Oval chainrings

[bonker]

Do chainrings get more oval with wear?

I've been commuting happily for 15 months on mine but I've noticed the tight spot and loose spot on the chair seem to be much more pronounced.

Is that a wear thing? Can't see a bend or anything in the chainring.

 

[Theseus]

Does the chainring fit using bolts or is it an integrated part of the cranks?

If the former, then my guess would be that it has slipped a little and is no longer perfectly centered on the spider arms.

If the latter, then I can't help you.

 

[4F]

Does the chainring fit using bolts or is it an integrated part of the cranks?

If the former, then my guess would be that it has slipped a little and is no longer perfectly centered on the spider arms.

If the latter, then I can't help you.

My first thought was loose chainring bolts as well.

 

[bonker]

Oval rings

I'll have a closer look at that.

 

[4F]

From Sheldon

Set the rear axle so that the chain pulls taut at the tightest part of the cranks' rotation. One at a time, loosen up each of the stack bolts, and tighten it back just finger tight. Spin the crank slowly and watch for the chain to get to its tightest point. Strike the taut chain lightly with a convenient tool to make the chain ring move a bit on its spider. Then rotate the crank some more, finding the new tightest spot, and repeat as necessary.

This takes a little bit of your hands learning how hard to hit the chain, and how loose to set the stack bolts, but it is really quite easy to learn.
Tighten up the stack bolts a bit and re-check. Tighten the stack bolts in a regular pattern, like the lug nuts on a car wheel. My standard pattern is to start by tightening the bolt opposite the crank, then move clockwise 2 bolts (144 degrees), tighten that one, clockwise 2 more, and so on. Never tighten two neighboring bolts in a row. You may prefer to go counterclockwise, but try to get in the habit of always starting at the same place and always going the same way. This reduces the chances of accidentally missing a bolt. Once you have the chainrings centered and secured, adjust the position of the rear axle to make the chain as nearly tight as possible without binding. Notice how freely the drive train turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible.

 

[swee'pea99]

+1. I did this, following those very instructions, and was amazed how easy it was and how well it worked. Only took about 15 mins all told. (I seem to remember reading somewhere that you have to be careful not to overtighten the bolts...get them tight, but don't add grunt or you run the risk of thread-stripping.)

 

[Norm]

My clunker has Biopacehttp://en.wikipedia.org/wiki/Biopace!

 

[brodie]

From Sheldon

Set the rear axle so that the chain pulls taut at the tightest part of the cranks' rotation. One at a time, loosen up each of the stack bolts, and tighten it back just finger tight. Spin the crank slowly and watch for the chain to get to its tightest point. Strike the taut chain lightly with a convenient tool to make the chain ring move a bit on its spider. Then rotate the crank some more, finding the new tightest spot, and repeat as necessary.

This takes a little bit of your hands learning how hard to hit the chain, and how loose to set the stack bolts, but it is really quite easy to learn.
Tighten up the stack bolts a bit and re-check. Tighten the stack bolts in a regular pattern, like the lug nuts on a car wheel. My standard pattern is to start by tightening the bolt opposite the crank, then move clockwise 2 bolts (144 degrees), tighten that one, clockwise 2 more, and so on. Never tighten two neighboring bolts in a row. You may prefer to go counterclockwise, but try to get in the habit of always starting at the same place and always going the same way. This reduces the chances of accidentally missing a bolt. Once you have the chainrings centered and secured, adjust the position of the rear axle to make the chain as nearly tight as possible without binding. Notice how freely the drive train turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible.

The above might work with cheap chainsets but it certainly doesn't with good quality parts, eg Campagnolo Record.

On my cranks and rings, the fit is exact, there is no movement even before the bolts are fully tightened.

 

[fossyant]

I don't bother with mine, just set it OK, check it isn't too tight all round... (it can move about)...... Check your chain isn't worn..... they do, even on fixed.....makes a difference....

Well Campag Record won't be on a commuter will it ?..... (or shouldn't - get it on a track bike)