As the title says, can a Shimano BL-M425 brake lever be used with a BR-M615 caliper? I have an old BR-M447 caliper that I want to replace, and I was wondering if it would be possible to exchange it for a BR-M615 while still keeping the old levers.

  • Could you flesh-out your question more? This got flagged as low-quality because of length or content.
    – Criggie
    Sep 18 '16 at 20:07
  • In addition to whether the oil displacements are the same, this is also asking what the consequences are of using a mismatched hose, since BL-M425 uses BH59 and BR-M615 uses BH90. I think the brake hose mismatch probably makes this a no-go, but I can't say I know what would actually happen if you tried. Oct 20 '16 at 22:11

Because the hose attachments are the same, you can do it, but the performance of the brake is going to suffer for the following two reasons:

  1. As pointed out by Nathan, the hose inner diameter is different for the recommended hose for each component
  2. The desing of the levers of both types of brakes are a bit different as well, the newer master pistons at the levers push a bit more oil.

So you can assemble the brake and it will work, but the feeling at the levers is going to be a bit weird, and you migth not get the full stopping power out of them.

Finally, you migth also want to update the rotor, the newer ones are designed for the narrow type rotor, you can check the "Disc brake caliper and Rotor compatibility" on the following link: Shimano docs

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