# Chainstay to chainring clearance - is 1mm enough?



## sweeners (Jul 23, 2008)

Hi,

I'm building up my new bike and put on the chainset at the weekend but I've only 1mm clearance where the chainstay and the small chainring ring meet. I've installed it on the basis of getting the 43.5mm chainline and now that everything is tightened up, that looks spot on - as best I can measure it.

The problem is the small ring comes very close to the chainstay. Not the teeth so much, but the shoulder of the ring that the teeth stick out from. See the pics, which if anything make the space look more than is there in reality. I'd say its 1mm at most.

The parts involved are
60cm Colnago Master XLight Frame (Steel, Italian BB)
Campy Record 2006 Alloy Chainset 53-39 (square taper)
Phil Wood 102mm bottom bracket

So should I wait till I ride it and see if its a problem, or sacrifice the correct chainline now for some more clearance?


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## Nielly (Sep 21, 2009)

How is the chainline relative to the cassette? If you run a straight edge from between the two chainrings it should land in the middle of the cassette. Is the crankset centered? Measure the crankarms from the seat tube. I wouldn't think that it would necessarily be an issue as the torque from pedaling tends to flex the cranks more in the vertical plain. But as you say if it is actually much closer to the chainstay than the picture makes it look it might be worth giving up a little for the "perfect chainline". You probably wouldn't notice much difference.


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## budmol3 (Dec 7, 2008)

It looks like that's a compact crank, a 39 or 42 would hit the chainstay with that setup which leads me to believe it was designed to have the chainrings further out.


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## Mel Erickson (Feb 3, 2004)

I assume you're using the BB that was designed for the crank? 102mm is the correct spindle length but it needs to be ISO and not JIS. However, an ISO crank won't fit as far down on a JIS spindle and would actually be further from the stay than on a correct ISO spindle. I'm guessing the spindle is ISO. The correct chainline is what you're after and using a different BB with a longer spindle will throw your chainline off. You should also check out Sheldon Browns (RIP) site http://www.sheldonbrown.com/bbsize.html, although there's not much on Campy he does show how to properly measure chainline. If your chainline is correct I'd say you're good to go and wouldn't worry about the minimal clearance.


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## percy (May 17, 2004)

Not sure about this 'cause I don't know squat about Campag, but is your inner chaining facing the wrong way? On my Shimano chainrings, what you refer to as the "shoulder" is oriented toward the outboard side on the small ring (mine happens to be a triple ... don't know if that changes anything.

Personally, I'd be a little concerned about the clearance since it wouldn't take much debris to get in there and start scratching your beautiful frame.


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## Richard (Feb 17, 2006)

I think Mel is right. But if you're concerned, a 1mm spacer behind the drive-side BB cup probably won't hurt anything. I did that on my 8 speed Record equipped bike and it shifts through the entire range perfectly.


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## Doctor Who (Feb 22, 2005)

My road bike was tight like that and in sprints or hard climbing, the ring would lightly rub the chainstay. Get a longer bottom bracket or see if you can't shim out the BB.


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## DHallerman (Mar 28, 2008)

*Pw Bb*

Actually, if the Phil Wood bottom bracket truly is 102mm in length, then it is the ISO version, since PW does not make a bb that length in JIS.

However, double check the length, since PW does make a 103mm bb that's JIS.

Dave, _who prefers at least 5mm between the small chainring and the chainstay_




Mel Erickson said:


> I assume you're using the BB that was designed for the crank? 102mm is the correct spindle length but it needs to be ISO and not JIS. However, an ISO crank won't fit as far down on a JIS spindle and would actually be further from the stay than on a correct ISO spindle. I'm guessing the spindle is ISO. The correct chainline is what you're after and using a different BB with a longer spindle will throw your chainline off. You should also check out Sheldon Browns (RIP) site http://www.sheldonbrown.com/bbsize.html, although there's not much on Campy he does show how to properly measure chainline. If your chainline is correct I'd say you're good to go and wouldn't worry about the minimal clearance.


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## DHallerman (Mar 28, 2008)

Richard said:


> I think Mel is right. But if you're concerned, a 1mm spacer behind the drive-side BB cup probably won't hurt anything. I did that on my 8 speed Record equipped bike and it shifts through the entire range perfectly.


Phil Wood bottom brackets don't take spacers.

However, you can adjust the cartridge by 2.5mm in either direction, just through the two mounting rings.


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## backinthesaddle (Nov 22, 2006)

Doctor Who said:


> My road bike was tight like that and in sprints or hard climbing, the ring would lightly rub the chainstay. Get a longer bottom bracket or see if you can't shim out the BB.


This^^^^^^^^^^^^^^^^^^^^^^^^^^^^


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## andulong (Nov 23, 2006)

You can fix that with a good smack of a ball peen hammer to the chainstay. Just kidding of course.


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## sweeners (Jul 23, 2008)

*So long and thanks for all the fish ....*

Thanks for all your input/suggestions:

Just to clarify - the BB is 102mm, and yes it's definitely a 53-39 chainset, compacts are for girls, *everyone* knows that, even me (middle-aged with a dodgy knee), and yes the chainrings are orientated the correct way. And Neilly, good advice - yes the chainset lines-up with the rear cassette so it looks totally centered. Everything looks right except the closeness of the chainring to the chainstay.

Anyway, to cut this thread short, I'm going to do the following, though if any of you think this is a big "whoooaaa, hold on .... ", then feel free to pipe up: 

I'm going to leave the install as it is and put some protective tape on the chainstay. Then once its all built I'll try it out gently on some flat. If all ok, then some hills. If it rubs, I'll move the BB 2mm to the drive side (Phil Wood is adjustable, no need for shims). 

Then I'll post a ride report and some photos. And then you can close down this website. That'll be March sometime though, so still plenty of time to discuss who's plastic is least flexy and all that other moo-moo-malarky. Then I'll leave as it is for the next 30years and let my son decide from there.

Thanks,
S.

p.s. can you tell I'm just in from the pub?


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## MCF (Oct 12, 2006)

"compacts are for girls, everyone knows that"...post pics after you tear up your chainstay...l love carnage pics!! Make sure you ride it nice and gently, like a girl would! What kind of bike requires you to ride it nice and gently....good luck with that one!


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## Nielly (Sep 21, 2009)

I was just looking at my steel pinarello and it doesn't appear that I am running much more clearance than yours and never had a problem. On mine though I'm running a campy BB and an even less "girly" 42 inner and I would have a little more space with the 39. It doesn't look there would be any way for you to run a 42 on yours and I guess if you don't plan to than it's no problem.


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## ukbloke (Sep 1, 2007)

sweeners said:


> I'm going to leave the install as it is and put some protective tape on the chainstay. Then once its all built I'll try it out gently on some flat. If all ok, then some hills. If it rubs, I'll move the BB 2mm to the drive side (Phil Wood is adjustable, no need for shims).


If it were me I would err on the side of caution rather than risking any damage to the frame. So why don't you start off with the extra 2mm spacing on the drive side and see how that works out? If that works fine in terms of shifting, then you don't need to worry about the tight clearance at all. If you don't like the shifting then you can consider incrementally bringing in the chain-line first by 1mm then by 2mm.


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## Fredrico (Jun 15, 2002)

Looks like about 2 mm from the pictures. Same as my old DeRosa with 42 inner ring. Never had any problems. Even had a 44 on it a few times. The narrower the BB, the less Q, the nicer the spin is on the legs. If the BB is installed correctly, it shouldn't flex and rub the chainstay.


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## brblue (Jan 28, 2003)

since the frame is steel (is it?) I think it can be cold-set so the chainstays move away from the crankset, for maybe another mm or 2, if you really fell u need that (maybe for larger chainrings).
take good care of the paintjob though...


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## Mel Erickson (Feb 3, 2004)

brblue said:


> since the frame is steel (is it?) I think it can be cold-set so the chainstays move away from the crankset, for maybe another mm or 2, if you really fell u need that (maybe for larger chainrings).
> take good care of the paintjob though...


Cold setting a frame is done to increase the rear dropout space, say from 126 to 130. What you're talking about is reshaping the chainstays by bending them outward very near the bottom bracket and then rebending them inward to maintain the proper dropout spacing. I've never heard of this being done and seriously doubt that it would be possible without damaging the frame. Don't even attempt this unless you're a framebuilder with proper tools.


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## DY123 (Oct 5, 2006)

Any follow up on what happened after a few rides? Any rubbing?


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## sweeners (Jul 23, 2008)

*1mm is enough!!*

Ok, at the time of the last post, I still had most of the groupset to buy and install. 

If any one is still interested, once I got all the bits (I got Chorus 11speed), and tried it out on two rides there was no rubbing on the chainstay. I did have a serious worry though - the driveside cup of the Italian bottom bracket decided to loosen. Just a tiny bit, but once it was on the move, it wasn't going to stop. I re-installed to the same chainline/clearance with more torque and loads more threadlocker. Its stayed put since. No movement of the cups and no rubbing/cutting of the chainstay. 

Thanks for all the help/advice and lads, the bit about the "compacts for girls" was only a joke.


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