Does anyone know the differences between BH59 and BH90 brake hoses?

I’m trying to work this one out too, so maybe we can share some info…

After a couple of hours digging thru online stores and Shimano tech docs I’ve come to the conclusion that the latest Shimano brake systems like XT M785 and SLX M666 use BH90 hose, and these fittings where it attaches to the lever – ie. a short nut and silver barbed hose insert.

However, the older versions like XT M775 and SLX M665 use BH59 hose, a longer shroud nut, and a gold coloured insert – see here . As far as I can see, the olives are the same, but can’t be sure.

I’m interested in whether the two systems are compatible – ie. can I attach a BH59 hose with the ‘old’ fittings on it to one of the ‘new’ levers?

Sorry for the thread hijack Rampage, but sounds like we’re kinda after the same thing…

The new hose is the same external size but is more narrow internally. They both use the same olive but different inserts. So the old hoses will fit new levers but why would you want to? The new hose is designed to give better braking. I can understand fitting new hose to old brakes but not the other way round.

Thanks for explaining that Mister P. In answer to your question of why I’d want to use old hose with new levers, I’m trying to get the servowave functionality on the cheap by just buying some new levers, and keeping my existing (non-servowave) hoses and calipers. Do you think that would work?

I bought the new SLX levers to put on my old SLX calipers.
I think I will just buy the new calipers as well!
Thanks.

perthmtb, as your first post I found out the same.
I did try the old hose and connecting items to fit fine, the threaded nut sticks out further than the new one. Also the brakes were spongy but this might be because I didn’t really bleed them much.

Hi Rampage, good to know! Was the longer shroud nut sticking out a problem, or did the rubber cover hide it?

Bit worried about the sponginess – could just indicate air got in there as you switched them over, or potentially more worrying scenario that the old fittings weren’t sealing properly at the lever. Was there any sign of leaking oil around the fitting, or did it look like a good seal?

Anyway, good to hear that you’re going down the route of new calipers, but unfortunately my budgetary controller won’t allow me, so I’m still thinking of a mix n match approach!

The nut sticking out was just cosmetic really. The rubber boot wouldn’t fit on though.
In the end I put it back to original and bought a new M666 brake and sold the M665!
There was no leaking and everything seemed to work as it should.

Thanks Rampage. As you may have seen from my more recent threads, I eventually gave up on the mix n match approach, and have ordered a set of M666 also. Not cos I didn’t think it’d work, but cos the budgetary controller took pity on me and released a few more pennies!

I forgot to mention in my earlier reply that there are actually two types of SM-BH90. There are the type that come with a straight connector at one end and a banjo at the other. Then there is the type with straight connectors at both ends. So if you are fitting new hoses to older brakes such as M775 XT you need the second type.