What would the approximate power be?
 

Cyclops Fluid 2 trainer, 53x17 at 88 rpms. I typically do that for 30 min. ( and then various other combinations for the rest of an hour) and it gets me a good sweat going by the end. I have no power meter, only heart rate monitor. Anybody know what the approx. power for that gearing/rpm combination would be? Thanks!

Quick guess is that it's about 22 mph. I have the same trainer so… I started looking through my trainer rides. Apparently I rarely go over 18 mph on the trainer. 21 mph and it took me about 330-340 watts. If you can do that kind of power for 30 minutes that's pretty spectacular, like really spectacular, unless you weigh a lot or are super tall or both.

For the Fluid resistance is based on speed, among other factors, but it really goes up and down with speed. Therefore if you have a rear wheel speed pick up that'll be more useful in terms of measuring relative effort.

Also try to be consistent with the set up. Use the same tire pressure (inflate before every ride) and use reasonable same roller pressure (my lever is spring loaded so it's pretty hard to mess it up). If it slips when you jerk the wheel it's probably too loose or the tire is underinflated.

For me I have 700x23 tires, 100 psi, and if I jerk the wheel pretty hard it either barely slips or doesn't slip. I can get about 1000-1050w registered on the powermeter (SRM) but rarely make hard efforts and typically stay in the 10-15 mph range. Today I did 2 hours and broke 13 mph avg for the first time in a while.

It all depends on the tire pressure and how tight you got the roller on the tire I think. When I had a Kurt Kinetic, I had a hard time getting consistent power day to day.

I was going to guess between 200 and 300. We have one. I think the tire pressure is less significant than on rollers etc. and the fluid generates so much resistance.

The guess would be better if we knew your weight, composition, max HR and what your HR when working out.

Use a calculator like Sheldon Brown's Bicycle Gear Calculator to come up with a speed for the 53x17

Look at TrainerRoads power curve for the Fluid 2 at An update on VirtualPower for the CycleOps Fluid 2 - TrainerRoad

I'm 54 y/o and max heart rate was 195 but that was about 6 years ago last time I checked; maybe lower now. I don't know that one's weight has anything to do with the watts being generated, only watts per kg. I typically cross 160 bpm at around the 26 minute mark.

Thanks, I'll check that out.

My computer gives an average of 30.6 mph (best I can remember but it is over 30 mph) for the 30 minute period. I typically have the back tire pumped to 115-120, no slippage when jerking the wheel or quick accelerations. As I said, I don't have anyway to measure power and have no idea what I generate. I kind of guessed it to be in the neighborhood of around 270. You made me smile suggesting 330-340 and I'd be very happy if that was so.

Your speed for 53/17 @ 88 RPM cadence (assuming a 700x23c tire) is about 21.4 MPH. As for power, temperature seems to have a significant effect on the Cycleops Fluid 2 resistance unit. I've seen some reports of as much as a 30W change during the first 20 minutes of use. It's also not entirely clear how much variation there is from unit to unit. Data suggests you're in the 300 - 350 range, but the only way to get actionable numbers is with a real power meter.

30 mph doesn't make sense, it's way too fast, it would take a massive effort, for me it's in the 800-1000w range (and due to trainer limitations, at least on mine, I can't rock the bike, so it's super awkward for me).

If it's 30 kph that would be closer, like 18 mph, which would be a realistic average speed if you're pedaling and going 21 mph (meaning you're typically going 21 mph but you coast etc to stretch, etc, in other words taking into account zeros). For example when I do a ride I'm consistently seeing 180-200w but my avg will be 140 or whatever due to the easier bits when I stand and such. It's like a car also - if I avg 55 mph on the trip computer I realistically went 65+ consistently on the highway.

It's very possible your computer isn't set to the right tire diameter so I'd check that. An undersize tire (or oversize computer setting) can really mess things up.

Finally, as 330-340 watt is a pretty high level, I'd check to make sure your fluid trainer hasn't leaked a bit/lot.

The best way to check out your trainer is to get someone else's bike with a powermeter (with your wheel on it, so a non-wheel based powermeter) and ride at a range of speeds and note power numbers (they bounce around a bit). Or you can use a PowerTap wheel and get approximate resistant levels. The first option is better since it'll replicate your set up the most accurately (since the rear wheel, skewer, tire, etc are the same). You should recheck your approximate readings every now and then to make sure that your trainer stays consistent (no leaking, tire wear affecting power/speed ratio, etc).

If you want to know your power, measure it with a power meter. If you don't have a power meter to train with, knowing your power is meaningless.

Why do you want to know?

Age, Lean body mass and HR% would be the primary predictors. W/Kg would be a predictor of how fast you go with those watts.
Better cyclists tend to be able to put that power out longer.

What I did for both my son and I was just find an uphill grade and see what Strava said. In calm wind (no group ride) with accurate weights put in your profile going up something 5%+ Strava guessing is pretty good. On the flats and lower grades Strava guess can't figure out the aero part so well.

HR and weight don't have anything to do with what watts are being produced to move a wheel on a trainer at a certain speed. There's no actual motion of the rider's mass.

I didn't say it did. It may have some to do with the deformation in the tire.

I'm basing the power output on the rider - not on the trainer. I think from fluid trainer to fluid trainer (with all equipment) there is more variability than two riders of the same profile. i.e. If I saw him I could guess.


But if you show me two same gender riders, neither that have invested in power meters, 130lbs lean body mass, about the same age, working at the same HR% I'd bet they'd be within 10% of each other over 20 min.

VO2 max would be a much better predictor than age, lean body mass, and HR%. For example, if you got some random 5'9" guy in his mid-20s at a reasonable body fat level for a pro, it wouldn't make him a Greg Lemond. However if you got someone that's about Lemond's size that has a 90-ish VO2 max then you're going to have a pretty strong rider. Maybe not a Lemond but the rider would certainly be pretty good.

When I was in my mid-late 20s, 130-140 lbs, pretty lean (skin caliper test at 4 spots got 5 mm), it didn't change the fact that I couldn't climb or TT to save my life. In fact I was probably close to some pros in terms of size/etc but I have a low VO2 max so I wasn't anywhere near a pro. My size also didn't predict how well I'd sprint, which seems to be genetic since I can always sprint no matter how little or how much I've trained.

W/kg predicts how well a rider does on a hill, i.e. kg becomes significant. In a flatter or windier environment it's more about watts per aero drag. This is why a high w/kg won't necessarily make a good time trialer (except uphill) but a powerful big rider with a lower w/kg can still TT well.

Tire deformation is based on tire pressure and roller pressure. With a spring loaded roller I can come pretty close in terms of watts necessary to go a certain speed.

My response was in context to where the question was posted and the information provided. I assumed the OP did not have their VO2 Max number at hand.

you guys are missing the point. the op wants to know the watts at a given gear and RPM on the trainer. what his HR, watts/kg, RPE, % of LT etc are, is completely irrelevant.

The only thing that is relevant is the tire pressure against the trainer drum.

If CDR at 170# or whatever gets off the bike and I get on the bike at 108# and no one changed anything about the bike setup or attachment to the trainer, we both need to output the same watts to make the wheel go around at the same speed. Maybe it's at 80% of his LT and 120% of mine, and 40% of fudgy's and 160% of rkwaki's but it's the same raw watts. amiright?

Sure you're right, but everything devolves into a freaking side show around here, so it's your expectations that are off base. :rolleyes:

Ask a question, get two and a half pages of non-sense, then get into real answers. I don't see a problem.

Ugg, I got the wrong info on the cassette cluster off the internet. I counted the teeth on the particular cog I was talking about and it was a 19 (since the bike is in the trainer and I didn't want to take it out). No leakage on the trainer unit and I have the correct wheel diameter entered in the computer. I always make sure the unit has warmed up before I start the interval (you can tell it has when the resistance suddenly increases). Well, looks like my power just went way south I reckon.

So, I don't get where we are...

You were turning a 53/19 at 88rpm, but your computer was showing north of 30mph despote having correct wheel circumference, is that it?

I don't understand how that could be.

I'll also say, as a user of a Fluid2, that a 53/19 at 88rpm is probably not much power at all.

I don't know either. I completely reset the computer and it is now reading as it should. As someone else said, it should be around 21.4 for 53x17 at 88 rpms and it does now. Perhaps speed was set for kph instead of mph and I just couldn't tell...the letters are so small on this particular cateye and my eyesight isn't so good anymore. I'm going to warm up tomorrow and try the 53x17 at 86-88 rpms and see how it goes. I'm guessing that 53x19 at 88 rpms is somewhere north of 250 watts.

So if you gave your weight, age, gender, body fat % and about the time you work out - we could SWAG your power better than the training information you've given. Or go ride with some guys that know theirs and compare.

Those details have nothing to do with the power it takes to turn the pedals at a certain gearing and rpms (as valygrl correctly wrote above).

We disagree. If you could give us a real RPM of the spindle of the trainer and some real tire deformation then we could get power if Fluid trainers were constant - ours is not.

My point is who you are is a better power predictor than the all the other variables needed to work through to figure out the power required to turn a power trainer at a certain RPM.