SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.



Recently I measured my Kogswell 59x700C P/R's fork -- the one designed for 40mm trail on this frame. It's 400mm axle to crown, give or take:

Kogswell Fork

The blueprint says this fork should be 365mm, which is impractically short for a 700C-wheel frame. (?!?!?)

Kogswell 700C P/R Blueprint

I also just got a Wixey digital angle gauge, and used that to measure all the
angles on my 59x700C P/R frame. They all vary pretty far from the as-designed values. My bike has a head angle around 71.5-72º, which is supposed to be 73.6º.

Kogswell Head Tube Angle

The seat angle measures 70.6º vs. the specified value of 72.4º.

Kogswell Seat Tube Angle

Finally, as you can see on the blueprint above, the BB drop is supposed to be 79mm, while the actual value measures to around 70mm.

This makes me wonder if, overall, the fork was manufactured too long. If it was 20mm shorter, it'd be closer to the blueprint, and both of the frame angles would be a full degree steeper (10mm of fork change makes the head angle about half a degree steeper). FWIW, there ARE about 20mm of spacers between the fork crown and the front fender, indicating that the fork is longer than it needs to be.

Kogswell Fork Crown Fender Spacers

Using these actual values plugged into my trail calculator gives a trail of 54mm and flop of 16mm. So the bike is not even low trail after all! :(


Anonymous Chris B. said...

This sucks. wonder if there is enough fork out on the ends to cut and re-braze some drop outs?

You might have to re-rake a little.

12:27 PM  
Anonymous Kurt said...

You're not the only one. I have a 700c P/R and my geometry is similarly screwed. There's no way I would have bought the thing if I'd thought it was a mid trail bike. I can't say I dislike the handling though, even with my handlebar bag.

10:06 PM  

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