Anyone know anything about disc brakes?

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  • Then going shimano hydraulic.

    Yes lad.

  • Hang on, what's the point of 4 pots anyway?

    It allows a larger, longer pad to be used while still having the load from the pistons spread evenly over the pad. It's a pretty marginal benefit, but there is some.

  • Only acceptable 4 pot caliper

  • Yup, 4 > 2.

    Many MTB 4 pot (shimano, magura, formula, sram) have more pad area too, so little bit more meat = lasts more than a day in the mountains.

    Harder to get 'just so' as a longer profile pad = has to be set spot on so you don't get pad rub at the edges of it. Magura E4 (right name?) that come on loads of bikes now a bit of a pain to get centred.

  • Only acceptable 4 pot caliper

    Only hydraulic caliper I've ever needed:


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  • I love that you're still rocking m755's. My pal had them on his bike in 2002ish and I don't think I've ever found a Shimano brake that was as powerful as them since.
    I see them come up on ebay quite often and I'm always tempted.

    This guy on insta some how found a haul of NOS. Where have they been all this time?

  • What pads for these brakes and where can I buy them?
    Pls thanks.

    (Trp e-23 e MTB)


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  • Awesome. Ta.

  • The connoisseurs choice. So burly. They look like motorbike calipers.

  • look like motorbike calipers.

    As I said, the M755 is a scaled down motorbike brake, maybe even more in the levers than the calipers

  • What is it that makes them like a scaled down motorbike brake? I’ve perhaps naively thought that any hydraulic mountain bike brake is like a scaled down motor bike brake. Curious to know the difference now.

  • What is it that makes them like a scaled down motorbike brake? I’ve perhaps naively thought that any hydraulic mountain bike brake is like a scaled down motor bike brake

    Obviously there are many different designs, and all bicycle brakes are derived ultimately from motorcycle designs because moto came first. What distinguishes M755 and similar brakes of that early generation is how little the layout changed from common utility moto brakes (not swanky race brakes with their remote reservoirs and radial master cylinders). Over the next twenty years, there has been more divergence as bicycle designers seek light weight and compactness to suit the constraints of human power, rather than just shrinking a basic moto layout.

  • Was moving my 105 R7020 bits over to the new bike. Bleeding my brakes as normal. Rear was done in a flash and all good there. Front one, for the life of me I couldn't get all the air out of the system and it just feels mushy. When I put everything back on, lever goes all the way to bar, no sharpness in the braking then pistons seemed to reset very slowly after braking. I had a look around the shifter and noticed this crack that isn't on the left shifter. Is this the cause of my pain, or is this a superficial crack and there is something else amiss?


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  • If you want Shimano compatible flat-mount 4-pot brake calipers, then Hope RX4+ fit the bill. Swapped my ultegra calipers for them last year and they're great.

  • New lever, the flange connecting bolt should only be tightened to 5-6Nm.

  • So put too much torque down? I used a light touch to cinch it down, just i had done with the left. Guess I'm gonna need to get a replacement. Bugger

  • So put too much torque down?

    Not necessarily your fault, that seems to be a common failure on 7020/8020 levers. There's a grub screw in the side which acts as a weak point/stress riser/crack initiator


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  • Yeah, the interwebs seem to indicate it's a poor design. But one that seems to also afflict GRX as well. So it feels like playing lottery with whatever option I can stomach to overspend on

  • how did you get on with this? I have the same thing, need FM calipers and flat bar levers. I can't even fit an adaptor in my frame, so keen to know a good combo.

  • It'll be fine.

    New titles of this topic.

  • You probably fucked the olive.

  • So put too much torque down?

    Or the olive misaligned inside causing it to be too tight.

  • Possible, at any rate, new shifter is the order of the day

  • Ok, don't want to brake this like I did the old shifters. Screwing this on, and there's a fair bit of resistance now. Cant tell if it's up the 5nm limit. Does this have to sit flush with shifter or can I stop here? Worried about cranking down and splitting it, can't afford another mishap


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Anyone know anything about disc brakes?

Posted by Avatar for Sanddancer @Sanddancer

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