Tiagra etc rear mech- why not on a MTB?

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  • Tiagra etc rear mech- why not on a MTB?
  • fr0sty125
    Member

    I don’t think they like rocks…

    Premier Icon Northwind
    Subscriber

    Ratios are different- 10 speed road shimano is compatible with 9 speed mtb though.

    hora
    Member

    Neither do alot of rear mechs though.

    Ratios are different- 10 speed road shimano is compatible with 9 speed mtb though.

    Really? 🙂

    Mister P
    Member

    You could quite happily run a Tiagra medium cage on a 2×9 MTB set up if you ran an 11-32 cassette. But this is the latest model RD-4601 only, the earlier versions were not rated to a 32T so they could foul the cassette.

    works fine as long as 9sp and 9sp. i ran the other way with mtb on a road. Key thing is the capacity – not just the cassette range it can handle but the difference on front chainrings.

    for 1xwhatever then should be fine. No different to a saint mech surely?

    Premier Icon Northwind
    Subscriber

    hora – Member

    Really?

    Aye, I ran 9-speed XT rear on 10-speed 105 (with a 10-speed mtb cassette)

    Back in The mid ’90’s I ran a shimano 105 rear mech on my triple set up for years for clearance. Couldn’t get all the gears but was plenty rugged enough for a rigid hardtail in the peaks.

    I can highly recommend short cage road mechs for 1×9… have them on 2 of my bikes and they are crisp and sleek.

    IA
    Member

    Ran 9sp shimano road mechs on my DH bikes for years. Work fine.

    Shorter 12:27 road blocks though.

    Premier Icon flowmtbguy
    Subscriber

    I think it comes down to this: an MTB rear mech will last longer so long as you don’t smash it on a rock or otherwise get it wrapped around your cassette with a dodgy overshift.

    So if you’re prone to breaking rear mechs rather than wearing them out, then a cheapo road mech is fine.

    A saint rear mech will handle the beating that just being attached to a bike will give it much better than a tiagra.

    both will die equally if smashed into rocks.

    hora
    Member

    Why not? As long as its mid-cage and has enough allowance for bigger cassettes and is 9spd v 9spd.

    Why not??

    Premier Icon flowmtbguy
    Subscriber

    Plus you can get a nice Sora mech for less than £15! So even if they wear out 8 times quicker than a saint, you’re still quids in!

    not so good for the environment though… hmm

    sam42
    Member

    Currently running an old 9spd short cage dura-ace rear mech on a slx 11-28 cassette with an xtr shifter, in a 1×9 set up. The mech’s rated at 27t top capacity cassette wise but with a short chain it clears a 28 easily. Shifts are crisp and it weighs less than any of the other short cage options that were available at the time and it’s nice and small. The only negative is 36-28 as a lowest gear can get a bit demanding on an all-dayer.
    Its got plenty of battle scars on it too so i wouldnt say durability is an issue either.
    If you dont mind a narrow window of gear ratios id say go for it.

    Ratios are different

    If you mean cassette ratios, then yes – they are. If you mean something else, then I’m not sure what you mean.

    It used to be the case a short cage mech (like an old 105) could just handle a triple chainset and 12-28 cassette. A lot of DHers also use them on small cassettes.

    Will a modern 10spd road mech work on a mountain bike? My guess is that if you run a double chainset and a small ratio cassette, then yes. If you run a regular MTB cassette then no. But I’d check with someone who has access to the latest Shimano tech guide first.

    I think it comes down to this: an MTB rear mech will last longer so long as you don’t smash it on a rock or otherwise get it wrapped around your cassette with a dodgy overshift.

    I disagree. Road mechs get covered in all sorts of nasty muck – durability becomes a moot point unless said rocks are involved.

    sam42
    Member

    By “ratios are different” Northwind means the actuation ratio, i.e. the amount of cable pulled by the shifter per shift if you will. As I understand it current shimano MTB mechs and shifters pull more cable than their road stuff in an effort to give lighter shifting.

    Road mechs are plenty rugged enough and if you’re going to start smashing rocks into them then no mech will last long. I can’t really see the benefit of running a road mech over a short cage mtb mech unless you happen to have one spare. But at the cost of the Sora mechs it might be cost effective.

    Premier Icon cookeaa
    Subscriber

    I’ve got a Tiagra on the back of my DH bike, it’s being used with a road cassette, I did have a 105 on another MTB for a while, used that with a 1×8 (11-28) setup, it’s fine if the application doesn’t exceed the mechs tooth capacity.

    Of course it’s not a fancy doodle shadow+ mech, so it’s relatively noisy and not very up to the minute… but I’m unlikely to shed a tear if I mash it into a stump… hey ho

    OCB
    Member

    I ran a 105 (9spd mech on a 1×8 setup) on the back of my trials bike (and that does say trial, not trail) and it coped perfectly with the couple of seasons of ‘natural’ riding comps I did when I rode it ‘properly’. That was a tight road cassette tho’, so cage length wasn’t an issue. That mech then went on to sit on the back of a road bike, where it continued to work perfectly (until it was replaced by a longer caged mech to suit wider ratios).

    I [also] ran an Ultegra on the back of my Peregrine for ages too, (22-32-44f and 12-28r), and that one survived years of dirt perfectly happily as well – until it also got replaced when I shoved a 12-32 on the rear, as, as with the 105, covering that increased range was asking a bit much of a mid-cage rear cage.

    Both are now in the store, and will get used again at some point I’m sure.

    hora
    Member

    Im sure my 01 XTR mech is built flimsier than todays mtb mechs? Or it was just lucky. Hit a fixed rock in a trail and any mech will die

    Sora mechs were popular with DH’ers on a budget not so long back- cheapest short cage mech by far and allegedly have a nice strong spring.

    antigee
    Member

    its also a bit like cross dressing but in this case it might not be issue 8)

    By “ratios are different” Northwind means the actuation ratio, i.e. the amount of cable pulled by the shifter per shift if you will. As I understand it current shimano MTB mechs and shifters pull more cable than their road stuff in an effort to give lighter shifting.

    Possibly – I haven’t got round to 10spd yet… 😳 This would make sense, given SRAM’s big-upping of the 1:1 ratio.

    9spd is cross-compatible, so to speak, unless I’m much mistaken.

    Mister P
    Member

    As the OP is talking about 9 speed MTB then I refer you all to my original comment –

    You could quite happily run a Tiagra medium cage on a 2×9 MTB set up if you ran an 11-32 cassette. But this is the latest model RD-4601 only, the earlier versions were not rated to a 32T so they could foul the cassette.

    Stop being so damn officious and correct, Mr. P! 😛

    rootes1
    Member

    9 speed shimano MTB shifters…

    these work fine with the 8/9/10 speed shimano [list]road[/list] rears like tiagra/ sora / 105 etc

    only issue is that some rad rears can not deal with diner plate rear sprockets..

    also you often get a rear cable adjuster on road mechs which has disappeared from mtb ones

    Mister P
    Member

    Stop being so damn officious and correct, Mr. P!

    Sorry 😳

    Premier Icon Popocatapetl
    Subscriber

    My daughters 20″ Dawes Redtail is running a Tiagra 9 speed rear mech. Her bike is a six speed twist grip and its had no problems with alignment. 😀

    Premier Icon cookeaa
    Subscriber

    This is a handy guide and it now has a number of 3.4mm for Dynansys cable pull which by my reckoning makes the dynasys cable pull ratio 1.16:1 While SRAM’s own 10 speed “1:1” is actually 1.27:1… everyone clear?

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