Re: [CR]Calculating fork rake? (fwd)


Example: Component Manufacturers:Cinelli
From: <themaaslands@comcast.net>
To: Classicrendezvous@bikelist.org (Classic Rendezvous)
Subject: Re: [CR]Calculating fork rake? (fwd)
Date: Thu, 16 Oct 2003 20:12:23 +0000

Ann wrote:

<< ....helping my neighbor, Jenna, put together a nice little steel 1980 Rossin she got. We are totally unable to insert any stem, - and I had a lot of stems to try - in the steerer tube. I had my local frame repair resource check it out and Tamara is convinced that the tube is either slightly bent or deformed in some way and it would be best to replace the entire fork.

Now I can get a pretty inexpensive chrome fork from QBP, thats just fine. Question is, this is a very small frame, like a 48 cm and I want to measure the fork rake on the existing fork. It looks like it has a lot of rake, to avoid some portion of toe clip overlap. Obviously I'd want to compare the original fork to the one in the QBP catalog.

Is this something I can do without engaging a mechanical engineer? With you know, tools at home, like a tape measure and a calculator? >>

To which our illustrious leader responded:

Measuring the offset can be done (not exactly but close) by:

- laying the fork down, tips up on a flat surface, making sure that the steer tube in parallel to that surface. - From the flat surface, measure up to the center line of the steerer (A) - From the flat surface, measure up to the center of the drop out. (B) - subtract A from B.

A small Italian bike like that is likely to have a whole bunch of offset...way over 50 mm.

To which I would like to add that you must also take into account the distance from the seat of the headset race to the center of the drop-outs to return the bike to the dimensions intended by the builder. It might also be worthwhile that you try to see if a French stem fits in the steerer. Whil eit would be odd to have Rossin with a French steerer, I have seen stranger things.
--
Steven Maasland
Moorestown, NJ