Dura-ace short cage derailleur

[ShinSplint]

I'm looking to change my 10 speed cassette, from a 12-25 to an 11-28, but i'm concerned as to whether the short cage rear mech would be a problem.


Has anyone done this conversion, and does it work without problems?

i've looked on the Shimano tech website but am unable to find the answer.


Any help much appreciated.


Cheers

 

[Herzog]

I'm running a 11-28 cassette (10 speed) with 34/50 crankset using a short cage mech (all Ultegra) and have had no problems.

 

[albion]

Methinks each unit has a set pull capacity (often 30 teeth for short cage?).
This means all can work as long as some small chainwheel large cassette cog gear changes are manually avoided.

The above needs a maximum pull of (28-11) + (50-34)
= 17+ 16
= 33

So if the big gear cog /big chainwheel (28 / 50 gears) are avoided while cycling then things run fine. (edited for typo 3pm)

 

[ShinSplint]

Thanks for your replies. Sorry, I should have mentioned, its a standard 53/39 chainset ! What you reckon? Would the 53 ring / 28 cog gear work ok? Thanks again

 

[accountantpete]

My 53/39 and 12 -27 at the back Campy works ok.

The basic rule is subtract the small from big chainring = 53-39 = 14.

then subtract small sprocket from big sprocket - 28-11= 17

Then add together and to work it should be circa 28/29.

I this case it is 31 (14+18) so doubtful unless you avoid the big front small rear options.

Why not settle on a 12-27?

You should also note that a 11 -28 will have some very big gaps in the gearing!

 

[brockers]

I think this has been discussed recently, and Shimano short cage is apparently good for a 33 tooth difference, so with a 34/50 front (a difference of 16) and an 11-28 back (diff of 17), you get 33. Pushing it if you ask me, and as accountantpete says, you're getting big gaps. I'll see if I can track down that thread, but It's Friday night, I've had a long day, and there's wine to be drunk. So don't hold your horses.

 

[Herzog]

Brockers is right, 33T is the max difference for short cage:

http://bike.shimano.com/publish/content/global_cycle/en/us/index/products/road/di2.html