I think the time has come to replace my rear cassette, it has begun skipping in a certain gear. I'd also like to give myself a bigger granny gear (something like a 28 or 30 would do). I haven't done much in the way of maintenance/buying new parts before so am after some advice.

Bike - Bianchi ML3 Alloy Reparto Corse.
The current cassette is a 9 speed.
Rear derailleur Shimano 105
Front derailleur Tiagra.
Chainset is 105 (looks like 53/39 which I think I'm happy with).
Shifters 105 brake-mounted.

So I guess chain will need changing as well, and possibly chainset (it has done a reasonable number of miles).

My question is - when I'm looking at cassettes I see there are a few 9 speed options, eg HG 50, PG 950/970 SRAM, Ultegra CS6500. I'm happy to pay a bit more for something decent. I guess what I have now is SRAM, but I don't know for sure! I very much doubt it's Ultegra. If I did go for the Ultegra would that mean I have to buy an Ultegra chainset too? And what about the derailleurs & shifters, would they need to be changed to Ultegra as well? I don't know what combinations 'just work'. And what about Dura Ace etc?

I am looking at 9 speed because I seem to remember someone saying to me that 9 speed is the most my frame will accommodate, I don't know whether that is right. I can't find any frame specs that tell me that information which is really annoying (maybe I'm looking in the wrong place).

Thanks for the help, apologies for the noob questions.


  • 1
    Can you check the rear derailleur for a code engraved into metal? Probably something of the form "RD-5501" With this info, we can look up shimano's published spec on the max and min tooth counts for your cassette plan.
    – Criggie
    Commented Apr 6, 2021 at 22:35
  • You are not going to notice any difference at all between an HG50 cassette and and an Ultegra CS6500 cassette with the same gears. Commented Apr 7, 2021 at 13:13
  • The Ultegra components use better materials and have more precise shaping for the shift lanes (they don't cost more for nothing) so should shift better and last a bit longer. @AndrewHenle
    – Noise
    Commented Apr 7, 2021 at 19:47
  • 1
    @JoeK Umm, I've raced on Tiagra cassettes. You know what the difference is between an Ultegra cassette and a 105 cassette? Other than the color, the Ultegra cassette uses aluminum instead of steel for the lockring so it's lighter. About one whole gram lighter. But hey, it's your money if you want to burn it. Commented Apr 7, 2021 at 20:08
  • There is less difference between 105 and Ultegra than there is between Tiagra and either. It's possible to race effectively on Claris if you need to but the higher groupsets don't just ''weigh less'' or ''look prettier.'' Thankyou for your insights.
    – Noise
    Commented Apr 7, 2021 at 21:07

3 Answers 3


Generally speaking, a frame/wheel hub that is fitted with a 8/9/10 speed cassette can take any of 8/9/10 speed because they're all the same width, just pack an extra cog or two in by thinning down the chain and inter-cog spacing.

11 may be possible but it depends on how the cassette can overhang inboard of the freehub without grinding. 12/13/14 speed is right out, unless you're buying a new bike.

The reason for staying with 9 is that you don't need to change the shifter and possibly rear derailleur. The cost of these parts adds up, so going to 10 speed gives you only one more cog but costs a lot more. Minimal change from maximal expense.

You're right the chain absolutely needs changing. The chainrings may be adequate as-is, but its wear-dependent. Also check your derailleur's jockey wheels - there its sideways slop more than tooth wear.

Mostly all 9 speed stuff is interchangeable. At 10 speed the standards start diverging, with differences in MTB/road, and tiagra doing its own weird mixed up standard.

Personally I'd replace with a 9 speed chain and cassette, check for wear in jockey wheels and chainset, and then keep riding. Shout yourself some new bartape too, and the bike will feel awesome.


Focusing on the quote below:

I am looking at 9 speed because I seem to remember someone saying to me that 9 speed is the most my frame will accommodate...

Fortunately, this is wrong. Rear dropout spacing for rim brake road bikes is still 130mm. The frame is not the issue. You could put a 12s group on that frame if you were willing to buy one. It would be an expensive undertaking, because you would have to replace the rear wheel at minimum. When Shimano introduced 11 speed, it slightly changed the dimensions of the rear hub body. Replacement 11s freehub bodies are available for some wheels, but not all.

Also, the chainset does not need to be changed entirely even if the chainrings are worn. You can simply buy new chainrings. It's possible that it's more cost effective to get a full new chainset if you shop used. If you are upgrading the groupset, I would lean towards a new one.

  • Took your advice on the chainrings - just bought a couple of new TA Alizes to stick on the 105 Commented Apr 9, 2021 at 21:03

You can simply get any 9 speed cassette. All 9 speed parts are pretty much interchangeable. Edit: Except for Campagnolo, as per Carel’s comment.

You’ll also need a new chain (which you’ll have to shorten to the right length).

If you go for a cassette with bigger sprockets you’ll have to make sure that your existing derailleur has enough capacity.

  • 2
    Not any cassette, Campagnolo is out of the game because the free-hub splines are different, but SRAM or Shimano will fit. Same with chains, any 9-speed chain, except again for Campy, which has a slightly different width. And go for a master-link or quick-link joined chain for ease of installation.
    – Carel
    Commented Apr 7, 2021 at 11:21

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