After 2 years calipers no longer retract fully (pistons) causing annoying rubbing sound. What options do I have to upgrade it (perhaps something more durable) providing I still want to reuse the same hose and handles.

If possible just to replace calipers - screw off - screw in, attach the same hose - enjoy.

Would I have to bleed it, use mineral oil?

  • What maintenance have the brakes had in that time. BL MT400 are normally pretty reliable, replacement may not improve things.
    – mattnz
    Commented Sep 10, 2023 at 21:46
  • Can you add some clear photos? Remove brake pads from caliper and show them, and also a shot into the caliper showing the pistons (though don't extend them without pads, and a rotor or a spacer between them)
    – Criggie
    Commented Sep 10, 2023 at 21:54
  • 1
    However your quoted code of BL-MT400 is for a hydraulic brake lever - which part is not retracting? Also, there is no cable because this brake is 100% hydraulic so the black wire thing is a pressure hose, or just "hose" not cable.
    – Criggie
    Commented Sep 10, 2023 at 21:57
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    @Criggie - I have edited the post and made changes according to your suggestions. Thanks Commented Sep 11, 2023 at 10:09
  • Have you tried just cleaning the calipers?
    – Burki
    Commented Sep 12, 2023 at 9:51

2 Answers 2


You can replace just the calipers. If you want to re-use the hoses, your options are any post-mount Shimano calipers with an in-line style caliper hose connection.

If the hoses were the minimum acceptable length now, you may need to replace them anyway since pairing the old barb and olive with a new, different brake doesn't always work and isn't how the system is designed to work, because the olives conform in place as they're tightened and putting them in new calipers can result in leaks (doesn't always but can). It's better to trim the end and start fresh even if you're reusing the hose.

There is no getting around the need to bleed the new systems and yes you'll use Shimano mineral oil or another compatible one.

  • I am taking it that I need calipers that are compatible with BH59? epicbleedsolutions.com/blogs/articles/… Commented Sep 11, 2023 at 10:18
  • Something like Shimano MTB BR-MT500 would probably make sense? Commented Sep 11, 2023 at 10:37
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    @PekotskiBit MT500 is a good utilitarian choice. It doesn't strictly have to be a brake Shimano designates as for BH59. BH90 is stiffer and gives a more on/off type feel with less lever throw, and the brakes that they want perceived as higher performance all purportedly need it, but nothing bad happens if you mismatch. You would need a barb/olive for BH59 though if that's what you have now. Commented Sep 11, 2023 at 14:39
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    @PekotskiBit BH59 has a slightly larger golden barb compared to BH90 silver barb. Olives are the same. The hose is interchangeable otherwise. BH90 is quite new, all the brakes used to use BH59 under 10 years ago, road and mtn
    – Noise
    Commented Sep 11, 2023 at 15:53
  • Thanks @NathanKnutson - appreciated. Commented Sep 15, 2023 at 22:39

I'm not a bike expert but maybe lubricate it or use WD40? Or replace it if it's really old.

  • Welcome to the site - this reply has attracted downvotes because it doesn't really address the question, which is about a hydraulic brake caliper. You really don't want oils near a brake surface like the rotor and pads, so this is dangerous advise.
    – Criggie
    Commented Sep 11, 2023 at 18:54

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