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My MTB is vintage 2005 with XTR ST-M685 dual levers and disque brakes, BR-M966 fork post mount and BR-M965 at the rear. The BR-M966 has started leaking oil from the piston. Finding a replacement caliper seems to be impossible and I am thinking about putting abother model in the front (e.g. an BR-M820 Saint post mount). I am a moderate cyclist with a 26" hardtail.

I have come across a helpful post on Is the banjo bolt the same between the Shimano XTR and Shimano Saint rear brake caliper? with a technical discussion on hoses, but is it a risky approach? Anybody who can share their experience?

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  • If you are concerned about hose compatibility, why not just replace the hose too?
    – Klaster_1 Нет войне
    Commented Jul 23, 2021 at 19:43
  • The hose is not the issue, I think I can get this working. I am more concerned about braking itself after I have installed the M820. Will the oil suffice to push the new pistons? Do I need to worry whether the old rotor and the caliper will work together?
    – Phil Royceman
    Commented Jul 23, 2021 at 21:40
  • Chances are there won't be any issues since all Shimano calipers are generally considered cross-compatible. Maybe such old calipers are different, but I would have tried this option first.
    – Klaster_1 Нет войне
    Commented Jul 24, 2021 at 7:09
  • Ok, I think it makes sense to try it first. The alternatives would be rather expensive. Tx.
    – Phil Royceman
    Commented Jul 24, 2021 at 10:34

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Replacing the BR-M965 will need an IS adapter because it's one of the adapter-less Shimano brakes.

The banjo bolt between these two brake generations is the same so that should be fine. That would not be the case in any of the many combinations where it's not the same.

In practice lever and caliper combinations not intended by Shimano like this are basically never a problem in terms of fluid movement or anything else. Shimano may say otherwise.

Another approach if you have even a little hose slack would be snip them and use one of the more XC-ish calipers that take a barb and olive.

The rotor/caliper clearance considerations are rarely meaningful unless some part of the frame/fork is weirdly dimensioned. That's true of most brake changes.

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  • Thanks for your feedback and for assuaging my concerns re compatibility. The M820 Saint is available as a PM for front, see bike-discount.de/en/buy/…, I dont need an IS adaptor for my PM fork, or do I? As for the banjo, can I just use the existing hose from the M966 caliper and plug it onto the Saint?
    – Phil Royceman
    Commented Jul 30, 2021 at 14:39
  • You won't need an adapter for the front, only to replace the rear 965. And yes, I looked at the EV documents for 965/966 and M820 and the banjo and banjo bolt type appears to be the same. Those little o-rings at the banjo are good to replace while you're in if possible on a brake this old.
    – Nathan Knutson
    Commented Jul 30, 2021 at 15:43
  • Good idea, this o-ring replacement. Thanks! I checked them and indeed they are the same for both M820 and M966 (Y-8SY28000). Now all I need is some idea what to do about the raining in the Alps :-)
    – Phil Royceman
    Commented Jul 31, 2021 at 11:02

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