Fork Rake Question

[M3001zip]

Hello, what is the difference between a 40 degree and a 45 degree rake.Is one better for time trials
then the other? THANKS

 

[Sheldon Brown]

A shy person wrote:

> Hello, what is the difference between a 40 degree and a 45 degree rake.Is one better for time
> trials then the other? THANKS

Applicability to time-trial use has nothing to do with fork rake.

The combination of fork rake (sometimes called "offset") and head tube angle determines the
"trail" of the steering. This relates to the handling of the bike, which is not generally an issue
in time trialing.

Shorter-rake forks are appropriate for bikes with steeper head tube angles.

Sheldon "Match The Frame" Brown +-------------------------------------------------------+
| Military conscription is the worst form of slavery. | A more enlightened age will consider it a
| War crime. |
+-------------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

 

[Harris]

M3001zip <[email protected]> wrote:
> Hello, what is the difference between a 40 degree and a 45 degree rake.Is one better for time
> trials then the other? THANKS

I think you mean 40 mm and 45 mm, not degrees. For a given head tube angle (usually about 73
degrees), more rake (a.k.a. fork offset) will produce less trail. Less trail results in less
stability. Time trials generally don't require quick steering, so a generous amount of trail
wouldn't be a bad thing.

See: http://www.phred.org/~josh/bike/trail.html

Art Harris

 

[Thomast41]

I agree with Art Harris on this point. I generally design TT machines with shorter than normal rakes
to increase high speed stability. You will sacrifice some low speed handling. The effect of
increased trail gets noticable at speed.

Tom @ TET

 

[Scott Hendricks]

Sheldon Brown <[email protected]> wrote in message
news:<[email protected]>...
> A shy person wrote:
>
> > Hello, what is the difference between a 40 degree and a 45 degree rake.Is one better for time
> > trials then the other? THANKS
>
> Applicability to time-trial use has nothing to do with fork rake.
>
> The combination of fork rake (sometimes called "offset") and head tube angle determines the
> "trail" of the steering. This relates to the handling of the bike, which is not generally an issue
> in time trialing.
>
> Shorter-rake forks are appropriate for bikes with steeper head tube angles.
>
> Sheldon "Match The Frame" Brown
>

Applicability to time-trialing has everything to do with fork rake, if you're concerned about the
effect of wind on a deep-dish rim'd front wheel.

Time trial specific bikes typically use a 4.0 fork w/ a 73 deg or slacker head angle to achieve
trail numbers sufficiently high enough to aid in the stability of the front end in crosswinds. If
you can find a 3.8 offset fork, so much the better.