Will a 105 M7000 RD work (indexed) using 8sp shifter, and 8 sp cassette & chain?

[79stef]

As in the title. Will a (10/11 speed) Shimano 105 M7000, or similar, rear derailleur work when paired with a shimano 8 speed shifter, a (M737) 8 speed cassette and an 8 speed chain?
My guess is that it would, as the ratio comes from the shifter itself - the only slight sticking point, potentially being the slightly thicker chain passing through the jockey wheels?

Has anyone got any experience with such a set up?

 

[foz]

the pull ratio is different so it will only work if the shifter is used in friction mode (assuming a DT shifter). an 8 speed chain will probably give problems but a 9 speed might be OK.

 

[79stef]

the pull ratio is different so it will only work if the shifter is used in friction mode (assuming a DT shifter). an 8 speed chain will probably give problems but a 9 speed might be OK.

Ok. So does that mean that an 8 speed shifter, pulling 1mm of cable on this derailleur will move it a different amount to, let's say a 'normally' paired (XT-737) derailleur?

I ask, because I was under the impression that the pull ratio is set by the shifter and not the derailleur.

 

[foz]

sorry my mix up, pull ratio for shimano 10 speed road is 1.7 so if everything else is 8 speed then it should all work just fine. It's 10 speed MTB that is different... you'll still need a 9 speed chain though, or longer jockey wheel bolts and space the cage out a little

 

[79stef]

Thanks @foz
In that case, I am going to give it a try.

 

[legrandefromage]

I don't think it will work, every click of your 8spd shifter may move the dérailleur too far.

The chain will be too thick for the cages, as mentioned above

Click clatter clatter clatter

 

[79stef]

I don't think it will work, every click of your 8spd shifter may move the dérailleur too far.

The chain will be too thick for the cages, as mentioned above

Click clatter clatter clatter

Ah, ok. This is what I wasn't sure of...
I thought that the pull ratio was defined solely by the shifter. But if the mech also plays a part and the shifting is then off, I'd rather stick to what I know - 8 speed everything.

 

[foz]

If the pull ratio is 1.7, the same as 7/8/9 speed Shimano, then it will work if the shifters match the cassette

 

[79stef]

@foz You are indeed correct that the pull ratio of the 105 M7000 is 1.7 (thanks google). So with the 9 speed chain and 8 speed shifters and cassette, should work (as well as any 8 speed set up which uses a 9 speed chain)
I'm going to give it a go and if I'm not happy with it, I'll 'upgrade' it to a 10 speed (shifter, cassette, custom chain and all!)

 

[Frankenorange]

This for anyone interested in mullet gearing

https://www.scribd.com/document/392...nce-Behind-the-Magic-Drivetrain-Compatibility

Just multiply the shifter cable pull by the derailleur shift ratio to get the cog pitch and the jobs a good'un. Basically; if the sum does not equal any available cog pitch( or at least within a tiny part of a millimeter) then that combo will not work.

Have fun.