design changes to their chainrings. 

You could also push the issue with your LBS. They should (IMO) work with Spec on your behalf.


----------



## Coolhand (Jul 28, 2002)

Seems like a front derailler issue. As long as you are not using a Red front derailler, those rings are ok.


----------



## roadie01 (Apr 13, 2010)

I'll weigh in as an ex LBS wrench.

The front deraileur on any system should not be there to hold the chain in place it's function is to shift not keep the chain from skipping on the gear teeth. Should the chain skip the deraileur will push the chain back on to the ring but only if the chain comes off the teeth in the small space occupied by the front dereaileur. 

All of this assumes something foolish like cross chaining is not going on. You should not be sprinting in the big ring and any more than half way up the rear cassette. 

First as stated previously in this thread check the chain rings and make sure they are straight and not worn. 
Next check the chain to insure that it is not worn "stretched". 
Check for bent teeth on the chain ring. 

Inspect the frame and cranks carefully. While not likely if the frame is cracked it could flex to the point the chain comes off. I doubt any mortal would produce the power required to make an SL3 flex to the point of the chain coming off. Mark Cavendish can't do it! 

If the chain rings are straight and not worn and the chain checks out. Try a different outer chain ring that is stiffer. http://www.specialized.com/us/en/bc/SBCEqProduct.jsp?spid=58184
If the problem goes away your flexing the chain rings. 

Just as PJ stated work with your local Specialized dealer. Make sure they are doing more than just checking the front deraileur adjustment. Are they test riding the bike? Can they repeat the problem?


----------



## flymosquera (Feb 25, 2011)

Hello Thanks for your great respond. The chain rings are basically brad new as well as the chain and the complete bike. It has 2 month I dont think it is going to worn out in 2 month. I have the same chain rings that you posted the link for. Does are the chain rings that the bike comes with.

Mark cavendish doesnt use specialized crank set. He uses the shimano dura-ace crank set. 

Yea they have checked everything and its fine. It only comes out when I sprint. Which is when I put the most force into the crank. And it has happened like 5 times already. Last time It happened It fell at 42 mph and it was pretty scary. No i dont want do even sprint because I dont want to end up crashing. 

thanks for all the help


----------



## jone954 (Feb 25, 2011)

hey this is like the 3rd time I hear this issue. There is a guy that rides with us and he has a 2011 s-works sl3 as well and he has been having the same issue. And he is a strong guy so when he accelerates very quickly or sprints it has happen a few times. 

He still doesnt know what the issue is, but it sounds he is having the same problem as you.


----------



## roadie01 (Apr 13, 2010)

I'm afraid I'm not much help then unless your in the Salt Lake City, UT area and we can meet up so that I could physically try to repeat the issue.

Sorry I forgot that Canvendish rides the DA crank. The point is he doesn't flex the 'frame' enough to cause the chain to come off. 

My best reconmmendation is continue to work with your local shop and see if they can repeat the problem. Or you could contact Specialized directly.


----------



## TomH (Oct 6, 2008)

Bent doesnt mean worn out. Ive bent brand new rings and had stamped steel rings flex enough to jump. 

Front der issues are simple. Easy to fix and even easier to identify and isolate. Since the shop cant isolate the repeat the problem, it makes me lean even more towards bent/flexing rings. The lbs tech probably isnt taking it on a long ride and powering up hills. 

Get the shop to toss on a good shimano crank. I bet the problem goes away instantly. If/when it does, see if they'll work with you on a replacement crank or at least credit you for the faulty spec crank.


----------



## velomark (Apr 24, 2009)

flymosquera said:


> Hey everyone,
> 
> I bought a 2011 specialized tarmac sl3 s-works about 2 month ago. That bike came with the specialized fact carbon crank set. I have been having an issue that the chain fall to the out side of the crank when I get up and sprint or just accelerate quickly. I want to know if anyone out there is having this same issue with the specialized crank set.
> 
> ...


I'm having the SAME Issue on my 2012 Tarmac Pro SL4! I have crashed a few times because when the chain jumps and you're doing 30 over rollers, it's not pretty. One time I missed a sharp right because I couldn't get my weight right and I went between two moving cars! It's not the FD. It's the freaking crank! I tried a standard Red instead of the Mid Compact Specialized, I could hear it flex, but it didn't jump off.


----------



## velomark (Apr 24, 2009)

flymosquera said:


> Hello Thanks for your great respond. The chain rings are basically brad new as well as the chain and the complete bike. It has 2 month I dont think it is going to worn out in 2 month. I have the same chain rings that you posted the link for. Does are the chain rings that the bike comes with.
> 
> Mark cavendish doesnt use specialized crank set. He uses the shimano dura-ace crank set.
> 
> ...


I feel the same way. I have a $5,300.00 bike that I'm afraid to ride fast. Is it the Mid-Compact?


----------



## roadworthy (Nov 11, 2011)

Reading this thread...seems like a perfect storm to me that will only affect a small cross section of riders.
Result?
I would say...

big watt rider 

+ too flexible stock outer ring which would be fine for 95% or riders out there

+ maybe..front derailleur limit screw set too outboard

+ rider error

To preface rider error. One shouldn't shift under max pressure to the pedals...especially if a strong rider. Bad things happen when you do this i.e. this thread...jump your chain...or bend a ring.

So...what do strong guys do with this issue?

Investigate getting another outer ring that is stiffer. Consider a Dura Ace crank if you can't find a stouter outer ring to fit your Specialized crank.

Adjust big ring limit screw as inboard a position as possible without rub and still climb to big ring.

Learn to ride the bike without max. force on pedals when shifting. This is common sense for most but apparently eludes others.


----------



## velomark (Apr 24, 2009)

roadworthy said:


> Reading this thread...seems like a perfect storm to me that will only affect a small cross section of riders.
> Result?
> I would say...
> 
> ...


If someone is shifting the big ring under load, then they do not need to be riding a $5K+ bike. Neither of us are shifting. This is happening when we are sprinting. Already in the highest gear. I do believe the crank is flexing. We are trying a new crank.


----------



## roadworthy (Nov 11, 2011)

velomark said:


> If someone is shifting the big ring under load, then they do not need to be riding a $5K+ bike. Neither of us are shifting. This is happening when we are sprinting. Already in the highest gear. I do believe the crank is flexing. We are trying a new crank.


Here's the thing. These bikes are tested exhaustively at the factory in development. That means they have big meaty guys that can push 1300 watts mashing on the big ring as part of test development. Or...maybe there is a set up error with your bike...spider is loose...front derailleur isn't adjusted properly...front ring is slightly bent...yes by shifting under load...chain is worn or has a bad link that derails it etc. 

Now maybe you are in Thor or Bonnen territory and can generate 2000 watts and flex rings enough to fly the chain off. Most mortals can't however. If you don't mind me asking...have you ever had your max. power output measured with a power meter? What is your max sprint speed? Can you sprint to low 40's mph in still air?


----------



## velomark (Apr 24, 2009)

No, not Tom Boonen, but the wrench at the shop can recreate the same problem too, and he's not a big guy either. These cranks are not made for sprinting...I can only spin out the top gear on a descent.


----------



## velomark (Apr 24, 2009)

So we changed the FD, Chain rings, Chain, Cassette, Rear Wheel, Crank arm, BB Bearings... what else you got for me?


----------



## roadworthy (Nov 11, 2011)

velomark said:


> No, not Tom Boonen, but the wrench at the shop can recreate the same problem too, and he's not a big guy either. These cranks are not made for sprinting...I can only spin out the top gear on a descent.


Sorry...I disagree. The Specialized crankset and chainrings are excellent and made for racing. Especially if you can't achieve high RPM in 53-11 in a sprint.
But...if you are convinced there is nothing wrong with the bike and the crankset is tight and rings straight etc...you have replaced the chain...if I had that condition, I would borrow a DuraAce crank from the shop and test it. They don't come any stiffer than DA.


----------



## velomark (Apr 24, 2009)

They are offering me a Red Crank. I tried the same bike with the Specialized Crank, chain comes off. Tried same bike with a Red Standard, chain stays on.... go figure... I think I just don't pedal correctly... Given that there have been two other people in the past day that have reached out online with the same issue, I think specialized knows about it. Otherwise, why would they offer me a new crank?


----------



## roadworthy (Nov 11, 2011)

velomark said:


> They are offering me a Red Crank. I tried the same bike with the Specialized Crank, chain comes off. Tried same bike with a Red Standard, chain stays on.... go figure... I think I just don't pedal correctly... Given that there have been two other people in the past day that have reached out online with the same issue, I think specialized knows about it. Otherwise, why would they offer me a new crank?


Perhaps you are right. Maybe there are some flexy Spesh cranks out in the field, Spesh knows about it and are resolved to replace them based upon customer complaints. If you do get a replacement, I hope it works out for you. 
Good luck.
PS: if Specialized is willing to replace the entire crank and not just the big ring...because profit is in the mix, I would be inclined to believe there is something inherent in the crank that is the issue. I will tell you on a personal level, I am not a fan of the removable spider...but this is only anecdotal. I believe the crank design itself to be good...hirth joint just like Campy.


----------



## velomark (Apr 24, 2009)

I am concerned that the Standard will not be the best crank for me. I am not spinning out a 52-11 so I am worried about at 39/28 as my biggest gear.....

The wrench says he does not want me on a compact.....


----------



## roadworthy (Nov 11, 2011)

velomark said:


> I am concerned that the Standard will not be the best crank for me. I am not spinning out a 52-11 so I am worried about at 39/28 as my biggest gear.....
> 
> The wrench says he does not want me on a compact.....


Yeah...but your wrench isn't you and only you know if the gearing is just right.
I ride 50-38 with 12-25 cassette and works for me. So if you can't use 52-11, consider a compact with a slightly bigger small ring like a 36. I will tell you that only time I would ride 50/34 would be in the mountains because I don't like the big gap in gearing in front.
Only way to know about best gearing is to experiment...just like with fit....trial and error will get you to your best result.


----------



## velomark (Apr 24, 2009)

I live in California. It's all mountains....


----------



## roadworthy (Nov 11, 2011)

You may not prefer this path but another option is...a triple. A triple offers the greatest gearing differential and the closest spacing...and also the highest redundancy. Most don't get why redundancy matters. The best manifestation of this example is a 50/34 compact...big hole in the middle gearing and constant shifting in front because the hole exists right at the 16-18 mph zone where a lot of riding occurs when riding rollers or hills. Again, you have to try a lot of different combos to figure out what may work best for you. The thing is...the big ring comes in handy while descending...so you need the big gear inches as you know. But...you also need short inches for climbing.


----------



## velomark (Apr 24, 2009)

I need to tell these guys that the compact is the way for me to go....


----------



## velomark (Apr 24, 2009)

This whole thread is about the Specialized 52/36 flexing and dropping the chain.....


----------



## roadworthy (Nov 11, 2011)

velomark said:


> I need to tell these guys that the compact is the way for me to go....


Because of being constrained by BCD, smallest ring you can run on a full size crank is 38t. Unless a real strong rider, most of us if riding in the mountains need shorter climbing inches and why a compact makes a lot of sense...even with a 28t cog in back.
You may settle on something like a 50/36. Believe Spesh even makes a 52/36 if not mistaken.
Good luck.


----------



## dcorn (Sep 1, 2011)

Is everyone here talking about the chain coming off of a mid-compact crank? I got an SL3 S-works with the fact crank back in January, but is has the SL rings in 53/39. I can't really tell if I'm flexing it or not, but I do get intermittent chain rub on the FD during a hard sprint in the big gear front, little sprocket rear. Chain has never fallen off though.


----------



## roadworthy (Nov 11, 2011)

velomark said:


> This whole thread is about the Specialized 52/36 flexing and dropping the chain.....


I missed that...thought you have a full size Spesh crank. So will share with you some theory which may resonate. There is reason why bolt circle diameter pertains to what rings you can ride. It mostly relates to the smallest inner ring one can ride but there is a consequence to the big ring. The farther the teeth are from the BCD, the greater the bending stress on the chain ring. A compact has a smaller BCD than a full size crank of course to accomodate a smaller inner ring.. Comparing a mid size compact to full size crankset...the BCD is smaller to allow for a smaller inner ring. What this does is create a weaker big ring if the thickness of the ring isn't increased accordingly if running close to the same diameter big ring...in this case 52t. This size outer ring mounted on a compact BCD will be a weaker ring unless the thickness of the ring is increased.
My guess is...Specialized realized this after production release. 

This btw doesn't affect a lot of Spesh bike owners....only the relatively small subset of those that can put out a fair amount of sprinting power that use the mid compact crank. 
Many if not most that opt for a mid size compact are not big watt riders. They choose this gearing in fact to compensate for not having big power. No doubt there are exceptions of course as noted in this thread.
This doesn't excuse the dynamic...should have been caught in development...just stating why it probably exists. Also, many times these issues are an interaction...weaker big ring design based upon above...meets substandard metallurgy for example...may have missed a heat treat operation. 
Good luck moving forward with resolving it....sounds like you may get a new crank in the deal and hopefully it will meet your expectations and Spesh has addressed this..


----------



## velomark (Apr 24, 2009)

For me, yes the Mid Compact. I think it has to do with the distance between the BCD and the teeth. The distance forms too much of a lever and the chain pulls itself off of the ring... in a sprint....I want to go down to a compact. Too many hills here on teh West Coast.


----------



## velomark (Apr 24, 2009)

Yeah they are being really cool. I just want a compact instead of hte Standard they are offering. I can sprint, but there are a lot of long climbs where I am from in Northern California.


----------



## Scott in MD (Jun 24, 2008)

This is a good post. I have been wondering about pros/cons with Spesh cranks. I wonder sometimes about the sub-component design (right crank arm + spider.) 

Spreaking of compacts, my regular roadie ride is ~60 miles with 3400 feet of elevation gain ... and a 50+ MPH downhill, and one looooong hill that drops ~100 feet per mile steady for 9 miles (called "9 Mile Hill, by the way) and I am pretty happy with 50/34 X 12/27. On next bike, when I upgrade from older 6600 Ultegra and can swing 11/28 on back, I might try 50/36X11/28. 

I don't miss 53X11 very much, but I use 34X27 on every ride.


----------



## dcorn (Sep 1, 2011)

velomark said:


> For me, yes the Mid Compact. I think it has to do with the distance between the BCD and the teeth. The distance forms too much of a lever and the chain pulls itself off of the ring... in a sprint....I want to go down to a compact. Too many hills here on teh West Coast.


Well think about it. It has nothing to do with the chainrings. If you are flexing anything, it's the crank spindle going through the frame. With the forces you put on the pedal, the only force on the chainring is in the same plane as the chain, All the force goes on the bearings in the bottom bracket and the crank spindle and wants to bend the spindle. If that's flexing, then yeah the chainrings will angle out. But I don't exactly see how flexing anything will make the chain fly off. Technically, I feel like the chainring would flex out, rub against the FD cage and either just make a lot of noise, or get push the chain to the inner ring.


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> Well think about it. It has nothing to do with the chainrings. If you are flexing anything, it's the crank spindle going through the frame. With the forces you put on the pedal, the only force on the chainring is in the same plane as the chain, All the force goes on the bearings in the bottom bracket and the crank spindle and wants to bend the spindle. If that's flexing, then yeah the chainrings will angle out. But I don't exactly see how flexing anything will make the chain fly off. Technically, I feel like the chainring would flex out, rub against the FD cage and either just make a lot of noise, or get push the chain to the inner ring.


Sorry to disagree but what you write is incorrect. Flex of the crank itself...especially one as stout as a BB30 Spesh crank is pretty nominal...or negligible. It is the outer chain ring in this case that is flexing and quite sure it is do to the almost full size outer ring with a compact base circle...aka long cantilever of ring from support to tooth tip. 

The way it works is...when in the big ring with strong rider standing on the pedals trying to rapidly accelerate the bike, the chain puts a bending moment on the ring. The chainring is basically a cantilever with a big weight tied on the end where the chain connects. The ring is literally between a rock and a hard place...the rock is the mass of the bike + rider aka inertia and the hard place is a strong guy mashing on the pedals. If there were any spindle flex for example, the bearings of the BB would bind. BB's don't flex per se...but the BB where it attachs to the frame can displace or flex. For these high end bikes, amount of BB flex is very small.
Hope that makes sense.
PS: as it turns out chainring flex is kind of a big deal...especially in racing. It is one reason that many strong riders reach for a DA crank...in spite them not even being available in a 30mm spindle diamter which in theory is stiffer than 24mm diameter they come in. Shimano goes to great lengths to make their rings hollow which gives them unusual stiffness and great energy transfter and of course excellent shift quality.
Here is a tidbit about Shimano's solid rings being superceded by their hollow rings because they didn't play nice with the Di2 front derailleur:
http://www.competitivecyclist.com/p...ura-Ace-7900-Powermeter-System-7623.44.1.html


----------



## dcorn (Sep 1, 2011)

Like I'm saying, if BB flex and spindle flex are negligible, where do the side forces on the chainring come from? Obviously I can see a strong riding putting a ton of torque on the drivetrain, but the chain is designed to handle that force, which is always in the same plane as the ring itself. Unless the crank arm is somehow flexing itself and the spider, I don't see any side loading being put on the chainring. 

Again, if the shifter is what is causing the chainring to bend, I can completely understand that. Because that is the FD pushing the chain into the ring, which is a sideways force. If you are telling me that nothing in the system except the rings has any relavent deflection, then a heavy rider mashing on the pedals and not shifting won't bend those rings.


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> Like I'm saying, *if BB flex and spindle flex are negligible, where do the side forces on the chainring come from*? Obviously I can see a strong riding putting a ton of torque on the drivetrain, but the chain is designed to handle that force, which is always in the same plane as the ring itself. Unless the crank arm is somehow flexing itself and the spider, I don't see any side loading being put on the chainring.
> 
> Again, if the shifter is what is causing the chainring to bend, I can completely understand that. Because that is the FD pushing the chain into the ring, which is a sideways force. If you are telling me that nothing in the system except the rings has any relavent deflection, then a heavy rider mashing on the pedals and not shifting won't bend those rings.


Where does it come from? The load on the big ring isn't purely longitudnal aka in the plane of the chainring. There is no such thing as a perfect chain line. The farther the chain line is inboard on the rear cassette, the more 'lateral' the force/deflection is on the big ring. As a big rider pushes on the pedals the large ring will therefore deflect toward the inboard position of the rear cog and bow the ring inward...and why the chain is derailled to the the outside of the ring...with front derailleur staying in position. Another way to look at the ring is a beam with pure longitudnal loading. Think of a narrow rod with one side connected to a wall...and other with a pure longitudnal force pushing on the other unsupported cantilevered end. If the lateral force exceeds the longitudnal modulus of the rod, it will bend or bow. This is what happens to a chain ring under excessive load. It basically buckles locally...but incidentally...not to yield...but still in its elastic zone of force versus deflection. Elastically deforming the ring under extreme load is enough to locally bend the ring enough to throw the chain.


----------



## dcorn (Sep 1, 2011)

Again, I can understand the chainring flexing a tad from being cross chained. I kind of considered that, but isn't the crank ring somewhat even with the outer sprockets on the cassette? When would the chain be on the outer ring and pulled that much to the outside to the point where the chain would come off? 

Your explanation up there is confusing as hell because of the terminology, a drawing would be much better haha. I don't see that chainring bending THAT much to the point where it tosses the chain, especially locally and elastically.


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> Again, I can understand the chainring flexing a tad from being cross chained. I kind of considered that, but isn't the crank ring somewhat even with the outer sprockets on the cassette? When would the chain be on the outer ring and pulled that much to the outside to the point where the chain would come off?
> 
> Your explanation up there is confusing as hell because of the terminology, a drawing would be much better haha. I don't see that chainring bending THAT much to the point where it tosses the chain, especially locally and elastically.


dcorn...I think you are on to something revolutionary! Chainring bending under load is not a problem. Think of the money the industry could save. Commonize all BCD's because who needs a larger bolt circle for std size rings! Since chain ring bending isn't a problem, mfr's could even make their chainrings out of copper...or even rubber! Chainrings could be held on with 2 bolts and be made paper thin! You could save Shimano ten's of thousands of dollars by regresssing their chainrings back to plate stock versus the piece and tooling cost to make them hollow!
You acorn...yes you...could revolutionize the crankset industry....awesome.


----------



## dcorn (Sep 1, 2011)

Resorting to jackass mode? 

You keep bringing up shimano, but there are dozens of chainring makers out there who aren't resorting to hollow designs. Mostly everyone else just uses machined 7075. Are there threads out there about every other chainring model bending under load? Contador uses s-works chainrings, I hear he puts down decent power.


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> *Resorting to jackass mode*?
> 
> You keep bringing up shimano, but there are dozens of chainring makers out there who aren't resorting to hollow designs. Mostly everyone else just uses machined 7075. Are there threads out there about every other chainring model bending under load? Contador uses s-works chainrings, I hear he puts down decent power.


Project much dcorn?
Since when does Contador ride a 52t outer ring with compact BCD? Also...do you have any idea if the thickness of the rings he rides is stock? How about the metalurgy? The average guy has no idea what a pro rides..from the carbon lay up to the specs on the crank they use that 'look' like off the shelf Specialized. 
I know basic engineering statics and dynamics isn't in the wheelhouse of the average guy out there that rides a bike. As a result, many believe in magic...lol.


----------



## dcorn (Sep 1, 2011)

roadworthy said:


> I know basic engineering statics and dynamics isn't in the wheelhouse of the average guy out there that rides a bike. As a result, many believe in magic...lol.


Good thing I have that mechanical engineering degree thingy on the wall...


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> Good thing I have that mechanical engineering degree thingy on the wall...


OK...in that case here is your assignment.
Construct a free body diagram and calculate bending stress on a 52t outer ring with 110mm bcd with chain on 13t, 3rd inner cog with 1300 watts put into the crankset acclerating the bike up a 3 degree slope from 20 mph.
From there is will be obvious why section modulus, i.e. cantilever length from base circle to tooth involute distance matters. It would be ideal in fact if you could solve the static load calculation of force/deflection relative to cantilever length based upon 7075 Al modulus of elasticity as a function of chain ring thickness.
Once this equation is calculated it is elementary to plug in the reduced cantilever distance of a 135mm bcd with the same ring diameter i.e. tooth count aka 52t. Then it will be apparent given the same chain ring thickness and same material modulus how much greater the deflection of the big ring is under the same load conditions...and why a particular bcd is chosen for a given chainring diameter.
You can turn in the assignment by the end of the week.


----------



## dcorn (Sep 1, 2011)

How far away are the sprockets on the cassette from each other? Or more simply, if you were to draw a line straight back from the big ring, how far off that line is the 3rd sprocket you are talking about?


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> How far away are the sprockets on the cassette from each other? Or more simply, if you were to draw a line straight back from the big ring, how far off that line is the 3rd sprocket you are talking about?


Either measure your bike or use a std. measurement for chain line...you can find it on the web. 
Good luck.


----------



## benny and the jets (Jun 4, 2007)

As a shop mechainc, I've had this issue. It was definitely the 53 tooth chainring flexing.

We put an FSA ring on and it's been fine since


----------



## dcorn (Sep 1, 2011)

benny and the jets said:


> As a shop mechainc, I've had this issue. It was definitely the 53 tooth chainring flexing.
> 
> We put an FSA ring on and it's been fine since


Interesting, so it happens on the big BCD as well... 

Which FSA ring?


----------



## Scott in MD (Jun 24, 2008)

Nice job, Benny. Concise, helpful and didn't insult anyone. >>IgotRepforyou<<


----------



## roadworthy (Nov 11, 2011)

Scott in MD said:


> Nice job, Benny. *Concise*, helpful and didn't insult anyone. >>IgotRepforyou<<


Concise? How about not particularly relevant. The subject is a 52t chainring which is compact BCD specific and hence the controversy. Maybe 53t chainring flex with a full size BCD has some relevance...but I have never heard of any flex/chain jump issues with Specialized full size cranks.


----------



## benny and the jets (Jun 4, 2007)

roadworthy said:


> Concise? How about not particularly relevant. The subject is a 52t chainring which is compact BCD specific and hence the controversy. Maybe 53t chainring flex with a full size BCD has some relevance...but I have never heard of any flex/chain jump issues with Specialized full size cranks.


My customer had the chain coming off the outside of the slightly worn 53 tooth S-Works chainring on S-Works cranks running the carbon spider. 

It would happen under load in the 4 smallest sprockets (11,12,13,14) and it happened a couple of times at the finish of races.

We fitted as brand new 53 S-Works chainring and still had the same issue.

I fitted an FSA Super Road or Pro Road (can't remember exactly which one, but it was black and had red/white graphics on it so it matched the bike nicely)

After changing to the FSA chainring we have had ZERO problems with the chain coming off.

Just trying to offer some help and advice


----------



## roadworthy (Nov 11, 2011)

benny and the jets said:


> My customer had the chain coming off the outside of the slightly worn 53 tooth S-Works chainring on S-Works cranks running the carbon spider.
> 
> It would happen under load in the 4 smallest sprockets (11,12,13,14) and it happened a couple of times at the finish of races.
> 
> ...


And you just did. Basically you expanded the issue to include Specialized full size cranks...which are raced throughout the world...a much larger population of cranks and a bit harder to accept. A bit easier to grasp that this issue would exist with strong rider with larger cantilever of larger ring aka 52t meets smaller BCD aka compact...but having a basic design flaw on all Specialized cranks?...with their chainrings?...hmmm.


----------



## dcorn (Sep 1, 2011)

Well like I said earlier, I have a bike with the S-works crank, carbon spider, 130BCD and 53 tooth S-works SL chainrings. When I sprint in the higher gears, big ring/little sprockets, I get rubbing on the FD. That being said, it's intermittant, like everytime I push down with my right foot, it rubs, but nowhere else on the chainring. 

It could be the FD is out of adjustment, but then it should rub around the entire pedal stroke and whenever the chain is moving. It could possibly be a bent ring, but the bike is maybe 4 months old with ~500 miles on it and zero crashes or other impacts. Doesn't seem like the chainring is flexing unless my right foot pedal pressure is that much higher than my left. 

What say you?



Oh, and Benny, I wasn't trying to be mean or harsh. I'm actually glad you brought up your experience because it relates more to mine with the bigger spider BCD.


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> Well like I said earlier, I have a bike with the S-works crank, carbon spider, 130BCD and 53 tooth S-works SL chainrings. When I sprint in the higher gears, big ring/little sprockets, I get rubbing on the FD. That being said, it's intermittant, like everytime I push down with my right foot, it rubs, but nowhere else on the chainring.
> 
> It could be the FD is out of adjustment, but then it should rub around the entire pedal stroke and whenever the chain is moving. It could possibly be a bent ring, but the bike is maybe 4 months old with ~500 miles on it and zero crashes or other impacts. Doesn't seem like the chainring is flexing unless my right foot pedal pressure is that much higher than my left.
> 
> ...


Not sure you were asking me, but will give my opinion. It maybe your crank set up. Many don't seem to get that. In fact the internet is littered with guys who complain about their BB30's when there is nothing inherently wrong with the design. So what's wrong? Set up aka axial preload. Whenever you pedal there is both a vertical and axial load on the crank. If the bearings in the BB weren't properly bedded in installation and crank axial preload was spaced based upon bearing to bearing centerline...and the bearings bed over time, you now have more axial movement of the crank when you pedal. Harder you pedal the more the wave washer is displaced and the more the chainring laterally displaces. Front derailleur doesn't move of course because its attached to the frame and hence rub.
Since you are an engineer...and I am as well, you know fully well that these designs are tested extensively under worse case conditions during development. In fact, DOE's are generally performed to determine the margin of the design.. Yes outliars of bad quality get out the door that exceed the design robustness margin from time to time, but many times the issue can be found in assembly. I have found very few that seem to understand how to set up an integrated BB properly...including most bike shops.


----------



## dcorn (Sep 1, 2011)

roadworthy said:


> Not sure you were asking me, but will give my opinion. It maybe your crank set up. Many don't seem to get that. In fact the internet is littered with guys who complain about their BB30's when there is nothing inherently wrong with the design. So what's wrong? Set up aka axial preload. Whenever you pedal there is both a vertical and axial load on the crank. If the bearings in the BB weren't properly bedded in installation and crank axial preload was spaced based upon bearing to bearing centerline...and the bearings bed over time, you now have more axial movement of the crank when you pedal. Harder you pedal the more the wave washer is displaced and the more the chainring laterally displaces. Front derailleur doesn't move of course because its attached to the frame and hence rub.
> Since you are an engineer...and I am as well, you know fully well that these designs are tested extensively under worse case conditions during development. In fact, DOE's are generally performed to determine the margin of the design.. Yes outliars of bad quality get out the door that exceed the design robustness margin from time to time, but many times the issue can be found in assembly. I have found very few that seem to understand how to set up an integrated BB properly...including most bike shops.



Of course your opinion is welcome, especially because you are an engineer. Bike shop mechanics as well. Or anyone who knows more than me about bikes. I actually had the crank serviced last weekend because I was getting a clicking noise when pedaling hard (which I've heard is another common trait of spec BB30 cranks...). But yeah, I'm not sure if it's still rubbing like before, but I'll have to go out and test it in different gear combos and see whats going on. So what are you exactly saying could be the culprit? The bearings are moving around in the bottom bracket causing the entire crank to move slightly?


----------



## roadworthy (Nov 11, 2011)

dcorn said:


> Of course your opinion is welcome, especially because you are an engineer. Bike shop mechanics as well. Or anyone who knows more than me about bikes. I actually had the crank serviced last weekend because I was getting a clicking noise when pedaling hard (which I've heard is another common trait of spec BB30 cranks...). But yeah, I'm not sure if it's still rubbing like before, but I'll have to go out and test it in different gear combos and see whats going on. So what are you exactly saying could be the culprit? The bearings are moving around in the bottom bracket causing the entire crank to move slightly?


Clicking is a common trait of an improperly installed BB30 crank. Clicking/creaking is the bearings moving. But creaking is miniscule displacement of the bearings generally. Your likely issue is the lack of preload on the bearings keeping the crank from displacing laterally. No doubt you know what a tolerance stack up is. Everything has a tolerance. If the crank isn't properly spaced such that the wave washer is in the proper amount of compression..too little will promote the chainring to move when side loaded..and too much preload will accelerate bearing wear. There tends to be a cause and effect relationship between creaky BB30 bearings and improper axial preload as well. Unless there is preload on the bearing inner races, the balls can click or vibrate.
So the issue can be related.


----------



## millerasm (Mar 28, 2012)

was told specialized now suggest on their PF30 carbon Mtn Bikes (Epics, Stump jumper, etc) to use some kind of gasket maker on the Press fit cups to make sure there isn't any movement with the cups. then to install the Bearings. i had a carbon epic with XTR cranks and the cups came loose and hollowed out the frame a little, they were spinning with the cranks. specialized warranted the frame and then told my LBS to use gasket maker to keep the cups in place and prevent any movement what so ever


----------



## roadworthy (Nov 11, 2011)

millerasm said:


> was told specialized now suggest on their PF30 carbon Mtn Bikes (Epics, Stump jumper, etc) to use some kind of gasket maker on the Press fit cups to make sure there isn't any movement with the cups. then to install the Bearings. i had a carbon epic with XTR cranks and the cups came loose and hollowed out the frame a little, they were spinning with the cranks. specialized warranted the frame and then told my LBS to use gasket maker to keep the cups in place and prevent any movement what so ever


millerasm,
Did Specialized give you a material spec for that? A generic 'gasket maker' while adhesive, doesn't seem particularly appropriate. Would say pretty much now the position of bike companies...most but perhaps not all, is use green Locitite...640...or similar on all bearings and bushing press surfaces to mitigate slippage. This keeps the Delrin bushings in place i.e. from spinning and spoiling the virgin carbon BB shell ID interface. If you think about it...the bushings should never have enough rotational force applied to them to spin in the frame. The inner race of the bearing should never offer enough shear force to spin the outer bearing race which would in turn spin the Delrin cups pressed into a BB shell. This suggests something was wrong with the bearings for this to happen...perhaps the bike was ridden in foul weather and the bearings weren't adequately serviced...or...a bearing just went bad and spun inducing this condition. Some might not know what a 'spun' bearing means. This rarely occurs when the inner race freezes to the balls to the outer race causing the entire outer race to spin in its bore. This is a pretty rare phenomena...as even if the inner and outer race bond, the crank still could spin within the inner race I.D...unless that interface is spoiled as well. So something caused the crank to freeze up and spin the plastic bushings pressed into the carbon BB...could be a defective bearing...but more likely...crank was improperly installed with excessive preload...or bearings were inadequately serviced.


----------



## millerasm (Mar 28, 2012)

roadworthy said:


> millerasm,
> Did Specialized give you a material spec for that? A generic 'gasket maker' while adhesive, doesn't seem particularly appropriate. Would say pretty much now the position of bike companies...most but perhaps not all, is use green Locitite...640...or similar on all bearings and bushing press surfaces to mitigate slippage. This keeps the Delrin bushings in place i.e. from spinning and spoiling the virgin carbon BB shell ID interface. If you think about it...the bushings should never have enough rotational force applied to them to spin in the frame. The inner race of the bearing should never offer enough shear force to spin the outer bearing race which would in turn spin the Delrin cups pressed into a BB shell. This suggests something was wrong with the bearings for this to happen...perhaps the bike was ridden in foul weather and the bearings weren't adequately serviced...or...a bearing just went bad and spun inducing this condition. Some might not know what a 'spun' bearing means. This rarely occurs when the inner race freezes to the balls to the outer race causing the entire outer race to spin in its bore. This is a pretty rare phenomena...as even if the inner and outer race bond, the crank still could spin within the inner race I.D...unless that interface is spoiled as well. So something caused the crank to freeze up and spin the plastic bushings pressed into the carbon BB...could be a defective bearing...but more likely...crank was improperly installed with excessive preload...or bearings were inadequately serviced.


i knew it was some kind of loctite product. what had happened to the cups were they had movement up and down on the left crank only when pulled the un prepped carbon had worn slightly. needless to say i got it corrected, so im very happy with the outcome, specialized has a customer for life in me, and i tell everyone i know to get there bikes.


----------



## roadworthy (Nov 11, 2011)

millerasm said:


> i knew it was some kind of loctite product. what had happened to the cups were they had movement up and down on the left crank only when pulled the un prepped carbon had worn slightly. needless to say i got it corrected, so im very happy with the outcome, specialized has a customer for life in me, and i tell everyone i know to get there bikes.


The type of loctite spec'ed for keeping bearing surfaces in place has little in common with gasket material FWIW.
Gotta love Specialized warranty support and agree they are great bikes.
Glad you got it resolved. Specialized clearly has complicity in this issue because they have morphed their spec's as they have performed beta testing on their customers. There is no substitute for customer miles...hard to replicate in the laboratory during development. What has been witnessed with Specialized and other bike companies is...they have come to terms with longer term durability of BB30 and PF30 and have revised their spec's on installation procedure...most bike companies now spec loctite as discussed. Virgin carbon fiber has many admirable qualities. A predominant reason that carbon fiber is inserted with alloy as with headsets and BB30, is carbon fiber has very low abrasion resistance...a very poor bearing surface. So if there is movement...even in the case of plastic bushing against it...CF will wear as you have experienced first hand. Loctiting adjacent bearing surfaces mitigates wear because there is no movement i.e. abrasion.


----------



## Scott in MD (Jun 24, 2008)

I think the BB30 bottom bracket bearing cup on my 2010 Cannondale Slice is aluminum ... that is to say an aluminum sleeve inside the carbon shell.I guess the Specialized bikes are bare carbon? Is this a reason to wait on a new Specialized till they sort out their PF30 / BB30 OSBB design?


----------



## roadworthy (Nov 11, 2011)

Scott in MD said:


> I think the BB30 bottom bracket bearing cup on my 2010 Cannondale Slice is aluminum ... that is to say an aluminum sleeve inside the carbon shell.I guess the Specialized bikes are bare carbon? Is this a reason to wait on a new Specialized till they sort out their PF30 / BB30 OSBB design?


More Specialized bikes are BB30 like your slice than Specialized narrow version of PF30...which is the subject of discussion here. There is nothing wrong with either as has been also discussed. What is wrong in the technical sense...is...Specialized is morphing their position on best practice to install each BB and owner's inability to install them properly which leads to the premature failure or poor performance aka creaking. In one sense Specialized is partly to blame but if objective, most understand that all designs are a work in progress and as more customer miles are accumulated, best practices will emerge. That is what is happening with the increased popularity of BB30 and PF30. Conventional wisdom now is all interfacing surfaces should be loctited. If done properly, there shouldn't be a problem.


----------



## dcorn (Sep 1, 2011)

Same thing was done with my bike. Shop mechanic said my bike must have been built up before Specialized told shops to put loctite on the BB cups. No more clicking since the BB was rebuilt with the press-fit loctite. Hopefully the BB shell wasn't damaged.


----------



## Chris-X (Aug 4, 2011)

*The word is "outliers."*



roadworthy said:


> Not sure you were asking me, but will give my opinion. It maybe your crank set up. Many don't seem to get that. In fact the internet is littered with guys who complain about their BB30's when there is nothing inherently wrong with the design. So what's wrong? Set up aka axial preload. Whenever you pedal there is both a vertical and axial load on the crank. If the bearings in the BB weren't properly bedded in installation and crank axial preload was spaced based upon bearing to bearing centerline...and the bearings bed over time, you now have more axial movement of the crank when you pedal. Harder you pedal the more the wave washer is displaced and the more the chainring laterally displaces. Front derailleur doesn't move of course because its attached to the frame and hence rub.
> Since you are an engineer...and I am as well, you know fully well that these designs are tested extensively under worse case conditions during development. In fact, DOE's are generally performed to determine the margin of the design.. Yes outliars of bad quality get out the door that exceed the design robustness margin from time to time, but many times the issue can be found in assembly. I have found very few that seem to understand how to set up an integrated BB properly...including most bike shops.


I usually don't give a damn about spelling but you're so pedantic that I thought I'd let you know you continually spell the word wrong.

BTW, you've accurately described the issue of the thread.

dcorn, the flexing/bending of the big ring is an issue. I'm sure you've felt weight of a chainring; they're pretty insubstantial. I'm surprised they hold up as well as they do.


----------



## dcorn (Sep 1, 2011)

Pretty sure my BB clicking is gone, but I'm still getting the intermittant chain rubbing. Never dropped the chain on the outside of the ring though. Worth it to swap out the chainring? Mine is the S-works SL rings, so they definitely have less material and lighter weight than even the normal S-works rings. 












Then again, that's what Contador rides...


----------

