Shifter/mech compatibility - Road/MTB

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thenorthwind
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Joined: 29 Jun 2015, 2:01pm

Shifter/mech compatibility - Road/MTB

Postby thenorthwind » 15 Apr 2016, 9:09am

I'm looking at a pair of used road Tiagra STI 3x9 shifters (I think ST-4503) and wondering whether they will work with my more recent Deore MTB derailleurs. Is the pull length the same or is this a non-starter?

hamster
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Joined: 2 Feb 2007, 12:42pm

Re: Shifter/mech compatibility - Road/MTB

Postby hamster » 15 Apr 2016, 9:10am

All the Shimano 9 speed stuff is the same road / MTB at the rear. Front changers have always used different pulls.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Shifter/mech compatibility - Road/MTB

Postby Brucey » 15 Apr 2016, 9:18am

the front mech will have a different cable pull for sure; you need a 'road' front mech to work with those shifters. If you are using an MTB chainset/chainline, it can be a struggle to find something that works, because a lot of 'road' front mechs won't work on an MTB chainline. Some folk have made the MTB mech work by using a shiftmate or by altering the cable mounting on the mech to alter the shift ratio.

At the rear you need to be conscious of which model Deore mech you have; it needs to be a 9s one rather than 10s or 11s, but it should work OK if it is a 9s one.

cheers
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cycleruk
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Re: Shifter/mech compatibility - Road/MTB

Postby cycleruk » 15 Apr 2016, 9:39am

What chainset are you using or considering ?
It's usually the front dérailleur that causes the most issues.
Should be no problem with your MTB rear mech' as long as it's pre-10 speed.
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thenorthwind
Posts: 90
Joined: 29 Jun 2015, 2:01pm

Re: Shifter/mech compatibility - Road/MTB

Postby thenorthwind » 15 Apr 2016, 10:40am

Rear mech is, as far as I know, 9 speed specific rather than 10, though is fairly recent. My understanding is that 9 speed rear mechs will do 10 speed with the right shifter though, so not sure why it would matter?

Front mech is an ancient Suntour braze-on, but it's an old MTB frame, so not sure (also not sure if it's original). Using a parts bin square taper triple at the moment - not sure whether it's road or MTB, though more MTB-like sizes (think big ring is 44). Considering a new (road) triple anyway so not such a problem.

I'm trying to keep things as cheap as I've built the bike up flat bar, but want to try out drops before making a decision.

Cheers

hamster
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Joined: 2 Feb 2007, 12:42pm

Re: Shifter/mech compatibility - Road/MTB

Postby hamster » 15 Apr 2016, 10:52am

Shimano changed the leverage of rear mechs for 10 speed MTB, then they changed road at 11 speed.

So road 7-10 speed rear all use the same leverage as MTB 7-9 speed rear.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Shifter/mech compatibility - Road/MTB

Postby Brucey » 15 Apr 2016, 11:39am

hamster wrote:Shimano changed the leverage of rear mechs for 10 speed MTB, then they changed road at 11 speed.

So road 7-10 speed rear all use the same leverage as MTB 7-9 speed rear.


yes, except that

- Shimano used indexing on 6s systems to start with, and they use the same shift ratio as 7-10s (road) and 7-9s (MTB) , so actually it should read 6-10s (road) and 6-9s (MTB). Also;

- dura-ace 6 - 8s systems use a different shift ratio to other 'road' systems. The net effect of this is that DA cable pulls 'vary by one' from other shimano systems. Thus a 9s shifter and a DA rear mech works fine on 8s, and a 8s DA shifter on a 9s mech works fine on a shortened (8-from-9) 9s cassette. [BTW Sun Tour Superbe Pro used the same shift ratio as DA, AFAICT].

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

pwa
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Re: Shifter/mech compatibility - Road/MTB

Postby pwa » 15 Apr 2016, 11:45am

Shimano 10 speed MTB rear mechs will not index with Shimano Road levers (of 9 or 10 speed). Shimano 9 speed MTB rear mechs will index with Shimano 9 and 10 speed levers. As far as I know the MTB front mechs do not work well with road STI levers.

Manc33
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Re: Shifter/mech compatibility - Road/MTB

Postby Manc33 » 20 Apr 2016, 1:29am

At the front you can "get away with" using a FD-R773 (or the FD-R443) with a mountain bike front shifter.

I used this setup myself with a XTR left shifter and a FD-R443 and FD-R773 and the only "problem" (not really) I had was you have to have cable slack at the end so, on the granny ring. Its a big push from granny to middle, but it still works and the shift from middle to outer to middle is just the same.

The strict truth is no one thing ("flat bar"/road/MTB) is compatible with any other one thing as far as front derailleur cable pull goes, but the R443/R773 front derailleurs are a go between, where they can work with MTB shifters, but probably won't work with road bike shift/levers. The cable throw on road shifters is shorter as is the swingarm on the front derailleur.

The nice thing about the FD-R773 (apart from it shifting gears miles better than the FD-R443 can) is you can have full size road chainrings up to 52t. I had a 52-38-24 with a 11-32t cassette and had it running like a charm (it only took about a year lol). Then I dismantled that bike and got on my current one... but if you want a true touring triple you're not going to stretch it really beyond 52-38-24 because that causes a 28t front difference when its meant to be 22t. I think there is a way to have a 53t but it involves the C word (Campagnolo). :)
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