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Newbie question on fork rake ...(8 posts)

Newbie question on fork rake ...jkh
Jan 2, 2002 10:42 PM
I found this description on one on-line store:

"40mm rake forks are more stable, and better for bikes with steeper head tube angles (74º and above, typically found on smaller frames), while 45mm rake forks are more nimble, and best suited to bikes with shallower head tube angles (73.5º and below, typically found on medium and larger sized frames)."

I thought a longer rake (45mm) would yield a longer wheelbase, and hence a more stable ride; whereas a shorter rake would yield a short wheelbase and a more nimble ride.

Am I wrong? Please help me to clarify this. Thanks.
re: Newbie question on fork rake ...josh_putnam
Jan 2, 2002 11:14 PM
The key to front-end geometry is "trail", the distance the contact patch of the tire lags behind the intersection of the steering axis with the ground. If you increase fork rake, you move the hub forward, closer to the steering axis intercept, and thus reduce the self-centering tendency of the steering. In other words, more rake = less stability, within the usual range of rake and trail values found on modern road bikes.

The illustration below is from my article on steering geometry at http://www.phred.org/~josh/bike/trail.html
I got it, thanks.jkh
Jan 2, 2002 11:50 PM
Nice infrared shots, by the way (nm)Brian C.
Jan 3, 2002 8:18 AM
NO!!!!!!!!!!!!!!!!!Rusty McNasty
Jan 3, 2002 5:14 AM
A greater RAKE will decrease the TRAIL, making the bike squirrely at high speed. Novices should always read a GOOD book on the subject BEFORE replacing forks.
Isn't that what he saidDave Hickey
Jan 3, 2002 6:51 AM
He said more rake=less stability. You say a greater rake will make the bike squirrely at high speeds. Aren't you two saying the same thing?
Isn't that what he saidmackgoo
Jan 3, 2002 6:54 AM
It's funny we both posted basicaly the same thing at the same time. I'd give ol Rusty the benefit of the doubt and say he responded to the question and didn't look to see what was already posted.
NO!!!!!!!!!!!!!!!!!mackgoo
Jan 3, 2002 6:52 AM
Although the poster got it backwards whih does seem to be the intuitive way to look at it. The response did correct him you know.