Framebuilders - Anyone have experience with re-raking a fork?
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08-02-12, 04:35 PM
I'm riding a 1995 Trek Multitrack and I really like it except that with the stock fork it has a ridiculous amount of trail (74+ mm). I previously owned a bike with a trail rating in the mid-60mm range and preferred the handling much more. I recently bought a Dimension fork with 10mm more rake than my stock fork and installed it and I'm much happier with the handling (trail 63mm). The only issue is that the fork is very thin and I'm not real comfortable with it's strength, given that I weigh over 350 lbs. Plus, it looks funny.
I've been looking for more suitable forks and aside from going custom, there isn't that much out there. Plus, for the price of a custom fork I'd probably be better off just buying a new frameset. I'm researching the option of simply re-raking the original fork but I don't know if it's possible. The diameter of the fork just below the canti boss is around 31mm (vs 25mm for the Dimension fork), so it's pretty beefy. I've read that heavy tubing isn't a good candidate for re-raking but I don't know what constitutes "heavy". I would like to add 10mm of rake to get it to 50mm, which is equal to my Dimension fork.
Is this even feasible with a thick fork like this? Is it cost-effective vs buying a new frame? The fork is 1" threaded and cro-moly.
08-02-12, 07:11 PM
It's easier to put more rake in fork blades than it is to reduce the rake. Adding 10mm shouldn't be a problem for an experienced framebuilder with a fork blade bender and the correct ramp for your fork, but there may be some reluctance to do it to an existing fork because of liability issues.
08-08-12, 05:09 AM
My history with forkbending as as follows. When I first returned to cycling I felt the handling of my Trek 610 was too sensitive (52 mm offset, medium trail) and twitchy with tubulars compared to my vintage Masi. I found a builder who would reduce the rake of the 610's fork by about 10 mm, achieving about 58 mm trail. The calculation comprehends the fact that the head angle was changed. He did so and aligned the frame leading to a much better-balanced bike, but it still did not match the handling of the Masi. When my interests turned to longer-distance riding with a front load, I wanted to change the Trek into a front-loader with 700x32c, which would have needed reducing the trail to the low 40s. I wanted to re-rake the same fork to get about 60 mm offset. I could not find a builder who was willing to take this on. Reasons given by builders here were based on concern with cold-setting the same fork blades too many times: once when originally shaped, once when deraked, and once when re-raked. Fork tube material is CrMo. I finally found a builder who would build me a new fork out of lower-cost Dedaiaccia 4130 tubing with a wide crown. The price was right, so I went for it, getting 65 mm offset and about 35 mm trail with 700c x 28 tires. It turns out that frame could not have handled 32s with the clearances I'd like to see.
You have two issues: adequate offset and adequate fork strength. It might be best to find a builder to make you a new steel fork with a carefully chosen tubeset, that solves both problems at one stroke.
08-08-12, 06:49 AM
I can understand builders being reluctant to change a production fork's characteristics. I e-mailed a local frame builder and they recommended against that much change in a fork but said they would get me an estimate on a custom fork. I'm still waiting for the estimate but if it's anywhere near the fork prices I've seen for online builders, I would be better off just buying a whole new frameset.
My other option is that in 1996, 1997, 1998 and 1999, Trek made some 7xx model bikes with 50mm offset forks. The tech manuals are available online for these years and the headtube length stayed the same as my bike so I'm also looking for one of those specific years and models to salvage a fork (if a lower model) or to switch bikes (if an equal or higher model). It took me three months to find the bike I have now so I'm not too hopeful I'll find exactly what I'm looking for.
08-08-12, 02:24 PM
You might try asking in the C&V forum. Those years don't qualify as C&V by many peoples standards but there are folks there that have collected an ungodly number of bikes. I bet somebody there has the fork you're looking for.
08-13-12, 09:09 AM
One thing to keep in mind when changing the rake of an existing fork is that it will change the 'span' (length) of the fork.........add rake and the fork will get shorter, take some away and it will get longer. It's hard to predict exactly how much the span will change if you were to change the rake by 10 mm but I'd estimate about 3-4 mm.
I think the only good way to get to where you want to be is to have a fork made. You'll get the best results with the most safety.
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