mr jones

Hey. I've got a few questions about adding front Avid BB7 MTB Disc Brakes to my 2006 Specialized Hardrock Sport currently sporting V-brakes. So please, if you can, excuse my ignorance


Included: post mount (74mm) caliper with International-Standard (51mm) fork or frame adapter; Roundagon 6-bolt/44mm-BCD rotor; and pads


So I want to know, can I use my current brake lever (Tektro RS-360)?

I don't have the standard front rim and hub, so I'm wonder if my current setup will sport these Avid disc brakes. Shimano Deore HB-M525 VIAM, SunRims RHYNO LITE. The hubs are obviously support disc brakes, but the rims as well?

One last thing, the rotors come in three sizes (160mm, 185mm, and 203mm). Will I feel much difference in stopping power between the sizes? I do light trail riding (hard packed dirt/rocks, some roots, etc) and mostly city/street riding in dry and wet conditions.

TIA

Old School

You should be good to go. The brake levers for your V-brakes will work fine and the Sunrims are disc-compatible. I did this upgrade on my Trek MTB using these rims and have been very pleased.

Unless you are a heavy rider or do a lot of downhill, the 160mm rotors should work well. The larger size rotors can dissipate more heat, but since you use the same calipers/pads for all rotor sizes, there should not be a lot of difference. Install, adjust and go ride!

mr jones

Great, thanks for your help!

Mondoman

OS - I would naively think that larger-diameter disc rotors would allow greater maximum braking torque, even using the same calipers, since the lever arm length is increased.

blamp28

I just did this disk upgrade on my Trek Fuel and LOVE them! I used the 160mm rotors since I ride primarily cross country. They stop very well and have great modulation but the best thing about them is that they work just as well after a creek crossing where my Single Digit 7s would usually fade for a while until they dried some.

FlatFender

you would be 100% correct.
going from a 160mm to a 203 on my bike made a huge difference in breaking. Much better now.

Old School

I humbly yield to the Honorable Latvian from Seattle. The following is from the U.S. Patent office describing disc brakes...

The braking torque is a function of the reaction, the distance from the axis of the rotating disc at which the reaction acts, and the co-efficient of friction between the face of the friction element and the face of the second brake member. The reaction itself is a function of the pressure applied to the brake and the area of the friction element. Conventionally the reaction is considered as a point force acting at the center of pressure of the friction element and the radial distance of this center of pressure from the axis of the disc is known as the effective radius of the friction element.

While the force and friction would be the same regardless of the rotor diameter (remember you use the same caliper), the radial distance from the axis of the disc has increased which in turn increases braking torque.

mr jones

I went with 160, but I was sent 185. So rather than exchanging them, I kept it and now it's installed. It is HUGE , to me anyways. Now that my V-brakes are off. The area on the fork where the V-brakes were attached..the stubs or whatever. Is there something I can cover that up with...some kind of cap. I called my LBS, but didn't have any. Any ideas of somewhere I can get them online?

JiveTurkey

Some forks' cantilever posts can be removed with a wrench--you can probably tell by looking at them closely.

blamp28

You can usually remove them with a wrench. I plugged the holes in mine with small plastic plugs from the hardware store for a nice clean look.

maddmaxx 

Problem Solvers and others make small threaded caps that screw into the threaded hole after the vbrake studs are removed. There are different hole and thread sizes though so you need to get the right ones. Online try Jensed USA or any of the shops using the QBP distributor.