Shimano Hydraulics - XT & SLX - intercompatibility and bleeding

[Custom24]

Two questions

1. Will an SLX M666 Brake Lever work with an XT M785 caliper?

2. I see a complete "fully bled" set of XT caliper and Lever for sale from Chain Reactions. Why would that stay "fully bled" in the post? Shimano advise somewhere to not turn the bike upside down because I think of introducing the need to bleed the brakes.

Background is on my MTB currently the front brakes are XT M785 and the rears are M666 SLX. The rear caliper is broken, and I'd like to upgrade, the caliper at least, to XT. I'm not sure if it is going to be more cost effective to just replace the entire rear brake system (£60 approx from Chain Reactions currently), or just the caliper (£30 from various, but would then have to buy a bleed kit and oil separately)

I've not bled hydraulics before.

 

[Cubist]

Question 1. Yes.
Question 2. Because sometimes you get the component parts and have to assemble them yourselves. Do t worry about turning your bike upside down, it only affects the performance for the first stroke of the brakes.

You can get some astonishing bargains if you search around.

Currnt Deore (M615) SLX (m675) and XT (M785) are virtually identical. M666 mysteriously changed into M675 overnight. I have both and they are identical. Deore don't have tool free reach adjust, SLX have tool free reach adjust and XT have tool free reach, and free stroke adjuster screws. XT reservoir caps are shiny, like chrome shiny.

In operation they all feel the same good powerful and effective brakes. I have both types of SLX and one bike with XT.

Bleeding is simple. You need a syringe, some mineral brake oil, a piece of narrow gauge plastic tubing. You can get a kit off eBay from epicbleedsolutions for next to no money.

To fit the new reservoir/lever use an 8mm spanner to unscrew the inline connector at the lever end. Use a sharp Stanley knife to cut off the last cm or so of hose that has the old olive and insert stuck in them. Make sure the cut is absolutely square. Slide the plastic cover back onto the hose if you took it off, then the inline connector. Then the new olive. Then hold the end of the hose in a pair of pliers and push the barbed insert into the end, tapping it home with a small hammer whilst holding it firm with the pliers. It must fit flush.

Now push the end of the hose into the female end of the reservoir, slide the olive up to the end, and then hold it as firm as you can as you screw the male end of the inline connector into the female. To visualise what is happening, the flat end of the insert is pushed up against the inside face of the reservoir, lining the hole up with the outlet. The olive is soft brass and is squashed into place along with a bit of the hose, forming a hydraulic seal compressed as the two halves of the connector come together. Tighten it as much as you can with hand force, but don't overdo it with long tools, it is possible to knacker the connector.

With your bike upright in a stand loosen the reservoir /lever clamp and turn it horizontal. Use a star key/ t10 to undo the reservoir cap screw and put it somewhere safe. Tie a rag around and under the reservoir as you are goin g to spill some fluid.

Take the pads out of the caliper and put some folded card between the Pistons. Use gentle pressure with a plastic tyre lever to push the Pistons back into their housing, or if you aren't hamfisted, use a flat bladed screwdriver between the pads before you take them out.

Next, put an 8mm ring spanner around the bleed nipple on the caliper, and fit the Syringe half full of mineral oil onto the nipple. Turn the ring spanner to open the bleed nipple a half turn, and use the syringe to force fluid into the system. This will push any air up the hose and out of the reservoir port. As soon as you are pushing clean fluid out of the port, turn the ring spanner to close the nipple, then replace the reservoir port cap screw.

Clean up with IPA and replace the pads. The first time you put the wheel back in you'll need to gently pump the lever to push the Pistons to the right position, and that's it.

 

[screenman]

We have a cup that screws onto the reservoir, great bit of kit not a drop spilt.

We bought some XT fully bled and then had to shorten the pipes. I have always bled them the same as I do car brakes.

 

[Cubist]

We have a cup that screws onto the reservoir, great bit of kit not a drop spilt.

We bought some XT fully bled and then had to shorten the pipes. I have always bled them the same as I do car brakes.

That cup is included in the epic bleed kit I think. Much quicker to force bleed via the caliper imho.

 

[screenman]

You could well be right, just old habits. As you know either way it only takes a few minutes to set up, bleed and put the tools away again.

 

[Custom24]

Question 1. Yes.
Question 2. Because sometimes you get the component parts and have to assemble them yourselves. Do t worry about turning your bike upside down, it only affects the performance for the first stroke of the brakes.

Thanks Cubist

I should have been clearer - I meant "why would they stay bled in the post" ( meaning "if Shimano advise against even turning the bike upside down, then surely sending the whole thing through the mail can't be good?"). But your answer reassures me anyway that a bled system packaged in the mail will still be bled when it reaches me. It makes sense - otherwise there would have to be a leak or something. And yes when I've turned the bike upside down, a couple of strokes of the lever has returned things to normal. I just always thought that I really ought to bleed it as well, for some reason known only to Shimano.

Your instructions above seem to me to be for keeping the caliper and replacing the lever, whereas it would be the opposite.

Any thoughts on the problem that led to the need to replace the caliper in the first place? Here Do you think the caliper is written off? How to prevent a recurrence - how to avoid the piston getting stuck in the first place? The bike had been sat up for a while because I've been using the road bike instead, so maybe that did it.

I'd not noticed any difference between the SLX and XT really, I just assumed that the XT was better build quality, and hoped that by upgrading I'd avoid the issue that led to the SLX to fail. But that might be just nonsense. I suppose the XT on my MTB has just been subjected to less gunk than the SLX because it's on the front rather than the rear, hence why it's still working and the rear SLX is not.

Do you use the genuine (and expensive) Shimano mineral oil, or something else?

 

[Cubist]

Thanks Cubist

I should have been clearer - I meant "why would they stay bled in the post" ( meaning "if Shimano advise against even turning the bike upside down, then surely sending the whole thing through the mail can't be good?"). But your answer reassures me anyway that a bled system packaged in the mail will still be bled when it reaches me. It makes sense - otherwise there would have to be a leak or something. And yes when I've turned the bike upside down, a couple of strokes of the lever has returned things to normal. I just always thought that I really ought to bleed it as well, for some reason known only to Shimano.

Your instructions above seem to me to be for keeping the caliper and replacing the lever, whereas it would be the opposite.

Any thoughts on the problem that led to the need to replace the caliper in the first place? Here Do you think the caliper is written off? How to prevent a recurrence - how to avoid the piston getting stuck in the first place? The bike had been sat up for a while because I've been using the road bike instead, so maybe that did it.

I'd not noticed any difference between the SLX and XT really, I just assumed that the XT was better build quality, and hoped that by upgrading I'd avoid the issue that led to the SLX to fail. But that might be just nonsense. I suppose the XT on my MTB has just been subjected to less gunk than the SLX because it's on the front rather than the rear, hence why it's still working and the rear SLX is not.

Do you use the genuine (and expensive) Shimano mineral oil, or something else?

They are more or less closed system, so only a leaky seal should see them needing to be bled.

Shimano don't sell spares or rebuild kits, and piston seals are the main culprits in calipers. Given they are so cheap I would source a Deore or SLX caliper. The fitting of the caliper would be the same. Forcing fluid in via the bleed nipple will fill the caliper then go up the hose into the reservoir.

Any mineral brake oil will do. Halfords sell small pots for about a fiver, or you can use Citroen hydraulic fluid for about a tenner a litre. Different colours though, so you won't get a warranty replacement home.

 

[Cubist]

I've just read your other thread and it does sound like you farked the piston!