Centering Chainring

I remeber seeing a sheldon article on how to do this but can't find it now. Anuone else able to find it/willing to give it a go?

Use the search, there was a couple of lengthy threads on here about a year ago that you may be able to dredge up.

I distinctly remember writing a lengthy post in one of them.

i remember it too.

it's on sheldons chainline page, i think.

Success, it was halfway down his page on conversions.

Chain Tension

he chain tension on a fixed gear is quite critical, and is regulated by moving the rear axle back and forth in the fork ends. If the chain is too tight, the drive train will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding. If the chain is too loose, it can fall off, which is quite dangerous on a fixed gear.

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.

Hmm, all sounds a bit improbable, can't quite picture it. Let us know if it works (i've got this problem as well at the mo)

b-but...that would mean questioning Sheldon, which means Sheldon could be fallable, do you know what you've done?! The end is nigh!!!!!!!!!!!!!!!!

put chain at tight spot, loosen chainring bolts, then re-tighten, move crank one whole revolution, repeat. until it's better..........NO CHAINRING/COG/BOTTOM BRACKET/CRANK will be 100 % round.
FACT

mine is 99.99% after tax round. fact :)

..........NO CHAINRING/COG/BOTTOM BRACKET/CRANK will be 100 % round.
FACT

Claim:
[INDENT]We produce our chainrings one at a time in a single setup which means that once the piece of material is placed onto our jig then it does not come off until it has been completely machined. So both the bolt holes and the teeth are produced together in the one setting so no high spots....read that again.....no high spots.
[/INDENT]I have one on order, and mates capable of measuring.

sheldons method works, i know it sounds strange but it works

yes but 100% round would mean perfect circle. Strictly speaking that is unachievable.

so murtle is the winner of todays challenge

next.

Shit. I hate to agree with that Beatle-haired mumbling idiot.. but he's on the money tonight. :)

i'm always smokin' hot, baby

Claim:

[INDENT]We produce our chainrings one at a time in a single setup which means that once the piece of material is placed onto our jig then it does not come off until it has been completely machined. So both the bolt holes and the teeth are produced together in the one setting so no high spots....read that again.....no high spots.
[/INDENT]I have one on order, and mates capable of measuring.

Their claim may be true, but as soon as you put it on a crank and attach with chainring bolts the chances of it being perfectly centred are slim to F-all.

Cool, just tried this and it kind of works. Still have a tight spot and a loose spot, but not as bad as it was

this is interesting. never even thought to try it.

I must get around to trying this, my eccentricity is on the bad side.

Nice one! tight spot gone, It feels so much better track standing now.

But I buggered my chain :(

what do you do if you have one of those one piece cranksets then eg sugino maxy?

live with it or buy a new chainset

live with it or buy a decent chainset

:)

Is Chainring centering only really neccessary if you have considerable tight and loose spots in your chain?
Having read this thread, i went and checked my chain. It's almost as if a third of the chain, is ever so slightly tighter than the rest - but this is hardly noticable, and might even be a thing of my imagination. Is it advisable to try and center my chainring anyway?

try it and see if your quality of life improves dramatically?

Then report back and I'll probably not bother cause I can't be arsed.

perversely I have spent copious sums on the roundest, most CNC'd precision rings, crankarms and cogs and then I run my chain so slack it doesn't really matter anyway.

Hmm I understand that Sheldon's technique and believe it should work as long as the outer circle (where the teeth are) of the chainring is pretty round, but what if there is no room for the bolt adjustment? I've got miche condor stuff (crancks, chainring) and the inner edge of chainring fits sniffly in the spider edges, should I then just get out a file and create some space there?