Home Forums Bike Forum Flat mount calipers not sitting at correct diameter

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  • Flat mount calipers not sitting at correct diameter
  • Mowgli
    Free Member

    I’ve noticed that both calipers on my Tempest are sitting 4-5mm too far in on the rotors, such that the outer 4-5mm of the disc isn’t contacting the pads at all. The pad is only sweeping about 2/3rds of the rotor width with the outer 3rd left untouched. They’re Rival calipers with 160mm rotors. Has anyone else had this – can the calipers be shimmed up/out perhaps?

    thols2
    Full Member

    Put some washers under them.

    Daffy
    Full Member

    If they’re post-mount, as above, there’s usually some domed washers that’re required between the caliper and the mount.

    If it’s flatmount/direct mount there’s supposed to be an adaptor ~5mm thick under the calliper.

    Something like this:

    Link to adaptor

    Mowgli
    Free Member

    It’s a flat-mount frame/fork and flat-mount calipers, and I’m using front and rear mounts already – not bolting the caliper direct to the frame/fork. It does look like a 5mm spacer would put the caliper at the right level though.

    Daffy
    Full Member

    I think I’d be asking PX about that.

    igm
    Full Member

    It’s not a mount for a 140 disc is it?

    The 20mm difference is only 10mm radius and it’s difficult to judge from the pictures but that could be 10mm?

    If it’s only 5mm then I’m wrong.

    Better, provided the dis doesn’t foul the calliper, that the pad is a little far on than a bit off the disc.  The former is what you see and isn’t worrying unless it’s catching the arms. The latter means uneven pad wear which eventually stops the brake braking as the pads press on each other beyond the disc.

    jameso
    Full Member

    Wrong adapter shape/brand for the brake? Seems odd that both F+R are off by the same amount.
    Also you have a Sram caliper on what looks like a Shimano rotor – I don’t if the pad depths are the same and pad depth needs to match or be less than the rotor track depth.

    Mowgli
    Free Member

    It does seem that adapters from different brands are slightly different shapes. Some even come supplied with shims it seems. So much for ‘standards’! Suspect it’s a case of mis-matched calipers, adapters and rotors ending up with a bit of tolerance stack up.

    Daffy
    Full Member

    The adaptors seem correct and correctly fitted according to the SRAM instructions for flat mount.

    The only way that could happed is if the calliper was sitting too low, thus moving it nearer the bike, but if it was THAT low, the disk would foul the inside of the calliper.

    How much space is there between the highest portion of the disc and the entry/exit from the calliper? it should be 1-2mm. If it is the right distance, the only thing it can be is the pads.

    Onzadog
    Free Member

    I did see the other day, that Hope have diagrams of the mount dimensions on their site. Might be worth having a look and a measure up to compare.

    Mowgli
    Free Member

    I’ve stuck some washers under the calipers which has sorted it for now. I think you might be right about the pads – these aren’t Sram originals, but some cheapo ones from one of the German sites which could be slightly out of spec. Can’t remember what brand. Will compare with some proper ones.
    Cheers!

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