# How important is exact torque on the rear cassette?



## Typetwelve (Jul 1, 2012)

I fully understand the importance of properly torquing down smaller bolts on a bike, especially a carbon frame. I recently purchased a nice in-lb/N-m torque wrench to fully avoid over tightening.

I recently bought a shimano/SRAM tool for removing the rear casette for cleaning and maintenance. The problem is that the proper torque required for the casette is more than my current wrench allows (it only goes to 25 N-m...I believe the casette is 40).

Now...I really don't want to have to drop $50+ on another, larger torque wrench just to tighten one item (I don't work on my car or anything else that would require a torque wrench of that size).

What I'm wondering is is it really that critical on that piece? Is a good, "stout" tighten good enough? (I'm not a crank it down insane tight type of guy btw)

I guess if its critical then ill drop the $$...I'd just rather not spend it if I don't have to.

Thanks in advance!


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## Tlaloc (May 12, 2005)

You just spent thousands of dollars on your new carbon bike but $50 for a tool to work on it correctly is too much? This is called penny wise but pound foolish. You can get a torque wrench for this at your local auto parts store. Tools are an investment. You will use them more than once. Buy a torque wrench.


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## PlatyPius (Feb 1, 2009)

Typetwelve said:


> I fully understand the importance of properly torquing down smaller bolts on a bike, especially a carbon frame. I recently purchased a nice in-lb/N-m torque wrench to fully avoid over tightening.
> 
> I recently bought a shimano/SRAM tool for removing the rear casette for cleaning and maintenance. The problem is that the proper torque required for the casette is more than my current wrench allows (it only goes to 25 N-m...I believe the casette is 40).
> 
> ...


I have never seen a bike mechanic torque a cassette, nor have I ever used a torque wrench on one. I've never had one come loose, nor have I ever gotten one too tight. Torquing a cassette is, IMO, silly. Unless, of course, you habitually under-tighten everything...


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## wim (Feb 28, 2005)

Not critical at all, no need for a torque wrench. Your "stout" will do, with some people (yours truly included) going a bit further to "grunt tight" on those lock rings. I'm sure there are people who use a torque wrench on a cassette lock ring. But I've never seen anyone do that. (Just as Platy said above. Didn't see his post before posting mine).

I wonder about "cleaning and maintenance," though. I used to take cassettes off all the time to play around with gearing, or sometimes for a spoke replacement. But I've never taken one off for "cleaning and maintenance" on one of my own bikes.


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## RoadrunnerLXXI (Jun 3, 2012)

Speaking of torque specs, I want to purchase a preset torque wrench without paying an arm and a leg. I am looking at a Bontrager and a Topeak which has a preset at 5Nm and 6Nm respectively, great for those handlebar, stem, bottle cage and seat post bolts. Anybody have any experiences with either one? Any recommendations?


Bontrager: Preset Torque Wrench (Model #08370)

Topeak® Cycling Accessories ? Products - ComboTorq Wrench & Bit Set


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## Len J (Jan 28, 2004)

I've never used a torque wrench on a cassette either. A little past where the locking clicks and I've never had one loosen nor not be removable. 

Of course I've never had a carbon hub either. 

Just make sure you have it going on straight 


Len


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## Typetwelve (Jul 1, 2012)

Tlaloc said:


> You just spent thousands of dollars on your new carbon bike but $50 for a tool to work on it correctly is too much? This is called penny wise but pound foolish. You can get a torque wrench for this at your local auto parts store. Tools are an investment. You will use them more than once. Buy a torque wrench.


Like I said...I do own one for that exact reason. I don't want to go off and jack up my carbon frame. The adjustable one I have is a nice unit and will do 99% of what I need it to do on a bike.

I was simply asking about the rear cassette only. I have standard alu wheels (ROL Race SL) and hubs (no carbon) so I was thinking torque on that one item wouldn't be a giant deal. I asked my LBS mechanic yesterday and he said he didn't torque that one part either.

As for the cleaning, my cassette can get pretty grimy and cleaning while still mounted is a pain, I figured taking it off from time to time would be easier.


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## Tlaloc (May 12, 2005)

Typetwelve said:


> ...I asked my LBS mechanic yesterday and he said he didn't torque that one part either.
> 
> As for the cleaning, my cassette can get pretty grimy and cleaning while still mounted is a pain, I figured taking it off from time to time would be easier.


Your mechanic is lazy and careless if he doesn't use a torque wrench even though one is sitting right there in his tool box. Yes, your casette will get so dirty that it's better to take it off and clean it.


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## Len J (Jan 28, 2004)

Tlaloc said:


> Your mechanic is lazy and careless if he doesn't use a torque wrench even though one is sitting right there in his tool box. Yes, your casette will get so dirty that it's better to take it off and clean it.


Any mechanic that needs a torque wrench for a cassette on a regular wheel isn't very experienced IME. 

Len


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## RoadrunnerLXXI (Jun 3, 2012)

Typetwelve said:


> Like I said...I do own one for that exact reason. I don't want to go off and jack up my carbon frame. The adjustable one I have is a nice unit and will do 99% of what I need it to do on a bike.
> 
> I was simply asking about the rear cassette only. I have standard alu wheels (ROL Race SL) and hubs (no carbon) so I was thinking torque on that one item wouldn't be a giant deal. I asked my LBS mechanic yesterday and he said he didn't torque that one part either.
> 
> As for the cleaning, my cassette can get pretty grimy and cleaning while still mounted is a pain, I figured taking it off from time to time would be easier.


I do the same thing. I take the cassette off to do a thorough cleaning before reassembling it. Though I only do during the winter, before riding season and maybe once during the riding season since I use White Lightning dry lube, which help keep the drivetrain a bit cleaner.

Btw Typetwelve, don't you just love that some people just post without even reading the threads and make assumptions without having all the info?:mad2:


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## PlatyPius (Feb 1, 2009)

Typetwelve said:


> Like I said...I do own one for that exact reason. I don't want to go off and jack up my carbon frame. The adjustable one I have is a nice unit and will do 99% of what I need it to do on a bike.
> 
> I was simply asking about the rear cassette only. I have standard alu wheels (ROL Race SL) and hubs (no carbon) so I was thinking torque on that one item wouldn't be a giant deal. I asked my LBS mechanic yesterday and he said he didn't torque that one part either.
> 
> As for the cleaning, my cassette can get pretty grimy and cleaning while still mounted is a pain, I figured taking it off from time to time would be easier.


I never remove my cassettes to clean them. I "floss" them regularly, so there isn't any grunge build-up to worry about. 

Remove rear wheel.
Spray cassette with Clean Streak or a similar cleaner.
Take a red shop towel (or equivalent) and hold the corners on one side. Pull tight. Stick edge of rag between cogs and move side to side. The cassette will advance, spinning all of the way around eventually. Move to next cog. Ditto until all have been cleaned. Takes me about 2 minutes.

Oh, and ignore *Tlaloc*... it obviously has some socialization issues that it's dealing with today.


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## Vixsav (Sep 24, 2011)

Use you 25nm wrench and then tighten it a bit more. Its not a carbon part so not as critical and like the others said, I've never had a cassette loosen after installation but if it does you will probably immediately notice the change in shifting preciseness.


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## Mike T. (Feb 3, 2004)

Sufficient torque on a cassette lockring is very important - whether you *measure* it with a torque wrench or not is a different matter. Like Platy, I've tightened lots of them; ever since they came on the market. And as one has never come loose or have I stripped a lockring, I guess my "feel" is fine. And yours will be too. You do get some help as the lockrings have tiny ratchety teeth that help stop them coming loose.


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## cxwrench (Nov 9, 2004)

Tlaloc said:


> Your mechanic is lazy and careless if he doesn't use a torque wrench even though one is sitting right there in his tool box. Yes, your casette will get so dirty that it's better to take it off and clean it.


like every other mechanic that's replied to this thread i don't use a torque wrench for lockrings either. there is really no need. 
and if your cassette gets that dirty, you're not cleaning it often enough.


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## ziscwg (Apr 19, 2010)

No torque wrench here either. I just know 40 nm is pretty tight. So, I put a decent amount of muscle behind it. I have never had a cassette come loose or had a hard time getting one off.


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## MR_GRUMPY (Aug 21, 2002)

I torque mine to "one grunt". I recomend the same unless you've got one of those aftermarket aluminum lockrings, to save 20 grams.
.
.


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## marathon marke (Nov 14, 2011)

Tlaloc said:


> Your mechanic is lazy and careless if he doesn't use a torque wrench even though one is sitting right there in his tool box. Yes, your casette will get so dirty that it's better to take it off and clean it.


Oh brother. Better chalk me up as one of those "lazy" mechanics too. But then I started wrenching at a shop back in 1980, so my laziness is quite long-lived.


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## Len J (Jan 28, 2004)

marathon marke said:


> Oh brother. Better chalk me up as one of those "lazy" mechanics too. But then I started wrenching at a shop back in 1980, so my laziness is quite long-lived.


Lol. Long lived and well-honed. 


Len


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## DocRogers (Feb 16, 2006)

If you don't yet own a torque wrench you will probably find yourself needing one at some point - though probably not for a lockring.


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## spookyload (Jan 30, 2004)

MR_GRUMPY said:


> I torque mine to "one *Grump*". I recomend the same unless you've got one of those aftermarket aluminum lockrings, to save 20 grams.
> .
> .


Fixed it for you.


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## headloss (Mar 3, 2013)

Len J said:


> Any mechanic that needs a torque wrench for a cassette on a regular wheel isn't very experienced IME.


I suppose I agree seeing as you said *need*
However, it is still good practice and shouldn't be frowned upon if someone chooses to use one. For one, it's a liability issue. For another, it's that extra touch that is so often lacking. I never use a torque wrench working on my own bikes, but I frequently use one at work. It's a precision instrument; if I am paying someone top dollar I would expect them to use it.


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## Typetwelve (Jul 1, 2012)

headloss said:


> I suppose I agree seeing as you said *need*
> However, it is still good practice and shouldn't be frowned upon if someone chooses to use one. For one, it's a liability issue. For another, it's that extra touch that is so often lacking. I never use a torque wrench working on my own bikes, but I frequently use one at work. It's a precision instrument; if I am paying someone top dollar I would expect them to use it.


I used to wrench on cars, especially rebuilding engines. The reason why I started this thread is like any machine, there are bolts that NEED to be tightened to spec and others that really don't. Sure, some engineer somewhere will put a torque spec on every bolt in an engine...but it doesn't always need to be that way. Other times however, it is critical.

I didn't even hesitate to get a torque wrench for anything envolving screws on my frame. I knows the importance of proper torque, especially when talking of small amounts like 5 N-m. That's not much and if you try to do it by feel alone...too little and it falls apart on the road...too much and CRACK! Goodbye fancy carbon frame.

The rear casette is just one of those things that said to me "get me close enough". At 40 N-m...it's the hardest setting I've come across so far, is there anything on a bike that's higher than that? If not, and it's not that critical, there's really no need to buy one expensive tool just for one part, and a part that's not seriously critical.


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## wim (Feb 28, 2005)

Typetwelve said:


> like any machine, there are bolts that NEED to be tightened to spec and others that really don't.


Well said.

As for higher torques on bicycles: Cassette lockrings are sometimes spec'd to 50 Nm; cup-and-cone bottom bracket bearing cups can go up to 70 Nm, and the Hirth joint bolt in Campagnolo's Ultra-Torque cranks is spec'd at 42 Nm, with Campagnolo recommending to increase torque to max 62 Nm if there are issues. There may be even more high-torque places on a bike, but I can't think of them right now.


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## tihsepa (Nov 27, 2008)

wim said:


> Well said.
> 
> There may be even more high-torque places on a bike, but I can't think of them right now.


You forgot about the little nuts on the valve stems. 

Seriously, why the resistance to doing things right and torquing them? If you dont have the time to do it right the first time, how are you going to find time to do it a second time?


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## wim (Feb 28, 2005)

tihsepa said:


> You forgot about the little nuts on the valve stems.


You're right. 30 Nm minimum on those. That's difficult to get with your fingers, so I always use a pair of those nifty Chanellock® pliers on those.

The resistance is to using a torque wrench in places where none is needed. To be honest about it: I'd feel like an idiot using a torque wrench on a cassette lock ring and my boss (who's an excellent mechanic) would think I'd gone daft should he observe such foolishness. Campy Ultra-Torque Hirth joint bolt? Another matter altogether. I use a torque wrench every time to make sure I've got it tight enough. I have a tendency to go too easy on fasteners.


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## tlg (May 11, 2011)

Tlaloc said:


> Your mechanic is lazy and careless if he doesn't use a torque wrench even though one is sitting right there in his tool box.


Or the mechanic is knowledeable and experienced. Perhaps he knows that the use of torque wrenches is accurate to +/- 25%. Whereas by feel bolts can be torqued to +/- 35% accuracy. Not a whole lot of difference. An experienced mechanic is likely more accurate than an inexperienced "joe" using a torque wrench.

Machinery's Handbook, 25th Edition, page 1404
Torque Method Accuracy 
By Feel +/- 35% 
Torque Wrench +/- 25% 
Turn-of-nut +/- 15% 
Preload washers +/- 10% 
Bolt elongation +/- 3% 
Strain gauges +/- 1%

Torque spec's are a fuzzy science. Typically torque values are given as a range. And it's rarely specified if the torque specification is wet or dry, which creates ~25% difference in torqe value. 
Shimano's cassette torque is 261 - 434 in. lbs. That's a 173 in.lb. spread (40%)! 
A 40% spread in specification + 25% accuracy + 25% Wet vs. Dry = a whole lot of percent's! 

Joe #1 could set his torque wrench to 261 in.lb., with dry threads, & an inaccuracy of -25% resulting in a final torque of 196 in.lb.
Joe #2 could set his torque wrench to 434 in.lbs, with wet threads, & an inaccuracy of +25% resulting in a final torque of 678in.lb. 

Joe #2's cassette would be 3.4x tighter. I don't think we need to worry about "lazy and careless mechanics" not using a torque wrench.


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## Eric_H (Feb 5, 2004)

Only thing I'll add is that it is possible to over-tighten a lockring and damage the freehub. Specifically the DT 240S freehub for Campy. The shoulder/flange the cassette tightens against is very thin metal and I did managed to crack one by overtightening. DT has a torque spec of 25-30 N-m on the lockring, whereas Campy's spec (and Shimano's) are much higher at 35-50 N-m. I just used my usual long crescent wrench on the lockring tool and tightened to "low-level grunt" torque, which had worked for 20 years on various cassette lockrings and hubs. 

The shoulder is thin on the Campy freehub because it is wider than the Shimano 8/9/10 freehub and in order to use the same hub dimensions DT just made the shoulder more thin. I have not examined a DT freehub for Shimano 11 spd but I suspect it may also have less material at the shoulder compared to the 8/9/10 version.


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## TmB123 (Feb 8, 2013)

I've never used a torque wrench on a lock ring, but have had mine come loose on me not long after getting the bike. That's about the last part in the world that I thought would ever come loose. It jammed the rear wheel up while out riding. 

Assembled by a non experienced mechanic I guess


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## headloss (Mar 3, 2013)

tlg said:


> Or the mechanic is knowledeable and experienced. Perhaps he knows that the use of torque wrenches is accurate to +/- 25%. Whereas by feel bolts can be torqued to +/- 35% accuracy. Not a whole lot of difference. An experienced mechanic is likely more accurate than an inexperienced "joe" using a torque wrench.
> 
> Machinery's Handbook, 25th Edition, page 1404
> Torque Method Accuracy
> ...


There is more than one type of torque wrench and those percentages vary... which type are you referring to?

I would add that given the propensity for a torque wrench to go out of calibration, these numbers can be even further off. That said, a torque wrench still ensures a universal standard of sorts. A mechanic can be experience but poorly trained to begin with. What good is a mechanics "feel" if the mechanic himself was never properly calibrated? Point being, I don't trust the average kid in a bike shop to have the experience to go by feel and most qualified mechanics aren't the ones who end up wrenching our bikes at the end of the day.

But, being realistic... what's the worst thing that can happen by slightly over tightening or under tightening a rear cassette. To go back to the OPs question, I don't really think a torque wrench is necessary. I'd still use one if I was working in a shop and signing my name to a piece of paper. That's my prerogative as a professional mechanic trained in the use of precision instruments.

For the record, a good dial-indicator torque wrench is +/- 5 to 10 while a handwrench is +/- 60%. That's no small difference. I guess it matters how you want to pick the numbers. I'm using the readily accessible http://www.skf.com/files/880426.pdf


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## wim (Feb 28, 2005)

headloss said:


> I'd still use one if I was working in a shop and signing my name to a piece of paper. That's my prerogative as a professional mechanic trained in the use of precision instruments.


One certainly can't argue with that. But a point can be made that with a cassette lock ring, you'd be using a precision instrument on a fastener that doesn't really allow a precision measurement. For one, torque values used when fastening one part to another are basically stand-ins for the amount of stretch a bolt or screw of a certain size should be subjected to so as effect a certain clamping force. Since there's no bolt involved, the torques given for almost two-dimensional cassette lock rings can only be approximations.

The other thing is that most cassette lock rings rely on a serrated interface with the smallest cog to stay tight. This means that during tightening, the serrations need to be moved over center at torques which are quite high ("the click"), then mesh again with a resultant reduction in torque. It's entirely possible (if not probable) that a precision torque wrench will indicate sufficient torque at that over-center point when clamping force after that point has been passed is not yet to specs.


Point being of all this: an experienced hand *may* actually be the better tool with a cassette lock ring than a precision instrument.


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## Mike T. (Feb 3, 2004)

wim said:


> One certainly can't argue with that. But a point can be made that with a cassette lock ring, you'd be using a precision instrument on a fastener that doesn't really allow a precision measurement. For one, torque values used when fastening one part to another are basically stand-ins for the amount of stretch a bolt or screw of a certain size should be subjected to so as effect a certain clamping force. Since there's no bolt involved, the torques given for almost two-dimensional cassette lock rings can only be approximations.
> The other thing is that most cassette lock rings rely on a serrated interface with the smallest cog to stay tight. This means that during tightening, the serrations need to be moved over center at torques which are quite high ("the click"), then mesh again with a resultant reduction in torque. It's entirely possible (if not probable) that a precision torque wrench will indicate sufficient torque at that over-center point when clamping force after that point has been passed is not yet to specs.
> Point being of all this: an experienced hand *may* actually be the better tool with a cassette lock ring than a precision instrument.


This ^^^^. Thanks for saying it Wim. I mentioned the serrations in my earlier post. Between the large spread of acceptable torque values for this part, the big potential for any torque wrench to be out of calibration (how many owners have them re-tested?) and the serrations creating a false reading, maybe perceived torque is as good as anything. And I'll just bet that the vast majority of cassette lockrings never see a torque wrench in their lifetimes. And how often do we see loose ones? Or stripped ones. I guess the serrations are there for a very good reason.


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## wim (Feb 28, 2005)

Mike T. said:


> I mentioned the serrations in my earlier post.


I read your earlier post, but forgot about that mention of yours. My apologies, getting old and forgetful.


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