Disc brake break-in?

Question

Just got a bike with discs (BB7). The feel of the braking is so-so on the first ride (5km commute from LBS to home). I think the cable for the rear needs a little tightening.

But even so, I don't feel the big change I had been advertised when moving from cantis. I know I will get more reliability on the wet and mud but still...

So I was wondering, is there anything such as a break-in period for brakes? Is there something specific I should/should not do? Is there something specific I should/should not verify to find whether my set-up is right or not?

Answer 1

Disc brakes, both mechanical and hydraulic, require the pads to be bedded in before they reach optimal performance. There are many different views to the best way to do this but manufactuer instructions generally revolve around several start/stops increasing the pressure on each stop to build up heat and speed up the process.

I personally don't do anything special and just use the brakes just bearing in mind that they are bedding in (ie. no hard braking into a tight corner) until I have the feel of them and are willing to trust them.

Here is the Avid bed-in procedure:

warning: the bed-in process requires you to perform heavy braking. you must be familiar with the power and operation of disc brakes. braking heavily when not familiar with the power and operation of disc brakes could cause you to lose control of your bicycle which could lead to a crash which could lead to serious injury and/or death. if you are unfamiliar with the power and operation of disc brakes you should have the bed-in process performed by a qualified bicycle mechanic. then you should [practice your riding and braking techniques on a flat and level surface prior to aggressive riding]. to safely achieve optimal results, remain seated on the bike during the entire bed-in procedure.

1. Accelerate the bike to a moderate speed
   (approximately 19 kilometers or 12 miles per hour), then firmly apply the brakes until you are at walking speed. Repeat approximately twenty times.

2. Accelerate the bike to a faster speed
   (approximately 32 kilometers or 20 miles per hour). Then very firmly and suddenly apply the brakes until you are at walking speed. Repeat approximately ten times.

important: do not lock the wheels up at any point during the bed-in procedure.

1. Allow the brakes to cool prior to any additional riding.

this concludes the disc brake pad and rotor bedding in procedure. you did a great job! you are now ready to ride. enjoy!

Other set up to check on mechanical disc brakes is:

• Check the caliper centered, loosen up the mounting bolts and spin the wheel. Pull the brakes tightly and while holding the brake on redo up the mounting bolts.

• Check the gap between pad and rotor, with a mechanical disc brake this is a manual exercise and different to hydraulics. Each brake will have a different method here is a link for BB7s. This process also checks the cable slack.

Answer 2

"...feel the big change I had ....." This may be your problem. Well adjusted high end canti's with good rubber, in the dry, are more than capable of out performing many discs. BB7's are very good cable brakes, and will out perform cantis in most conditions, but in ideal conditions the cantis might even be better in shear stopping power.

Are you sure your expectations are not too high?

Discs excel in less than ideal conditions - rain, mud grim etc, and have lower maintenance requirements. They also give better feel and control than canties so feathering and such like become easier.

So if you have followed @DWGKNZ answer, ask someone (your LBS) with expriance in disc brakes what they think - just make sure its not someone used to high end discs on 250mm rotors.....

If you need more stopping after all the above, you may be able to change to pads to improve performance.