Largest cassette for short cage?

mikebikemike

I've 6700 Ultegra gearing on my posh road bike (compact chainset). I'm hoping to do some long rides in the lakes soon. To aid this I'd like to stick the largest possible cassette on the back to help me up some of the passes. I've asked a few folks and there's no definitive answer with suggestions between 28 and 32 teeth on the big ring.

Can any one advise? Also would there be any other changes needed?
I think it's around a 25 a.t.m. would I need another link or two in the chain?

sungod

http://techdocs.shimano.com/media/techd ... 702204.PDF

says short cage 6700 rd capacity 33t, largest sprocket 28t

unless the current chain has been set slack, yes you'll need a longer chain, if the current ont has any wear fit a new chain to go with the new cassette, get some kmc links so you can easily swap chains

follow instructions in the document to set b-tension and correct chain length

mikebikemike

Thanks for that and good tip re new chain.
I wonder when they say max 28 they really mean it and it could be worth trying a 30? Manufacturers usually are a little cautious in there maximum tolerances

triquin

mikebikemike wrote:

Thanks for that and good tip re new chain.
I wonder when they say max 28 they really mean it and it could be worth trying a 30? Manufacturers usually are a little cautious in there maximum tolerances

I have used a 12-30 sprocket with a short cage Dura Ace 7900 mech with no problems. Got to be worth a shot with Ultegra.

Pete

arthur_scrimshaw

mikebikemike wrote:

Thanks for that and good tip re new chain.
I wonder when they say max 28 they really mean it and it could be worth trying a 30? Manufacturers usually are a little cautious in there maximum tolerances

Before you add extra links it's worth checking the length of your chain, the last three new bikes I've bought had chains too long when I've come to replace them. I use the park tools 'Largest Cog and Largest Chainring Method'

arlowood

On my previous bike I swapped an 11-28 for a 12-30 (Tiagra in that case) with a DA short cage derailleur. Had no problems whatsoever - the chain was still long enough to cope.

Now running a 105 short cage with a 12-30 - again Tiagra but for more money you can buy an Ultegra 12-30 if you wish. This time it was a bike build job and I just used the following calculator to measure my new chain at the outset.

http://www.epicidiot.com/sports/chain_l ... tm#results

Again no probs with mech coping with the 30 tooth sprocket. You should be fine with your Ultegra set up.

I think the tech docs limits are pretty conservative so there is always a good margin of wriggle room to push the boundaries.

Don't think you would get away with a 32 as largest but I have not tried it with a short cage mech - maybe others have.

I think a 12-30 with a compact chainset should give you plenty of scope for those killer hills

maddog 2

officially 28t but in practice 30t is fine, with a tweak of the tension screw. Some people can even get 32t but this is rare and pushing it in terms of overall chain capacity (big-big becomes a real stretch for the mech).

I've fitted four 12-30 cassettes to bikes now (mainly for the Fred W.) and all were short cage. Three went in with minimal hassle, the fourth need the tension screw on max and the chain one link shorter than I would normally run. The differences are largely due to hangers not being identical, some giving a tad more clearance than others.

mikebikemike

Good to know - a Fred Whiiton challenge is on my "to do" list but I want to test myself and the bike out on some shorter lakes rides before taking that on