Promax mechanical disc brake adjustment

[02gf74]

Even lowly mechanical disc brakes should work.

OP said near beginning about doubt if v brake levers are fitted. Are they? V brakes have more cable pull . The symptoms indicate they are not.

Have the callipers been usedx with the same levers before?

Clrearance between pad and disc is typically 0.5 mm or a bit less, at small distance the disc may rub at some point if slightly warped but can be gently bent back to shape.

If op had 1 mm clearance each side i.e. 2 mm, that is too much.

Lever should move about 1/5 of full travel before pads touch disc.

 

[killjoy]

Re:

To resurrect an old thread.

I also have a front promax disc which I cannot get to work probably.

Once I have set it up I find that can apply the brake and still push the bike forward BUT if I try to pull the bike backwards the brake works perfectly.

 

[mechanical_vandal]

Re:

Once I have set it up I find that can apply the brake and still push the bike forward BUT if I try to pull the bike backwards the brake works perfectly.

This is just physics making it easier to lock the wheel when it's being dragged rather than pushed.

I'll get told it's unhelpful but honestly, if faced with these brakes, I'd chuck em. You can get a set of used BB7s for under £50 which in 10 minutes can be made to work 10x better than these Promax things ever will. You have to value your time pretty lowly to make fixing the Promaxs the economic option.

 

[killjoy]

Re:

I agree the best option is to replace them with a 'better' make, be it mechanical or hydraulic. Just have to find the cheapest replacement.

 

[The History Man]

I had promax and replaced them quick smart. Tektro Lyras work very well. Next build has BB7s but if i'm honest, none of these are a patch on the hydraulic sets (4) i have. It's getting them close enough without a little rub that's the secret as the large cheesy one said.

I may try the promax again but understand your frustration. When I first got the bike with them on I, as you, thought i must have set them up wrongly or badly but they were just sh*te. Lyras were set up in same way without issue.

 

[jimo746]

Re:

Have you checked the pad wear and any contamination on them? also give the disc a clean to be sure.

I found adjusting the pads to within a gnats whisker of the disc gets them working well. But you need a nice true disc for it to not drag the pads on the disc.

These brakes are cheap for a reason, of the cheap cable discs I've tried and repaired I'd say that even after a lengthy set-up maybe half of them were still rubbish and a £10 set of V-brakes would have performed better. But then you can't expect XTR performance at budget prices, they should at least be capable of stopping the bike though!

 

[xerxes]

Re:

These brakes are cheap for a reason, of the cheap cable discs I've tried and repaired I'd say that even after a lengthy set-up maybe half of them were still rubbish and a £10 set of V-brakes would have performed better.

I serviced a friends bike, a Carrera Subway, with a cheap set either Promax or Tektro cable disc brakes, I can't remember now, and despite a good amount of faffing I couldn't make them as "stoppy" as the knackered old set of Avid V-brakes I had on one of my bikes. :?