Road shifters and mountain (front) derailleurs.. what works?

RichJS

Likes Dirt
A lot of the compatability guides for mixing MTB and road components only mention the rear derailleur, I guess understandable given the popularity of 1x .... I'm looking for the kind of range that 2x brings and wondering - does anyone here know if cable pull for front derailleurs the same, or typically close enough to work with drop bar shifters on mountain derailleurs?

EG: Shimano 10sp, 11sp - get a Wolftooth Tanpan for the rear derailleur. But what about the front? Does the cable pull match / close enough for either 11 or even 10sp groups?

SRAM 11sp - get a Shiftmate 7 to match 11sp road shifters to SRAM or shimano MTB derailleurs on the rear, it seems. How about front?

SRAM 10sp road and mtn cable pull matches so allegedly fully compatible. Downside is that lower max tooth counts for the 10sp compared to 11sp rear mechs limit the advantage of 10sp - also, some people claim that oversized 10sp cassettes work fine while others say they shift poorly.
 

Oddjob

Wheel size expert
I have just recently been down this road.

The most straight forward is to use di2. The indexing is all done in the derailleur and brifters will work with XT derailleurs no problem. You also get the bonus of integrated hydro brakes if you want.

I'm morally opposed to 11 speed so went the mechanical route. 3x10 Ultegra brifters with a Jtek shiftmate for the XT fd and a 9 speed SLX rd. I'm told that a 2x11 brifters will work with a 10 speed mountain rd as well. I could never get the shiftmate to work with the 10 speed rd.

For brakes I used the TRP Hy/rd which are very good, but can cook them selves on really long hills with sintered pads.

Sent from my SM-G900I using Tapatalk
 

RichJS

Likes Dirt
The most straight forward would be to say "screw it" and go to flat bars! As nifty as di2 sounds, I'm aiming a bit lower price-wise (EG 105 to SLX.) And it's for an off-road tourer so potentially even going cable brakes, but if hydro then IS-mount rather than flat adds more drama - mountain calipers on road hydro levers?

I'm looking at 2x and Shiftmate specifically mentions 3x for the Shiftmate 7 .. is the implication that 2x can get away with no adapter?
 

Oddjob

Wheel size expert
The most straight forward would be to say "screw it" and go to flat bars! As nifty as di2 sounds, I'm aiming a bit lower price-wise (EG 105 to SLX.) And it's for an off-road tourer so potentially even going cable brakes, but if hydro then IS-mount rather than flat adds more drama - mountain calipers on road hydro levers?

I'm looking at 2x and Shiftmate specifically mentions 3x for the Shiftmate 7 .. is the implication that 2x can get away with no adapter?
No idea but I don't see why not.

Sent from my SM-G900I using Tapatalk
 

The Duckmeister

Eats Squid
I haven't come across any definitive answers for front shifting cross compatibility. My gut feeling is that Shimano's current generation of Road Stuff is the stuff most likely to play somewhat OKwith MTB front derailleurs, because it does run on a longer cable pull than previous generations, and MTB stuff has traditionally needed a longer pull than road, due mostly to the lever geometry (a theory given some weight by the fact that for many years Shimano flat-bar road shifters needed to be paired with a specific front derailleur that worked on a longer cable pull than the regular models) but exactly how well it might work I do not know. As mentioned above, Di2 is the most sure-fire way of getting it to work; as long as the derailleurs are paired for either road or MTB (i.e. both Dura-Ace/Ultegra or XTR/XT, but not one road & one MTB) they'll work with any shifters.

SRAM I have no idea about. Traditionally their road & MTB front shifting has been compatible with Shimano, but that's working off older derailleur geometry, so crossover compatibility is highly questionable. Anyway, SRAM could never get their front shifting dialled, which is why they started the push to 1x.......

As far as rear shift systems/ratios/compatibility/whatever, here's the rundown as far as I've managed to discover:
All Shimano up to 9-sp, plus road 10-sp. with the exception of current-model 4700 Tiagra work on the same ratio, so can be mixed & matched in any combination. (1.7:1 actuation ratio, if you want to know; derailleur moves 1.7mm per 1mm of cable pulled).

Shimano road 11-sp. + 4700 Tiagra 10-sp. is another set, on a 1.4:1 ratio.

Shimano MTB 10-sp. is a stand-alone family on a 1.2:1 ratio.

Shimano MTB 11-sp. runs on a 1.1:1 ratio, which probably accidentally is the same as SRAM 8, 9 & 11-sp. MTB gear (12-sp in both camps I don't know about).

As just noted, SRAM 8, 9 & MTB 11-sp. runs on a 1.1:1 ratio (not quite the marketed 1:1, but close).

All SRAM 10-sp. + 11-sp. road/cross runs on a 1.3:1 ratio, meaning it's probably close enough to fudge to an acceptable degree of function with both Shimano MTB 10-sp. and road 11-sp. It also means you can use a "CX" 11-sp. (eg. Force 1) derailleur in a MTB 10-sp. system to extend the cassette range capacity, but probably not with a 2x up front.

As far as hydro brakes go, ALL Shimano road & MTB levers & calipers will work in any combination. The 1st-gen road R785 calipers were nothing more than reprinted M785/666/675 calipers. Those and the reshaped RS785 and the various flat-mount calipers are all interchangeable with all models of road hydro levers, therefore due to the stem of the family tree, the MTB levers as well. You could run 4-pots with road levers if you really wanted to!

SRAM claimed to have tweaked the master/slave cylinder ratio to improve modulation with their road hydro brakes at the expense of a little bit of outright grunt, but it's probable that most of the difference compared to MTB brakes is in the master cylinder, so feel with MTB vs road calipers should be fairly similar.

As always, never ever mix Shimano & SRAM hydro brake levers & calipers due to being designed for different fluids. Even when different systems use the same juice, it's not wise to mix different brand levers & calipers, as they could well use different cylinder ratios, which may adversely affect brake performance.
 
Last edited:

RichJS

Likes Dirt
Thanks for the list - very handy. Maybe I will have to just get my hands on some different front shifters, a shift cable and a micrometer to measure the pull..

I have bikes with 5700 and Rival 10 to SRAM 10sp front derailleurs, works OK. And thanks to a previous post here I bought an m8000 rear as a spare for when my X0 9sp mech dies. Previous X0 9sp mechs cost me $150 and now the going rate seems to be double that, vs under $100 for the m8000.

I wish you hadn't mentioned Di2 and 4-pot brakes. Now I want an off-road tourer with R8070 shifters, XT Di2 everything else and M8020 4-pot calipers. Maybe with some Fox Live Valve forks just to complete the wankery.
 
Top