Rear Derailleur. Will I be Shunned?

[Smokin Joe]

The only people who care will be the five minute wonders who've been lifelong cyclists since it became the fashionable thing to do. When it is all over they will go back to sneering at people who have the wrong badge on their car.

Proper cyclists don't care what you use as long as it works for you.

 

[si_c]

Do it, it'll work fine.

Shimano's new road groupsets have taken a lot of their design from their MTB ones anyway so you can pretend you are a trendsetter.

 

[ColinJ]

I run an 11-36 with a medium cage 105 deraileur.

Perhaps I could have got away with it, but the original rear mech had a 33 tooth capacity and the bike now has a 38 tooth range.

 

[Venod]

Perhaps I could have got away with it, but the original rear mech had a 33 tooth capacity and the bike now has a 38 tooth range.

You can push the capacity and sprocket size a little bit, 32t is supposed to be max for the derailleur I have, but with the latest 105 medium cage will take a 34t and probably a bit larger at a push.

 

[wafter]

Isn't there some compatability issue (cable pull ratios..?) that prevents the use of more modern Shimano MTB mechs with road shifters...?

 

[freiston]

It must be something to do with yellow bikes: back in the early 80s, I swapped out the Shimano 600 short cage RD on my yellow bike for a Suntour VGT long cage RD (after changing the block for something bigger). I was shunned before and after the swap so I cannot help with your query 😉

 

[freiston]

Isn't there some compatability issue (cable pull ratios..?) that prevents the use of more modern Shimano MTB mechs with road shifters...?

This article would suggest yes. But the smaller ratio of the 11 speed MTB mech over the 11 speed road mech might make it more manageable with friction shifting 😉

 

[ColinJ]

Isn't there some compatability issue (cable pull ratios..?) that prevents the use of more modern Shimano MTB mechs with road shifters...?

I was told that my 10-speed Tiagra shifters would work well with a 9-speed XT rear mech and that turned out to be true. Shifting doesn't feel 100% accurate in that there is occasionally a slight hesitation going up onto a couple of the bigger sprockets but when that happens a very slight additional 'nudge' with the gear shift lever is enough to help the chain climb up to the next sprocket. Once the chain has settled on the new sprocket, it stays there. I've got used to it now and simply push the lever slightly beyond the click-stop and then release it.

PS It is possible to adjust the action so there isn't that hesitation, but the problem then is that the chain sometimes doesn't drop down onto smaller sprockets when shifting in the opposite direction. It works better the way I described above. Most shifts just work without any extra encouragement, but it isn't a big deal to push slightly further on the shift lever when that is needed.

 

[freiston]

I was told that my 10-speed Tiagra shifters would work well with a 9-speed XT rear mech and that turned out to be true. Shifting doesn't feel 100% accurate in that there is occasionally a slight hesitation going up onto a couple of the bigger sprockets but when that happens a very slight additional 'nudge' with the gear shift lever is enough to help the chain climb up to the next sprocket. Once the chain has settled on the new sprocket, it stays there. I've got used to it now and simply push the lever slightly beyond the click-stop and then release it.

PS It is possible to adjust the action so there isn't that hesitation, but the problem then is that the chain sometimes doesn't drop down onto smaller sprockets when shifting in the opposite direction. It works better the way I described above. Most shifts just work without any extra encouragement, but it isn't a big deal to push slightly further on the shift lever when that is needed.

From the link I posted above, in relation to Shimano 6, 7, 8 & 9 speed rear mechs (both road and MTB):

Rear shift ratio is 1.7, that is for 1 mm of cable pull/release, RD is moved left/right by 1.7 mm. Shimano calls this 2:1 ratio for marketing reasons.

All these RDs are compatible and any 6 to 9 speed RD will work perfectly with either 6, 7, 8 or 9 speed shifter. Regardless whether it’s a MTB, or road shifter, or RD. They are also compatible with Shimano 10 speed road shifters, except the Tiagra 4700 series.

So I suppose it depends if your 10-speed Tiagra shifters are 4600 series or 4700 series.

Edit: From that linked artice, I understand that the 4700 series has a pull ratio of "around 1.4" and so is compatible with the following Shimano mechs - 11 speed road mechs, 10 speed Tiagra 4700 mechs and 10 speed GRX mechs, and Campagnolo "Old" mechs.