The Disc Brake Naughty Corner Thread

[Brucey]

Discs are rarely 100% free of residual stresses, arising from both manufacturing and service stresses. Materials do vary but most discs appear to be made from a martensitic stainless steel. Good discs are heat treated late on in the manufacturing process; cheap discs are not. Often 'discs warping'
is actually residual stresses coming out of a cheaply made disc.

cheers

[Manc33]

IMHO the virtues of BB7s are that they are relatively better (including maintenance requirements) than most other cable discs. They are most powerful in MTN variant with matched levers.

I've got both the road and MTB calipers. What's odd to me is the road calipers cost far more then the MTB calipers and it's pretty much the same caliper. I suppose the industry just assumes roadies have more money to spend.

Yes the road calipers are OK and performed pretty much how you said. The MTB calipers seem to have a bit more bite, but it's not much more than the road variants.

I know my old 7800 rim brakes were miles better and read the 9000 calipers are 25% more powerful, what They were always too expensive for me to justify getting them but they must almost be on a par with hydraulic discs.

Back in the day when discs first came about, endless arguments went on about how if you setup XTR v-brakes perfectly with good pads, they stopped you as much as was needed. Everything's changed now and even DA has a disc brake in the groupset. Discs always made more sense to me. For them to take this long to filter through to road bikes is a bit baffling.

[Brucey]

rim brakes were still being used by some MTB racers until fairly recently, for the simple reason that the bike could be built lighter and therefore faster. What killed off rim brakes completely in MTB race circles was the advent of the larger wheel size; no-one really bothered to make such a bike with rim brakes because it was so niche, and the wheels are so flexy rim brakes might not be practical anyway.

FWIW I have MTBs with disc brakes and I still have MTBs with rim brakes. Rims are (were) cheap, and don't take long to replace if you know what you are doing. Cost-wise on an MTB it all disappears in a sea of tyres, transmission and crash damage parts that need replacement anyway. Coincidence or not I can't say but its worth noting that I have had far more trouble with disc brake wheels than rim brake wheels on my MTBs, even though the parts have all been heavier and ostensibly more robust in the disc brake wheels.

cheers

[jb]

Road discs get more hammer than the majority of MTB discs IMO. If you live in hilly country they can be on almost constantly for over a mile where as MTB brakes are used in short bursts for most of the time (not counting the top end riders of course).

The rotors on my road bike certainly weren't cheap and both pairs started worping after about 0.075mm wear. Which might be normal.

I've changed them for a different make now and await results. But of course they will get to a point of failure at some point, it's weather or not you feel you've had your money's worth when they get to wanting replacement.

[peetee]

My observations suggest that the big issue with most V brake fitted bikes is that the trend to fit wide tyre and narrow rim combinations coupled to frame geometry that allows easy removal of wheels means that it's next to impossible to set the brakes up to maximise performance. This has opened the flood gates to a tide of disc-fitted bikes with superior braking and the perception that v brakes - and any rim brake, for that matter - are inferior and unworthy of consideration.

[jb]

My observations suggest that the big issue with most V brake fitted bikes is that the trend to fit wide tyre and narrow rim combinations coupled to frame geometry that allows easy removal of wheels means that it's next to impossible to set the brakes up to maximise performance. This has opened the flood gates to a tide of disc-fitted bikes with superior braking and the perception that v brakes - and any rim brake, for that matter - are inferior and unworthy of consideration.

Well there you are, disc brakes take no or very little setting up after initial fitment when replacing pads, where as Vs & canties are a right faf to get spot on. Ease of instalment wins over absolute performance every time for the majority, it also makes them safer.

[reohn2]

My observations suggest that the big issue with most V brake fitted bikes is that the trend to fit wide tyre and narrow rim combinations coupled to frame geometry that allows easy removal of wheels means that it's next to impossible to set the brakes up to maximise performance. This has opened the flood gates to a tide of disc-fitted bikes with superior braking and the perception that v brakes - and any rim brake, for that matter - are inferior and unworthy of consideration.

Well there you are, disc brakes take no or very little setting up after initial fitment when replacing pads, where as Vs & canties are a right faf to get spot on. Ease of instalment wins over absolute performance every time for the majority, it also makes them safer.

Discs IME offer easy setting up and better overall performance than rims,not that I find setting up V's to be difficult but not as easy as BB7 discs which are a doddle once the routine is learned and followed.

[Brucey]

Apart from occasional episodes of squealing (which can afflict any brake it seems, and are probably best regarded as a part of Life's Great Mystery) I don't think I've ever had an intractable problem with a canti/V installation.

In fact I often struggle to comprehend how or why other folk seem to have any trouble at all with them; they are very simple devices, about as complicated as a lump of wood really.

Once set up, I usually go through multiple sets of inserts without having to fiddle with the brakes much at all.

By contrast most disc brakes are something of a finicky PITA; at the slightest excuse there is a new rub, a new movement of the rotor or something.

FWIW I have long held that 'the best way' with most mechanical disc brakes is to have a (third) spare caliper which is overhauled, inspected and ready to go with new pads in it. This way you can be sure that the mechanism in the caliper is always in good shape; there isn't a caliper made which is impervious to the effects of the weather, and this forestalls problems that inevitably emerge sooner or later otherwise.

cheers

[peetee]

My observations suggest that the big issue with most V brake fitted bikes is that the trend to fit wide tyre and narrow rim combinations coupled to frame geometry that allows easy removal of wheels means that it's next to impossible to set the brakes up to maximise performance. This has opened the flood gates to a tide of disc-fitted bikes with superior braking and the perception that v brakes - and any rim brake, for that matter - are inferior and unworthy of consideration.

Well there you are, disc brakes take no or very little setting up after initial fitment when replacing pads, where as Vs & canties are a right faf to get spot on. Ease of instalment wins over absolute performance every time for the majority, it also makes them safer.

And some hydro discs are a PITA to bleed. Don't get me wrong though, I am not poo pooing discs, just stating that V's have more potential than current bike trends will allow.

[Manc33]

When I swapped my BB7's to another frame, the front one decided to start squeaking on random days. Whether it's raining or not doesn't enter into it, either. Pulling the front brake lightly a few times stops it temporarily but soon enough it's back squeaking again.

[jb]

The spring that separates the pads may be weak - try a new one from a new set of pads.

Or, the space in the callipers that the pads fit into may be dirty preventing the pads retracting properly.

[Manc33]

I remember putting new brakes on my bike a few years back and went for a 15 mile ride, I got home and realised the only time I pulled the brake was to stop at my house at the end. I set off again down a few hills and deliberately pulled the brakes. I hate braking and if I can get away with never braking, I will. Why pedal if you're just going to brake, that's like punching yourself.

[Cyril Haearn]

You must be very young and carefree
I dislike braking, I only do it with my feet,not many big hills here
Love going uphill, hate going down

[shobo]

I've had hydro discs on road bikes for about 4 years. They are fantastic. I've experienced none of the supposed disadvantages. It is so easy to replace the pads when you've done it once. BUT on two occasions, the gear index system inside the shifters has broken, once when the cable stop sheared off, once when the cable guide wore out and wrecked the internals. On both occasions I had to replace the entire hydro shifter - which is very expensive - OUCH !!

[Manc33]

You must be very young and carefree

No I'm just slow and I avoid hills for the most part, to ever need to brake much.