# Dumb flywheel trainer with Assioma pedals and rear wheel cadence/speed sensor

Greetings,
I’m using a basic flywheel resistance trainer (Kinetic) with Assioma power meter pedals and a rear wheel cadence/speed sensor (Lezyne). All of the sensors are sending their data to my laptop via Bluetooth and I’m running TrainerRoad on my laptop for my workouts. After a workout is complete, the laptop sends the data file to the TrainerRoad backend server which then sends the data automatically to Strava.

Does anyone know if the distance and speed data displayed in Strava is simply displaying the straight data from my speed sensor? I assume this is just a count of wheel revolutions for distance and a distance over time for speed? Does anyone know where the setting for wheel circumference is…to true up the accuracy?

Lastly…physiology… when I use a watts/speed calculator like this one:
https://www.gribble.org/cycling/power_v_speed.html

I weigh roughly 180lbs (6’ 6") and if I assume my bike weighs 20 lbs fully loaded, when I’m pushing 200W, that equates to roughly 20mph. But this calculator is assuming you are riding outdoors with air resistance and rolling resistance. So…I would think that 200W would yield a speed higher than 20mph indoors on a trainer. But when I look on Strava at my own data from my own workouts, 200W is around 17mph.

Can anyone help me understand what I’m looking at and why my indoor mph is less than I would expect? I train to power and HR, so speed and distance aren’t incredibly important but I’m curious…and thinking about how my training will translate to outdoor rides in the spring time.

Thoughts?
Dave

Speed data is worthless on an indoor trainer.

I wouldn’t even bother going down that rabbit hole. If it were me I’d just remove the speed sensor entirely.

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• Yes.
• Yes.
• The wheel circumference is in the TR app Setting section. But there is no “accuracy” option like you imply. Just simple rpm x size type data.

TR does not offer any “smart” option for speed / distance based on rider data or estimated conditions. You need Zwift, RGT Cycling or similar apps for that type of data.

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Thanks…so…how would you set up training goals if you would like to be able to average 17-18mph for a century ride? How do I back into a sustained power output goal from a mph goal?
Thanks!

Thanks! Is the data sent from the wheel sensor just a revolution count and the distance is calculated by TrainerRoad using the wheel circumference setting? Does TrainerRoad send Strava revolution counts or distance using the wheel circumference calculation?
Thanks!

• That is my understanding.

If you rack up enough outdoor rides with your power pedals you’ll begin to see how your speed corresponds to different power levels. Obviously this will vary based on elevation profile, wind, aero position, etc but you will see how the two relate for you.

Average speed will be largely dependent on terrain and whether you’re riding solo or in a group.

Concentrate on watts and the rest will follow.

Ballpark numbers for you right now would be 300w FTP and 0.70 IF (210 watts NP over 5.5 hours) to reach that goal.

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I’d agree with this. A recent long ride I did was 18.1mph for 4:50, NP 228w. That was wearing winter kit, road bike, mudguards, fully loaded, making very little effort to be aero. I’m ~80-81kg, 180cm, so 210w for the OP seems about right.

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Thanks for this advice. This is my first year doing power training and I’m starting indoors so I don’t have any outdoor rides with power to compare to…hence my questions.

Can I ask you how you calculated the 300W FTP and 0.70 IF (210 watts NP over 5.5 hours)? I’m a numbers guy and would love to play with the calculations (i.e. what if I’d like to try to average 20mph over 100 miles…what FTP, IF, NP…etc.) Is there a website or pub you can point me to?

Thanks again for this great advice!

It’s anecdotal based on my own experience riding solo centuries in that average speed range with about 5,000 feet of climbing and average weather conditions.

< 3,000 ft would be considered a “flat” century, and 10,000+ would be more of climbing specific/L’Etape type of event.

Also notice I used some pretty round numbers.

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I can answer this with 100% accuracy

You went 0 miles at 0mph

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I’m sure you can play with internet calculators but here is an actual ride, I’m a little shorter and a little heavier than you:

That was mostly solo and few stops. I have some faster centuries but those were in groups.

Thanks - great info!

This looks like a good resource - thank you! What do you personally do with bestbikesplit?

Most people use Best Bike Split to help determine a pacing strategy given their FTP and course profile (distance, elevation, etc). In your case you could play around with the FTP number to determine what you need to get to in order to hit 17-18 mph for your century.

I was just monkeying with the free version of bestbikesplit.com… that is exactly what I’m looking for - thanks!
Dave

I like to use this tool for computing how many W gets you what speed: http://bikecalculator.com/

Going into your question on how indoor your Watts relate to speed in Strava and how/why this differs from the calculator, and given you are a numbers guy :

• First there is the calibration/accuracy of your pedals. Accuracy is about 1%, so if calibrated properly this should not differ much.
• Then we have drive train losses perhaps 2%-3% if your chain is clean., your pedals measure your power output, but your trainer will only see net power after subtracting drive train losses.
• Depending on your tire pressure and how hard you press against the roller, this will give a different trainer rolling resistance.
• The Kinetic trainer has a build in power / speed profile that assumes your trainer rolling resistance is some base value and will then produce back wheel speeds vs Power comparable to riding outside on a flat surface, including outside rolling resistance and air resistance.
• finally there is the wheel circumference setting in the TR app that takes the back wheel revolutions and translates to speed.

Kinetic published a power profile of their fluid trainers, it looks like they think 200W should get you to 18mph:

If you are seeing 17 mph, that looks like 180W to me on the graph. So those 20W could be 10W drive train loss and 10W from Trainer rolling resistance being different from what was assumed in the design of the trainer. Or any other allocation, adding in accuracy of the pedals, accuracy of reading the chart and how well your trainer actually represents that chart.

Glad to help. Are you targeting a particular event or route for your century? Will this be your first one?

I did mine two years ago, which is was started me on the path toward structured training. Prior to that I had been cycling recreationally with two group rides and one solo ride a week - working up to a max distance of 40 miles. I trained for my first century using a plan from Peak’s Coaching Group, which actually worked very well, but was also first venture into structured training so likely anything would have given me improvements. However, I ultimately moved to TR as I wasn’t all that enamored with the winter training plan I purchased, and I liked the idea of having access to TR’s full library and all of the training plans with a subscription. I’ve probably spent more on TR subscriptions than if I had bought one or two year’s worth of PCG plans but still feel the money is well spent considering Plan Builder, the podcast, this forum, and hopefully one day a master’s training plan.

I did a second century last fall without specifically training for it. Just followed TR’s base-build-repeat since I wasn’t signed up for any races and didn’t want to go into the specialty yet. Other than some sore neck muscles from doing all of my riding inside without a helmet on, the century went well.

This year I’m targeting one road race and a couple of fondos / centuries, so I’m using Plan Builder. So far so good.

Good luck on your century!