Question about replacing parts on a bike only used on a trainer

Equipment
1

I have a bike that is exclusively used on a trainer. The geometry matches my road bike well, except that the crank length is different. I want to fix this issue, but struggling to find the exact crankset in the appropriate size. Given I only use the bike in ERG mode for Trainer Road and will likely update to a virtual shifting equipped trainer in the near future, does it really matter what crankset I get? ie. could I just eliminate all the shifting components?

With virtual shifting, Zwift has their solution, does anyone know of plans for other platforms to adopt similar technology?

2

I don’t have too many insights regarding virtual shifting, but I’d recommend finding a crank that will work with your groupset if you can. It needs to work with your chain, derailleur, and cassette at least.

It doesn’t have to be the same model, but something compatible would be wise in my opinion. What do you currently have on there?

3

It’s an ultegra 6800. I’ve found a cheap 105 12 speed, but not sure if the 12 speed will be compatible with the 11. I think it will probably fit…

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4

I’m running a 12 speed Ultegra crankset on my 11 speed Ultegra 8070 bike and it works great. I think it should work for you.

5

Shimano is very particular about what’s technically compatible, but I’d say that a 12-speed crank will likey work with an 11-speed group just fine.

Putting a wider chain on a thinner chainring is better than putting a thinner chain on a wider chainring, and since you’re using ERG mode, I can’t really see any issues… :man_shrugging:

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6

If you are using ERG, it really doesn’t matter too much. I am still using a classic Mavic SSC crank (the starfish design) from 1991 on my trainer only bike. It is a mix of 8, 9 and 10 spd components. Yeah, it doesn’t shift great in the front if I am just freeriding in Zwift, but I rarely do that anyway and when I do, front shifting is not that big of a deal.

It is flawless in ERG.

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7

This is supported by the fact that Shimano is just sending out one style of crank for the current crank recall, no matter if you are running 10, 11 or 12 spd.

I am still using an 11spd crank on my 12spd Di2 and have never had any issues, either. (Obviously the reverse situation to the above)

8

I’ve swapped 10 and 11 speed cranks a few times no problem and use 11sp chains on both. AFAIK chain inners are identical and only the side plates are thinner to fit in tighter/more geared cassette. Ive never had 12sp but I can’t see it being any different.

9

Just go on ebay and find the exact same model crank you have in the correct size.

10

I was looking at the Zwift frame and thought that could be a nice trainer solution with no derailleurs but Zwift virtual shifting is compatible with Zwift so far. That wouldn’t work for me.

If I were building a trainer bike from scratch today, I’d just find any used frame in the right size or buy an open mold Chinese frame and then fit it with a 1X crankset, and some inexpensive shifters/derailleurs. If one needed new, the mechanical Chinese groupsets (Sensah, Ltwoo) would probably be just fine for a trainer.