Mineral oil shot out my road shifter, bad? (and how to reduce throw on 105)

Decided to rebleed my front 105 R7000 brake with genuine Shimano mineral oil, suspected the old oil had gotten dirty (it looked dirty) causing its boiling point to decrease – had gotten nasty brake fade down a long descent.

Got lot longer throw after the bleed, even with a 9 mm shaved down brake block. Then tried a 7 mm thick bearing as a block and when I tried to push out the brake pads post bleeding again (forcibly, throw had gotten too short and reservoirs were now overfilled), fluid shot out from the reservoir in the shifters somehow and the brakes lost nearly all power.

I rebled the brakes, pushed out the pads again and they seems to still work ok. Then I took the wheel out, moved the pads a tad closer together squeezing the lever gently, and reinstalled the wheel – voila much shorter throw (for now). No problems during hard braking either.

Will my front brake suddenly fail now or do the Shimanos have a weep port or some sort of relief mechanism?

Aand someone else managed to do the same thing, looks like I’ll be fine: https://singletrackworld.com/forum/topic/ultegra-shifter-leaking-after-pushing-pistons-back-fixable/

It just sounds like you overfilled the system. The reservoir isn’t intended to resist pressure so the excess fluid leaked out. Once you bled them properly and got the air out, they worked properly. If they’re working properly now, there’s no reason they will suddenly fail.

suspected the old oil had gotten dirty (it looked dirty) causing its boiling point to decrease – had gotten nasty brake fade down a long descent.

Looking dirty won’t actually cause the boiling point to change. Having water in the system will, but Shimano use mineral oil and the water won’t mix with the fluid, it’ll just sit at the lowest point in the system. It won’t make the fluid look dirty.

Brake fade in the true sense is caused by the pads overheating, not by the fluid boiling.

My r8000 have two adjustments, one adjusts lever reach and the other adjust the throw, not sure if the r7000 levers have the same. It’s a Allen key on the side of the shifter body.

Thols: Thanks yes think I’m OK, fluid seems to have been forced out under the diagraph/seal (which you can’t buy so puncture it and you need another shifter – read one case where it was punctured in which case bleeding didn’t fix the brakes :S).

Brake fade in the true sense is caused by the pads overheating, not by the fluid boiling.

Isn’t that dependent on pad material? I hear resin pads can overheat and lose power, whereas sintered pads (which I run) generally don’t, but put more heat into the caliper/mineral oil. Dirt/crud particles in the oil, and possibly non OEM oil according to Shimano “all mineral oil is not made equal”, could lower boiling point from what I’ve read, but haven’t seen a proper explanation. In any case running 160 mm MT900 rotors with ice-tech and freeza + OEM oil + sintered finned Shimano pads so should be fine now, just hope they don’t eat my precious rotors too fast.

@akira: R7000 doesn’t have free throw, but you can emulate it by moving the pads closer together without the wheel installed (at your own risk – make sure the pistons don’t pop out). I hear bleeding the R8000s with the free throw set to max can let you move the bite point in, otherwise it only lets you increase it from a default setting.

Yeah to be fair the free throw adjustment doesn’t really do very much.

Isn’t that dependent on pad material? I hear resin pads can overheat and lose power, whereas sintered pads (which I run) generally don’t, but put more heat into the caliper/mineral oil.

It’s a slightly pedantic point. All brake pad materials will fail if they get hot enough, but metallic pads will handle higher temperatures than organic pads. If the pads are overheated, they lose friction and you will lose braking power. You will still have a hard feel at the lever, but it will feel similar to having pads that are contaminated by oil. That’s the technical definition of brake fade.

It’s common to also call boiling fluid “brake fade”, but it’s a different thing. In that case, the brake lever will pull back to the bars because there’s vapour in the system. It’ll feel just like the brakes need bleeding. Pedantically, that’s a different thing to brake fade, but it’s common to call both things “brake fade”. However, if you are trying to fix brakes that don’t work, you need to understand the cause of the problem. If the pads have been glazed from overheating, changing the fluid won’t make any difference. Still, refilling with fresh fluid and giving them a bleed is never a bad thing to do.

It’s a slightly pedantic point. All brake pad materials will fail if they get hot enough, but metallic pads will handle higher temperatures than organic pads. If the pads are overheated, they lose friction and you will lose braking power. You will still have a hard feel at the lever, but it will feel similar to having pads that are contaminated by oil. That’s the technical definition of brake fade.

My understanding is that sintered pad fade in practice doesn’t happen/is very limited and that the oil will boil before this happens? Hence the extra importance of ice-tech + freeza rotors + fins with sintered pads.