Ultegra 6870 & 10 speed backwards compatibility?

[RichTheRoadie]

There's numerous folk out there who have tried the 9070 rear mech with 10spd spacing with no issue - because of the way Shimano have spaced their 11spd cassette it seems to work just fine.

[gjash]

My understanding is that cog spacing is the same with shimano 10 and 11 speeds. At least it seems to be since I can run 10 speed cassettes with 11 speed shifters.

In that scenario the shifting will not be perfect since the 6870 RD will be shifting to 11sp cog spacing. If you want 10sp cassettes, you will need a 6770 RD and can use 6870 everywhere else.

The RD determines the the cog setup. 6770 = 10sp 6870 = 11sp. All other components are compatible, though not optimal. The 6870 FD will trim based upon 11sp chain and chainring architecture, so you may have some misalignment, though you won't know how much until you try it.

[BdaGhisallo]

The 10sp and 11sp cogs are the same width, but the spacing between the 11sp is a hair narrower than 10sp. I can't track down the actual numbers but you can impute the difference from the different dimensions for the 10sp and 11sp chain.

From BikeRumor:
The 11-speed chain is 5.62mm at the widest point, and the current 10-speed chain is 5.88mm.


Now it may not make a difference in the real world, but they are different.

[nagge]

Could i use 6700 shifters with a 6800 rear derailleur and 11s casette to make it 11s?

[rijndael]

Could i use 6700 shifters with a 6800 rear derailleur and 11s casette to make it 11s?

No.

[BdaGhisallo]

Could i use 6700 shifters with a 6800 rear derailleur and 11s casette to make it 11s?

Mixing and matching mechanical and DI2 10 and 11sp are different animals. With mechanical, the cog number the system can control is dictated by the STI levers. 7900 and 6700 are 10sp only. 9000 and 6800 are 11sp only.

It is with DI2 that the RD dictates the cog number. 6770 is 10sp and 9070/6870 is 11sp.

[nagge]

Ok, thank you.

[RichTheRoadie]

The 11-speed chain is 5.62mm at the widest point, and the current 10-speed chain is 5.88mm.

Now it may not make a difference in the real world, but they are different.

Yes, but use an 11spd chain on the 10spd setup and you'll be fine.

It works - I know people doing it.

[iceman83]

hi,
I have an ultegra 6770 and I wanted to bring it to 11s.
Can I just replace my RD-6770 with RD-6870 with, 11s chain and cassette 11s?

[iceman83]

...and the chainring 6750 is compatible with chain 11s?
The SM-EW67-A-E and ST-6770 are compatible with FD-6870 and RD-6870? thanks

[RichTheRoadie]

You'll need the 6870 rear mech and a firmware upgrade - then you're good to go.

[Chello]

6870 RD is only 11 speed. I guess you could try limit screws but the electronics will always be programmed for 11.

[RichTheRoadie]

Ah, my bad - I meant if you wanted to upgrade to 11spd.