I've been running M7100 callipers with older levers for years. A couple of years back I cracked a piston on the rear and replaced it with another M7100 which has recently started micro leaking.
I fitted a new one today, 30-40 minute job maybe, I've done plenty before, but try as I might I couldn't get the lever really firm. I re-bled with the bleed block several more times with the same result.
With the wheel back in I could get the lever to the bar if I pulled really hard (never been able to do this before).
In the end I tried another set of pads and even bled again with the pads and pad separator in; again the same result.
I accidently pulled the lever with the pads in, but pad spacer out and a funnel of oil attached to the lever and somewhat overfilled the brake (by normal standards) but now everything feels balanced.
Safe to ride? I was hoping to go out tomorrow. I'll have a spin around the block to bed the pads in (replaced the front too).
The new calliper didn't include a bleed block so I don't know if anything's changed size-wise.
To be a tad more succinct, the previous 3 M7100s I've bled have all have a virtually immoveable levers after a single bleed with the bleed block. This new one has noticeable travel translating into more travel before biting with the wheel back in - multiple re-bleeds haven't resolved this.
Overfilling (which I did accidentally whilst frustrated) has balanced things up nicely and it works well But will it end in a ball of flames?
It’s funny you should say that as I replaced my non series SLX equivalent MT401 levers with MT 501 and had exactly the same experience. Apart from I replaced the levers not the callipers . I have re-bled several times and even drained all the fluid out, removed the calliper and hung it every which way trying to ensure all the air worked it’s way out, but I cannot get either the front or rear to feel solid. I left the bike out in the sun for a few hours over the weekend and when I went to squeeze the rear lever it almost went to the bar so there must be air in it somewhere. Doesn’t help you I’m afraid. I gave up in the end and am just riding it like that, they feel more solid in use…🤷♂️
I actually always overfill my Shimanos on a bleed.
I don't use a bleed block.
I pump the pads together a smidge, then bleed.
Pushing the pads back out just enough to clear the rotor before refitting gives me a rock solid bleed and a very powerful feeling... feel.
Been doing it like that for years. No balls of flames yet.
Thanks. It's probably fine. It's the marked difference between 2 identical callipers that's thrown me.