Formula B4 SL Disc Brake System

4.44/5 (9 Reviews)
MSRP : $199.00

Product Description

B4 SL. The lightest disc brake available ! MAGNESIUM Lever and caliper, alloy mounting bolts ( rotor bolts are steel) New Caliper with 15 % more power and intercooler holes. Color is powdered raw Magnesium. 300 grams including the rotor and all bolts. Two opposed-piston caliper with self-adjusting pads Re-attachable hydraulic tube fittings, easy to shorten 140,160 monolithic stainless steel disc (6 holes) Equipped with I.S. fittings. Yes we do have a designated Front Post Mount caliper available Oversize discs adapter available as upgrades to run larger discs. 140 mm rear and 160 mm front are standard rotor sizes Please specify Front IS / Postmount or rear brake

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Reviews 1 - 9 (9 Reviews Total)

User Reviews

Overall Rating:4
Value Rating:4
Submitted by Gilian Lee a Cross Country Rider from Canberra, ACT, Australia

Date Reviewed: October 3, 2004

Strengths:    Very lightweight.
Easy to setup.
Excellent support from N.American distributor!

Weaknesses:    Not as powerful as Hayes. Note: using Stan's rotors and organic pads.

Bottom Line:   
Very good brake using Stan's aluminium rotors and pads (never used OEM original rotors and pads). Great for lightweight people (such as myself). I have rebled it using the new 2 syringe bleed kit and this has made it better. Feels the same as my XTR disc brakes when bled properly (lot of modulation).

There is a lot of lever movement before contact with the rotor (unlike Hayes with small lever movement with 'on-off' power).

I don't suffer from 'disc rub' unlike that experienced with the Hayes and XTR disc. XTR disc would persistently rub and drive me crazy (Hayes wasn't that much better).

Brake is perfect for a lightweight rider for XC.

Expand full review >>

Duration Product Used:   3 months

Similar Products Used:   Hayes, Shimano XTR disc.

Bike Setup:   Check it out at

Overall Rating:4
Value Rating:5
Submitted by Luis a Weekend Warrior from Lisboa, Portugal

Date Reviewed: April 15, 2004

Bottom Line:   
Got replacement brakeset for old b4SL.
Seems Formula is taking 2003 B4SL and giving (by warranty) the 2004 B4SL+, that has aluminium parts that correct the recurring bleeding issue.
Wow...what a relief! I always thought that were the LBS shop mechanics that didnt know how to bleed them, but seems it was some design failure that caused the constant "have to bleed brakes" problems.

5 chilis for value since they got me 2 new brakes systems(excluding rotors and bolts that didnt need replacement) one year after purchase date.
4 chilis for overall because these new ones work very well.

Expand full review >>

Favorite Trail:   Arrabida

Duration Product Used:   1 Year

Purchased At:   El Corte Ingles, Lisboa

Overall Rating:5
Value Rating:5
Submitted by Michael a Cross Country Rider from PA

Date Reviewed: December 3, 2003

Strengths:    modulation, lightness

Weaknesses:    ealier versions tended to have some weak parts, brakes levers in particular

Bottom Line:   
This is realy a 2004 product review of the Formula B4SL Plus brake. As mentioned I had the first generation B4SL brakes and had problems. I was however convinced that the Formula B4SL was a great brake from my experience with them prior to developing problems and didn't want to switch brakes. The 2004 became available to me and I jumped on them. Good thing I did. They are fantastic! Any negative I had about the 2003 have been resolved. The plastic flimsy parts are all gone. The modulation couldn't get any better. The stopping power is super. However I must mention that I upgraded to the next larger disks both rear and front. I highly recommend these brakes if you want great modulation and superb braking power. I my opinion with the larger disks they are now not just a XC specific brake, they can be used anywhere except possibly as a downhill or shalem specific brake. Thorsten form ThorUSA is great to work with.

Expand full review >>

Favorite Trail:   all technical single track

Duration Product Used:   Less than 1 month

Purchased At:

Similar Products Used:   shimano xtr, hope mini

Bike Setup:   yeti asr, scarab elite fork, chris king head set, thompson seat and stem, xtr deraliuers, xt shifters, lx crank set, american classic hubs, velocity vxc rims

Overall Rating:5
Value Rating:4
Submitted by Chris a Cross Country Rider from Stuttgart

Date Reviewed: October 16, 2003

Strengths:    Very light disc brakes (lightest on planet?), easy to install and set up, good breaking power

Weaknesses:    needs some time to break in, poor plastic screws for setting up brake lever distance to handlebar, price

Bottom Line:   
At the beginning, breaking power was not very good and they squeaked! But after using this disc brakes for some time, applying some copper paste on the backside of the brake pads and milling the mounting surface on fork and frame correctly, I started liking these!!!

They are intended to be used for XC-Racing, and therefore I would not recommend them for downhill. Despite of that, I used them at Garda Lake in Italy where you can have very long downhills (I weigh around 150 lbs): up to 2000 m of altitude downhill! In that case, the brakes begin to squeak but they don't show fading!

Only thing I don't like: these poor plastic screws for setting up brake levers.

Other than that: very good disc brakes!

Expand full review >>

Favorite Trail:   Tremalzo Trails (Lake Garda, Italy)

Duration Product Used:   1 Year

Price Paid:    $400.00

Similar Products Used:   Magura Louise

Bike Setup:   Rocky Mountain Element Race with Fox Forx F80RLT, wild mix of different components :-)

Overall Rating:5
Value Rating:5
Submitted by Mike T. a Cross Country Rider from Ontario Canada

Date Reviewed: September 26, 2003

Strengths:    No maintenance or repairs of any kind needed.
The support from the N.Am importer - - if needed. Lightness, quietness, power.

Weaknesses:    I don't like the plastic Torx bleed plug at the lever end but this is being changed for 2004.

Bottom Line:   
I've been using this brake for a full year and I think this entitles me to re-evaluate it.

There are still no problems with my brakes. Other than the bleeding with the new 2-syringe kit and method (copy & paste below from original review) I have done nothing to these brakes.

From my original review -

"In the early days of this SL I wasn't totally impressed with the power of the brakes and solidity of the levers - especially the rear brake. I felt an amount of mushiness there that I put down to their light weight. I assumed that this was the downside to lightness, after all I was 185lbs and not a 140lb racer. Then the N.Am distributor Thorsten sent me a new style bleed kit which contained two syringes and a brass adaptor that allowed the 2nd syringe to screw into the hole near the reservoir where that plastic plug resides. There is a new bleeding method too where the fluid is passed back & forth through the system between the two syringes to get out ALL the air bubbles."

This is still a perfect brake for my XC riding. It is light, quiet, powerful enough, smooth, has perfect modulation and is supported by a factory who listens and a distributor who cares.

Expand full review >>

Duration Product Used:   1 Year

Purchased At:

Similar Products Used:   Formula B4 & 4R. All Magura XC disc brakes.

Bike Setup:   Seven Sola, Pace RC31 fork, Moots Ti post & stem, Boone Ti rings, SRAM shifting.

Overall Rating:2
Value Rating:1
Submitted by Luis a Weekend Warrior from Lisbon, Portugal

Date Reviewed: September 3, 2003

Strengths:    Light, nice touch and parts are available with ease. Strong brakes if well tuned.

Weaknesses:    Well, light means fragile... If you're a racer with sponsorship and personal mechanic go for it. If not get a Hayes or Hope.
Here's the last six months experience:
-Broken disk. (yes you've read it well) Got a new one from warranty
-Broken the handlerbar conectors when mounting because I used a little (LITTLE) strength.
-Disks keep getting oil
-Some noises because of disk getting out of true

Not for use in non-race conditions.

Bottom Line:   
How much you like your money?
Get Hayes or Hope Mini.

Expand full review >>

Favorite Trail:   Arrabida, Azeitão

Duration Product Used:   6 months

Price Paid:    $230.00

Similar Products Used:   Hope Mini, Magura Julie & Marta, Shimano Deore and Hayes

Bike Setup:   Specialized Hardrock A1 COMP 2003, LX transmission, Crank Brothers Eggbeater pedals, RS Judy TT, Mavic X139 wt Hutchinson Python 2.0, Thomson Elite seatpost and stem, Easton EA30 bar wt Crank Brothers grips and Selle Italia SLR Gel Flow

Overall Rating:5
Value Rating:5
Submitted by Ken a Cross Country Rider from Renton WA

Date Reviewed: May 25, 2003

Strengths:    Light, great modulation, look well built, dot4 fluid is available anywhere, and is cheep, Feel really strong for how light they are, but not recomended for Downhill

Weaknesses:    Dot4 can strip paint, had to adjust the positioning a couple of times to avoid light rubbing. I may not have had the disc adapter properly torqued? If you have to blead the caliper, the little plastic screw can be easily stripped, be sure you have full engagement before turning, and use a quality driver, a lot of the torks bits are crap

Bottom Line:   
This being my first experiances with disc brakes, You can take it for what it's worth, but I can definetly see why everyone likes them. The modulation is better than even my supremes. I seem to be able to brake closer to the edge without locking up. They squeek when wet, but they still stop, which is more than can be said for rim brakes. With the B4sl's there is really no weight penalty to the brakes, the wheels may be a little bit more, but there are some pretty light disc wheels out now. My neighbor's Hays drag all the time, and squeek even dry, but they are older, If mine change I will post an update. If I had to pay retail, I would have probably thought about it more, but for $220 for a full 2003 set, what can I say?

Expand full review >>

Duration Product Used:   3 months

Price Paid:    $220.00

Purchased At:   MB review classifieds

Similar Products Used:   just v brakes, I replaced a set of avid arch supremes which are the best rim brakes around.

Bike Setup:   Titus Motolight, 8spd grip shift, fox float 100 RLC fork, King disco hub.

Overall Rating:5
Value Rating:5
Submitted by Michael Bennett a Racer from Ottawa, Ontario, Canada

Date Reviewed: May 1, 2003

Strengths:    - Light (631g/pair);
- Powerful; and
- Incredible modulation.

Weaknesses:    None so far.

Bottom Line:   
First, some real weights as weighed by me on a digital scale with all parts, fully bled, full length lines, etc.:

Formula B4 SL:
Front lever/caliper = 195g
Rear lever/caliper = 215g
Front 160mm rotor with bolts = 123g
Rear 140mm rotor with bolts = 98g
Total = 631g

As a comparison, my previous set of Hope Minis (with 165/165mm rotors) weighed 852g with everything and my B4s weighed 713g (with 160/140mm rotors).

Weights aside (but you probably are reading the B4 SL review because of it's weight), I used my Minis for nearly a year and was impressed with them. They are beautifully machined (as all Hopes are) and provide sufficient stopping power and excellent modulation. However, my new B4 SLs are blowing the Minis off the trail!

First, the B4 SLs are damn light and as a Expert XC racer, weight is important...but not at the expense of braking! Second, the B4 SLs are more powerful than the Minis or B4s and have a modulation that I cannot's incredible! I can regulate the power while descending tight-n-technical singletrack with 1 finger. All the while, the brake is responding to slight finger pressure changes. Truly confidence inspiring.

Keep in mind, the B4 SL is the lightest disc brake on the market -- excluding brakes with Stan kits, etc. These are XC brakes only. I weigh 135lbs and race Expert XC on same very technical courses and the B4 SLs are the perfect brake.

If you are looking for Formulas, email Thorsten @ ThorUSA. He'll set you up with brakes and will provide you with some of the best after-sales customer service in the biz.

Ride Hard,
Mike B.

Expand full review >>

Favorite Trail:   Fat B*tch's Garter Belt

Duration Product Used:   6 months

Purchased At:

Similar Products Used:   Hope C2 Pro, Hope Mini, Formula B4, Hayes, Shimano, Grimeca, etc.

Bike Setup:   Seven Ti disc-only singlespeed w/ EBB, Morati Ti rigid fork, FSA Carbon Pro cranks and Platinum Pro Ti ISIS BB, Titec PhatHead Ti stem, 959 pedals, King SS rear disc hub, Hope Bulb front hub, Moots post, SLR saddle, etc.

Overall Rating:5
Value Rating:5
Submitted by Mike T. a Cross Country Rider from Ontario Canada

Date Reviewed: January 12, 2003

Strengths:    Light weight. Attention to fine details. Customer support. Modulation.

Weaknesses:    DOT brake fluid (if that's a negative). I can't think of any others. I have zero issues with them.

Bottom Line:   
I've had a set of B4SL on my bike ever since they hit N.America in early September 2002. They are the lightest disc brake set on the market and they weight 630g for a complete set (on my scale) right out of the box. The installation was easy and quick with no problems encountered.

Of course like all new disc brakes they need bedding-in before full power is achieved but this was quick and most of it was done while going up and down my driveway while waiting for a riding buddy to arrive.

To become the lightest disc brake set on the market you have to pay careful attention to all details. The castings of the master and slave cylinders are in magnesium, all the bolts are of Ergal - a top quality aluminum - and the rotors are 160mm for the front and 140mm for the rear. This smaller rear rotor saves 27g or 0.95oz over the 160.
But the B4SL lever body casting is beefed up from last year to make it more durable in crashes and this makes the light weight of the brake even more impressive. The slave cylinders have Intercooler holes which is a fancy name for holes in the castings which allow heat out and save weight.

For their size and weight the power generated by this brake is quite adequate for XC racing and riding. Just don't fool yourself that this is a FR or DH brake for large boys. It's the ultimate lightweight XC brake and that's accomplished by lack of mass both in the slaves and the rotors - mass that in larger brakes helps absorb, transfer and dissipate large amounts of heat. That dinky 140mm rear rotor is going to have its limits. But for my 185lbs and normal XC terrain it has proved itself quite adequate.

If you do need more power they have upsized rotors for you - 185 on the front and 160 or 185 on the rear. All need their adaptors.

I've used Formula B4 brakes before (is that a pun?) and my old 2001 B4 and this 2003 SL must be the kings of modulation - they are so smooth and predictable in their delivery of power that wheel lockup is not an issue unless you decide the wheel is going to lock up.

In the early days of this SL I wasn't totally impressed with the power of the brakes and solidity of the levers - especially the rear brake. I felt an amount of mushiness there that I put down to their light weight. I assumed that this was the downside to lightness, after all I was 185lbs and not a 140lb racer. Then the N.Am distributor Thorsten sent me a new style bleed kit which contained two syringes and a brass adaptor that allowed the 2nd syringe to screw into the hole near the reservoir where that plastic plug resides. There is a new bleeding method too where the fluid is passed back & forth through the system between the two syringes to get out ALL the air bubbles.

After this bleeding those brakes were not the same brakes I'd used minutes before. They were SO solid. This solidity resulted in much more power on the trail - especially from that rear brake.

I'm into the fifth month of use now and have found no negatives. There has been ZERO maintenance since that bleeding session. Other than some squealing when the brake is wet or sometimes when it's cold (not every time) I wouldn't know the brake is there. I haul on the levers and the bike stops. What more is there?

Formula have put a pile of effort into this brake (and all their brakes) and it shows in many small details. All their hose connections and plugs are sealed with tiny o-rings which makes for total leak-free operation. Just be careful with them when servicing the brakes! Plus Formula believe in providing all the small parts (pistons, seals etc) so you can service and re-build the brakes - try that with some other brakes. One of their better improvements is the new bleed screws - now integral with the hose mounts and MUCH better than the old ones.

The levers and lever-blades fit the hands nicely and the blades are adjustable for reach for my tiny hands. Split clamps allow easy removal from the 'bars.

If you want light weight combined with quality, factory and importer support then this is an excellent choice.

A fine job Formula!!

Expand full review >>

Duration Product Used:   6 months

Purchased At:

Similar Products Used:   Magura Marta, Louise, Clara, Julie. Formula B4, 4R, DH.

Bike Setup:   Seven Ti Sola. Pace RC31 rigid carbon fork. Gigantex carbon cranks. SRAM shifting. Moots Ti post & stem.

Reviews 1 - 9 (9 Reviews Total)

Review Options:  Sorted by Latest Review | Sort by Best Rating

Formula B4 SL - any good?

In my low budget efforts to weight weenie my new Flux (and, yes, [I]overanalyze [/I]each new part) I have come across a great deal on Formula B4 SL's - less than $300 fr and rear. These are around 300gr per side, less than Martas. Now that the newer gen Formulas are all the rage, can anyone recomm ... Read More »

Formula B4 / B4 SL

What is the difference between the formula B4 and B4 SL? Is TI hardware the only difference? Also what model years have advantages and disadvantages? I will likely be using custom TI rotors as well.Read More »

Marta vs. Formula B4 SL

After deciding on going with Martas over XTR discs I wanted to know if there were any opinions on these two systems. The Martas look to be a more polished system, but I haven't seen any comparisons. Help a brotha out ...thanks.Read More »

Formula B4 sl's help needed

Hi someone said that they have stopped making B4sl brakes. I am looking to buy a set. The UK dist is still stocking them and they are on Formulas website. Do you think they are worth getting ThanksRead More »

Formula B4 sl or Magura Marta sl ?

I am looking to upgrade and put a lighter set of brakes on my scalpel and have pretty much narrowed my choice down to these two. I have noticed that alot of the online bike stores dont sell the formula b4 sl. Whats up with that? Anyone have any advice on which set I set buy? Thanks RDRead More »

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