Chain ring rubbing on frame

31-03.-2008, 09:46 PM	#1
hedzup Registered User Join Date: Mar 2008 Location: Perth Posts: 7	Chain ring rubbing on frame Hi all, My chain ring has started to rub on the frame of my bike (see photo). I suspect the problem is a worn bottom bracket but can't feel any roughness or stiffness when I turn the cranks by hand. There seems to be a small amount of play in the bottom bracket but it doesn't seem to be excessive (but I'm not sure what is excessive). Does anyone have advice on how I can check whether it is the BB or a bent chain ring. The chain ring is a shimano biopace which is why the area of rubbing extends beyond the visible portion of the inner chain ring. The rubing is not constant but seems to come and go. Thanks AB

31-03.-2008, 10:36 PM	#2
Insaneclimber Registered User Join Date: Aug 2006 Posts: 158	Re: Chain ring rubbing on frame Hey man Any play in the bottom bracket is too much, so i would guess that your problem lies there. as for checking straightness of chainrings, just drop the chain off and give the cranks a spinn. While there spinning eyeball the teeth from above you will easily see if its warped. PS a couple of mm either way don't matter too much. I would suggest at least dissassembling your bb to check the bearings and the tightness of the cups.

31-03.-2008, 11:14 PM	#3
Powerful Pete Registered User Join Date: May 2004 Location: Rome, Italy Posts: 3,322	Re: Chain ring rubbing on frame Yup, there should be no play that you can feel in your BB. Disassemble and re-assemble. If you are not comfortable doing this at home do take it to your local shop and have them do it. And please do clean that chain and those chainrings! __________________ De Rosa Planet Campagnolo Per Sempre! PAOLO BETTINI CAMPIONE DEL MONDO x 2!

31-03.-2008, 11:51 PM

Peter@vecchios

Registered User

Join Date: Dec 2007

Posts: 569

Re: Chain ring rubbing on frame

Quote:

Originally Posted by hedzup

Hi all,

My chain ring has started to rub on the frame of my bike (see photo). I suspect the problem is a worn bottom bracket but can't feel any roughness or stiffness when I turn the cranks by hand. There seems to be a small amount of play in the bottom bracket but it doesn't seem to be excessive (but I'm not sure what is excessive). Does anyone have advice on how I can check whether it is the BB or a bent chain ring.

The chain ring is a shimano biopace which is why the area of rubbing extends beyond the visible portion of the inner chain ring.

The rubing is not constant but seems to come and go.

Thanks

I would pull the cranks and OVH or replace the BB. I would suggest using a slightly longer BB spindle if you replace. That ring is really close to the frame.

AB

I would pull the cranks and OVH or replace the BB. I would suggest using a slightly longer BB spindle if you replace. That ring is really close to the frame.

02-04.-2008, 06:06 AM

oldbobcat

Registered User

Join Date: Sep 2003

Location: Boulder County, Colorado

Posts: 486

Re: Chain ring rubbing on frame

Quote:

Originally Posted by Peter@vecchios

I would pull the cranks and OVH or replace the BB. I would suggest using a slightly longer BB spindle if you replace. That ring is really close to the frame.

Or, if the BB is otherwise OK and there is extra spindle on the other side, re-install the RH cup with a spacer ring or two.

02-04.-2008, 12:50 PM	#6
hedzup Registered User Join Date: Mar 2008 Location: Perth Posts: 7	Re: Chain ring rubbing on frame Hi all, Thanks for the replies. I went into a fantastic bike shop yesterday and they replaced BB with a version with a slightly longer spindle and gave me lots of useful advice (including replacing the biopace with something a bit rounder when the chain rings wear out ). Cheers AB

02-04.-2008, 02:01 PM

alfeng

Registered User

Join Date: Jul 2005

Posts: 1,880

Re: Chain ring rubbing on frame

Quote:

Originally Posted by hedzup

My chain ring has started to rub on the frame of my bike (see photo). I suspect the problem is a worn bottom bracket but can't feel any roughness or stiffness when I turn the cranks by hand. There seems to be a small amount of play in the bottom bracket but it doesn't seem to be excessive (but I'm not sure what is excessive). Does anyone have advice on how I can check whether it is the BB or a bent chain ring.

The rubing is not constant but seems to come and go.

This is after-the-fact because the BB was just replaced ...

If pressng the non-driveside of the crank toward the frame had moved your inner chainring AWAY from the chainstay & pulling the non-driveside crankarm away from the frame made the chainring rub against the chainstay then you probably needed to adjust the adjustable cup which must have loosened from the frame.

Usually (for those who might encounter a similar problem in the future), you would need to remove the non-driveside crankarm ... then loosen the lockring (which is probably loose), tighten/adjust the cup (which you would have done if you had overhauled the BB), tighten the lockring ...

OR, installing a cartridge-type BB (probably 113mm -- but, who knows what size your shop installed?!?) will preclude the problem of left-right play in the spindle.

02-04.-2008, 04:32 PM

hedzup

Registered User

Join Date: Mar 2008

Location: Perth

Posts: 7

Re: Chain ring rubbing on frame

Quote:

Originally Posted by alfeng

I should have mentioned that the existing BB was a sealed bearing type.

02-04.-2008, 05:38 PM	#9
RedRider2009 Registered User Join Date: Nov 2007 Location: SE Wisconsin Posts: 134	Re: Chain ring rubbing on frame That is the bike to bring if you go on a camping trip and need a fire! Good Luck __________________ "Pain is temporary. It may last a minute, or an hour, or a day, or a year, but eventually it will subside and something else will take its place." -Lance Armstrong

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