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Like I hoped, after a few months of hunting, I was finally able to find a really good deal on a road bike, in the winter. With the money saved, I was also able to buy a smart trainer to use with Zwift.

I need a spare cassette for the trainer. My current setup that came with the bike is 105 CS-R7000, 11-30T I'm thinking of getting a second cassette with a different range - I can see that they generally all start at 11 teeth and can even go up to 34T, but actually I'm thinking of getting 11-28 instead as where I live is pretty flat and i don't expect to use the 30T at all.

Should I get a different size cassette? Which one should I use on the trainer (given that Zwift has Alpe d'Huez etc) and which one should I keep for my road use? Is there any point in getting Ultegra (my bike is 105) and I clearly don't care for the weight on the trainer, but I've heard reports that Ultegra is more durable?

  • Depends what your goals are. Do you want to train specifically for your local flatter terrain, or do you want to tackle monster ascents in Zwift? – Argenti Apparatus Dec 29 '18 at 21:44
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    Be aware that if you buy a cassette with a larger range, you will likely have to adjust the length of your chain. – Gary.Ray Dec 30 '18 at 4:15
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Should I get a different size cassette?

Probably. You'll need one eventually, as they do wear out.

Which one should I use on the trainer (given that Zwift has Alpe d'Huez etc) and which one should I keep for my road use?

Having a cassette more closely-spaced than 11-30 is probably good for a trainer, as you can more closely target specific power levels and cadences - as long as they're within the narrower range of a tighter cassette.

Is there any point in getting Ultegra (my bike is 105)

IMO, no. I've raced on Tiagra cassettes as well as 105 and Ultegra, and I never noticed any performance difference between even that cassette and any Ultegra or 105 cassette. And I have quite a few of both - 11-23s, 11-25 (IIRC, that's the Tiagra one), 12-25, 11-28s, and 12-27s. I'll swap cassettes as needed. When racing, I'd chose the narrowest cassette that, if possible, allowed me to stay on the large chainring the entire race. For training, I tend towards wider cassettes such as 11-28 or 11-30 to enable hill climbs at low to moderate levels of effort, should that training ride be a longer, lower-power ride.

and I clearly don't care for the weight on the trainer, but I've heard reports that Ultegra is more durable?

Meh. In my opinion and in my experience, the only real difference between 105 and Ultegra cassettes is the color. Ultegra is darker. The minimal weight difference comes from 105 cassettes having a steel lock ring, and Ultegra cassettes having an aluminum lock ring that cuts an entire gram or two from the weight.

So no, don't spend more for an Ultegra cassette over the same 105 cassette. Only spend more if you need a specific gear range only available in Ultegra.

  • Buy the cheapest equivalent cassette because (a) there's no need for saving weight and (b) the cassette will not be subjected to the 'stress' from being used on a road. – Carel Dec 30 '18 at 14:48
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Where I am, market price for Ultegra is around 50% higher than 105. So it would need to be 50% more durable to justify buying Ultegra for durability; not sure if that sounds likely to me. Up to you whether it’s worth it, based on your own costs, but think of it in those terms if you aren’t trying to save weight or racing.

Meanwhile do you need to change the range on the road cassette? Impossible to answer, you’ll need to get out and ride and make up your own mind. 11-30 should cover you for lots of circumstances until you get a feel for what your legs can achieve, both now and as you get fitter.

I try and think, “buy what you can afford to replace” because it all wears out sooner or later.

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