UKC

Ideally I want to run a compact chainset with a 12-28 rear cassette to do my annual beasting on the Provencale hills but if I leave my 53-39 on and were to use a 12-32 cassette and longer chain can I just swap the short cage for long cage on my existing rear mech?

Is the difference simply the cage?

I don't want to swap the chainset because it has the power meter on it and I'd like to have that on to give me something to look at as I endlessly grind away on the climbs. It's a 130BCD so compact chain rings won't fit

In reply to woolsack:

I think that would work fine, my cage is held on with a bolt so could easily be swapped. Can't find cages for sale though.

In reply to woolsack:

I suspect a 32 sprocket may be a bit big for the ultegra mech (regardless of the cage length). The cage length allows a greater difference between the longest and shortest chain run, but you may find that the top jockey wheel interferes with the sprocket.

Also, how were you planning on changing the cage? Mechs are not generally designed to be dismantled so I'm not sure where you'd source a cage from or why you'd want to.

A practical solution would be to swap the rear mech for a mountain bike one - you'd have to do a bit of googling to make sure it's compatible, but it's definitely been done.

In reply to woolsack:

I put a 11-28t 105 rear cassette on my bike about a year ago, and it worked just fine with minimal adjustment, certainly didn't need to change the cage or even chain. The bike (Boardman Team) is running 105 groupset with an FSA compact crank

In reply to Oujmik:
I've found someone selling water jet cut carbon Ultegra cages on Ebay, looks like it is just one side though. I'll get the 32 sporoket and work a solution from there. The MTB rear mech might be the way forward
I think that is what Mr Froome had on his bike for last years tour

Working the numbers, there isn't much in it from a 34-28 to a 39-32. Might look a bit odd though. I just about managed with 39-28 last year

In reply to woolsack:

Buy a 38 front ring, put the 12-28 on and rule 5 it

E

In reply to woolsack:

I've ran a 32 with an ultegra long cage mech no problems. Planning to try a 36 next time i ride the Fred Whitton.

In reply to woolsack:

This is a bit of a mystery as you can buy a 12-32 ultegra 11sp cassette, but the specs on the 11sp rear mech say max of 30... not sure what mech Shimano expect you to use.

In reply to Enty:

I knew you'd say that!

Trouble is I've signed up for the Cingle and in August. I'm going to need all the help I can get!

In reply to woolsack:

Ah The Cingle! That's different.
I had to rescue a guy yesterday. Nearly hypothermic descending after his 2nd climb.

Id love to ride it with you but i did it in May so no need to do it again this year

E

In reply to Enty:

Am I allowed the 32 sprocket just for that one day?

In reply to woolsack:

i have a long cage 105 if you're interested? up to 30T works ok as far as i know, but then your short cage is also likely to work as the limit is the length of the upper arm of the RD and not the cage length (which is more about taking up the front chainring jump on road bike RDs.. or somesuch..

In reply to malk:
I've ordered a 38t front inner and a 12-30 cassette, I think that is as good as it will get. I'll see if my current rear mech is happy and if not cast about for a different rear mech. I have a long cage Ultegra one on my winter bike

In reply to woolsack:
hoping you're not expecting to notice any difference between 39->38?

In reply to malk:

Marginal gains all add up! I have a compact chainset and put a 12-30 cassette on the back, which was the biggest my std Ultegra rear mech would take. The difference it made compared to the 12-28 original cassette was astonishing, it got me around the Fred, up the Ventoux and others. Might look out for a 33 front ring for the really steep stuff.

In reply to malk:


39-30 1.3
38-30 1.26

Psychological difference but better than the 39-28 (1.39) I have now

In reply to danm:
what do they say? an extra sprocket on the back is worth two on the front?

In reply to malk:


I notice the difference.

E

In reply to woolsack:

32 will work fine with short cage Ultegra - I ran a SRAM PG980 mountain bike cassette on my Trek for a hilly sportive with no problems.

You may need to wind out the B-screw a bit to stop any rubbing.