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Fork RAKE question?(17 posts)

Fork RAKE question?king of Norway
Oct 31, 2002 12:33 PM
I recently picked up a Bianchi Frame to build up as a second bike. It came without its fork which, according to the website,has a rake of 45 degrees. All the forks I've been looking at (Reynolds, Look, Weyless-Supergo) have rakes of 43 degrees.

Should this be any concern to me, and how would a 43 degree fork affect this bike if at all?
Toe overlapDave Hickey
Oct 31, 2002 12:48 PM
How big is the frame? If it's a smaller frame(less than 52cm), toe overlap might be a problem. If it's larger, it will shorten your wheelbase giving the bike quicker handling.
No,No,No!!!!Alexx
Oct 31, 2002 1:54 PM
Reducing the OFFSET (a.k.a. "rake") will increase the TRAIL, thereby causing the bike to be:
1) More stable at high speeds, and
2) SLOWER handling.
Please read any book on vehicle dynamics, should you doubt this. (It will likely be in one of the early chapters, as this is pretty basic stuff for engineers).
I was wrong.... I went from a 43 to a 45. sorry everyone.Dave Hickey
Oct 31, 2002 1:58 PM
I had it backwards. Sorry, I went from a 43 to a 45 fork. T
Headtube angleSteveS
Oct 31, 2002 7:32 PM
You forgot headtube angle.

When I got my Spectrum with a 73.5 headtube angle, I told Tom Kellogg that I Did Not want a fast handling bike.So, rather than using a typical 40-43mm rake, he suggested a 45mm rake in order to make the handling "dead solid neutral." (his words)

Depends on the headtube angle.
Sorry, that's backwards.Chen2
Nov 1, 2002 1:41 PM
Going from a 43 to a 45 will make it turn quicker, not slower, because the trail would be reduced.
~Al
re: Fork RAKE question?desmo
Oct 31, 2002 12:56 PM
I put a Reynolds Ouzo Pro on my 2000 Veloce. I can't remember the exact numbers, but it was 1 or 2 degree steeper than the stock fork. If anything it handles better (at least to my liking), and has not hurt the straight line stability at all. Like Dave said toe clearnce is a possibility but unless it really close now you should not have a problem.
Rake, Trail, OverlapChen2
Oct 31, 2002 1:32 PM
First, rake numbers are millimeters of offset, not degrees. Going from a 45 to a 43 would cause slightly less than a 2mm difference in toe overlap.
Second, going from a 45 to a 43 will not cause the bike to turn quicker, in fact it's just the opposite. Reducing rake will increase trail which helps the bike continue in a straight line, making it feel more stable. The change in wheelbase is insignificant.
~Al
Steering geometry URLChen2
Oct 31, 2002 1:34 PM
http://www.phred.org/~josh/bike/trail.html
If that's true, then explain this to meDave Hickey
Oct 31, 2002 1:43 PM
I changed forks on one of my bikes. The old fork had a 45 rake. The fork I changed to is 43. If went from having no toe overlap to having about and inch of overlap. The only think that changed was the fork rake(it's even the same model of fork). If you look at manfactures websites, a lot of road bikes have the smaller frames with 45 rake and the larger frames with 40. According to most, it's because of overlap. The only reason I'm doubting you is because I'm basing my information on real world experiences.
Chen2, I just look at my bike.... I was wrongDave Hickey
Oct 31, 2002 1:59 PM
I had it backwards, I went from a 43 to a 45. Sorry
43mm rake to 45mm --> 1" toe overlap?????opencl
Oct 31, 2002 6:51 PM
How did this happen? ????
This is true...jose_Tex_mex
Oct 31, 2002 2:55 PM
It's steerability vs stability, they play off of each other. However, it is highly unlikely that going from a 43 - 45mm or 45 - 43mm rake will cause any noticeable steering or stability issues.

Also, ever notice that most bikes made for kids have a straight fork? This is to help them in the stability area. Since their speeds are usually low there's not much of a steerability issue

Same sort of idea with Rock Shox and mtb bikes - no rake in order to help stability.
This is true...Lactate Junkie
Nov 1, 2002 9:25 AM
Just because a fork is straight, doesn't mean it doesn't have rake. RockShox and all other suspension forks have rake, it just is put in by angling the blades at the crown. There are NO bicycle forks that do not have rake.
This is true...jose_Tex_mex
Nov 1, 2002 3:23 PM
True, they do not have to be curved to have rake. I'll have to check my Rock Shox as I have never really looked that close.

However, I do have a fork that is straight. It comes right out of the head tube and there is no offset at all. It's not that old and was on a bike with a head tube of slope less then today's bike.
Here's another siteB2
Oct 31, 2002 2:43 PM
that lets you plug in part of the data and it calculates the rest. Kind of intersting to plug in various different values and see how things are affected.

http://www.kreuzotter.de/english/elenk.htm

Bryan
Great Link, Thanks!! (nm)Chen2
Nov 1, 2002 1:38 PM