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Disc Brake Adaptor / bolts advice

kevinharleykevinharley Posts: 554
edited March 2013 in MTB workshop & tech
Hi all,

I'm building my son up a bike with an on one inbred frame plus various bits kicking around in the garage, bits bought second hand, bits yet to buy (on a very limited budget) ... and a few bits of free or very cheap bits from a mate.

I've got a set of Formula Oro disc brakes to fir, with 160mm rotors.

The rear triangle of the frame has tabs for disc brakes, and I assume I need something like this? ... tor#basket
Will it come with the bolts & washers (ie to bolt adaptor to frame, and brake to adaptor?) ... if not, what do I need?

Do I need a similar adaptor to the front, or do I use bolts and washers, and bolt the brake directly onto the fork mounts? If just the bolts, any suggestions as to what size / type / make I need?

Sorry, basic question, I know ... but thanks for your help.


  • The RookieThe Rookie Posts: 27,804
    What mounts on the fork? If they are IS look like the rear then you need a similar adaptor to the rear, if they are PM, you'll need a PM to PM adaptor or bolt them on direct for 160mm discs.

    That adaptor comes with the bolts to bolt to the frame, you then need bolts and washers to bolt the caliper to the adaptor.

    Most people will have a pile of spare bolts/adaptors (I do) and will sell them to you for less than that.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • kevinharleykevinharley Posts: 554
    Thanks 'The Beginner'!

    I'm pretty sure the fork must be PM mounts then ... you would bolt the calipers on with the bolts facing forwards (ie in line with the line of the bike) as opposed to being bolted side on ... does that make it a PM mount?

    That being the case, were you offering to sell me some of your spare adaptors and bolts ... and if so, what price for IS adaptor plus bolts for rear brake, and just bolts for front brake?

  • kevinharleykevinharley Posts: 554
    One further question:

    My son is planning on running his bike single-speed (good man! :wink: ), and the on one frame has horizontal dropouts, so, as the chain stretches, and you move the back wheel out to re-tension it, will that affect the positionning of the brakes?
  • The RookieThe Rookie Posts: 27,804
    That is a PM (Post Mount), yes.

    Will PM you about bits....

    Yes horizontal dropouts do affect calliper location, some droputs have different mounting holes, sliding dropouts move the calliper, otherwsie you just have to tweak chain length to get the 'least worst' fit you can.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • redveeredvee Posts: 11,922
    The Inbred has horizontal dropouts for wheel movement and slotted calliper mounts to compensate for this.

    I've added a signature to prove it is still possible.
  • kevinharleykevinharley Posts: 554
    Cheers redvee ... had just recalled that after I'd posted! :oops:
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