BCDrums

Last year, I bought a Schwinn IC3 stationary exercise bike for my lovely bride, and she rides while watching TV. I decided to do the same, and want to record my mileage into Ride with GPS to add to my good-weather road riding.

The bike is not web-connected. It has an on-board “console,” really like an old-school Cateye bike computer, that reads out MPH, distance, time and cadence, derived from a single RPM sensor on the flywheel. The MPH and distance it reports seem inflated to me. For the last few years, my average speed has been 15-15.5 MPH at 85-90 RPM cadence and this unit reports 19 MPH at the same cadence.

I am wondering if the console data is accurate or not. Does the fact that I am not riding a varied terrain of rolling hills translate to a higher average speed, or is the console just wrong?

More clues: in order to send the data from this bike to RwGPS, I bought a Wahoo speed sensor and mounted it to the flywheel. The sensor talks to the Wahoo Fitness app on my phone, which can forward my ride data to RwGPS. The app allows me to enter a circumference for the wheel, so I used the circumference of my road bike’s wheel and tire. The result was a crazy-high speed and distance, 23 MPH, so I changed the circumference to the actual size of the flywheel, and got an average speed of 17 MPH, not much different from the bike’s onboard console at 19 MPH.

Does anyone have some idea as to whether I should expect a higher average speed on a stationary bike? Or is the bike’s on-board meter inaccurate?

Thanks for your thoughts.

Wildwood 

Will my little tykes oven be the same temp as my adult oven.


don't want to burn the cookies.

gpburdell

Kind of apples and oranges here.

Any speed/distance stuff will be whatever you choose to calibrate it to be. The flywheel isn't a tire, you're not covering ground, and you likely haven't any real idea as to the gearing ratio from the crank to the flywheel like you might with a bicycle on a trainer.

Also, since there's no wind drag, you'll tend to see more speed for the same power output at any given cadence.

If it were me, I suppose I'd set the wheel size to whatever gave an approximation of my usual outdoor speed for a given cadence/effort. It's still going to be an approximation so I wouldn't get too wrapped up in trying to achieve any sort of accuracy.

UniChris

Indeed - an OP is starting to get into a speed regime where (apart from climbs) wind drag is the major consumer of wattage. Remove that and of course "speed" goes up.

On an actual moving bike the power lost to wind drag will start to vary with the cube of velocity (the difference in wattage between 19 and 20 mph is substantially more than that between 15 and 16), while the power consumed by the exercise bike's resistance mechanism is likely nearly linear with cadence if a strap, or the square of cadence if magnetic.

Indeed... have been debating if the snow I'm watching fall outside means today is the day I'm finally sticking some sort of algorithm in an esp or arduino and attaching it to the wires coming off the verified-functional cadence sensor on my salvaged exercise bike. I keep telling myself I'm going to build a custom cycle computer for on-road use, and something where I could fiddle with it from a connected laptop while "riding" seems like a starting point anyway...

PeteHski

Speed and distance reported on that type of bike are pretty meaningless. Only a smart trainer/bike with accurate power measurement and real world simulated physics model (including your own weight, height, road bike, tyres etc) can provide a realistic speed and distance covered over a simulated course. What you have there is a very crude approximation of speed on some generic road bike riding on flat smooth ground with no wind. IME they are nearly always much faster than what you can achieve outdoors, especially if your outdoor ride involves hills and windy conditions.

SoulAmazing

hahaha damn

Thanks.

To the OP i feel slower on my stationary but speed sensor indicates I'm faster on it. Like others said the factors of riding to the outdoors will attest to what you're seeing. Either way you're pedaling.

burnthesheep

Virtual training setups take into account road grade, a CRR estimate, the physics/aero actually somewhat tweaked to rider height and weight, etc....... This is why "distance" and "elevation" work out reasonably well for smart trainers and things like Zwift. None of that exists for a simple stationary, so distance becomes irrelevant.

Stationaries and fluid trainers and such, just worry about time spent doing work. If you need to track wear and tear, speed sensor works fine to track miles on fluid trainers using your real bike. Most gyms with stationaries probably track equipment hours, not distance, to perform maintenance.

Outdoors also, I go by time and intensity. Not miles. If I ride cyclocross, I might average 12mph but work just as hard as riding my TT bike at 24mph. So.....distance is worthless to fitness.

BCDrums

Good point about the heart rate monitor, hadn't thought of that. A chance for a new gadget...

Yes, I think this is the way I'll go.

I hadn't considered wind drag, or absence thereof. Good point. I'm watching the snow too, will later try to convert shoveling to road mileage...

Good advice. Thanks all, for the ideas.

UniChris

Hmm, maybe if I stuck some wheels on the fan bike, took off the lower front quadrant guard and rigged some sort of deflector chute on the upper, I could go clear the bike path 4 inches at a time...

(They do claim it's a light fluffy snow)

70sSanO

Just adjust the circumference setting until you get to 15-15.5mph. You can probably use the road wheel and flywheel numbers to calculate the circumference. You will be close enough for what you are doing. When you get back on the road, you can compare and adjust for next winter.

A heart rate monitor is nice, a fitness watch might be a good choice. It won’t help you now since you don’t have an outdoor baseline. But it will be helpful going forward.

John

indyfabz

Distance travelled will be less.

MattTheHat 

In my experience with both a wheel-on smart trainer and a Wahoo Kickr bike, yes your average speed will be higher. With the same power output the trainer’s “speed” is higher than road speed. I always put the difference down to not slowing down for corners or stopping for red lights. Simulate both with the same frequency as when you ride the bike and you’ll likely find the speed matches more closely.

PeteHski

It all depends on what app you are using to calculate speed and how your own road bike and road surfaces actually compare with the virtual bike and physics model. I find Zwift is pretty optimistic on speed, while Rouvy is very close to reality on routes I've ridden IRL.

curbtender

You could use your Garmin to calibrate your results.

Iride01 

You aren't going anywhere on a stationary bike or trainer. So really you shouldn't even think of speed or distance when on them. IMO.

I only look at time, power and/or resistance level when on a trainer.

Homebrew01

Yup. Just ride, get a workout and don't "sweat" the numbers.

BlazingPedals

Exactly. On average, a stationary bike goes... 0 mph. It's stationary! Any number on the speedo is imaginary. The important numbers are work (heart rate?) and time.

wolfchild

Just get a good workout and don't worry about chasing any numbers.

ChamoisDavisJr

And so endeth the lesson.

But how can I reach my “mileage” goals on Strava if I don’t inflate my numbers?

Set your trainer wheel circumference to zero on your trainer app that way it reports no speed or distance.

Trainers are for time only and power if you’re tracking it.

Pretend miles are pretend.

MinnMan

No.

sean.hwy

From my experience ( we have two saris h3 direct drive smart trainers ) several friends with other direct drive and friction trainers.

The friction trainers or at least the few people that I know is way optimistic ( gives you more watts, speed than you have ). I see their strava times/ride with them etc.. and it does not add up.

If you are on really smooth road, no cars, wind etc.. your flat speeds outside is very very close to zwift. Where I rides it's almost 99% not like that so it takes more watts to do 20 mph on the flats than in zwift. I compared it to my assimo power pedals.

Up hill is accurate in zwift as long as you plug in the correct data. 10% hill takes x watts todo y mph.

downhill is a joke. You have unlimited gearing on zwift bike. Your bike can pedal 50 mph. I have nothing to compare it to. I never pedaled that fast IRL. So your avg mph will be faster in zwift if you can pedal 50 mph down hill while IRL might only be 30 ish mph. You're slighter faster on the flats and even faster if you draft people which never happens IRL on solo ride.

So, yeah hard to compare a zwift ride for 50 miles at 3k elevation at avg 18 mph vs IRL 50 miles at 3k elevation at avg 13 mph.

PeteHski

Yeah I think Zwift represents perfect roads on a perfectly calm day. If your trainer power is accurate and your weight data is correct, then it's a reasonable physics model. Drafting in Zwift is actually less effective than in real life (deliberately modelled that way) but you get a lot more opportunity to draft than you typically would IRL. I agree climbing is pretty accurate, downhills unrealistic if steep.

genejockey 

Yeah, as lots of other have said, on a "dumb trainer" distance is meaningless. And if you don't have a power meter or heart rate monitor, you really don't have any way to gauge your effort. When I was still using a dumb trainer, I used an HRM. From years of riding, I knew my HR zones, and I would adjust my gearing accordingly, to spend the desired amount of time in the zones I wanted.

Regarding Zwift's model, I think the downhills seem unrealistic because there are no turns to brake for. Long descents IRL rarely come without corners, and some of the descents in Zwift are miles long with no braking. Bike Calculator gives a speed of 51 mph for a 90kg rider on a 9kg bike, going down a 0.5 mile descent of 8% in the drops, so I don't think the speeds are really that unrealistic, given all of that.

ClydeClydeson

There is no direct comparison to calculate equivalent road miles to trainer miles. Lots of more expensive trainers may have power meters that more directly equate to power meter reading on a bike, but even that isn't "1 mile trainer = 1 mile on road" - you can compare and say "I maintained an average of X watts on the trainer for H hours, and I previously did H hours at X watts on my road bike, therefore it was a similar workout" and make assumptions about mileage based on that if you wish.

You can do a comparison using a heart rate monitor, as well, and this would be cheaper than a power meter, but heart rate isn't as repeatable a metric in my experience.

PeteHski

You can simulate real world road routes with various apps like Rouvy, FulGaz, even Zwift with some of their non-fictional routes. If done accurately on a good quality trainer, then it's plenty close enough. It's not like you have exactly the same comparable conditions when you ride outdoors anyway. Is 1 mile on your local route in calm conditions equivalent to 1 mile on the same route in a headwind or heavy rain? Of course not. Mileage in general, whether measured indoors or outdoors, is nothing more than a rough guide to your accumulated workload. That's why people measure things like TSS to get a better idea of workload. If I ride 10 miles up a 10% gradient climb, that is going to involve a LOT more effort than riding 10 miles on a flat road. So "real" road miles are just as meaningless as trainer "virtual" miles as far as training load is concerned.