Replacing really ooooold disc brakes?

Beezerk
Beezerk Posts: 18
edited August 2018 in MTB workshop & tech
Hi, the Giant MPH brakes on my old mtb are pretty naff, I've tried bleeding them, replacing the oil but they're still garbage lol.
I'm looking at replacing them at a reasonable cost but all new disc brakes seem to have a different mounting, I believe mine are IS mount but all modern ones seem to be Post mount (I stand to be corrected here).
I've seen there are brackets which look to convert from Post to IS, is it really just a simple task of buying newer disc brakes along with a couple of those brackets and clagging them on?
I don't want to really spend a fortune as it is an old bike which I've been slowly upgrading but as I'm biking more and more its become apparent I need new brakes (and probably discs) to keep me a bit safer.
Any advice?

Comments

  • The Rookie
    The Rookie Posts: 27,812
    Beezerk wrote:
    I'm looking at replacing them at a reasonable cost but all new disc brakes seem to have a different mounting, I believe mine are IS mount but all modern ones seem to be Post mount (I stand to be corrected here).
    Most likely yes, IS was the first mounting standard and I don't recall seeing an MPH in anything but IS.
    Beezerk wrote:
    I've seen there are brackets which look to convert from Post to IS, is it really just a simple task of buying newer disc brakes along with a couple of those brackets and clagging them on?
    Yes and no, the rear hose is certain to need shortening, its likely the front will as well.
    Beezerk wrote:
    Any advice?
    Shimano Deore, solid, powerful, reliable and not expensive (but not so cheap as to be unreliable).
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Beezerk
    Beezerk Posts: 18
    Awesome, top advice as usual.

    Thanks mate.
  • steve_sordy
    steve_sordy Posts: 2,443
    edited August 2018
    If they are really old, and you are still running with the original discs, then you need to check that the discs are still safe. The discs do wear thinner and can go below a safe thickness. The min thickness should be etched on to the disc.

    Hanging up in the garage, I have a 160mm dia Shimano disc that is 1.75mm thick. It has min thickness 1.5 mm engraved on to it. So that is an allowance of only 14%. I wore it down to 1.4 mm before I even knew that there was a problem, ie well past the 14% and on to 20%.

    If there are no warnings engraved on your disc, try Googling the discs or contact the manufacturer. If that fails and no-one here knows, then check the disc thickness on a part that is not in contact with the pads. If your contact thickness is less than 85% of that, then bin them.

    You might do better with solid discs though, the Shimano discs I referred to above were IceTech, the ones that are a steel/aluminium/steel sandwich. Discs are crucial to your safety, so don't take chances. If a front disc breaks, you will be OTB in a flash! :shock:
  • The Rookie
    The Rookie Posts: 27,812
    Icetech are much more critical as the two braking surfaces each side of the aluminium core are much thinner, so the same wear (loss of thickness) will leave them dangerously thin were a solid steel disc is still quite safe.

    A front disc braking is intended, its a disc breaking that causes problems......
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • swod1
    swod1 Posts: 1,639
    I run 6 quid all in one piece stainless discs and no problems at all, these fancy floating discs I've had nothing but trouble with.

    With the suitable adapters IS to post mount, you could run some deore disc brakes which would be an upgrade on what you have now.
  • Beezerk
    Beezerk Posts: 18
    Thanks again for the replies. After lots of reading up I bought some Clarks M3 from Chain Reaction, found a discount code as well so it made the deal even sweeter.
    I've fitted the front brake so far and tried it last night, works great.
    I was looking at the Deore brakes but the Clarks had discs and IS adapters included so happy days.

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