I was reading the specs on the 3 x 11 XTR Di2 and it states Max chainring size 40.
I don’t understand the reasoning for this, surely you just move the mech further up the seat tube.
I was toying with converting my 26″ Whyte 19Ti SS to gears but a 40 tooth chainring wouldn’t be enough for my type of riding (44 would be best).

Don’t know for certain, but could it be the mech can’t handle the difference between largest and smallest chainring?

XTR triple is 40/30/22.

For Di2 to work as intended, chainrings need to be super stiff as the front mech moves from A to B with no mechanical empathy. If the rings flex, then shift quality is compromised.

That’s the reason for the asymmetric BCD and the hollow forged rings.

For Di2 to work as intended, chainrings need to be super stiff as the front mech moves from A to B with no mechanical empathy. If the rings flex, then shift quality is compromised.

That makes sense, I suppose another (ugly) option would be to have an XTR mechanical front mech and a Di2 rear.
I already have a new FSA K Force Lite BB30 chainset lying around waiting for a home.

Or use a SRAM 11 speed cassette? The 10t gives you the extra 10% you lose by going from 44 to 40 at the front

Or use a SRAM 11 speed cassette? The 10t gives you the extra 10% you lose by going from 44 to 40 at the front

But then I’d end up with some huge sprockets that wouldn’t be any use with the granny ring and a huge price to match.

I was thinking more along the lines of 11-32 Ultegra 11 speed (if it would work).

and a huge price to match.

You are buying XTR Di2. Wouldn’t have thought that was much of a worry…

No, it’s more a case of the useless 35 and 40 tooth Shimano and 36 and 42 tooth Sram sprockets.

Think your overthinking it

If you are going to run a triple then a tighter ratio block makes a lot of sense IMO.

I can’t see why an Ultegra cassette wouldn’t work, it is the same spacing as a mtb one isn’t it?

That makes sense, I suppose another (ugly) option would be to have an XTR mechanical front mech and a Di2 rear.

and then you’d miss what, imo, is the best bit about Di2 – syncroshift…

if you’re worried about loosing the 44t, just go to a spin class and learn to pedal faster. you must be in a rush to get anywhere if you’re worried about it!

Isn’t it because XTR Di2 is designed to work with a sideswing front mech?

Dave,

one of the big attractions of XTR Di2 is the rear mech/front mech interface, ‘It’ decides for you when to shift the front, you just ask it to shift up or down.

Probably the reason I’ve not gone that way myself, I’m firmly in the 1X camp nowadays.

See H monkey above.

I can’t see why an Ultegra cassette wouldn’t work, it is the same spacing as a mtb one isn’t it?

I might be wrong here but I thought you couldn’t use road cassettes with MTB mechs?

Don’t forget that Shimano 11 speed road cassettes are wider than MTB ones.

You can run 1×42 on with Di2. The mech figures out that the cassette is different and adjusts itself (from what a friend with it said, I can’t afford it).
Not sure you’d ever need 3×44 unless you were trying to ride straight up a wall. Or towing a truck.

and then you’d miss what, imo, is the best bit about Di2 – syncroshift…

That’s what I thought, but it’s not an option for me anyway if the cassette spacing is different for road and MTB groupsets.
The wide ratio’s of the MTB cassette are not suitable for my needs.

if it helps, i used XTR di2 on my direct drive turbo trainer with a 11 speed ultegra cassette

edit – of i see, its more the inability to mount the 11 speed road cassette on a mtb hub ❓

edit 2:

The wide ratio’s of the MTB cassette are not suitable for my needs.

synchro shift is cleverer than you, i don’t know why you wouldn’t just fit is all and let the brains of the system do the work for you while you just shift up and down