Brake Calipers

DC Ayr
DC Ayr Posts: 33
edited May 2011 in Workshop
Does anyone know the difference(s) between a front & rear Dura Ace 7800 brake caliper? They are listed as separate items on Madison - both at the same price. CRC has them at different prices.
I've got a front caliper and there's nothing on it (part number wise) that distinguishes it as 'front'.

Comments

  • nicklouse
    nicklouse Posts: 50,673
    the length of the mounting bolt is the only difference.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
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  • DC Ayr
    DC Ayr Posts: 33
    Thanks nicklouse. That scuppers my plan for buying a cheaper front caliper for the back brake :(
  • Wheelspinner
    Wheelspinner Posts: 6,720
    Perhaps not.
    If they are otherwise identical (Nicklouse more expert than moi in these things!).. then the front should be usable for the back.
    In 99% of brake caliper sets I've seen the front mounting bolt is LONGER than the rear caliper one, since it has to go through the fork instead of the brake bridge, so you can probably neatly trim the bolt length to suit the back mounting. Requires care and will be tough as the bolt may be high tensile (?) but should be possible.
    Open One+ BMC TE29 Seven 622SL On One Scandal Cervelo RS
  • Flamez
    Flamez Posts: 105
    Ultegra also come in 45 and 55 mm drop to allow for mudguards etc,...
    Condor World Series 2012
    Boardman Team 2011
  • Yossie
    Yossie Posts: 2,600
    +1 for Wheelspinner: put the caliper on the bike, mark where you need to cut the bolt (sharpie will do), get two nuts the right size and lock these against where the sharpie mark is.

    Place carefully in a vice using the bolts to hold it in place - not the caliper body itself, cut gently with new hacksaw/Dremel. Use b'stard file to take off rough edges.

    As you undo the nuts theyw ill clean up the thread and re cut the end of the cut thread.

    Slap on loads of copperslip et volia.

    HTH
  • DC Ayr
    DC Ayr Posts: 33
    Thanks guys - I'll check the bolt length on the frame, front & rear. If it fits both, then great. if not I'll get my hacksaw out.
    I'll let you know how I get on.
  • Wheelspinner
    Wheelspinner Posts: 6,720
    Just remember you may also need to rotate the pads / pad holders 180 degrees. I think most brake pads are directional, as in they are designed to work with wheel rotation in a specific direction. If you install the front caliper facing (effectively) backwards, the pads will be the wrong way round.

    Whether it makes a difference or not, I don't know. Never actually tried, but I'd guess there's a chance they will be grabby and squeal more if pointing the wrong way... cut grooves in them etc will behave differently.
    Open One+ BMC TE29 Seven 622SL On One Scandal Cervelo RS
  • Yossie
    Yossie Posts: 2,600
    The directional thing is also a safety issue - if you look at the way the pads are on your bike when they are set up right, the closed side of the brake shoe is pointing forward and the small allen bolt is at the back: this means that if the bolt comes out there is no chance that pad can be forced out by the braking action leaving you ploughing into a hedge with no brakes.

    +1 for Wheelspinner's comments as well.

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