Disc brake upgrade?

meanredspider

@Rolf F - I'm not entirely serious in all my arguments but, as much as there's technology for technology's sake, the road bike world is incredibly conservative. I'm not expecting Di2 or discs to transform my ride, but I also don't understand why I would buy yesterday's technology when I'm buying a new bike.

As for disc brakes, it's not just cars but just about every braking system on the planet.

I don't accept the hype. I'm an extremely experienced engineer currently working on new products - I can make my own judgements. I've been running my Boardman CX for a while now and I'm bowled over by how good the brakes are - it's a common theme for Boardman CX riders.

I'm also interested as to why disc brakes are currently banned on the pro circuit if they offer no advantage.

The Boardman has also taught me how easy disc brakes are to maintain - I have absolutely no idea where the comments about complexity come from. I haven't even begun to experiment with pad compounds.

Your own test shows that, even with a light rider at modest speeds in the dry, the discs are nearly 20% more effective. The small weight differences pretty much cancel themselves out - there's more downforce but there's more weight to stop too.

Anyhow - I'm sure we won't agree. I also think we have different needs and experiences that lead us to our views. For me, for the conditions I commute in and the Highland terrain, discs are so much better than road rim brakes.

supersonic

Just take a look in the MTB section about disc brakes and maintenance - is the most common problem. Alignment of calipers, warped rotors, squealing and juddering brakes, rotor braking track not matching, levers pulling back too far with no adjustment, no end of bleeding problems, quick pad wear, trail size fixes if you pull the hose out and so on. Of course, as previously, some models fare better than others, but for some people discs are a bane. When they go wrong, they really go wrong!

Maybe these people are more used to caliper brakes and need to relearn. But I have relearned, have tested dozens of brakes yet Vs still work so well for me. But I can see why discs work so well for others.

The Rookie

I have cheapish (clarkes) cable discs on my commuter, partly as on a commuter I want good (instant) wet braking, partly as the frame I bought (cheap - like very cheap!) has no other mounts, all I've done in over 1500miles so far is tweak the adjusters at the calliper (I've binned the adjusters on the lever to save weight as I never used them).

The Juicy's on my MTB have done over 250miles all off road in all conditions and I've never touched them.

Disc unreliability I think is more an issue with (poor) tinkering by owners than with the kit itself! Many riders don't have a clue, I have been assured the squeal on the MTB is down to contaminated pads, when I know very well it's the combo of hard sintered pads and fairly felixible alligator discs, they howl like a banshee as soon as they get warm, but I like the low weight/performance balance though I may go kevlar pad if I ever wear the sintereds out.

Simon

Mr Plum

I've been weighing this one up for a while myself - my next commuter/winter training bike will definitely discs, at least on the front anyway. Due to the associated costs it doesn't seem like a feasible upgrade to my 2010 Tricross (new fork, new wheel, disc/calliper - looking towards £250) but it's something I'll look for in the future.

jds_1981

supersonic wrote:

Just take a look in the MTB section about disc brakes and maintenance - is the most common problem.

Alignment of calipers,

I've avid disk brakes on my bike - self aligning

warped rotors,

I'm yet to warp my disk brakes. Have put my wheels out of true many times though and that can affect rim brakes

squealing and juddering brakes,

Mine squeal which is just annoying (juicy threes, known for this) and can judder a bit under really heavy braking. Doesn't appear to affect braking though.

rotor braking track not matching,

dunno what this is

levers pulling back too far with no adjustment,

Not had this, unlike the regular adjustments have to make to road bike brakes due to pad wear & wire stretch (& rarely fraying)

no end of bleeding problems,

bleeding is a once a year or so experience

quick pad wear,

Not compared to my road bike brake pads in winter

trail size fixes if you pull the hose out and so on.

Equally valid for snagging a standard brake cable & snapping


You're like a dinosaur man :P

I've found disk brakes to be less maintenance & better in the wet. You obviously not so much.

Ngalbrai

Have a kona honky inc with bb7's and 28c tyres. Also live in sydney so have tested them extensively in the wet. I would say they are pretty good, can fling yourself over the handlebars or lock the rear wheel if you were so inclined, they do inspire confidence with consistent braking ability, more limiting is tyre traction on soaking road. FAR better than road calipers - reason I got the Honky was that I wanted drops and road(ish) geometry but that I could actually stop. Originally had shimano something or other, BB7s far better. Dont compare, as others have said, with good hydros on MTB though.

the_moodster

I did the same as you and started commuting on a road bike with drops. I switched to a hardtail mtb (rigid forks, skinny tyres) because I found I was much happier with hydrolyic discs at my fingertips. The road bike is now a hill climb weekend warrior

Ps. never had any problems with any of my discs that I didn't cause myself, remember for every complaint you see there are ten perfectly happy people saying nothing.

rolf_f

meanredspider wrote:

Your own test shows that, even with a light rider at modest speeds in the dry, the discs are nearly 20% more effective. The small weight differences pretty much cancel themselves out - there's more downforce but there's more weight to stop too.

Anyhow - I'm sure we won't agree. I also think we have different needs and experiences that lead us to our views. For me, for the conditions I commute in and the Highland terrain, discs are so much better than road rim brakes.

Shockingly late reply!! Obviously, what I need to do with the tests is try again - in wet and dry, with more equivalent tyres (I think the MTB may have been on knobblies when I did the test) and with computers on all bikes (easy now I am on GPS - I was guessing the speed of the Look so it's performance could be better or worse than implied). Also, it was one of my first trial runs with the Look hence nearly going over the bars.

We don't entirely disagree - I do think you have made a good choice for a commuter (maybe the perfect choice) but I still wouldn't really want that bike for the weekend. And, I still wouldn't use the Volagi during the time of year when the really bad weather occurs because no amount of disc braking addresses the heavy wear and tear on the rest of the drivetrain. My Ribble shows no obvious signs of wear and tear in either drivetrain or rims despite being the primary commuter for 9 months of the year.

One point I can make for discs was that after replacing the discs when I took off the horrible Avid system, I found there appears to be no appreciable wear on them. The pads (sintered) have very short lives but not the discs. In the old days of scary steel rims, it was the pads that wore out rather than the rims. I can't help thinking that it should be possible to go back to that with alloy rims (only with some actual braking performance!).

meanredspider

Rolf F wrote:

Shockingly late reply!! Obviously, what I need to do with the tests is try again - in wet and dry, with more equivalent tyres (I think the MTB may have been on knobblies when I did the test) and with computers on all bikes (easy now I am on GPS - I was guessing the speed of the Look so it's performance could be better or worse than implied). Also, it was one of my first trial runs with the Look hence nearly going over the bars.

We don't entirely disagree - I do think you have made a good choice for a commuter (maybe the perfect choice) but I still wouldn't really want that bike for the weekend. And, I still wouldn't use the Volagi during the time of year when the really bad weather occurs because no amount of disc braking addresses the heavy wear and tear on the rest of the drivetrain. My Ribble shows no obvious signs of wear and tear in either drivetrain or rims despite being the primary commuter for 9 months of the year.

I can do the tests even more scientifically by strapping the G-meter from my race car to my Volagi and my 105-equipped Cayo. It will give far more precise results than GPS because the GPS polls the satellites at only about 1Hz - you can travel quite a way in a second. That said, I really don't need to - there's no comparison - at least not for me and my size.

I won't be using the Volagi when there's ice up here - that's 2-3 months of the year. I've been using 105 bikes for the past 3 years and, TBH, not had any appreciable problems with the transmission. The Volagi is really no different - the chainrings are a bit nicer but the chain is standard 10-speed and the cassette is 105. No cables to get crudded up on the transmission. I have some nice grooves in my Cayo rims though.

As for using the bike at the weekend, it's already faster than my Focus Cayo (carbon frame, carbon bars, RS80 carbon/ali wheels, no guards, 105 transmission) achieved in the summer months - and the V has guards & lights. The whole design intent of the Volagi is as a "Century" bike so long weekend rides are exactly what it was designed for. I'm yet to get the carbon wheels for it but I'm sure I will in the end.

tgotb

I have the following on my bikes:
Cross bike - BB7s (160mm and 140mm discs), set up "by the book"
Road bike - very carefully set-up rim brakes with very true wheels
TT bike - carelessly set-up rim brakes, internal cable routing

TBH, the road bike has the best braking of the lot, even in the wet. The disk brakes are good at times, but seem to lose effectiveness from time to time, at which point I have to take out the pads and lightly sand them. I've set them up very carefully, but they still require most of the lever travel to work, and have this problem with intermittent degradation. Brakes on the TT bike are hopeless; if I tried to ride it in commuting traffic I'd probably end up riding into the back of something.

My point is that the difference between well set-up and poorly set-up rim brakes is much greater than the difference between rim brakes and discs. Why not start by truing your wheels, getting some new brake pads (and maybe brake cables too) and setting them up carefully.

As an aside, my daughter's cross bike has cantilever brakes; however carefully I adjust them, they're still terrible!

meanredspider

TGOTB wrote:

My point is that the difference between well set-up and poorly set-up rim brakes is much greater than the difference between rim brakes and discs.

Well that kinda goes without saying. Poorly set-up rims are pretty much useless. Useless to OK is a bigger difference than OK to really good.

There sounds to be something wrong with your BB7 set up - I'm not sure what though. I run two different bikes with 2 different BB7 set-ups and neither exhibit the symptoms you describe. After bedding-in, there's just great and consistent braking with plenty of lever travel to spare.

The "Volagi" method of set-up (they have a YouTube video) seems to be the easiest:

1. Slacken the cable at the caliper
2. slacken off the caliper bolts
3. Adjust the pads hard up against the disc to achieve the 2/3 vs 1/3 alignment
4. Carefully tighten the caliper bolts alternately
5. Slacken off each pad by 2-3 clicks until free rotation
6. Retighten cable, taking up a bit of slack by rotating the caliper lever slightly

It can't take more than 3 minutes using just two tools and is pretty much foolproof. Then, from time-to-time I experiment with adding a click each side to see if I get any rub to take up wear.

tgotb

Yeah, they're set up pretty much like that. The two main issues I have are:
1. Lever travel. Here's how I understand the problem: You can set up a wheel to be true to well under 1mm, and the travel of a set of calipers is probably more like 10mm (5mm each side), so it's quite easy to set the brakes up to bite within maybe 1/4 of the travel of the levers. Conversely, the pads in a set of disc brakes have maybe 2mm travel. Given that it's not possible to set the pads to be consistently 1/2mm from the disc (even an expensive disc isn't true enough) you need to use a more significant proportion of that travel just to get the pads in contact with the disc. The end result is that with regular SRAM road levers and Road BB7s (which are sold as compatible) I need to move the levers around 3 times as far as I do on my road bike with the same SRAM levers and calipers.
2. Contamination. This puzzles me, because rims see a lot more dirt than discs, so I'd expect the rim brakes to be worse: In the wet, the brakes get very noisy (maybe because there's no toe-in). Additionally, over a period of time, the brakes become less effective. Both these problems get worse whenever I swap wheels (I have separate sets of wheels with road and CX tyres). The problem hasn't been as bad since I filed grooves in the pads, but it still happens. Once the brakes become less effective, the only solution is to remove and lightly sand the pads. This is very effective, restoring full braking effectiveness, which leads me to conclude I'm probably removing some contaminant.

Any advice on eliminating the second issue would be welcome (the first issue isn't a big deal, and I guess it comes with the territory). Given this is a CX bike, for which the only alternative is cantis, I'm still very happy with the discs!

meanredspider

I have to say that, when I swapped my Boardman over from SRAM Apex to 105, the levers on 105 were soooooo much better. Whilst SRAM might be compatible with BB7, I'd say Shimano (105 or Ultegra at least - I've only tried them) are much much better.

I haven't measured the trueness of my brake disc though I'd have said it was within 0.5mm. Lever travel isn't an issues though.

Can't say on the pads. Are they OEM? Perhaps they are contaminated completely - sounds like it would be worth trying a different brand or compound and maybe a different rotor. I get a bit of noise at the brakes if I go though muddy water but it soon clears and has no impression on braking. Wish I could say the same for rim brakes - my RS80s might last longer