Cycling UK Forum

I like disks.....but....

I have disks on my mountain bike. They are great for mountain biking. But..... they do tend to rub ever so slightly and can squeak. Now off road this is no problem at all due to all the other noise going on. But on road it is very irritating. I do know how to set them up but with time the squeaks creep in again and they need fiddling.

The pads are expensive and I have worn out 8 or 10 sets of pads a year on my mtb. I have also managed to heat the disks up a lot on some descents. I have bent disks in a crash on a couple of occasions. They can be bent back to an extent but it adds to the above problem.

The disks do compromise other elements of bike design. The disk wheels are dished to allow space for the disk. Front forks for disks must be stiffer and so maybe more harsh than nice slim touring forks.

It you hang your bike by the back wheel, you can end up with spongey brakes and bleeding problems earlier than if you keep your bike horizontal. And if thou crimp or bend a hose in transit, on a train for example, you have a more complex problem than you do with cables.

All this said, I would consider a disk braked tourer if I could be sure I could keep the brakes silent and if it were not for the fact that CSS rims and swistop blue pads seem to overcome many of the disadvantages of rim brakes.

our cable disked tourer, while not silent especially in the rain, ran quieter than the calliper brakes of my boardman in any conditions.

As for damaging the disks, I have yet to do this due to crash or rough handling. I know it can happen, but I think that anything that would damage the disks would have damaged the rims just as as much or probably more.

handling, weight and comfort issues can be designed out, it is probably due to makers not even thinking of using disks that these issues are present now.

our Burls Ti bikes were designed with disks in mind and never feel harsh, fully loaded or not. However, I have never ridden any other tourer so cannot compare, but compared to my boardman comp the Burls is just smooth.

The noises I experience are not while breaking. Rather they are due to the slight rubbing of the pads on the disk as you ride along. Ever so slight but really annoying. My V brakes are silent while riding as they never touch the rims unless braking. I think cable disks may be better as the pad moves further from the disk and is held off with a spring.

I have found the disks easy to bend in a crash - but that is mountain biking not touring.

hamish wrote:The noises I experience are not while breaking. Rather they are due to the slight rubbing of the pads on the disk as you ride along. Ever so slight but really annoying. My V brakes are silent while riding as they never touch the rims unless braking. I think cable disks may be better as the pad moves further from the disk and is held off with a spring.

I have found the disks easy to bend in a crash - but that is mountain biking not touring.

Hamish, I'm not denying your crash experiences, I too have crashed many times on my mtb, but have not, as yet, bent any disks.

As for the rubbing sound, yes i get them from time to time, minor disk warping, eased by minor disk straightening.

Urgh, after 5 days of cycling in the rain of the Jubilee weekend I really missed my disc brakes!

The mini-v's were still good though. A pain to adjust until I get a barrel adjuster put on, and annoying that I have to loosen the cable to get the wheel off. Plus the rear is a bit fiddly when the rack and panniers are on, compared to discs which are easy to access.

I may pop a disc brake on the rear, given I have disc wheels and rotors spare. It just means carrying two types of brake spares.

bealer wrote:....annoying that I have to loosen the cable to get the wheel off.

I would say you need to file your noodle end in a cunning way...

cheers

That's a good idea, I'll give it a try.

Brucey wrote:re the noodle issue;

you can file the end piece of the noodle so that you need less cable slack to disengage it. This has worked very well for some years on a friend's bike. If you put the flats on at an angle, it lessens the chances of accidentally unhooking the noodle.

I guess a typical mini-V caliper MA is about 3:1 then, although it could vary greatly with pad height.

This compares with;

~3.5 or 4:1 for a full 'V' brake caliper
~1:1 for an old-style side pull with about 50mm drop,
~1.3:1 for a typical DP with a 57mm drop

Both side pull (exactly) and DP (approximately) increase MA pro-rata with reduced drop. So I measure about 1.5:1 with short reach ultegras.

Now here is a question; even pretty crummy cantilevers struggle to go below 1.5:1 MA, yet there is a strongly held view that DP calipers are 'better' than many cantis. And few would leap to the conclusion that (say) mini Vs are about twice as good as DPs.....!

So, is this because;

a) the sums are wrong
b) it is mass hallucination
c) there is something else that systematically reduces the canti effectiveness (stiffness? flex vs pad angle?)

???

cheers

To round things off, especially as this thread is linked to, in "too good to lose", please Brucey can you,
1. Point out that the DP above is the post c. 2008 type (assuming that it is).
2. State what the MA (or is it VR?) is for the earlier Shimano DP brake.

Thanks in anticipation.
I think we had a partial list for levers but I haven't found it yet.
Edit 14/9/19
Follow the link in' Too Good to Lose -> Brakes -> Brake Mechanical Advantage' for a comprehensive 2019 list of levers and calipers

I've edited the list on p3 (where this is p1) of this thread.

cheers

Brucey wrote:I've edited the list on p3 (where this is p1) of this thread.

Do you know the numbers for SA levers and hub brakes or shall I go measure? Thanks for a great summary.

mjr wrote:

Brucey wrote:I've edited the list on p3 (where this is p1) of this thread.

Do you know the numbers for SA levers and hub brakes or shall I go measure? Thanks for a great summary.

For 70mm SA hub brakes (and 26-28" wheels) you are best off with a lever with an MA of about 3.5 or 4 to 1. The concept of MA at the other end of the brake isn't terribly meaningful. However the power of 90mm brakes is so high that you might get away with using levers for V brakes if the bike isn't too heavy. Likewise if the brakes are fitted to small wheels they work better, and you might be OK/happier with lower MA brake levers there too.

FWIW I think that if more power is needed in a 70mm brake with a large-ish wheel, or you need to use V brake levers for some reason, it may be possible to achieve this by extending the brake arm on hub. I plan to try this as an experiment.

On some new bikes with large wheels I have seen 70mm SA brakes paired with V-brake levers; this is all wrong.

cheers