mworden

I just ordered some new wheels (Pacenti SL23 rims w/ White Industries T11 hubs) to replace the stock ones on my Specialized Roubaix Compact. I need to figure out what I want to do about the cassette. The bike came with a Tiagra 12-30 10-speed cassette that I could just move to the new wheels and move back to stock wheels if and when I want to use them. Winter is coming on and I imagine that I'll want to use the stock wheels on the trainer once it gets too nasty to ride outside. On the other hand, as long as I am burning up the credit card, it might be a good time to consider a new cassette for the new wheels. I'm considering a Tiagra 11-25. I live in SE New England and the terrain is mostly rolling; nothing too steep for too long. I sometimes run out of high end but I'm rarely in the biggest cog on the back (and with my new wheels I'll be able to just fly up the hills, right?). Or maybe an Ultegra 11-28, which would give me the extra high end without as much penalty on the low as the 25. Any significant reason to prefer the Ultegra over the Tiagra here (presumably some modest weight savings, can't imagine performance is that much different)? Other thoughts? Are there compatibility or adjustment issues I might not be thinking about? I've never had to swap a cassette before but how hard could it be...? (famous last words)

mworden

Uh, that should be cassette options... (spelling challenged)

merlinextraligh

The difference is mostly weight, given the Ultegra has an aluminum carrier.

Some marketing material suggests that Ultegra shifts better, due to new improved tooth profiles. I'm not sure you could tell a difference in practice.

RPK79

I was in a similar boat when I upgraded my wheelset earlier this year. I opted for the ultegra cassette since the price difference was nominal. I did not change the gearing on the new cassette since I wanted to leave the old one on the old wheelset for the trainer and I didn't want to have to worry about chain length issues going from one to the other. Also, I was completely happy with the gearing I had...

mworden

Am I likely to have chain length issues switching from a 12-30 to a 11-28?

dtrain

Doubtful. But if you were to cut a chain for a 11-25 (for example) there would likely be issues putting the 12-30 back on.

achoo

I can't.

I have one of those Tiagra 11-25 cassettes. Got it for something like $10, figured it'd be useful. I've actually raced on it a few times. Shifting is no different from my 105 and Ultegra cassettes.

rpenmanparker 

Matching within one or two teeth is wise unless you have a totally different use envisioned for the two sets of wheels that would make changing the chain worthwhile. In any case I agree with the wisdom of having a dedicated cassette for each rear wheel. Don't overlook the fact that you may (likely) have to adjust your rear derailleur for micro differences between the two rear hubs when exchanging them to get best shifting on both. Just a minor inconvenience.

banerjek

Not a chance. Here's how things work -- cassettes with big cogs also have small cogs. You don't need to shorten your chain when you choose a tighter cassette because one of the things your RD does is pick up slack as you go from big cogs to little cogs. However, if you run chains at the minimum length, you need to put on a new one if you install a cassette with bigger cogs.

revchuck 

I've got Tiagra (12-30, same as yours), 105 and Ultegra cassettes. I don't feel a difference when I shift. The differences among them are weight and choice of cogs.

Since you've already got a wide range cassette, getting a narrow(er) range cassette might be a good idea. I've been on a 12-23 this year, and I really like it. There is a one-tooth progression from 12-19t cogs, then 21 and 23. That one tooth jump is really useful when on the small ring pushing up a hill or into a strong headwind. The 18t cog is where I'm at in the big ring in a paceline at 20-21 mph. A 12-25 is about the same, but substitutes the 25t cog for the 18t. I wouldn't get a cassette with an 11t cog unless I really needed it, since you usually lose the useful 16t cog. 12-23 is only available in Ultegra, but 12-25 is available in Tiagra and 105 as well as Ultegra.

zacster

Not quite. Sometimes the cage doesn't have enough wrap to pick up all the slack. In that case the chain would hang a little, or a lot depending on how big a difference, on the small/small combo. This doesn't make it unrideable. The other way, at minimum length, can cause real problems.

Cyclelogikal

Rolling terrain how about a 12-25. I use to use this combination where I live with steep climbs living in the mountains but my new Orbea Orca for some reason came with a 11-32. After riding that 32 gear up a few 18%-21% grades I was happy to have that. Did I lose some top end speed downhill............yep but rather lose a few mph downhill that burn the quads on steep climbs and be bonked!

Not saying you need an 11-32 for rollers but a 12-25 was a good combo for that until I hit the extreme grades and the 25 while doable will make you work.

dtrain

^ you GAINED downhill speed if you went from 12 to 11.