Re: [CR]Old racing bike geometry

(Example: Books:Ron Kitching)

Date: Tue, 01 Feb 2005 11:30:37 -0800
From: "Chuck Schmidt" <>
Subject: Re: [CR]Old racing bike geometry

I'm getting a lot of questions off list that I covered in a post:

Measuring: For fork rake I have a plexiglas gage called a "Gabe Meter" made in Germany in the early 1980s that has a v-block (with magnets) on the back that attaches at the top of the fork leg that has a scale you read at the pointed end of the QR.

Almost as easy is to use a 4' metal straight edge, lining up the center line of stem bolt, fork crown and upper fork blade, then calipers to measure to axle center.

For calculating trail:

For head angle and seat angle I use a 4' long metal straight edge along top tube and a draftsman's 14" adjustable triangle that has a degree scale on it to measure the angle.

I think this is much more accurate than one of those angle finders that relies on leveling the top tube first (fluid filled, with floating pointer?).

I also use the 4' metal straight edge and a vernier caliper to measure the BB drop.

Chainstay is measured to the middle of the drop out.

Here's an example: ~~~~~~~~~~~~~~~~~~~~~ 1960 CINELLI SC #7094 (center to center) Seat Tube -- 55.5cm Top Tube -- 56.0cm BB drop -- 8.0cm Chain Stay -- 42.5cm Wheel base -- 102.0cm Seat Tube < -- 73.0° Head Tube < -- 73.0° Fork Rake -- 5.5cm Trail -- 4.6cm* *wheel dia. 68.0cm ~~~~~~~~~~~~~~~~~~~~~

Also a lot of questions about "which bikes should I measure?"

I measured some of mine (eventually all) because I was curious as how they compare to each other (also the different eras). If you have any curiosity at all, I would assume you'd want to know how the bikes you ride compare in geometry.


Chuck Schmidt South Pasadena, Southern California