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Which fork rake for me - 40mm or 43???(8 posts)

Which fork rake for me - 40mm or 43???Kent
Feb 14, 2002 1:04 PM
I have a 58cm frame with a 74 degree head tube. I'll be building this bike for racing. Any reason I shouldn't get the 40?
La contesta es muy complicada. Qual tienes ahorita? 43?morrison
Feb 14, 2002 2:09 PM
Use lo mismo!
re:40mm or 43Chen2
Feb 14, 2002 2:55 PM
I'm not the expert on this but I have been studying angles, rakes, and trail. The 40 will give you more trail than the 43, this will help the bike maintain a straight line. Your steep head tube will give you quick steering, the 40 will slow it down compared to a 43. I just put a 43 on my 73 degree head tube, the 40 may have been better for me, but the 43 feels good. The only down-side I can think of is the 40, with more trail, MAY cause your bike to be more susceptible to oscillation (shimmy) on high speed descents, but that also depends on a lot of other possible variables.
-Al
He seems to know his sh!t. I was just practicing Spanish. nmmorrison
Feb 14, 2002 3:14 PM
What is the factory spec?Kerry Irons
Feb 14, 2002 4:58 PM
Certainly the frame was designed with a specific fork offset in mind. What is that number? There is more to fork offset than just frame size and head tube angle. Front center distance should be considered as well. The factory has the answer.
N/A...Kent
Feb 15, 2002 12:47 PM
Frame is a 58 cm GT zr1.0. Company is bankrupt with their website shut down. So I'm floating in the mist with this one.

What would trail be with a 40mm fork? & a 43mm fork?
get the 40...C-40
Feb 14, 2002 6:56 PM
The trail is only 55mm with the 40. That should yield steering that's plenty fast. More rake could lead to a real twitchy ride.

The smaller rake will make the bike more stable on high speed descents, not less, as one person commented.

A typical Colnago of this size would have considerably more trail (around 65mm).
Hold on there.Chen2
Feb 15, 2002 11:20 AM
I'm not saying which fork to buy but I think you missed my point. More trail (less rake, positive caster) will help a bike run a straigter line, but it is also a known fact that excessive positive caster (and trail) can cause or contribute to shimmy (oscillation) in wheeled vehicles. I don't have a bicycle reference to back this up but there are several for motor vehicles. Maybe excessive trail is not a factor with bicycles, but we all know that shimmy can be a problem with high speed descents. It would be an interesting experiment for someone having high speed shimmy to try replacing their fork with one having more rake, but at $350 a pop that could get a little expensive.
-Al