Mtn v road trigger shifters. Difference?

[jamesofyorkshire]

I like a flat bar on my road bikes. Obviously there is more MTN component choice for flat bars than road specific (top end anyway).

I have a new pair of XT M780 mtn trigger shifters. If I use a mtn rear derailleur, will these work OK? I realise after 9speed, Shimano wouldn't mixnmatch but mtn gear changers with a mtn RD should work OK? Road and mtn cassettes are the same width?

[RickH]

It would need a 10 speed MTB rear mech. IIRC Shimano changed the cable pull for MTB 10 speed (hence needing to use use 9 speed operated by road 10 speed shifters).

[jamesofyorkshire]

Sorry RickH, you've confused me....so those M780 shifters will work with any 9-speed RD (which I got to go with another road 10-sp trigger shifter)?

And obviously a mtn RD.....

Are mtn and road cassettes the same width overall? Aren't mtn bikes 135mm spaced at the rear as opposed to 130mm for road bikes? Does the cassette make up that difference?

[thelawnet]

Sl-m780-r is a mtb 10 speed rear shifter, so you need a 10 speed mtb rd to go with it.

Mtb and road cassettes are the same pitch, it's only the gear range that makes them nominally mtb or road.

The mtb and road derailleurs pull different amounts of cable to move the same distance, so shifter and derailleur must match.

In terms of the specific rd, on the road side Shimano have just brought in their 'Shadow' design which brings the rd closer to the frame, so some 10 speed rds have it and some don't, but on the mtb side that's on all 10 speeds

Then basically Deore and SLX are identical and have a choice of mid or long cage, Zee is the same but short cage, XT has the better jockey wheels, and Saint is the same as Xt but with short cage. Then you've got Shadow Plus which is the clutch system which you might want for off-road/cyclo-cross but probably not an advantage on asphalt as it's another thing to add friction or whatever.

Shadow Plus is an option on all the 10 speed groupset levels, again SLX and Deore will be the same.

M781 would-be a good rd, as is M780 which just has a different arrangement of connecting bolts so isn't designed for direct mount rd frames. Direct mount RDs seem to be one of Shimano's dead ends and they never did it for road, so I think you don't need to worry between m780 and m781.

I have an m786 with the clutch and it's nice as well.

[jamesofyorkshire]

So a 9-sp long cage road wont work? Just asking because I have a 9-sp long cage road RD with a 10-sp road shifter at the moment.

[531colin]

10 speed MTB rear has a pull ratio all of its own, it won't play nice with anything else.
Similarly, I believe MTB and road left shift pull ratios are different. In that case, all MTB left are the same, and all road left are the same, its just MTB and road are different.
after all, if they made them all the same, they wouldn't be able to flog you some new stuff, would they?

[thelawnet]

So a 9-sp long cage road wont work? Just asking because I have a 9-sp long cage road RD with a 10-sp road shifter at the moment.

My understanding is that a 10 speed road shifter pulls 2.3mm a click and a 9 speed pulls 2.5mm.

9 and 10 speed cassettes are respectively 4.35 and 3.95mm apart.

The 9 speed rear derailleur is designed to move therefore 4.35mm per 2.5mm, which is 1.74:1. If you pull it through by 2.3mm instead then that will therefore pull 2.3 *1.74 = 4.0mm. So the pull ratio is the same between 9 speed and 10 speed road. (These preceding numbers are not precise, but the result is close enough that the working result is obvious)

The 10 speed mtb shifter has a completely different pull amount, namely 3.4mm, so your 9 speed rear derailleur would pull 3.4*1.74 =5.78mm, which is plainly hopeless.

I suspect the use of more cable makes things easier to setup, and Shimano ended up retrofitting the 11 speed road ratio (pulling more cable than 10 speed road but still less than 10 speed mtb) on to 10 speed Tiagra.

[Brucey]

which parts do you have already and which do you want to keep? More than one way of skinning a cat and all that.

FWIW if you have a dropped bar 10s setup now the easiest route is probably to get some flat bar 10s shifters which are made to go with your derailleurs. You don't need 'lots of choice', you just need to be able to buy the right thing for the job.

cheers

[jamesofyorkshire]

I bought these in a sale a while back, not realising they wouldn't work with a road RD:

http://www.bike-discount.de/en/buy/shim ... peed-86695

I'm hoping to build up (another) road bike with flat bars and want to use those if possible.
I tried selling them on here when I became aware they wouldn't work with road derailleurs but had no takers and don't want to have them sat there doing nowt for evermore.



I have a set of SHIMANO TIAGRA SL-4700 2 x 10-SPEED RAPID FIRE ROAD FLAT HANDLEBAR SHIFTER SET on my current flat bar road bike, with a 10-sp Tiagra RD and SHIMANO Deore XT 11-36 10-sp cassette.
I want a similar kind of set up on the new bike but using these sl-m780 mtn shifters I have sitting new in a box! Yes, I have a couple of 10-sp road RDs but if they wont work, they wont work and I'll get hold of something that does.

[jamesofyorkshire]

thelawnet

'M781 would-be a good rd, as is M780 which just has a different arrangement of connecting bolts so isn't designed for direct mount rd frames. Direct mount RDs seem to be one of Shimano's dead ends and they never did it for road, so I think you don't need to worry between m780 and m781.'

I don't know what you mean by a direct mount RD frame. You mean a frame that doesn't use a gear hanger?

[Brucey]

MTN 10s shifters such as M780 ones will only work with

a) a 10s shimano MTN rear mech (it has a unique pull ratio) and
b) a compatible MTN front mech.

The latter may push you into having a MTB type chainset, not a road chainset, because MTN FDs don't work too well on 'road' size chainrings and/or on 'road' chainlines either.

FWIW the pull ratios of current 'road' 11s double FDs are very close to MTN FDs, such that (with a bit of cable mount tweaking) a double might work even with a mismatch of shifter and FD. However you won't get FD trims, either at all or that work properly, and you tend to need those on larger 'road' type chainrings.

Another option is to ditch the shifters and to use thumbshifters (or converted bar ends) instead. This allows you to use any FD and to trim it too.

Building the rest of the transmission around a pair of shifters is a bit of an odd thing to do, unless you have a completely free hand in choosing all the other bits.

cheers

[jamesofyorkshire]

Yes Brucey, I agree with you.

Anyway, thanks to you all for helping and answering my questions. So I should probobly make it easier on myself and sell those mtn shifters, even if it means taking a hit on them.

[thelawnet]

I bought these in a sale a while back, not realising they wouldn't work with a road RD:

http://www.bike-discount.de/en/buy/shim ... peed-86695
s.

I spec?

To be avoided I think.

I believe you'd need I spec brake levers or some sort of adapter jobby to use them without. https://www.sjscycles.co.uk/gear-spares ... -6uv-9804/

[jamesofyorkshire]

Maybe that's why I couldn't unload them.....