Formula B4 SL Disc Brake
By Jon Sharp

I have a soapbox that I like to stand on. My soapbox is called "Disc brakes for everyone". The problem is that, even after all the wonderful break-throughs in recent years, some people just don't believe there can be any benefit to discs. One of the most common complaints I hear is, "But disc brakes are so heavy!" Well, time to climb back up on my soap box and dispel the myth. Allow me to introduce you to the Formula B4 SL magnesium. Weighing in at 300 grams (that's the total weight for all parts, bolts, and even the oil), it's a bit lighter than most, if not all, linear-pull rim breaks. Do I have your attention yet?

In case you are unfamiliar with the B4 design, it's a two-piston open design. A design that's tried and true. The rotors are the same on the B4 (all the B4s) as on the 4 Racing we reviewed here. The quality is exceptional. As one might expect from the name, the caliper and lever are Magnesium. Formula claims a 15% increase in power over last-years B4. This power increase is due to an increase in piston diameter. Also new, there are holes in the caliper designed for cooling. The color of the caliper is a strange grey-ish "magnesium" powder-coat. Mounting bolts are aluminum, except the rotor bolts which are steel. As before, there is reach adjust via a small torx bolt in the lever. Unfortunately, this bolt is made of plastic. I might as well point out this shortfall right away, since it is the only thing that I had any problems with. Plastic just doesn't make good bolt material, and with a tiny amount of pressure (admittedly, a little too much), the bolt stripped out.

Installation was simple. Formula has a nice system for connecting the hoses, making it easy to shorten the hoses, if necessary. The brake lever felt solid and stout, not as wimpy as you might expect from such a light-weight brake. Break-in for the pads was actually pretty short--making these brakes quite rideable right out of the box.

There is nothing that matches the wonderful feel of a good hydraulic disc brake. The B4 SLs were no exception. Modulation was excellent. In fact, I found that the modulation was better with the B4 SLs than with the 4 Racing we reviewed before. I also found that they had good power, especially for XC use. I wouldn't go so far as to recommend them to free-riders; but, for general, or even heavy, cross country riding, they exceeded my expectations. Compared to other brakes on the market, the power may not be very impressive in and of itself, but what is impressive, is how much power they exhibited considering their light-weight. That said, I never felt the power was lacking, even when new.

Summary: The Formula B4 SL is a great cross-country disc brake. The weight is exceptional and the quality good. The problem I had with the plastic bolt is minor considering how little this bolt is used once dialed in initially. With the wonderful support now available from Formula (especially through Thorsten at www.thorusa.com), one would have no problems getting replacements for this bolt or any others. That being said, if you're hard on parts (or light in the wallet), you might consider the B4 Pro or the standard B4, both of which are quite light compared to other disc brakes on the market, but are cheaper and, perhaps, a little more durable. It's safe to say that with the addition of the B4 SL, Formula now has a disc brake for every occasion. If you haven't thought of Formula when looking for brakes, it's time to take a look.

Jon Sharp is a Contributing Editor to GearReview.com specializing in mountain biking.

For more information, contact:
ThorUSA
www.thorusa.com
- or -
KHS Bicycle Parts
1-800-507-6444
www.khsbicycleparts.com