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I have a BH road bike that I use to go to work. Most of the ride is rough, but flat (nothing steep). I don't race, so to me the bike is just a form of transportation that takes me from X to Y.

The bike shop told me that I had to change the 10-speed 11-28 cassette, but they don't have it available.

On eBay, I found a brand-new Ultegra 10-speed 11-25 cassette for $50, and I was considering replacing it with this one.

I know nothing about bikes, and had a few questions:

  1. Is it possible to change an 11-28 cassette with an 11-25 cassette?
  2. If it is, is it just a swap of the cassette or does this involve other parts?
  3. Will I feel a difference when I'm pedaling?
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3 Answers 3

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To add to Weiwen's answer, which I agree with:

  • Your low gear will be a little higher, with one more gear in the middle of the range.
  • You can replace the cassette at home if you want. To do this, you'll need a Shimano lockring tool, a chain whip, and a long-handled wrench to turn the lockring tool. And some grease for the threads. You can find videos showing how to remove the old cassette and install the new one.
  • To remove the old the chain (which you really should do), you'll need a chain breaker. To install the new one, you can either use the chain breaker to drive in a special pin on the new chain, or get a master link, for which you may need another tool, chain pliers.
  • $50 for a cassette is not an amazing price. No reason not to get that from one of the many online bike stores. I was able to find an 11-25 for $40 at Modern Bike.
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    The last point reminds me, a 10s 105 cassette is likely to be functionally identical. A new 10s Tiagra could be close enough to equal.
    – Weiwen Ng
    Commented Feb 23, 2023 at 23:22
  • Chain pliers make masterlink installation/removal way easier but I wouldn't say they're mandatory.
    – whatsisname
    Commented Feb 25, 2023 at 19:35
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If the bike shop told you to change the cassette because it was worn, they would have said the same about the chain. These items wear in tandem. It is recommended to get a chain wear tool (or have the shop measure it) and check repeatedly during a season. If you replace the chain before the wear limit, you can usually get 2, maybe more, chains to each cassette. So, physically you can just swap the cassette, but in this scenario the chain will almost certainly skip on some gears.

Anyway, yes, the bike will fit an 11-25. Do you use your current smallest gear? If you use it, then with an 11-25, the new smallest gear is going to be your current second smallest. 11-25 is for really flat terrain, or maybe for really strong (or extremely traditionalist) riders on hillier terrain.

To size the new chain, it is recommended to use the standard method recommended by the chain manufacturer or the Park Tools website. You will need a chain tool.

That said, if you are seriously unable to follow the guidelines, you could either have the bike shop do it, or you could just size the new chain at the same length as the old one (or take out one link). This will leave the chain slightly too long, and it will sag if you are in the small chainring and the smaller cogs. However, you shouldn't be in those cogs anyway.

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    While it might be ideal to adjust chain length, it is not really required, same length chain should be just fine. Small-small will have the same sag with the new cassette as current one, and if it works now, will still work.
    – mattnz
    Commented Feb 24, 2023 at 2:03
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    For me 10 and 11 speed cassettes easily survive 4 chains and I’m not religious about replacing at 0.75% wear. But I like to use the bigger sprockets.
    – Michael
    Commented Feb 24, 2023 at 6:36
  • Just to set the scale, what counts as really strong, and really flat?
    – ojs
    Commented Feb 24, 2023 at 11:31
  • @ojs In my mid 20s or early 30s in terrain around Washington DC, I used a 13-29 and it wasn't quite enough gearing but I could get by. I would say I was decently strong, ex US Cat 3. What I intended to convey was that in my early 20s, people might have mocked the use of even a 25t big cog - there was a rumor that the DS of ONCE made his guys use a 11-23 in the Vuelta - but that was counterproductive.
    – Weiwen Ng
    Commented Feb 24, 2023 at 13:46
  • @WeiwenNg That DS must have pooped his pants when Contador rode mere SRAM APEX with a compact crankset and an 11-30 cassette to drop everyone on Angliru in 2008. ¡QUÉ HORROR!
    – Andrew Henle
    Commented Feb 24, 2023 at 14:43
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To add to the other two answers, you don't need to stick with an Ultegra cassette.

The differences between a 10-speed Ultegra cassette and a 10-speed 105 cassette? Different color, and the Ultegra uses an aluminum lockring so it's an entire gram lighter than the same-size 105 cassette with its steel lockring.

CS-4600 Tiagra cassettes also work - I've raced on those, and I never noticed any shifting difference between Tiagra, 105, or Ultegra cassettes.

They all work.

And they all get rapidly covered with grease and gunk and dirt and no one but you will know what it is anyway.

The Tiagra cassettes also have the advantage of being one-piece, if I remember correctly. The one-piece makes it easier to install, remove, and store without losing cogs. It's also an advantage if you have an aluminum freehub - individual cogs on a cassette will dig into an aluminum freehub's splines, whereas the one-piece cassette will spread the pedaling load over a wider area and not dig into the freehub as badly, if at all.

The same goes for chains, since you're replacing your cassette you will also have to replace your chain.

Bog-standard KMC 10-speed chains work just as well as Ultegra chain.

Heck, in my experience, KMC chains work much better. The only chains I've ever had fail on me were all Ultegra chains from the same batch a bit over 10 years ago - they literally had a sideplate fail under load, separate from its pin, and have the chain fall apart - while pedaling. See https://www.google.com/search?q=ultegra+chain+CN-6701+failures - notice all the 2010/2011 dates? What if your new-old-stock 10-speed Ultegra chain is from that batch?

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  • The surface treatments differ between cassettes, with Tiagra probably not having any, 105 having some sort of nickel plating, and Ultegra having some unknown treatment. We don't actually know if this makes a difference in durability. For chains, the low friction treatments do differ, and it's been shown that there's a very small but measurable difference in friction.
    – Weiwen Ng
    Commented Feb 24, 2023 at 14:21
  • @WeiwenNg A bit late here, but how long does that initial, new-chain friction difference last once the chain gets outside and starts collecting dust and grime? My guess is "not very long".
    – Andrew Henle
    Commented May 8, 2023 at 15:38

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