9 speed mech for 10 speed cassette?

[Cubist]

I'm in the process of putting a build together, and had planned to go 9 speed, until I got a bit of a bargain XT chainset. I am therefore in a position where I have a complete 9 speed drivetrain except for the chainset which is now an XT double (M785). As far as I can determine the front mech and shifter can be limited to run as a double, and I'll need a 10 speed right shifter. What about the rear mech though? Will an SLX M662 long cage run a 11-36 10 speed cassette?

 

[GrumpyGregry]

iirc the rear cassette on 10 speed is no wider than that on 9 but the gapes are narrower. if 9 speed mech will cope with 11-36 9 speed (and the teeth gap on the double) the mech will be fine (provided everything mates with the 10 speed chain)

The mech is just a dumb bit of kit that goes where the shifter tells it.

but I stand to be corrected not having tried it on the current fleet. (though I've seen my road bike 10 speed mech on a 9 speed bike)

 

[boydj]

Your rear shifter needs to match the number of cogs at the back - therefore 9-speed. The mech itself can be classed as 10-speed - it only needs to be capable of taking the slightly wider 9-speed chain - or you can run a 10-speed chain.

 

[RecordAceFromNew]

I'm in the process of putting a build together, and had planned to go 9 speed, until I got a bit of a bargain XT chainset. I am therefore in a position where I have a complete 9 speed drivetrain except for the chainset which is now an XT double (M785). As far as I can determine the front mech and shifter can be limited to run as a double, and I'll need a 10 speed right shifter. What about the rear mech though? Will an SLX M662 long cage run a 11-36 10 speed cassette?

You have to be careful here Cubist. I presume you are talking about mtb*? 10 speed Shimano Dyna-Sys right shifter is peculiar in that it pulls around twice as much cable as their 9 speed, hence you will need a Dyna-Sys rear mech to work with that shifter. A 9 speed rear mech will shift around two cogs for its every click - great if you want to go up and down the cassette quick!

If I've got myself a bargain XT chainset irrespective of speed I would just continue to run everything else 9 speed as planned - I wouldn't even run a 10 speed chain unless I have to (and I very much doubt you have to - the difference in sprocket pitch between 9 and 10 at the chainset is most unlikely to matter). If you start changing shifter, your bargain would not be a bargain any more.

Hope it helps.

* if you insist, the way to retain the 9 speed rear mech is to use a 10 speed road flat bar shifter, but I think they are silver in colour...

 

[Cubist]

You have to be careful here Cubist. I presume you are talking about mtb*? 10 speed Shimano Dyna-Sys right shifter is peculiar in that it pulls around twice as much cable as their 9 speed, hence you will need a Dyna-Sys rear mech to work with that shifter. A 9 speed rear mech will shift around two cogs for its every click - great if you want to go up and down the cassette quick!

If I've got myself a bargain XT chainset irrespective of speed I would just continue to run everything else 9 speed as planned - I wouldn't even run a 10 speed chain unless I have to (and I very much doubt you have to - the difference in sprocket pitch between 9 and 10 at the chainset is most unlikely to matter). If you start changing shifter, your bargain would not be a bargain any more.

Hope it helps.

* if you insist, the way to retain the 9 speed rear mech is to use a 10 speed road flat bar shifter, but I think they are silver in colour...

Yes, all MTB parts. The stuff I have at the moment is a complete 9 speed SLX drivetrain.

I now know that I can run the so-called 10 speed chainset as a double with a complete 9 speed drivetrain, keeping the chain, rear mech and front mech. I would need to buy a larger range cassette, as my current 11-32 will not give a user-friendly granny gearing with a 28t inner ring. There is a Deore 12-36 or I could man up and get a 11-34. My current 24-32 lowest gear would only be a twiddling climb away from the 28/34 that that would give me.

My next option is to bite the bullet and go 2x10. Again, it appears that I can use the 9spd front triple mech as a double by limiting its travel with the limit screws (and apparently this works best if I index the inner ring to the "middle" click, and the outer to the "big ring" click.) I understood that I would need a 10 speed right hand shifter, and of course a 10 speed chain. My question was whether in order to do this I would need to change to a M663 10 speed SLX mech,or whether the M662 would work in the same way with 10 speed shifter. Visually they are very similar.

The cost isn't an issue. The stuff I have is all bargains sourced from various sources. The 9 speed shifters for example are one ride old and cost me 26 quid and I have seen a pair of 10 speed for sale at 29 quid. The rear mech I have just bought for 25 quid, and I have found a 10 speed for 30. New cassette and chain (the ones I have are perfectly saleable) and I'm done.

As for how much of a bargain the XT chainset was, let's just say it cost me less than half the cost of a 9 spd Shimano SLX double and bash!

 

[RecordAceFromNew]

The M663 and M662 won't be interchangeable for the reason I explained earlier. The former is Dyna-sys. The latter is 9 speed.

It seems your parts are pretty low cost ok . The question then is probably whether the extra cog is worth the issues associated with a flimsy/flimsier chain/cassette. Only you can decide that. I am sticking with 8 speed...

Regarding whether to index a double outer as a triple middle or triple outer, it seems to me with the former you can just leave the inner limited by the L screw at very low if any cable tension, it should then bypass "indexing" difference between clicks given the 10 speed chainset has slightly smaller sprocket pitch than a 9 (although the latter arrangement still works because the H limit screw will stop it going over, albeit at the expense of cable stretched beyond design). The latter arrangement will therefore likely be more stressed for more than one reasons, but could be a microsecond quicker shifting down. Based on the above logic, I would probably go for the opposite of what you were told.

 

[Cubist]

I've bought the 10 spd mech for 30 now. 10 speed here we come.