Ultegra 8100 backward compatibility

Anyone know if an R8000 lever (ST-R8070) will work with a new R8100 disc brake calliper (BR-R8180)? I don’t know any reason why it wouldn’t but looking to confirm.

I need to replace a calliper and wondering if I’m better off waiting for aftermarket release of the new one. I have some doubt the extra 10% width between pads will make any real world difference but willing to give it a try.

Disc brake rub is the bane of my bike maintenance efforts.

This was discussed in the Nerd Alert podcast and I think the answer is no. The new levers have more fluid for the new brakes.

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I would be surprised if the new calipers were actually available anywhere yet?

This helpful and somewhat long document should help. I used it to figure out a franken brake set on my MTB.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://productinfo.shimano.com/download/pdf/com/2.7/en&ved=2ahUKEwiZ4pnp4oLzAhUoxzgGHbjHBwEQFnoECCMQAQ&usg=AOvVaw2DZI8VSB9PnmejV7VN-GIb

They are not compatible. The new calipers have 10% more pistons travel so they require a lever that pumps more fluid, to move the pads to squeeze the disc.

Thanks for the link @RyanMc

In terms of availability, the R8070 don’t seem readily available at the moment either so I’m just thinking to either go for new on eBay/grey market route or wait for new calliper to be released.

It looks that this is the relevant section and if I read it right that ST-R8070 is compatible with new DA calliper (BR-R9170). The new Ultegra aren’t listed but I think it’s likely that if new DA is backward compatible so will Ultegra be.

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@Mini4wdking @Hamish_Moffatt

Thanks - if the distance between pads is 10% wider, then might it be reasonable to think that ‘max braking’ would just come later on the lever pull? So long as this point where pads are fully engaged with disc is before the end of lever’s range it should be ok?

Sorry if I’m simplifying too much based on my limited understanding.

It depends on how much more liquid is pumped by the new lever, every mm of travel of the lever.
It resembles the issue when in the mid '90 they introduce the MTB V-brakes that had a different cable pull, compared to the existing cantilevers. The old levers, made for cantilever brakes didn’t have enough travel to pull a sufficient amount of cable…
Or maybe, as you say, this time it will just result in a longer travel, but without affecting maximum brake power.
Who knows…
This definitely needs some testing!
But Shimano clearly states that this will not be compatible (that could also mean that the system will brake, but the travel of the lever will be too long to ensure a safe operation in every circumstances).

You’d think that the system would have to be bled perfectly with no air in whatsoever to have a chance of working properly

Have you seen Shimano say they’re not compatible someplace? It would seem to contradict above doc that says Ultegra 8000 levers compatible with DA9100 callipers

DA9100 calipers belong to 11s “old” series, that is the same as the Ultegra 8000.
The new 12s Ultegra 8100 and Dura Ace 9200 that are compatible each other, are not compatible with old 9100/8000 series.

Ah yes you are right - sorry my mistake & I see your point now

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(I’m catching up on old threads…)
10% extra pad clearance doesn’t necessarily mean that older levers will no longer work.

What it means is that the piston seal has been reengineered so it self adjusts to give that extra 10%. And the caliper is wider and pistons longer to accommodate that extra travel.

The piston diameter doesn’t necessarily need to change to get that extra 10%.

If the piston diameter hasn’t changed, then the newer caliper should work with older levers- even mountain bike levers. Obviously, with no adjustment, the levers would come closer to the bars before the pads hit the discs. This might result in the levers bottoming out on the bar. Current Ultegra and Dura Ace levers (and some mountain bike levers) have a free stroke adjustment that one should use to move the bite point farther from the bar back to where it normally was.

TIL that many 11-speed road bike levers already have Servo Wave.