Ultegra cassette options

Spatulala

before you groan, I have searched for this but the results are far from conclusive so I'm just looking to clarify

New bike, ultegra 6800 with compact, 11-28 cassette and short cage RD.

I understand that despite the suggested 28t max, it will run an 11- 32 without me having to swap for long cage RD, as long as I avoid 50/32 (Which I can't imagine ever using anyway).

Is this right, have you done it and confirm OK?

Also, my preferred cassette would be 11-30, but as far as I can see only SRAM 1190 offers this, and I'm not about to spend £165 on a cassette. Is that right, or are there others at a less eye-watering price?

Thanks. If I was staying in UK 11-28 would be fine but The Alps are calling, and the last time I was grateful for a 30/28 gear.

Thanks.

arlowood

From experience on 10-speed 105 5700 I know that you can get away with a short cage RD with 12-30 cassette and compact 50/34 chainset although Shimano specs say it's not advisable.

Just bought 105 5800 11-speed components and I've ordered the medium (long?) cage RD as this was specified to allow the larger 11-32 cassette. If you never plan to ride 50/32 then you might get away with a short cage RD but there may still be issues running 34/32 if the short cage can't take up enough chain before it fouls the cassette.

Maybe someone else has done so I will hold judgement until wiser heads contribute

DKay

I run 5800 and a 11-32t cassette with a compact on the winter bike. I use a medium cage rear mech, as I didn't think that it was worth risking it with a short cage. You may think that you'll never use the 50/32 gear, but you never know what can happen on a ride when you're really tired and not paying attention. The shifting on new 11 speed Shimano groupsets is so light and smooth across the whole of the cassette, that I would imagine that it would be quite easy to do.

It's simply not worth taking the risk.

cerutticolumn

I've just bought the Shimano 5800 groupset, and also wasn't sure about gearing. In the end I get the medium cage RD with the 11-28 cassette. That way, when I need the 32 - and I will - I've got the RD for it.

john-b

arlowood is on the right track.

An adjustment for the B screw (or a longer B screw) can account for a larger 32T cog, and additional links can solve the big chainring-big cog problem. But the real reason the mid cage (GS) rear derailleur has the longer cage body is to take up slack in the small chainring with smaller cogs.

The total capacity for a rear derailleur is calculated as the difference between the largest and smallest chainrings plus the difference between the largest and smallest cogs. With a compact double and an 11-32T cassette, that works out to 37T = (50-34)+(32-11). The short cage (SS) Ultegra RD has a total capacity of 33T. That means a chain sized to be long enough for the big chainring-big cog combination is going to have too much slop in the small chainring for the smallest few cogs, and a chain short enough not to have slop in the small chain ring-smallest cog will ruin the rear derailleur (and bend the hanger) if it's ever shifted to the big chainring-big cog.

An RD-6800 GS has a total capacity of 41T and IIRC sells for about US$75. Cheap at the price.

Spatulala

Ok that sounds like a comprehensive answer. 6800 Rd (£40) plus 5800 cassette (£25) sounds like the best solution, will I likely need a longer chain as well?

Thanks again.

john-b

Yes, you'll need more links.

Anytime I put on a new cassette I put on a new chain as well, because IMO chain stretch is the primary cause of cog wear. With a little maintenance, I average about three chains per cassette on my road bike. YMMV.

One other note while we're talking about capacity: That GS rear derailleur will work fine with your old 11-28T cassette, but if you ever decided to go with narrower gaps like an 11-23T or 11-25T you'd want to put that original SS rear derailleur back on.

saftlad

I had a cassette sitting in the garage waiting to get the rest of the kit together so thought I'd try it out whilst the bike was on the stand anyway. Compact chainset with 11-28 and short cage currently in place.

Changed the 32 onto the hub, put the wheel back on - everything changed just as smoothly as previously. Even big-big was ok, enough clearance from the sprocket so nothing need adjusting. Mind you, that was only turning by hand so not a lot of power going through it.

So it looks likely that if you wanted to run with a short-cage it would be ok as a stop-gap, but for longevity you're best off swapping to a medium cage and slightly longer chain.

DKay

Was small-small ok as well?

saftlad

Yep, just as smooth as before. Didn't have to adjust anything, straight bolt on and go

DKay

Interesting.