Framebuilders - Looking for 650c rakeless forks
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I'm looking for a source of 650c rakeless road forks. Anyone have any tips?
04-11-07, 11:38 PM
What do you mean by rakeless? A crown for curved blades where the rake is bent into the blades themselves or a crown with an offset angle so you can use straight fork blades (fork still has rake)?
Its a crown for curved blade but using straight blades. There is no offset to this fork. Steerer tube, blades and dropouts all run in a straight line.
This is to replace a fork from a Zipp 2001 aero frame. It originally had a staight bladed, no offset fork which provided lots of trail and good stability. I need a replacement.
04-15-07, 06:59 PM
It may have looked that way, but it is not the case. It did have some rake. The fork tips are offset from the crown, usually through angled blades.
Almost any fork company can provide a decent fork for you. I would call Zipp and ask what the fork height spec and rake was on this model so that you can find a similar fork for it.
P.S. Wound up composites will make any fork you need in most any height and rake. Alpha Q also has a very large selection.
Actually there was no rake. I was the technical rep for Zipp from '93 to '96. Kinesis made the fork to our specs and that was no rake, in the blade or through the fork tips. We wanted a straight line from the steerer tube all the way down to the front axle. The desire was to create a larger amound of trail allowing more stability while on aerobars.
We worked with Wound Up and they are probably one of the most talented carbon folks out there. Unfortunately the smallest amount of rake was 39mm and I believe that is the same today. Pretty expensive too. I checked out Alpha Q and have run into the same problem. Kinesis created the fork for us, but of course the production stopped when the bikes stopped being produced. I was hoping some frame builder could enlighten me to a source since I've been out of the business for some time.
There is a perception that less rake means more instability when in fact it is more stable. We used to test this by turning around a standard 43mm rake fork. If you had downtube clearance the bike would steer straight forever!
I did call Zipp and they were checking in the "back room" to see if anything was hanging around in the dust. No luck so far.
Sorry to correct you Dave but believe it or not there was one out there at one time. I was hoping that Zipp wasn't the only one using it.
04-16-07, 08:07 AM
Well, I stand corrected.
Throughout history their have been ultra high trail designs. Mostly used for motor pacing on board tracks where the fork rake was reversed as you guys did for your testing.
Also, acrobatic bicycles tend to have similar designs.
If you are really set on having such a thing you could have a custom builder make a steel fork with no rake in the blades and accomplish what you want.
Personally, too much of a good thing can be less than ideal and I did this as a lark once on a personal bike and although I learned to ride it quick enough I saw no real advantage to it.
P.S. If you ask Wound up to reverse the fork tips during the build you can get the fork down to 29mm. I have had this done for me once.
Hey, good idea with Woundup and I love the Derney Race poster. The late John Stenner was a sponsored rider of ours and National Time Trial Champion on one of our bikes in '92. He utilized the reversed fork and got the idea from Derney racing. We put it in production a year later, but opted for the straight fork instead of a reversed one.
04-17-07, 09:31 AM
It is my understanding that the reverse fork on a pacer bike was to get the rider closer to the motorcycle in front. The frames had very steep head angles so the trail was not exceptionally long. A smaller front wheel was used for the same reason and to also clear the down tube.
I experimented in the 1970s with almost straight forks and a 73 head angle. I found the bike would wander and feel very sluggish when climbing or sprinting out of the saddle. I believe in any design element it is best not to go to extremes. If more is better, it doesn’t necessarily mean that even more will continue to be an improvement.
04-17-07, 07:10 PM
Dave is right of course.
The trail on a straight fork would in fact be higher than that of the typical pacer bike with small wheel and reverse rake.
I am with Dave on the design element. More is not neccesarily better.
I found a straight no rake fork and it made a huge handling difference from the 37mm stock fork. Granted, that anything in negitive rake would be counter productive in stability just as too much rake would serve to have the same effect. For me the 0 rake seems to be just right. I wouldn't shy away from experimenting with rake although I think Dave is right that more is not better, just diminishing returns. There is a zone of practicality that might serve someone's needs and the 0 did it for me.
05-15-07, 03:11 PM
Freds2, where did you get your rakeless fork?
I had a custom 24" road fork built with 15mm of rake, and there is still too much wheel flop.
Actually I got it from someone who had a spare from a Zipp 2001 bike which is no longer made. I got lucky. This fork went on a recumbent which was very twitchy. There is some potential for flop at sever turning. The fork was originally intended for a 74 degree headtube and matches fairly well w/o flop. That suprises me about a 15mm w/ 24" front wheel. What's the headtube angle?
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