This was my biggest frustration with the pedals (besides them failing every 12-18 months). I've even done a few races (including HIMs) where I've forgotten to change the value. Your best bet is to change it as soon as you move the pedals over from bike to bike. The other issue is that if you pair them with both your watch and your biking head unit (assuming you use both), the values have to match or you don't really know what you're going to get.

Hmmm. That's what I was afraid of.

Are the pedals reading the crank length setting from the head unit/watch, or is it something that is set up in the powertap app then just displayed on the head unit? If the former, my thinking is that I could use my head unit for my road bike and my watch for tri bike and have the crank length values for each bike set in the respective devices.

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Strava

No idea how it works. If you only use one device with them at a time, your idea should work. I use both a watch and edge during races so i don't have to turn my wrist to look at power data so that was an issue for me. Now I just have separate power meters and my life is simpler

You can change it from your head unit before any given ride. I have different size cranks on my road and tri bike and this is not an issue at all. Takes maybe 90 seconds.

The length is set in the pedal by the head unit. So once you've set it once by any app/unit you're good. The problem is that most head units (at least the Powertap app and my Garmin 935) remember the length they last set to, so the value you see in a particular app/device may be wrong and confuse you (but again, this value won't be used if you use that app/device to record a ride). So better safe than sorry and set it whenever you think about it. I try to do it every time I move them to another bike, and to only use the Garmin.

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Citizen of the world, former drunkard. Resident Traumatic Brain Injury advocate.

Get another Garmin?

Since the pedals don't know how long the cranks are that they are attached, they cannot transmit that data.

Perhaps, Garmin could build something into their activity profiles that allows you to specify different crank lengths for "Tri" and "Road". That'd be neat.


If you don't want to buy a new bike computer, I would set your watch to 155 and try to remember to change your bike computer every time you switch. If you don't, it should be pretty obvious that the number on your bike computer doesn't match your effort or the watch...then for the event, figure out the conversion factor or use the watch.

You can use this to fix it after the fact: https://www.fitfiletools.com/#/booster#view

This drove me nuts so I matched my road crank length to my tri bike (admittedly only 170mm). Now I'm just sick of pulling them off and changing them over whenever I want to ride a different bike so I ended up buying a pair of assiomas to match.

Have p1 pedals. Love them. Same challenge as my road bike and Tri bike have different crank lengths. I tend to ride on or the other for periods of time depending on the upcoming events. Takes me 30 seconds to change my cranks lengths on my garmin fenix 5. A non issue for me. Much easier than changing cranks.

Ummmm, you mean like the different bike profiles on the Garmin 500? The one where you set one bike up called Tri with 165mm crank length and one called Road with 170mm crank length. Yup, that'd be really neat.

My understanding was that the length was stored in the pedals. I remember asking TrainerRoad about this and they told me to set them up with the Garmin head unit and then use it on the TR app.
I have similar issues with 165 on road and 145 on tri.
I ended up getting a P1s for the road bike when they were on sale on Black Friday.

Depending on which bike you are using, why not just set it to the primary bike. Let's say it is on the tri bike, then set it for the 155. Once on the road bike on 172.5, the power should just read lower by 11 percent (power = force x distance x RPM) of the real value....since distance is longer in this equation, you're just seeing a lower number than reality. Conveniently its around 10% lower so you can just eyeball it since really all you are worrying about is pacing.

To me this is like the difference between working out my cardio in different sport. Now that I am a swimmer, real swimmers are amazed by my impeccable pacinig at thee 1500m and and 800m even though I have almost no experience in these race.....but I have done countless 5K runs, and 15K bike time trial so even through the timing system is different, I know how to extract the right pacing out of my body.

So you could treat this as 2 sports. Tri biking measured in real watts. Road bike biking measured in a new unit. How about we'll name them fulcrum90 to denote that with this fulcrum your number is 90percent of a watt....problem solved. Should I submit this unit to Systeme Internationale so I can get my unit inserted beside James Watts'?

Sold my 500 a loooong time ago. Bummer that they removed that feature.

This is probably what I'll end up doing cause I'm lazy. That and in the process of switching all my bikes over to PT hubs.

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Strava

Actually, it was on the 510 (maybe the 500as well), but removed I think on the 520. No idea why it was removed - is a really useful feature.