I have a new to me bike which has DA 10sp groupset. It has 50/36 compact chainset and 11-25 cassette with a short cage DA rear mech.
Id like more range as im old and weak and live in a hilly area.
Will an Ultegra 11sp rear mech work with the 10sp STI unit? If so, would an mtb or road cassette be best? Or, are they not interchangable?
Id like to keep weight down, so dont mind spending on lighter components.
Thanks
Ian
11 speed won't work. 9 speed Shimano mountain bike mech should, or obviously any 9/10 speed Shimano road mech.
I *think*
Unless there's something odd about dura-ace, "any" vaguely modern (I think there's a 105 that's weird - 4700?) shimano road 10 speed or lower mech should do, as should any mtb up to 9sp
correction, it's Tiagra 4700 (and apparently GRX 10sp too)
https://bike.bikegremlin.com/1278/bicycle-rear-derailleur-compatibility/
correction, it’s Tiagra 4700 (and apparently GRX 10sp too)
Ah, yes - any 10 speed Shimano road mech that's not an 11 speed mech labelled as a 10 speed mech.
Ooh ok. Thank you for that. Will look at GRX 10sp rear. Will either a mtb or road cassette work?
Will look at GRX 10sp rear.
Won't work.
https://www.sjscycles.co.uk/derailleurs-rear/gs-shimano-105-rd5701-10-speed-rear-derailleur-black/?geoc=US
I have a 105 GS 10sp with the same front chainrings as you but a 11-34 cassette. Works perfectly.
Ultegra 6700 series rear derailleurs will work, as will 105 5700 series. If you’re lucky you can find the Ultegra 6700 12-30t cassette to suit. There is a tiagra 4700 series 11-32t cassette also, but that would need the corresponding long cage (sgs) tiagra 4700. Ultegra is only Medium cage (gs) derailleur. You could also drop your front inner ring to a 34t from a 36t.
There are two options I see would work
1) Many old MTB rear mechs (e.g. 9 speed XTR (M97X)) would work perfectly with your existing shifters and wide range 10spd road cassettes: Note though that you may find it hard to find suitable lightweight cassettes.
2) Upgrade to 11spd, e.g. with R7000 STI's/rear mech - may need to check if it works with the front mech.
The 4700 or GRX rear mech will NOT work with DA 7900 shifters, because they use the same cable pull ratio as 11spd road stuff.
^^^^ This. 9 speed Shimano MTB mech is your best bet for wide range cassettes.
You can fit an 11-32 Sram Red 10 speed cassette as a lightweight option.
(Incidentally, I've had this cassette working fine with a Dura Ace 7900 series short cage mech and shifter, but it does depend on the positioning of the mech hanger. Some frames probably would not work.)
Going to 11 speed may be expensive if your wheels are not 11 speed compatible. Most 11 speed road cassettes will not fit 10 speed freehubs; the Ultegra 11-34 does but that's the only one, and you would need new mechs and shifters, and possibly brakes as the cable pull ratio was changed on them as well.
FYI I'm running a 12-30t 10 speed cassette with a short cage 6700 Ultegra rear mech. Works perfectly and would give a noticeably lower gear than the OP's cassette. Although the "official" max is 30t I strongly suspect 32t would be fine.
Guys, that is great. Thanks very much.
I have a 9sp XTR in the spares box so will check it over. Im keen to stay 10 speed as the bike has done less than 100 road miles since it was bought an everything is like new.
^Perfect! Just a cassette and chain required.
Thanks for you help everyone.
Ian