Re-raking forks for low trail
On Sunday a group from Point83 got together at a local bikeshop and re-raked some forks. Val Kleitz (used to own Bikesmith and bike mechanic extraordinaire) was there for a couple of hours to lend some advice.
The goal of re-raking the forks was to add additional offset to decrease the bicycle’s trail. This improves the bike’s handling when riding with a front load, even a small one like a handlebar bag.
I brought 4 forks to re-rake:
1,,,,) A Jamis fork that was supposed to be disposed of anyway. It was built about 1.5cm too short and replaced under warranty. I did this fork first because I didn’t care what happened to it.
2) A 1986 Trek 400 fork. I’ve been trying to sell this at the Seattle Bike Swap for $5 or $10 for the last 3 years with no interest. I don’t own the frame that it was on any longer. It will have cantilever bosses installed for 650B and available as a low-trail demo fork to friends. It is already too short for 28mm wide 700C tires with fenders.
3) A 1983 Trek 630 fork. This fork has 25,000 miles on it and needs to be repainted. I reraked it the least, changing the offset from 10mm to 20mm.
4) A 1994 Bridgestone RB-T fork. This is from my RB-T, one of the ugliest in existance due to being touched up at random spots with purple nail polish by a previous owner.
Point83 and BOB list member Andre also brought a early Trek mountain bike that he was using as a load hauler with a large Wald basket. He wanted to re-rake this bike’s fork to have a trail of around 40mm for carrying heavy loads.
We primarily used two tools to re-rake the forks. A Hammill fork blade bender was used to increase the offset in each fork’s blade. This bender has a radius of 10″. Using the fork leg bender does take the fork out of alignment, so we used a VAR fork alignment jig to realign the fork after getting to our target offset.
Val showed us a great trick for checking fork offset. Draw a line on a sheet of paper and place the fork on the paper with the dropouts aligned along that line. Use an angle finder (or bubble level) to hold the fork’s steerer tube at 90 degrees. Now look down the steerer tube of the fork and down a line on the paper along the center of the steerer. This is easier and more accurate if one person holds the fork while the other looks through the steerer. If you measure that to the reference line for the dropouts you’ll get the fork offset. I checked this with two forks that I knew (the published) offsets for and the results were accurate. Andre drew this great drawing that shows how it works:
The bending worked for forks with no canti bosses or canti bosses set for 700C wheels. When we tried to bend Andre’s 26″ MTB fork we found that the canti bosses were placed too low and ran into the mandrel of the bender. This fork was re-raked using a Park leverage tool.
Even bending with a normal radius the fork height didn’t change too much. It was pretty easy for me to measure the Jamis fork (I had a reference wheel/tire which just barely fit before) and the dropout to fork crown changed by about 3-4mm when we increased the fork offset by 20mm (going from 45mm to 65mm).
This photo shows a stock (in grey) 1983 Trek 600-series sport touring fork and a re-raked one (in gold) which has had 10mm of offset added to it.
With these two photos you can see that the tire clearance did not decrease too much when adding rake to the fork. The tire is a 700×35 Panaracer Pasela, larger than what I’d use with these bikes. Tom Matchak’s article on re-raking gives you the math for figuring out how much the fork length will be reduced through re-raking. Note that his measurement is along the steerer and overestimates the amount of clearance lost in most cases.
I have a Heron Wayfarer that I built up in August and September. I had not previously owned a bicycle that had toe clip overlap problems so I was unaware of the issue. However, the Wayfarer has severe toeclip overlap with the 700 x 35 tires and 50 mm Berthoud fenders. I primarily use a Berthoud front bag, so I am wondering what the best option is to improve the handling with the front bag and eliminate the toe clip overlap problem: (i) rerake the fork, (ii) have a new custom fork built, or (iii) purchase a new frame and fork that does not have the toeclip overlap problem. Any advice will be most helpful.
You might be able to do II without spending a lot of money ono a custom fork.
Kogswell is having some forks built for retrofitting into older frames to lower the trail of the frame. http://www.kogswell.com (you have to be persistent when emailing Matthew sometimes). These are threadless, with a $40 option to thread them.
Jeff Lyon has some Taiwanese built forks that are unpainted. He will rake them to your desired offset and mount canti studs and sell the whole thing fairly cheaply. I did this on my RB-T (elsewhere in my blog) and John Speare also did this to two bikes last week. I don”t know if Jeff has more of these forks, but it is worth talking to him. They are threadless so you would also need to change your headset and stem.
700×50 fenders have toeclip even with lots of fork offset. My IvyCycles frame has 62mm of fork offset (17mm more than your Heron) and has toe clip overlap using the same tires and fenders that you are using. 650B is a better size for really chunky tires if you don”t like TCO.
It’’s a great subject, I think an adjustable rake fork is the way to go on new bikes, like a look ergostem on the road. Then a real fork gets built, like a normal stem is then fitted.
here’’s mine http://revanchebikeco.wordpress.com/2013/11/29/trail-rake-what-does-it-really-mean/