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Thread: Disc caliper spacers...

  1. #1
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    Default Disc caliper spacers...

    Pardon the stupid question:

    I've got a PM fork that is meant to work with a 160mm rotor. I also have Shimano post mount brake calipers.

    I have a Shimano adapter that should mate a 160mm PM fork to a 180mm rotor. The wheel in question has a 180mm TRP centerlock rotor mounted.

    After the first ride, the wear pattern on my rotor shows that the caliper is around 3mm too far outboard of the rotor radially.

    My solution, for now, is that I have filed the adapter to fit, such that it brings the caliper inboard radially.

    Am I missing something? Are rotors and adapters specific to one another in some way?

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    Default Re: Disc caliper spacers...

    Wheels Manufacturing and November, I'm sure there are more, sell spacers for CLD hubs to move the disc away from the hub. You should be able to install a spacer or two and put your caliper back where it originally was. Moving the caliper is for fine adjustment, sometimes you need the rotor to move.

    I have a disc brake gravel bike with two sets of wheels, one with 6 bolt and the other CLD. I shimmed the CLD to match the 6 bolt so I can swap wheels easily.
    Weight Doper

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    Default Re: Disc caliper spacers...

    OK so the geometry of moving a post-mount caliper (or any mount for that matter) out for a 20-mm larger rotor isn't as simple as it seems. I recently found this out when retrofitting a frame designed for a 140-mm rotor with a more sensible 160-mm rotor.

    I was switching from Sram to Shimano brakes but purchased a Sram/Avid adapter. Luckily I tightened down the longer side of the adapter first and noticed that the other ear of the caliper was floating several millimeters off the other side. If I had simply tightened both sides I would have stressed the crap out of the caliper and maybe cracked it.

    In regards to your situation, I'd try a Shimano rotor first. And then if you have filed the adapter properly, both sides of the caliper should land equally as you tighten the bolts. If that adjustment also offsets the caliper side-to-side, you may not have filed your adapter plumb/level/true. And also, how do you know if your brake shoes are parallel and if that 3-mm offset is due to caliper position or wonky pad-to-rotor contact?

    I hope you figure out how to enjoy the fuck out of your 180-mm rotors because they rock.
    Trod Harland, Physical Educator

    Not everything that is faced can be changed, but nothing can be changed until it is faced. — James Baldwin

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    Default Re: Disc caliper spacers...

    post a pic eh?
    Just sounds like the caliper is sitting “high”, but 3mm is no big deal. Just note your pad wear.

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    Default Re: Disc caliper spacers...

    shimano has two thickness of brakepads

    think normal J04c versus the hybrid b01s

    your rotor might be thicker to compensate for that. Lots of the tektro/trp brakes run the b01s pad size

    swapping to a nicer shimano rotor should fix this should it be the issue. Finally, so long as you are not notching the top of the pads it should be ok

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    Default Re: Disc caliper spacers...

    Thank you for the thoughtful responses.

    I started looking at my brake and rotor closely because the brake wasn't doing what I expected as well as it should. I noticed that the caliper was not aligned with the rotor radially, but the real problem turned out to be that one of the pistons was cracked, and skewed in its bore, hampering brake function.

    Thankfully, my LBS had a replacement caliper in stock, and hopefully it will stop raining enough for me to ride it soon.

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