How do I sort useless mechanical discs?

ajoten

Kona Dew Deluxe 05. Never been happy with the brakes. Get them set up, have one steep downhill bit I need to stop self on, they never grip properly again until the next time I take in to LBS (get one more hill's use out of them).

Currently the bike is unrideable as a consequence and I'm thinking of just binning it. Would cost too much relatively to upgrade to hydraulics.

I've adjusted the "action" so that the smallest twitch on the lever engages the caliper, but still squeezing with all my might does zip in terms of slowing self down. Yes I've changed the pads, and yes I've given them time to bed in... they just haven't.

Is this a common mechnical disc problem or is it just me - as in bad luck or not maintaining properly?

Currently I'm angry as it's proving a stupid waste of money.

nicklouse

what are the brakes?

ajoten

Shimano Deore I think.

jimmcdonnell

I have Shimano mechanical discs on my Focus Cross - and no, they just simply aren't as good as hydraulics.

One of your comments might be worth looking at in more detail though - you say they work fine for one hill then need re-adjusting? That sounds odd. Do you have cable that's not tightly secured at the brake end, and is pulling out of the attachment point when you grab a big handful of brakes? On my bike, the performance isn't great but it's predictable and dependable from ride to ride?

Other ideas - upgrade to a rigid cable like Nokon or Alligator - compression of the outer casing makes cable discs feel spongy. Are your pads ok? No contamination from oil or other unwanted chemical?

Could you upgrade just the front to hydraulic then do the rear as cash allows?

And the obligatory facetious answer - ride a road bike for a few days, then be amazed at how good your cable discs are when you get back on them...

bomberesque

I've had Avid BB7s for a couple of years now and like them a lot. I wouldn't spec them on a bike I was going to run downhill a lot on but for XC (and commuting) use they're superb.

and +1 for checking for cable slip as well as looking up some of the fixed tube cable outer replacements (Avid makes some, called Full metal jackets, iirc) that reduce compression along the length of the cable outer. I've not tried them myself but I've heard good things and it's cheaper than binning the bike.

ajoten

jimmcdonnell wrote:

And the obligatory facetious answer - ride a road bike for a few days, then be amazed at how good your cable discs are when you get back on them...

Unfacetious response: my Campag Centaur brakes ROCK.

But it's not that my discs are not very good. They simply do NOTHING at all now.

How would I know if the pads were contaminated?

jimmcdonnell

I have Ultegra on my road bike, and they're ok - I don't use that bike in the rain, mind - but I still find myself needing to plan ahead to stop at speed. And they're adjusted to within an inch of their lives, too. I've come back to road bikes after 25 years on cantilevers, v-brakes, rollercams, hydraulic discs. I don't think I'm going to ever feel as confident in a set of road caliper brakes as I know I do on any of the above. I'd like to...

As for contamination - hmm. Tricky one. Get the pads out and look to see if there's a noticeable glaze on them? Assuming you've owned the bike since new, I'd say that you're the best judge of contamination ie are you aware that you've ever had anything other than a solvent like carb or disc rotor cleaner near them? Unwanted contaminants like soap from a vigorous bikewashing, lubricant that might have sneaked onto the rotor from spraying on your hubs, flung off the chain etc?

A new set of pads isn't expensive, that might be a way forward?

nicklouse

ajoten
the deore ones are not that great and do need correct set up.

Contamination the only way is to replace then after cleaning the rotor with cycle cleaner (or meths) and then see how they work.

What do you use to clean the bike with?

what do you use to lube it?

changing them to Avid BB7 calipers should make a big difference.

bomberesque

jimmcdonnell wrote:

I've come back to road bikes after 25 years on cantilevers, v-brakes, rollercams, hydraulic discs. I don't think I'm going to ever feel as confident in a set of road caliper brakes as I know I do on any of the above.

Exactly why I bought a road bike with disc tabs and fitted BB7s to it. wet dry, hot, cold, snow, hail, these guys work just the same in all conditions and don't turn my rims black with runoff.

Mike400

I have shimano deore discs on my XC bike - they are certainly better than the V brakes I had before but wouldnt be happy using them for any serious abuse.

Work great in traffic / avoiding dogs on coastal paths lol and if you need to stop in a hurry they "grab" well enough.

Feel a bit spongy and need a lot of force on the levers to work their best IMO BUT utterly reliable and always consistant since I fitted them.

So in a nutshell better than most for commuting / XC stuff but not really suited to heavy abuse