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Head Tube angle and Rake(3 posts)

Head Tube angle and Rakesfbuff
Apr 11, 2002 9:39 AM
Former road runner making initial foray into cycling, please excuse the ignorance of the following.

I recently purchased a 55 cm Merlin Odyssey with a Reynolds Ouza Pro carbon fork. Merlin has a head tube angle of 73.5, the reynolds has a 40mm rake. Bought the bike at Excel, had an extensive fit session with Wade. Although this is really my first road bike, the fit seems to be solid. I have done approx 30-40 training rides since I got the bike, some as long as 80 miles, no problems.

I also recently purchased a used Seven Tsunami cross bike from a friend, mainly because the bike has S & S couplings that will allow me to take it on future vacations. The top tube length of the seven is approx the same as the merlin, seat tube is obviously shorter. The head tube angle of the seven is 71.5, and has an IF steele fork.

My question: I do not plan on racing cross, and would like the seven to ride / feel as close to the merlin as possible. I want to put a reynolds ouza pro fork on the seven. Given that the head tube angle is 71.5 vs 73.5, what rake would you suggest for the reynolds fork to be installed on the seven cross bike. Can someone give me a quick lesson on the basics of head tube angles and fork rake, and how they relate to bike handling.

Thanks in advance, future posts will be more to the point.

-SFBUFF
re: Head Tube angle and RakeChen2
Apr 11, 2002 1:53 PM
It's the "trail" that effects handling. The Seven's slacker head tube angle means more trail. Increasing fork rake decreases trail. So to make the Seven handle more like the Merlin you should put the 43 rake Ouzo Pro in it instead of the 40 to reduce trail. If you will look through previous posts regarding rake and trail you will find a post by "C-40" that gives the formula for calculating trail. You may want to go as high as 45 on the rake to match the Merlin. Increasing rake, decreasing trail will make the bike turn quicker. That 71.5 degree head tube angle is really "laid back".
~Al
trail calculationC-40
Apr 11, 2002 6:08 PM
Trail = (tire radius/tanH)- (rake x sinH), where H is the head tube angle. The trail on the Merlin is 61.2mm. To get the same trail with a 71.5 HTA would require a rake of 54mm. You won't find a stock fork with this much rake. A 45mm rake will give you a trail of 69.7mm.

More trail results in slower steering, less trail results in quicker steering. Numerically smaller HTA's and rake both slow steering by increasing trail.