Wednesday, September 4, 2013

Avid BB7 Road disc brakes (Off the Beaten Path brake test)

The Salsa Vaya I ride the majority of the time has Avid BB7's which have great stopping power in varied weather conditions.  So I was surprised to read this statement over at Off the Beaten Path in "How to Brake on a Bicycle" (in the comments section, by the post author Jan Heine. The comments were closed by the time I read the post):

Based on our experience, at least the common Avid mechanical “road” disc brakes (BB7 “road” model) have much less stopping power than a good rim brake. We have tested a number of bikes with different rotors and pads, even had a local expert fiddle with one of the test bikes, but there was little difference. The brakes feel great at first, but as you pull harder on the levers, you only get flex in the brake mechanism, but no more braking power.
Bill Davidson has a nice little demonstration. He takes a bike with those brakes, pulls the lever for the front brake to the bars, and then pushes the bike across the shop floor. The wheel continues to turn. He then takes a bike with a rim brake, and the wheel won’t turn.

So I went to my bike, pulled on the front brake lever, pushed the bike, and voila! the front wheel didn't turn.  It sounds like Mr Davidson's demonstration is with BB7's, but perhaps from the wording "these brakes" the blogger just means generic disc brakes.  I didn't have to pull all that hard.  Either way, I'm wondering am I or they missing something?

I don't have any experience with good rim brakes except for the cantilevers on my good cross bike, so I can't compare the two types of brakes much.  But my experience is that the BB7's have more than adequate stopping power.  I especially like being able to grasp the brake levers easily from the hoods without applying too much force in order to stop quickly.  And I hate fiddling with and adjusting rim brakes, so I prefer the disc brakes.

The main thrust of this article was that their experiments found that "on dry pavement,  the front brake alone halts the bike over the shortest distance."  It's a little hard to tell just how scientific their tests are.  Their is an interesting exchange in the comments section between Robert Hurst, the author of The Art of Cycling (formerly the Art of Urban Cycling) and Mr Heine where Hurst challenges the findings and says his experiments have found the shortest stopping distance was with both brakes.  I think everybody does agree that you get the most stopping force from the front brake.

(Hurst's website is The Industrialized Cyclist and he has tons of info on his Bicycle Research page.)


  1. They're claiming that BB7's can't lock up the front wheel, even with no rider weight on the bike? An unweighted bike weighs 10%-20% of normal bike-and-rider weights which means they are claiming that BB7's only have 10%-20% of the power of a decent brake. That claim is clearly false.

    The other statement, that one achieves maximum braking using only the front brake, is correct*. When you brake, weight is transferred off the rear wheel, and onto the front wheel. At maximum weight transfer, there is no weight on the rear wheel, and therefore no friction between the rear tire and the road. In practice, we don't usually brake that hard.

    * Don't try this on a cargo bike, or a bike pulling a trailer.

    - Ventura

  2. yeah I'm still confused by that statement re the BB7's, as I also sat on the bike and couldn't get the the front to turn while pulling the brake. I think I could even lock up the front tire while riding. Duly noted about the cargo bike and trailer. I pulled our dogs around in a trailer last weekend and hadn't thought about a quick stop, might have to practice that.

  3. The bb7 roads are the only viable game in drop-bar-disc town at the moment (excluding the $1200 sram hydro option). If you must go with discs and drops, bb7's are pretty much it.

    I think a part of the discussion excerpted above misses an issue here (maybe it's discussed in the comments on the original post/comments) -- but that's modulation. Jan implies that with his "feels great at first -- then nothing happens" statement. On great performing brakes, you get modulation that allows a range of stopping power as you pull more lever. The bb7s are awful in this regard. In my experience, you set them up to optimize mechanical advantage, then you must set the pads up right on the rotor, which makes for pretty bad modulation.

    I prefer rim brakes -- caliper or well-setup canti's (not v-brakes) -- in nearly all non-mountain bike situations (though I've recently become religious about hydro disc brakes for that scenario). I have teh bb7 roads on my winter bike, where disc brakes make a lot of sense when ice/snow freezes up on the aluminum rim, but otherwise my bikes are rim brakes. Well-set up canti's are ridiculous in their awesomeness IMO -- you get the best of everything for drop bar/brifter setups. My current faves are the CX-70s -- when you follow the set up directions, they are excellent. I have a dormant theory that suggests many cyclists (especially those who started in the last decade or so) have never ridden well-set up canti brakes, so have a skewed perspective of what great brakes might act like.

    That said, my buddy Glen recently built up a disc CX bike and is swearing by its greatness for fast trail riding (if not cx racing...). At my last job, HQ'd in seattle area, the internal bike email list had an on-going war/discussion about rim vs disc brakes for rainy weather commutes, with jihadists on both sides of the debate.

    As with most bikey stuff, in the end it's all opinion and preference backed by anecdotal observation and some mythology. I'm rambling... no point here. sorry.

  4. that's fine, rambling's ok here, thanks for your input.
    I still wonder if Jan actually has tried the demonstration he attributed to Bill Davidson (I'm guessing he's the Seattle builder with Elliot Bay Cycles?), and it makes me wonder about some of his other statements. I guess I'm a little stuck on it.

    I seem to get modulation out of my BB7's, but I know if I have them set up too tight they're a little touchy. When set up right for me, I pull a a little to just slow down a bit, or pull harder to stop quicker. I commuted on my good CX my bike for a week or so - I think the canti's are good on it - and still prefer the disc brakes for in-town/city riding. I wonder if hydro road disc brakes will someday be available on bikes in the $1000-$2000 range - that'd be nice.


  5. John, I assumed that BB7 roads were the only decent option for road bike disc brakes too. Then I got a Salsa Fargo 3, which came with the BB5 road brakes - I thought I'd be upgrading them to BB7's right away.

    I'm actually very pleased with the BB5's. They work reasonably well with one-finger effort from the hoods, and I have a couple thousand miles on the pads so far. No modulation problems with slowing, regular stops, or emergency stops.
    - Ventura

  6. yeah I test drove a Vaya 3 last year that had the BB5's and was surprised how well they worked.
    Those Fargo's are sweet, I've been thinking of selling my mountain or cross bike to pay for one.


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