Cadence (why so different indoor/outdoor)

Wondering if anyone knows why my average cadence is usually around 15rpm higher on indoor bike than it is when doing outdoor rides (rolling hill type runs)?

I don’t see it as a problem but i’m curious as to why.

Gearing on outdoor bike is 52/34 30/11 - cranks 172.5mm, i’m rarely on the 34, but prone to a bit of cross-chaining.

Indoor bike is a smart bike, a spin bike with magnetic resistance control … 20kg belt driven flywheel, 170mm crank length.

The indoor bike is set up/fitted as close to my out bike as i can get it… but it has limitations with how they’ve built it. But basically the bars sit slightly higher than my outdoor bike.

My ramp test (Vector pedals on the indoor) put me within 3Watts of what my Garmin/4iiii has my FTP as on my outdoor bike.

Could it be purely down to the crank length difference between the two?

Anyone any idea?


Do you have your head unit for riding outside set to ‘include zeros’ for cadence?

  • If so, and assuming you do even a moderate amount of coasting, that can pull down the “Average Cadence” data for a ride outside… as compared to a typical indoor workout that may have very little to no coasting.

  • Essentially, I think it’s best NOT to include zeros for cadence on head units.


You’ve nailed it! :grinning: :clap:t2:

Yeah, checked and cadence averaging is set to include zero’s.

Thanks! makes sense now.

Edit - my power was set Not to include zero’s

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What Chad said. Also, having a lower cadence on climbs isn’t unusual. Either by choice or by running out of gears. The corresponding downhill may have coasting or soft pedaling that would affect the average, also.

Shorter cranks would increase your cadence slightly all else being equal but not by much. Rationale from my understanding is what your body adjusts to is the pedal velocity moreso than rpm. Shorter cranks requires a higher rpm for the same pedal velocity.

If it’s a concern I’d check your outdoor cadence on a flat (ish) section vs averaging the whole ride.

Not familiar with the spin bike in question but if the flywheel doesn’t have a freewheel than that would be a large effect as well.


Thanks, no there’s no freewheel on indoor bike… there is zero respite, an hour is an hour.

Cheers :+1:t3:

Your indoor bike seems to have a very heavy flywheel, so I reckon it feels more like when you are at speed on the flats. They are similar because in both cases the fly/rear wheel have a high moment of inertia, and thus, even when you stop pedaling for a moment, your speed will be approximately the same. That is more amenable to a faster cadence.

With lower inertia, i. e. when you are climbing outdoors or are in a lower gear with a smart trainer, you have to be more consistent throughout your entire pedal stroke in order to not slow down. When you are climbing in the real world, there is a second contributing factor: due to the gradient, your body mechanics are slightly different, too, and you are more likely to sit more upright.

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Good that you found the source of the discrepancy.

That said, cadence will differ on outdoors rides depending on the type of ride. The same rider, on the same bike, will have different cadence on a flat ride, on a hilly ride, when going hard, when going easy, in a crit race with tight corners, and on a long road race. The cadence used in outdoor rides isn’t constant. It’s funny that some riders expect that their indoor cadence should somehow inform what their outdoor cadence “should” be.

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