Questions About Upgrading Shimano Group

[david]

Hi,

Thinking of replacing my older Dura Ace Di2 11-speed with Ultegra 12-speed.

Pretty sure everything will be doable, except I'm uncertain about the brakes.

I currently have the BR-RS785 calipers. My biggest question is what are the appropriate caliper mount adaptors for my frame? I've done some research, but it's a bit confusing and I don't want to buy a new group without first being absolutely sure the new calipers will fit my frame.

The front appears to be a flat mount (Enve fork). I intend to stick with 140mm rotors front and rear. Based on this fork, it seems to me that there should be an adaptor that will work. If you can help me identify which one, that would be great.

The rear might be trickier. As best I can tell, the frame mount is IS standard. Since this is an outdated type of mount, I'm unsure if there is a mount that will work.

I wish it were as easy as using the adaptors I currently have. But my understanding is that today's calipers have narrower mounting holes than the BR-RS785, thus requiring new adaptors front and rear.

Any help you can offer will be appreciated, especially if you can identify the part number of the correct adaptors.

Thanks.

[prototoast]

You can use your existing calipers with new shifters.

If you don't want to do that, IS to flat mount adapters exist, e.g., https://www.aliexpress.us/item/3256806250749603.html.

[david]

Originally Posted by prototoast

You can use your existing calipers with new shifters.

If you don't want to do that, IS to flat mount adapters exist, e.g., https://www.aliexpress.us/item/3256806250749603.html.

Wow, hadn't thought of that. It's an option. But if I do make the switch, I might as well get new calipers. Supposedly easier to bleed. And there's also that 10% extra clearance!

Thanks.

[benb]

These are so confusing.. what is it called when the frame/fork just has the mounts right there and the caliper mounts straight onto the posts?

Like flat mount but with no adapter required, all our MTBs are like that.

edit: Looks like Post mount, and road bikes have gone away from that to allow smaller rotors.

[david]

I looked at the Ali Express adaptor and did a search for IS to flat mount adaptors. I found two more. The adaptors I've found are not compatible with 140 rotors, so I'd need to switch to 160. Any reason to be wary that this might introduce other compatibility issues?

[david]

Also, is it true that the newer calipers have narrower mounting holes than the BR RS785?

I measured the spacing on the 785 and it's around 73mm. Would be nice if I could use the existing adaptor on the front, but if the spacing on the caliper is now narrower, I'll need a new one for sure.

[prototoast]

Originally Posted by david

Also, is it true that the newer calipers have narrower mounting holes than the BR RS785?

I measured the spacing on the 785 and it's around 73mm. Would be nice if I could use the existing adaptor on the front, but if the spacing on the caliper is now narrower, I'll need a new one for sure.

Front flat mount brakes come with their own adapter (it's 140 or 160 depending on which way you flip the adapter). You will have to take off the existing adapter, and then the new adapter will go straight into the fork.

[david]

Originally Posted by prototoast

Front flat mount brakes come with their own adapter (it's 140 or 160 depending on which way you flip the adapter). You will have to take off the existing adapter, and then the new adapter will go straight into the fork.

Thanks.

[david]

These look promising.

https://www.paulcomp.com/shop/compon...disc-adapters/

https://www.paulcomp.com/shop/components/disc-adapter/

Thoughts?

[prototoast]

Originally Posted by david

These look promising.

https://www.paulcomp.com/shop/compon...disc-adapters/

https://www.paulcomp.com/shop/components/disc-adapter/

Thoughts?

Neither of these are what you want. The first is a front flat mount adapter, which comes stock with new flat mount brakes. You don't need to spend your money.

The second is IS to post mount, which you already have on your frame.

Originally Posted by reuben

Last year I installed VO IS to post mount adaptors on an MTB. Easy peasy, even for me.
https://velo-orange.com/products/is-...brake-adaptors

I would think that their IS to flat work similarly well.
https://velo-orange.com/products/fla...brake-adaptors

Same comment as above. Neither of these are what he needs.

[macaroon]

Originally Posted by david

These look promising.

https://www.paulcomp.com/shop/compon...disc-adapters/

https://www.paulcomp.com/shop/components/disc-adapter/

Thoughts?

Expensive?
The same thing should be available on ebay/amazon/aliexpress for a tenth of the cost.

If you buy a new groupset it will come with flatmount calipers, and I would hope the appropriate mount for the front fork (which is flat mount).

For the rear, you'd need an IS to flatmount adapter (as linked in the thead above) but your disc size would need to increase.

[macaroon]

You could also keep your existing mounts and discs and swap the new Ultegra calipers for MTB calipers (which are post mount).

I've read about people suggesting Magura calipers as a better alternative to Shimano as they're more reliable (less likely to leak) and supposedly "feel" better.

[david]

Ah-hah.
I think I understand now.
Looks like the front will not be a problem.
But on the rear, I'd need a specific IS to Flat Mount adaptor. And it looks like the only ones available require a 160 rotor.
In which case, I should probably go to a 160 in the front. And, upon specifying that I want a 160 in the front, the new group would come with the appropriate adaptor.
Do I have that right?

[prototoast]

Originally Posted by david

Ah-hah.
I think I understand now.
Looks like the front will not be a problem.
But on the rear, I'd need a specific IS to Flat Mount adaptor. And it looks like the only ones available require a 160 rotor.
In which case, I should probably go to a 160 in the front. And, upon specifying that I want a 160 in the front, the new group would come with the appropriate adaptor.
Do I have that right?

I think you've got it now.

[macaroon]

Originally Posted by david

Ah-hah.
I think I understand now.
Looks like the front will not be a problem.
But on the rear, I'd need a specific IS to Flat Mount adaptor. And it looks like the only ones available require a 160 rotor.
In which case, I should probably go to a 160 in the front. And, upon specifying that I want a 160 in the front, the new group would come with the appropriate adaptor.
Do I have that right?

Yes. Front flatmount adapter is reversible (one side allows 160mm rotors, the other 140mm rotors).