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Surly Fork Rake(4 posts)

Surly Fork RakeDerf
Aug 14, 2003 7:43 AM
I understand the principles but I just do not have the "feel" of changes in fork rake.

I an thinking of changing my Surly cross check's fork from stock, with a rake of 44mm, to one with a rake of 41mm.

How will this change the handling of the bike?

Thanks,
Derf
re: Surly Fork Rakelaffeaux
Aug 14, 2003 11:40 AM
I have two CX bikes with the same seat tube and head tube angles. The tt on one is about 1/2" longer, but otherwise they are similar. The big difference is the fork rake - one is 44mm and the other is 32mm. The bikes handle very differently.

The bike with a 32mm rake likes to be pointed downhill and let go, while the other bike is more about finesse. It's hard to knock the 32mm bike of line, and turns are all about leaning the bike.

The smaller the rake, the more the front wheel will try to remain centered. I don't know how much you'll feel 3mm of difference though.
re: Surly Fork RakeDerf
Aug 14, 2003 4:07 PM
Thanks for the input. I did not think that the 3mm would make a large differacne. I am also more of a muscle rider. Maybe it will make my ride just a but more enjoyable.
Help!Derf
Aug 15, 2003 9:59 AM
I am confused. When thinking about the fork change it also occured(SP) to me that the fork lengths should be taken into consideration.

Per my calculations a change from a 400mm (fork A) to a 412mm fork (fork B) should change the head angle by -.01183 degrees using the formula arcsin[(old length - new length)/(wheel base)] with a wheel base of 1014.4

This changed the head angle from 72 (Fork A that has a rake of 44mm) to 71.988 (Flork B that has a rake of 41mm)

Plugging these into the model at http://www.kreuzotter.de/english/elenk.htm and using a tire diameter of 68.5 cm I came up with a trail of 10.7 for fork A and a trail of 10.7 for fork B.

Per this, my steering should not change. Are my assumptions full of it or do the change in the 2 variables give me a ride that is substantially the same?

Thanks for your help!!
Derf