Hey Russ. Make sure your power source is set to "power meter" and not your trainer. Also, spin a bit and see if power shows up on the device page. If that works, go into a workout and try again. I think it will work. If you still have problems, drop me a line at support@trainerroad.com and we'll get you figured out.

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast

It's all due to speed from the rear wheel. So gear + cadence = speed. If you change either the speed gets updated and we can measure that.

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast

What's the best way to compare Virtual Power vs Powermeter power?

My KK Road Maching VP seems to be ~15w higher than my powertap power- which is really messing up my GoldenCheetah data. any way to recalibrate?


he he. 2 years ago I wouldn't have understood the sentence I just wrote above.

We still don't have a roll down test. The code is actually in the beta version, but we're waiting for the inRide to get done so we can validate numbers. We're sharing our data with wahoo/kinetic.

You can try tightening your rear wheel until you get the numbers to match. We've found that's around 5 turns with our bike, but your bike might be different.

But...why not just use your powertap all the time? If you have a $1,000 power meter, I would use it. It will always be more accurate and consistent since you're getting data from inside/outside.

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast

yeah- I'm lazy. That would involve me taking my tri bike- which is my primary outdoor riding tool, and putting it on the trainer. Sometimes I don't decide which I'm going to ride until 5:30am when I sniff the morning air to see how cold it is- so it's nice to have a bike all set up and ready to go on the trainer. I live in year-round outdoor riding weather- so I switch off a lot.

I find about 3 turns compresses my tire quite a bit. Sorta' can't imagine doing it 5 turns. Does tightening it more increase or decrease the rolling resistance?

Tightening should increase rolling resistance. I think...pretty sure :).

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast

Am I missing an easy way to load up one of the preset training plans? Or is it just search and load as you go day by day?

Just search and load as you go right now, although we're trying to think of a nice way to integrate the plans right in the app. It's pretty high up on our list. I think it's one of our most requested features.

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast

Even more requested than the "create custom workouts based on a GPX file"? Is that still on the cards?

Yah, there's two ways to do this and we'll do this.

1) Create a time based workout based on a workout file with wattage. You go through and take the percent FTP and turn it into a nice workout.

2) Create a course based workout based on GPS coordinates. That one requires a physics model in our app to track progress. Workouts would be distance based and not time based. People with computrainers or the KICKR would get the most benefit out of this, although other people could still try to push big gears up virtual hills.


Number one will probably happen before number two, but we plan on doing both of them. This workout creator was the first step. We like to lay the groundwork for a lot of stuff while we build, and that's what we've been doing with the current workout creator that's in beta.


We just need like 3 support people and 7 developers :). Then we could really get moving on this stuff.

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast

Thanks Nate, that's great news. Wish I could help with the support/developer positions, but alas, out of the 10 types of people in the world who understand binary, I fall in with the 101 who don't! :)

Thanks, looking forward to seeing your implementation on that. Greatly appreciate your Bluetooth solution. It's been working well on my Mac with the suggested USB dongle.

I don't think tightening increases rolling resistance, does it? Tightening it decreases the radius of the wheel. lets say on trainer road you have the wheel circumference entered as 2100mm. this implies a radius of about 334mm. Then lets say you tighten the knob down 5mm. this would decrease the radius to 329mm and the circumference down to 2069mm. since you have 2100mm entered into trainerroad and your actual circumference at the point of tangental velocity is 2069mm, when trainerroad thinks you are going 20mph, you are actually only going 19.7mph at the point of tangental velocity. Trainerroad thinks you are pushing 262 watts when you are only pushing 254 watts (on a KK road machine). if trainer road thinks you are going 38 mph pushing 1279 watts, you are actually only going 37.4 mph pushing 1229 watts. a 50 watt difference.

there is no increased resistance because you are tightening. (technically there is, but it's such in incredibly tiny amount it irrelevant). since the friction remains static on the trainer roller that does not need to be accounted for. when you tighten down the roller onto the tire you are only decreasing the distance between the point of the actual tangental velocity on the disc (wheel) and the axis of revolution (basically decreasing the radius).

I'm probably going to post a video of how to properly calibrate a trainer in the near future. I'll post it on this thread when i do.

That's an interesting explanation. The tests I did with our motor setup all showed that an increase in power was needed to maintain the same speed as tension increased. I measured speed on the bike wheel without adjusting the wheel circumference with each adjustment. If the tire doesn't slip I'm having a hard time getting my head around the idea that the distance traveled by one rotation of the wheel would change with the tension on the tire.
Another way to test this would be to measure speed at the roller since, at least for the Road Machine that has a steel roller, the circumference of that won't change.
My theory is that the increase in area of the tire that is in contact with the roller is what causes the increase in rolling resistance.

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theSufferfest.com
Co-Founder of TrainerRoad.

I sent you a pm

Tightening, or increasing the pressure on the tyre, effectively increases rolling resistance of a bike on a trainer.

RacerMate Inc (ComupTrainer) uses the term "Press On Force" to describe the function of tightening or loosening the pressure with which the trainer's roller is pressing on the tyre. Increasing Press On Force (tightening) is like having a heavier bike/rider on the road. The extra weight presses the tyre harder onto the ground, increasing the rolling resistance.

If you doubt this, ride your trainer at 3 turns of the knob for 5 minutes at 20mph and without changing gears. Watch your power numbers (or check the average after). Then get off the bike, tighten the knob 2 more turns (increasing the press on force) and ride for 5 minutes at 20mph as before. Compare the power numbers. You will need to hold a higher average wattage to ride the same speed with greater press on force on your trainer/tyre.

I addressed this in my post. it is because you are changing the effective radius of the tangental velocity. as you change the radius of the tangental velocity the tangental velocity changes, change the linear speed of the roller. try decreasing the tire circumference in whatever program you are using by about 6 mm for every 1 mm you tighten the roller. you will notice you end up getting consistent power readings.

weight of the bike/rider has no effect on power output to maintain speed. weight only effects acceleration, not speed or velocity on flat ground. this is the same with a trainer. on a trainer you are not fighting gravity up a hill and you are not accelerating your body weight, as you remain non-moving on the bike.

So how would you describe riding with the brakes on your rear wheel? Isn't it similar - you have to overcome increased pressure/resistance

no it is not similar. the brake pads are stationary objects, rubbing against a moving object to slow them down. kinetic and static friction are both involved. the trainer roller/bike wheel relationship is entirely different. the roller/wheel is one object moving another moving object. only static friction is involved. the increased pressure you speak of is not overcome through your power output. it is overcome by however your bike is connected to the trainer.

okay i'll admit, an increased pressure can make it harder to turn the tires. BUT under the weight of an average human or the pressure applied by the roller, it's effects would be so incredibly small you can pretty much not even think about it. a ridiculously small value that isn't even worth considering. the change in radius has a FAR greater effect.

so basically,
wheel/brake - wheel tries to move the brake, but the brake wont budge. the force of the product of the moment of inertia and the acceleration of the wheels overcomes the product of the coefficient of static friction and the force applied by the brakes, and turns into kinetic friction. the wheels stop once the product of the coefficient of static friction and the force applied by the brakes is greater than the product of the moment of inertia and the acceleration of the wheels. at which point it becomes static friction again until the brakes are released. then no friction. this is also why adding the 12 pound flywheel to the kurt kinetic trainer makes it stop so much slower. it increases the angular mass (or moment of inertia) of the flywheel which in turn the brakes have to stop that too lol

wheel/roller - the wheel successfully moves the roller without breaking static friction.

I signed up for St George 70.3 in May. Which training plans on Trainer Road would be best to use to get me ready for the hills. I'm a fairly new cyclist ( about 2.5 years.) And this will be my first half.

Thanks Tiana

It's all about power to weight ratio to get up hills. That and you'll want enough gears to be able to get up the hills without going above threshold.

I suggest you start with our intermediate base plans (I and II) and go from there. That's a decent amount of bike work for the winter and it should raise your FTP. Come summer, pick a plan that fits into your schedule, so how many hours you want to ride and what kind of intensity your body can handle while maintaining your other sports.

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast

I followed TR's Intermediate Base I&II and Build I&II programs for IM Wisconsin, which is fairly hilly and it worked like a charm. Just counted backwards from the date of the race to fit in all 4 programs.

Seems to me that both are true. Tightening the roller against the tire will increase the rolling resistance just like being a heavier person. But- it also makes the wheel smaller. Given that I've read enough tire reviews where apparently small differences in Crr equate to 10-15watts- it doesn't seem unreasonable that Press-on-Force would make a similar difference in magnitude. So- these would counter each other out to some effect.

The question is- which effect is larger?- and are they close enough such that a different tire type or air pressure might make a third, equally sized change. I know one way to reduce my virtual power a bit- change from the Conti GP4000S I've got on there now (it's my road bike that goes on and off the trainer), and put on a training tire. Seems to me that there are really too many variables to make this a simple calculation. Yup Nate- we need that roll-down test.

In the end- I guess it doesn't matter all that much. I still put in over 500 in TSS last week, my legs are fatigued, and I'm good.

you're right in the fact that they both make a difference. quoting myself:


like i said the Crr does make a difference, but it will be much smaller than the effect you get from changing the radius. I will post how to properly set up a trainer to account for these changes, but i just dont have time right now. maybe this weekend. i'll also do a non-scientific test of it this weekend if i have the time.

Reid did say in a previous post:


so the Crr and the decreased radius do not cancel each other much.

you know we could just email the guys at KK and ask them.. i'm sure they would have an idea ;)

They agree with us, more tension equals more power to maintain the same speed.

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CEO at TrainerRoad
Co-host of the Ask a Cycling Coach Podcast