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Last October I started racing 'cross and bought a bike with the up-and-coming disc brakes (Avid BB7 on Van Dessel Gin & Trombones). I've ridden about a dozen races now and also did a bunch of trail riding between January and September.

There are several CONS that other reviews don't usually mention:

* Tight tolerance. There's only about 1 mm on either side of the rotor between the pads. In muddy or sandy races, I hear it grinding after one warmup lap.

* Screeching. The front brake almost always makes noise no matter how recently I've cleaned it. I'm using sintered pads but plan to try organic this week.

* Rotor rub. With the strict tolerance between rotor and pad, any bend in the rotor is instantly heard every time the wheel turns around.

* One way grab. On BB7 calipers, depressing the brake lever moves only the outer pad. My Shimano XT brakes on my MTB both move, which I feel gives flexibility for greater tolerance and keeps the rotor true.

* Too much power. The 160mm rotor in the back is too strong for the width of a CX tire. I frequently skid on pavement, dirt, and gravel. (Maybe this is a good thing?) In most races, the front brake is more useful anyway.

* Full cable. Installation directions recommend running cable housing the full length of the cable. But the frame isn't really made for that, so I have a floppy length of cable running across the top of the bike, held in with zip ties. Given the strength of the back brake, I think I can afford to ignore Avid's advice and run it open on the top tube (even if it makes rear braking less powerful).

I've never had problems stopping with disc brakes. But the noise, maintenance, and tight tolerances make me question whether I should abandon disc brakes until better calipers are designed.

The Gin & Trombones is easily converted back to cantilevers, so I might try them for comparison.

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Great insights here.  I have also enjoyed reading this article:

http://www.cyclingnews.com/features/tech-cyclo-cross-disc-bike-roun...

I am all for tinkering, but not ready for what disc takes for the 15-20 races this year with a dedicated race bike 

I've decided to give up on disc brakes and retrofit my bike, probably with mini-v rim brakes.

Today's MFG race in Seattle was wet and pretty muddy (first real mud of the year). On the first lap I heard grit grinding around the rotor. I had no problem stopping, but afterward my back rotor was making a horrible noise. The spring that holds the disc in place had come loose and dragged itself across the pad. There's a deep gouge in the pad, going all the way through to the back in some places.

This happened last year but I thought it was my poor mechanical skills that caused it. But these pads had been fine for several races until today.

Disc brakes are supposed to be great in mud, but I've found that they are too sensitive to malfunctions like this when it's dirty. I'd rather deal with more straightforward issues of mini-v brakes instead of the constant screeching and sensitive tolerances.

The only problem is that I had started building some disc tubulars. I'll see if I can return my White Industries CX disc hub (130mm rear) and buy a standard hub instead for this build.

I'm looking forward to the light weight, easier maintenance, and lower cost of mini-v brakes. I run alloy rims so I don't think I'll have a problem stopping.

Geoffrey--

I agree with your comments. I have only been on the BB7s for a few weeks on my new bike. I have a lot of experience with hydraulic discs, including some road riding testing a Volagi. The BB7s are a letdown compared to hydraulics, but I still prefer them in most instances to cantis. 

I do some general trail riding on my cx bike. On steep descents, traditional cantis (I have not ridden linear pulls, but hear good things) seem to only retard the rate of acceleration. This can make for exciting moments. While the BB7s don't have the modulation of hydraulic discs, they are a lot better than cantis. I am running 140mm rear rotor, so I don't have the problems you are experiencing with skidding. In fact, I feel like I am short a bit of power back there. I am switching to organic pads, which should give me that little bit extra I would like. It looks like the pros ride 140mm rotors front and rear to give them less power but more modulation, and make the feel more like the cantis they are used to.

I am looking forward to hydraulics. The ride on the Volagi with a TRP Parabox showed that the modulation is amazing and quite useful on a skinny tire.

The setup is fiddly. For the first couple of weeks, every time I removed and reinstalled a wheel, the rotor rubbed. Maddening. I seem to have them dialed now.

I got the screeching noise as well. Should be better with the organic pads. I also eliminated it with the metallic pads by cleaning the rotors with acetone and lightly sanding the brake pads to clean them. I would perform the same maintenance on rim brakes, so not a big deal.

@Hobbanero I tried organic pads and still hear screeching. Sanding the rotors and breaking them in properly may help.

I switched to TRP mini-Vs on the front last week and really enjoy them. They were powerful and cleaned quickly even on a sandy, muddy course on Saturday and Sunday.

Interesting thoughts.  I was also on disc brakes for the first time this year.

My wife and I both swapped over to discs.  My race bike has S700 hydro-r on it, pit bike TRP Spyre, wife's race bike has TRP Spyre and pit bike TRP Hy/Rd.

I did 20+ races and she did 12-15.  Both train all fall on our B bikes.

After spacing all of our race wheelsets (7 sets total) and our 2 sets of clincher wheels I found them to be almost completely plug and play.  The biggest hassle came on Mondays and Fridays, when I swapped back to/from race wheels to weekday clinchers ( i didn't spend as much time spacing those.)

We were running 160 front, 140 rear, mix of HS1 and Ashima rotors.  Occasional scrape in a muddy race, but overall, I found them to be nearly hassle free.  

Were they better?  I can't say i gained or lost places because of the brakes, but it was fun to play with.

Hydro is the real deal both in the S700 and the Hy/Rd.  The Hy/Rd was a bit more of a learning curve, but as long as I had a 5mm and 3mm wrench, I was fine for quick pre-race adjustments (2-3min tops)

Barely went through any pad material on my orgainics on the race bike, and swapped out the sintered pads on the Spyres on my race bike that had plenty of muddy training rides and gravel road grit  >1/2 pad life remained.  (just took them off to check).  I even did a 90 minute muddy race simulation in a local park (mudpie) trying to kill a set of cheap pads with the spores and wasn't able to do so.

Overall, was happy

I had TRP Hylex on for a season and a half. Front pads replaced with sintered (from a place in the UK) and the rear left with the red TRP OEM. Just noticed after the season turned wet (in NorCal) that there is quite a bit of wear on the pads now. Noise - yes! The first few applications squeal almost like they need bedding every time you take the bike out. I have had to bleed the rear a couple of times although the first time was when cutting the line to fit inside my Crux frame. Bleeding the Hylex is a PITA - no bleed valve. I am picking up a complete R785 set today (for a Di2 cross/adventure build) and they look much better and hoping with better heat shedding discs they will work well on long road and gravel descents. New frame uses external route for rear line (smart? I'll find out). I have two same brand wheels, Notubes Grail and Iron Cross, and they did not require any spacers - prolly the same hub - so that part was easy.

Downsides apart, I just love how hydro discs work though. 

Hello everybody, I'm Francesco from Italy and I have a trek boone 9 disc with TRP spyre with Shimano brake pads.

Personally,there are some wrong thinks....i realized that disc brakes are perfect for dry,and they're really an upgrade versus canti because in the corner I can stop faster and in less space vs the canti.I have better modulation and perfect braking power.

In the mud, my preference and my style it's for brake less then possibile. I prefere flow vs brake-restart, and it's a really different thing for the brake and pad life. When you have 10-15cm of heavy mud, it's a natural brake in every situation.

My trp spyre didn't have a single problem in every condition, thery are really strong and in many case they help me to make the difference when was the time to do it.In some races they help me for win,specially in the dry,and I love it.

Another thinks : I really love the cantis, and they have many many PRO, but between a canti bike and a LIGHT (yes, light,under 7.5kg like my boone) I prefer all the life the disc. Better in every case and light

Man, he even sounds fast.  Many of the same thoughts I have, am running same bike and same brake

I have been on disc brakes on an RLT used for everything from some CX races to trail riding.  I plan to stick with discs.  Sure I have to readjust the calipers when switching back to my non-race wheels, but I do that on my mtn bikes as well.  Do the rotors make some noise when wet and muddy? Sure, but not slowing me down.  Same thing happens on my mtn bikes.  Also the biggest advantage is that I can use my 29er wheels by just swapping the front rotor from a 185 to a 160.  I run 160 rotors front and rear on the RLT with a BB5 in the front and a BB7 in the rear.  I also run barend shifters, so I have left the option open to go to TRP Hylex if I want to...but would rather build a SS 29er with my play money first.  Having wheels that i can now use on every single one of my bike choices has simplified life.

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