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Dear MBT:
I ride mostly downhill with occasional free ride thrown in the mix. I noticed that on longer downhill runs my brakes (the front especially) tend to fade. I was told I should switch to a larger rotor. I’m currently running 7 inch rotors on the front and back. What do you suggest?
Dillon Shwentek
Dillon:
Switching to larger rotors will likely solve your problem. The main cause of brake fade is overheating the pads and rotor which in turn boils the brake fluid. These factors combined result in not only a decrease in braking performance but also a spongy feel at the lever. Since you said the fade is most prominent during long downhill runs, it suggests that you must be favoring the front brake to scrub off speed which in turn creates friction.
A larger rotor solves the problem two ways- First it offers more surface area to dissipate heat brought on by contact with the pads. Second a slightly longer rotation path means more time for the metal to cool before returning to the caliper. A brake system’s entire performance spectrum is dependant upon the rotor’s ability to adequately shed heat build-up.
Dear MBT:
I owe you guys a big thanks. Whether you realize it or not, you’ve saved me a nice chunk of change. Went to my LBS with my check book to pick up a Gary Fisher HiFi but wound up looming around a 2006 Jamis Dakar 2.0 on clearance. Came home and Googled the bike in search of reviews and came upon yours (Jamis Dakar.) Long story short, the Dakar is now my new toy and I’ve been riding her daily. Your critique was spot-on and best of all I had enough left over to get a Trek hardtail for my wife to tag along on during the weekend rides.
Norm Wittenburg
Norm:
Glad to hear you’re getting along with your new Dakar. We ended up receiving our 2006 test unit while the 2007s were being released on account of a similar bike shop year-end inventory reduction. The value to testing bikes that may not be on the bleeding edge is that (as you discovered) there are still great deals to be had on last year’s gems.
Dear MBT:
A few years back I had a Foes 2:1 which came equipped with a Curnutt low-leverage coil-over shock. I’ve since picked up a jig and some welding equipment and have been experimenting with my own frame designs. Do you know what mass-produced shock brand and model would come closest to duplicating the Curnutt’s design and function?
C. Guaco
According to our contacts, Brent Foes is now manufacturing a mass-produced Curnutt derived air-shock (the XTD-Air) which operates on a 2:1 leverage ratio. Drop Foes a line (http://www.foesracing.com/) and they should be able to get you on your way.
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