Straight block cassette for smart trainer?

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SilentDrone
Posts: 229
Joined: Fri Sep 22, 2017 5:55 pm

by SilentDrone

I have finally upgraded to a smart trainer for use with Zwift. For the past several years I’ve used a dumb fluid trainer that I’ve had for almost 20 years now. It just doesn’t want to give up the ghost. Anyway, I recently scored a deal on a wahoo kickr which should arrive in a few a day. I’m looking forward to finally getting to use Zwift with resistance feedback.

My question for you all is this, which is best for use on the smart trainer, a straight block 11-21 cassette or a wider 11-28?

Thoughts? Does it even matter? Thanks in advance.


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backdoor
Posts: 129
Joined: Tue May 21, 2019 9:54 pm
Location: Cascade Mountains WA

by backdoor

I'd say overall that a shorter block is great for fast twitch power building sprints, long block for spinning long climbs slow twitch. It doesn't really matter especially if you are training in ERG mode. In zwift some of the climbs increase rather rapidly over a short distance so when you shift on a straight block you might end up having to shift 2 or 3 times from the 17 to 21 vs 1 or 2 shifts on an 11-28 or 30. That being said you can adjust the "feel" of the climbs in zwift and in Rouvy and that can negate some of the shifting as well.

Bottom line it doesn't matter really. But you will be climbing 16% grades in a 21 or 23 :)

For what it's worth I use an 11-25 because it was what I had as extra lying around and sometimes wish for an 11-28 when I'm not in ERG mode so I can spin more on the steeper climbs.
Through the Valleys and over the Mountains...
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by Weenie


TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

It matters to an extent.

If you’re training for climbs, you should use an appropriately sized cassette and 100% trainer difficulty. This will slow down the flywheel and help simulate slogging up a climb at low speed. If you use lower trainer difficulty, you increase the flywheel/wheel speed…it changes your pedal stroke because the energy stored in the flywheel acts like a slight buffer against environmental changes.

AJS914
Posts: 4615
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

To me, the perfect trainer cassette would be something like the campagnolo 12-27. I never use my 11, 12, or 13 on the trainer. I also don't ever use my 32. I often start out in a 36x28 because it's easier to turn the pedals from zero rpms but then I quickly shift down towards the middle of the cassette.

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ms6073
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Location: Houston, Texas

by ms6073

Unless the OP has a dedicated trainer bike, seems like chain length would be a deciding/limiting factor. If not using a dedicated trainer bike, not sure why wouldn't you want to use the same make/model cassette installed on the trainer as is installed on your bike?
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AJS914
Posts: 4615
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

It just has to be compatible enough. On my wheel, I have a Campagnolo 11-32. On my trainer, I think it's a Shimano 11-28.

backdoor
Posts: 129
Joined: Tue May 21, 2019 9:54 pm
Location: Cascade Mountains WA

by backdoor

ms6073 wrote:
Wed Jun 23, 2021 3:32 pm
Unless the OP has a dedicated trainer bike, seems like chain length would be a deciding/limiting factor. If not using a dedicated trainer bike, not sure why wouldn't you want to use the same make/model cassette installed on the trainer as is installed on your bike?
This is a good point but really only applies if you are increasing the cog size on the trainer.

If you run an 11-28 on the wheelset for the bike you are using on the trainer anything smaller 11-25, 11-23, 11-21 will fit without issue.
Through the Valleys and over the Mountains...
2013 Ridley Helium - 6.9Kg
2017 Blue ProSecco - 9.0Kg
2018 Ridley Noah SL - 7.85Kg

SilentDrone
Posts: 229
Joined: Fri Sep 22, 2017 5:55 pm

by SilentDrone

Thanks for all the input. I have a dedicated trainer bike. It’s running the old 7800 dura ace 10 spd, with 50/34 up front. I also have a bunch of cassettes lying around in various states of wear, any of which has plenty of life on it due a trainer: 12-25, 12-27, 11-28, and the aforementioned straight block D/A 12-21 which is brand new still in the box. I bought it on a whim years ago because the idea seemed cool, but I’ve never even installed it because honestly it’s the worst choice for real life riding for me.

On my “outdoor” bike I have 50/34 and 11-32.

From the feedback, seems like the best choice will be the 11-28 for the trainer to make it as versatile as possible.


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boots2000
Posts: 1681
Joined: Mon Oct 15, 2007 9:28 pm

by boots2000

Wider- Because with a smart trainer and platforms like Zwift it makes the grades feel "steep".

I had the same idea/plan when I 1st got a smart trainer. I scoured the earth to find an 11 speed narrow gap cassette. I always used this on dumb trainers to keep the jumps feeling small.
Then I got on Zwift and started going uphill- I was pretty instantly out of gears and crunching a low cadence.
I put the 11-28 that the trainer came with back on.

by Weenie


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