XTR/DA or Eagle/Red compatibility

[BigBoyND]

I've got a bit of a crazy idea to get an XC MTB and putting drop bars on it to create a full-suspension gravel bike. I've got a bike already to handle light gravel, and this would be for everything rougher. Please set aside for a moment whether that is a good idea

1. If I buy a Shimano mechanical XTR bike, would any Shimano drop levers (Dura Ace or GRX) be compatible with the XTR RD and calipers?

2. If I buy a Shimano Di2 XTR bike, would any Shimano drop levers (Dura Ace or GRX) be compatible with the XTR RD and calipers?

3. If I buy a Sram Eagle Transmission AXS bike, would any Sram drop levers (Red) be compatible with the Transmission RD and calipers?

[UltraXC]

Shimano Mechanical Road and MTB are not officially compatible. You would need to use a converter like Tanpan YMMV. The calipers would work however.

Shimano Di2 MTB and road are compatible (11 speed). The front and rear deraileur must be the same ( MTB & MTB or Road & Road).

Sram Transmission and Shimano are not compatible at all.

[Aeo]

You can build the bike with SRAM non-Transmission parts, shifters and derailleurs. Then use Shimano cassette and chain (and compatible chainring)

Get the best from SRAM (wireless electronic) and combine with the best from Shimano (shifting performance)

Downside is you will have to run SRAM, Hope or Hayes brakes

[BigBoyND]

You can build the bike with SRAM non-Transmission parts, shifters and derailleurs. Then use Shimano cassette and chain (and compatible chainring)

Get the best from SRAM (wireless electronic) and combine with the best from Shimano (shifting performance)

Downside is you will have to run SRAM, Hope or Hayes brakes

Sorry, mixing Sram and Shimano was not meant to be my question (fixed the OP now). Are Sram MTB derailleurs and calipers compatible with road levers?

[BigBoyND]

Shimano Mechanical Road and MTB are not officially compatible. You would need to use a converter like Tanpan YMMV. The calipers would work however.

Shimano Di2 MTB and road are compatible (11 speed). The front and rear deraileur must be the same ( MTB & MTB or Road & Road).

Sram Transmission and Shimano are not compatible at all.

Good to know about Tanpan. Would avoid that.

This would be 1x. Are 12sp Shimano Di2 parts compatible across MTB RD and MTB calipers (fluid displacement) with GRX or road levers?

I'm not looking to mix Shimano and Sram (fixed OP typo). Last part of my question was meant to be about Transmission AXS RD and MTB calipers, with AXS road levers.

[kervelo]

[Are Sram MTB derailleurs and calipers compatible with road levers?

I am not familiar with the transmission component details, but the AXS levers are compatible with some MTB brake calipers.

See SRAM MTB/road brake compatibility map:
https://www.sram.com/globalassets/docum ... bility.pdf

[Upcountry]

1. If I buy a Shimano mechanical XTR bike, would any Shimano drop levers (Dura Ace or GRX) be compatible with the XTR RD and calipers?

2. If I buy a Shimano Di2 XTR bike, would any Shimano drop levers (Dura Ace or GRX) be compatible with the XTR RD and calipers?

3. If I buy a Sram Eagle Transmission AXS bike, would any Sram drop levers (Red) be compatible with the Transmission RD and calipers?

1) No... Shimano has different cable pulls for their mechanical levers and derailleurs on the road versus mountain... But with the new mechanical 12 speed GRX derailleur and levers, you can run an XT/XTR cassette with 10-51 range...

2) 11 Speed Di2 stuff is all interchangeable, so long as the front and rear derailleurs are from the same family(meaning either "road/grx" or "XT"). Most of their mtb calipers can be used with road levers, and use the same hoses(BH90). I've got a couple bikes running variations on this, including a 2x11 XT Di2 Titanium Drop Bar build with GRX levers and calipers.

3) AXS all works together as far as electronically. So you only need to make sure you can pair the levers with the calipers. With the prices being so low on the Rival and Force stuff, its probably worth buying the levers, hoses, and calipers together... You can then just pair those levers to whatever rear derailleur you have.

[BigBoyND]

Super helpful, thanks! For point the Di2 case, what about 12sp play together across the groups? Same as 11sp?

[UltraXC]

Super helpful, thanks! For point the Di2 case, what about 12sp play together across the groups? Same as 11sp?

There is no 12s Di2 for MTB... yet.

Based on how Shimano handled a "mullet" setup for mechanical GRX, there might be a dedicated GRX di2 mullet rear deraileur vs using a MTB option. That however is just conjecture.

[Salespunk]

Building a drop bar MTB right now. My setup is Red AXS levers (already had them otherwise would have bought the new Force) Transmission RD (newest direct mount setup) with a 12 spd Tranmission cassette/SL chain. I tried pairing the Hope RX4 calipers with my Red levers, but the RX4's are too wide to fit a lot of modern MTB rear ends and forks like the new Sid. As an FYI you can get Red post mount calipers super cheap at $115/ea so that is the route I went.

I might try one of my XTR cassette/chains with an older XX1 AXS RD. My second favorite setup after the new Transmission which is the best shift performance I have ever experience on a bike.

[Upcountry]

UltraXC is correct that there is no 12 speed di2 yet for the dirt side of things(GRX or XT/XTR)... The 12 speed GRX Di2 derailleurs are all but released, as their part numbers and specs have been shared on here. They're essentially electronic versions of the 12 speed mechanical, meant for either the large MTB 10-45/10-51 in a 1x format, or for smaller cassettes(I'm expecting an 11-40ish range to be added here) in a 2x format. Not entirely sure where this leaves an actual 12 speed Di2 MTB rear derailleur, but I'm sure they'll tweak it just a little and slap a XT logo on it, and release it with an updated flat bar lever(wireless).

Interestingly, I've grown a bit impatient with this release, and quickly wanted to ditch my Sram Force/Rival XPLR setup on my drop bar hardtail build. I simply couldn't stand the ergonomics of the levers, and didn't love the braking of Sram. So I've got a pretty mullet like setup on there for now, and its actually working quite well...
R8170 Di2 12 speed levers and hoses
M8000 XT 2 Piston Calipers
R7150 Di2 105 12 speed rear derailleur
M9100 XTR 12 Speed 10-45 Cassette
M9100 XTR 12 Speed Chain
Sram Force Quarq Dub Wide Crankset w/ Stone 36t Chainring

I wasn't able to find anyone using the 105 rear derailleur with larger than the spec'd 36t cassette, so I wasn't sure how it would handle it. I initially tried it on the XPLR 10-44 cassette. It didn't like the flat top AXS Force chain, so I tried it with a 12sp XTR chain, but that pairing didn't jibe well either, just not wanting to make the shift up the block in the smaller gears, despite fiddling with the offset in the app. So I took the expensive gamble of swapping my freehub to Microspline, and ordered the XTR cassette. I felt okay with this gamble, as I knew worst case, I'd have it for when GRX Di2 is release. To my surprise, it didn't take much to get the 105 rear derailleur to handle it all. A few turns on the B-limit screw gives it more than enough room to move through the gears as quick as you can tap the lever. Before setting it up, I did order two of the Gearoop eccentric upper pulley wheels that I'll probably try. This would allow for less tension on the B-limit screw, and a bit more chain wrap on the cassette when in the smaller end of the block. It doesn't seem needed, but I'll try it for comparison sake when they arrive. Obviously there isn't a clutch in the 105 derailleur, but with modern chainrings retaining the chain so well, I haven't had a drop yet in the limited time I've been on it.

[BigBoyND]

I didn't even consider GRX or 105 derailleurs. That could be a good route to go 12sp mechanical also!

[pdlpsher1]

So I took the expensive gamble of swapping my freehub to Microspline, and ordered the XTR cassette. I felt okay with this gamble, as I knew worst case, I'd have it for when GRX Di2 is release. To my surprise, it didn't take much to get the 105 rear derailleur to handle it all. A few turns on the B-limit screw gives it more than enough room to move through the gears as quick as you can tap the lever. Before setting it up, I did order two of the Gearoop eccentric upper pulley wheels that I'll probably try. This would allow for less tension on the B-limit screw, and a bit more chain wrap on the cassette when in the smaller end of the block. It doesn't seem needed, but I'll try it for comparison sake when they arrive. Obviously there isn't a clutch in the 105 derailleur, but with modern chainrings retaining the chain so well, I haven't had a drop yet in the limited time I've been on it.

This is very interesting. Thanks for sharing the info. Please provide an update on how this setup is working out.

It's too bad there's no 11-40 12-speed cassette by Shimano. I don't think one is coming.

[req110]

UltraXC is correct that there is no 12 speed di2 yet for the dirt side of things(GRX or XT/XTR)... The 12 speed GRX Di2 derailleurs are all but released, as their part numbers and specs have been shared on here. They're essentially electronic versions of the 12 speed mechanical, meant for either the large MTB 10-45/10-51 in a 1x format, or for smaller cassettes(I'm expecting an 11-40ish range to be added here) in a 2x format. Not entirely sure where this leaves an actual 12 speed Di2 MTB rear derailleur, but I'm sure they'll tweak it just a little and slap a XT logo on it, and release it with an updated flat bar lever(wireless).

Interestingly, I've grown a bit impatient with this release, and quickly wanted to ditch my Sram Force/Rival XPLR setup on my drop bar hardtail build. I simply couldn't stand the ergonomics of the levers, and didn't love the braking of Sram. So I've got a pretty mullet like setup on there for now, and its actually working quite well...
R8170 Di2 12 speed levers and hoses
M8000 XT 2 Piston Calipers
R7150 Di2 105 12 speed rear derailleur
M9100 XTR 12 Speed 10-45 Cassette
M9100 XTR 12 Speed Chain
Sram Force Quarq Dub Wide Crankset w/ Stone 36t Chainring

I wasn't able to find anyone using the 105 rear derailleur with larger than the spec'd 36t cassette, so I wasn't sure how it would handle it. I initially tried it on the XPLR 10-44 cassette. It didn't like the flat top AXS Force chain, so I tried it with a 12sp XTR chain, but that pairing didn't jibe well either, just not wanting to make the shift up the block in the smaller gears, despite fiddling with the offset in the app. So I took the expensive gamble of swapping my freehub to Microspline, and ordered the XTR cassette. I felt okay with this gamble, as I knew worst case, I'd have it for when GRX Di2 is release. To my surprise, it didn't take much to get the 105 rear derailleur to handle it all. A few turns on the B-limit screw gives it more than enough room to move through the gears as quick as you can tap the lever. Before setting it up, I did order two of the Gearoop eccentric upper pulley wheels that I'll probably try. This would allow for less tension on the B-limit screw, and a bit more chain wrap on the cassette when in the smaller end of the block. It doesn't seem needed, but I'll try it for comparison sake when they arrive. Obviously there isn't a clutch in the 105 derailleur, but with modern chainrings retaining the chain so well, I haven't had a drop yet in the limited time I've been on it.

Sounds good, can you post picture of your bike?