RE: [CR]Bike mechanic insanity


Example: Events:Cirque du Cyclisme:2007

Content-class: urn:content-classes:message
Subject: RE: [CR]Bike mechanic insanity
Date: Wed, 25 Jan 2006 21:35:41 -0800
Thread-Topic: [CR]Bike mechanic insanity
Thread-Index: AcYiIkj7FWmuFfipQv2MAgttIZliLAAFqKRA
From: "Mark Bulgier" <Mark@bulgier.net>
To: <wheelman@nac.net>, <classicrendezvous@bikelist.org>


Ray Homiski wrote:
> Wonder why more early bike mechanics have not committed
> suicide. [big snip]
> I installed the new rings on the crank. Now mind you this is
> an exact switch of TA for TA. Same spindle and all. Now when
> I install the crank on the BB the smaller ring hits the
> frame. It was a good 3-4 mm away before but now it
> interferes.

Ray,

This is nothing specific to TA or old bike parts - it's just as true today and is pretty much inevitable. You went to a small chainring that's fully 10 teeth larger - of course it comes closer to the frame. Looking down on the chainstay from above, note the angle the stay makes with the centerplane of the bike. That angle is the cause of the difference in clearance with smaller/larger rings. You can always use a shorter spindle with a smaller chainring, for a given frame.

Frames made for a triple with that large of an inner usually will have a fairly substantial indent in the outside of the chainstay for clearance. While the dent can be added later by a careful framebuilder, it's a little risky. Paint will almost certainly flake.

A simple fix to your problem is use the original 26 tooth small ring instead of the 36, but with the newer middle and big rings. I'm not guaranteeing it'll work but it probably will, and it'll definitely cure the chainring-chainstay clearance issue.

Mark Bulgier
Seattle WA USA