10 speed cassette/rear mech compatability

[wynne]

Had a mid cage ultegra 10 speed mech working fine with 11-32 cassette and 52/34 chain set for a few years now, including a lot of mountainous touring. As has been said a cheaper and possibly more reliable set up would be to use a 9 speed mtb mech as they have the same pull ratio as 10 speed road stuff.

 

[JamesM]

Longer cage (gs/sgs) won't actually give you larger sprockets, just more capacity. It's the mech body (105 vs xt for example) that gives you the larger sprockets.
I *think* that since the event of 10 speed, all road mechs now have the same maximum sprocket size. But it's worth checking.

True but Tiagra 10 speed rear mechs will work with a 30. They make a 10 speed Tiagra 12-30 cassette.

 

[shedobits]

My current 10 speed road setup is 50 - 34 and 12 - 30 using a short cage 105 rear mech [60mm between jockey wheels] with no problems.

It's almost standard practice here in the mountains with us old gits to fit a MTB cassette and rear mech, [this was to be my next upgrade]. Thanks for the heads up re 9 /10 speed rear mech BTW. I'll let you know how it all works out.

 

[BobCatMax]

This has been fascinating, i'm really glad I asked!

thanks for all the info gents, it would seem I have a few options..

1. - drop both front cogs by 2, leaving me with 48/32 up front and increase the back by either 2 or 4 to a 30/32. this should still be within range, right?

2. - find myself an mtb rear mech but still possibly struggle with the 2 front cogs.

3. - MTFU.

 

[JamesM]

A 10 speed mtb mech won't work with your Tiagra 10 speed shifters. A 9 speed one might work though but I'm not sure. A 10 speed road mech with a long cage would give greater capacity but may not work with a 32t rear sprocket. From what I can tell Tiagra is 30t max and 105 is 28t.

Also can you get a 32t to fit your 110 BCD (?) crank arms?

 

[BobCatMax]

a little more investigating and apparently 34 is the absolute minimum for 110BCD chainrings (except for 2 makes who will do a 33T, but who would notice 1 tooth difference?)

will be doing some more calculations this evening to try and shoehorn it all together

 

[BobCatMax]

So a bit more investigating shows that JamesM is right, the tech docs state that I can run a 12-30 cassette at the back and leave the two up front.

Not quite all I was hoping it would be to be honest, I think I'm going to struggle up some of the bigger hills in this CX sportive I'm doing...

 

[elPedro666]

I've run 34t cassettes on mechs that state 30 with no problems - just a gamble on how it all happens to drop together. Also run 20/38 chainrings (offroad obviously!) with no shifting trouble at all.

Good luck with the Sportive!

 

[BobCatMax]

hmmmm....

long discussion with my riding buddy about this last night, and i think i'm going to stick a 9 speed cassette on the back and see how I get on. I have a mech if the tiagra one doesn't work well enough.

I would much rather the shame of running a big cassette than the shame of walking up hills...

it is a 14%-er, but even so...

 

[mattr]

14%
Jesus, i'm 20 kilos overweight and massively unfit and i get up proper off road stuff that's steeper than that on 38/26 (lowest ratio on my cross bike).

I suspect what you really need is a healthy dose of MTFU!
;o)