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Ultegra 6870 & 10 speed backwards compatibility?

Posted: Sun Oct 20, 2013 8:12 pm
by jockster
So, if I had a 6870 Di2 rear derailleur and a rear wheelset with a 10-speed cassette, could I make it run?

I think I have heard that the 6870 Di2 levers would work with a 6770 RD & FD.

I would like to get the 6870 groupset for my main bike, but switching all my wheelsets to 11 speed would break my economy and it would make me sad getting a new 6770 group when the 6870 is out.

Ultegra 6870 & 10 speed backwards compatibility?

Posted: Sun Oct 20, 2013 8:12 pm
by Weenie

Re: Ultegra 6800 & 10 speed backwards compatibility?

Posted: Tue Oct 29, 2013 2:54 pm
by jockster
Anyone?

Re: Ultegra 6800 & 10 speed backwards compatibility?

Posted: Tue Oct 29, 2013 6:19 pm
by etownfwd

Re: Ultegra 6800 & 10 speed backwards compatibility?

Posted: Tue Oct 29, 2013 6:21 pm
by dha
Levers from any version of di2 (except 7900) will work with any front or rear mech. This applies to 6770, 6870 and Dura Ace 9070. You will need the latest firmware in all components for it to work.

The 6870 and a 10 speed rear might work, but I don't know of anyone who has tried it.

Re: Ultegra 6800 & 10 speed backwards compatibility?

Posted: Tue Oct 29, 2013 6:35 pm
by etownfwd
D'oh! Somehow I read that too fast and missed the Di2 part. Still, what dha said...

@dha - Thank you for the backstopping!

Re: Ultegra 6800 & 10 speed backwards compatibility?

Posted: Tue Oct 29, 2013 10:28 pm
by Tinea Pedis
Are you referring to 6800 or 6870 (Di2)?

Your OP could be confusing people.

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Tue Oct 29, 2013 10:57 pm
by jockster
Sorry. All about 6870 here - corrected my first post for clarification

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Thu Oct 31, 2013 8:26 am
by gjash
I'm running 6800 shift levers with my 10 speed wheels without a problem. The throw distance is the same so it just works. Eventually I'll move all my wheels to 11sp but for now it beats having waste good hubs by replacing with 11.

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Thu Oct 31, 2013 12:39 pm
by RichTheRoadie
If you can change your freehub to Campag, do that and run Campag cassettes - I'm using 9070 Di2 on a Chorus cassette and it works perfectly.

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Fri Nov 01, 2013 10:39 am
by gjash
BikeTart wrote:If you can change your freehub to Campag, do that and run Campag cassettes - I'm using 9070 Di2 on a Chorus cassette and it works perfectly.



Thanks for that! very interesting. You just saved me from rebuilding wheels for the price of a cassette.

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Mon Nov 04, 2013 9:09 pm
by jockster
@gjash - Do you have a 6800 rear derailleur as well?

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Tue Nov 05, 2013 6:55 am
by gjash
jockster wrote:@gjash - Do you have a 6800 rear derailleur as well?


Yes, that's right.

Re: Ultegra 6800 & 10 speed backwards compatibility?

Posted: Wed Nov 06, 2013 5:28 pm
by jockster
dha wrote:Levers from any version of di2 (except 7900) will work with any front or rear mech. This applies to 6770, 6870 and Dura Ace 9070. You will need the latest firmware in all components for it to work.

The 6870 and a 10 speed rear might work, but I don't know of anyone who has tried it.



So one would most probably be fine running a 10sp cassette with 6870 levers and rear derailleur then?

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Wed Nov 06, 2013 8:40 pm
by RichTheRoadie
It's the rear mech that determines whether the system 'thinks' it's 10 or 11spd. If you run a 6870 rear mech the system will think it is 11spd - then the only way to run it 10spd is to wind in a limit screw to stop it reaching the 11th sprocket.

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Wed Nov 06, 2013 8:40 pm
by Weenie

Re: Ultegra 6870 & 10 speed backwards compatibility?

Posted: Thu Nov 07, 2013 1:11 pm
by BdaGhisallo
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.