Non-round front gear wheel

[ish_gamzu]

been to various mechanics but think i now need some old school knowledge.

here the sitch: i ride a Giant Stiletto which has a fixed forward chain that transfers power to a another derailured chain (like a tandem--my rig is 7 feet long). the problem is with the front, fixed chain--we've tightened it to the max (it's an elliptical crank case) but part, probable half a revolution later, it has slack in it. i've changed the axle in the crank case but this problem persists. mechanics say that the front crank wheel is off-round, and that there's no such thing as perfectly round. okay, i accept that it'll never be perfect, but not that there's nothing at all to do about it.

years ago i had a bike repair book that gave instructions on how to file the teeth on a gear wheel. i guess that was to sharpen for wear, maybe when components were made of lesser stuff.

could i somehow put a file to one side of my front gear wheel to bring it closer to round? who can tell me how to accomplish this without making things worse, or where to find an instructional on point?

thanks,

nachum

[Joe_W]

Can you post a picture of the chainwheel? From what you tell it sounds as it it might even be a biopace chainwheel, those were elliptical for a reason... I wouldn't file it down, rather get a decent new one.

[cyclerUK]

http://www.jejamescycles.com/archive/giantStilettoRed07.html

It won't have a Biopace chainset.
The chainwheel should be reasonably round. Don't have the chain too tight but it shouldn't flop about.

[ish_gamzu]

(04-20-2010, 02:57 AM)Joe_W Wrote:  Can you post a picture of the chainwheel? From what you tell it sounds as it it might even be a biopace chainwheel, those were elliptical for a reason... I wouldn't file it down, rather get a decent new one.

here's one of many places to see the stiletto:

http://www.bikecyclingreviews.com/Giant_Stiletto_Its_Sharp.html - Similar

it's the crank case, not the gear wheel that's eliptical (so that tension can be set on the front chain, like a tandem)

need someone to source the old school method (lost art?) of filing a gear wheel to keep it/ bring it nearer to round.