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trainer resistance doesn't necessarily correspond with outside resistance. a watt, however, equals a watt

This.

You need to measure your effort on a trainer by power output, not by speed. Depending on the trainer, your size, how aero you are on the bike, wind speed, direction, etc. 20 mph on a trainer can be radically different than 20 mph on even a flat road.

Ideally you want a power meter to measure your effort; next best is heart rate, but its subject to drift working indoors as you get hot. Last is perceived effort.

The only relevance of speed on a trainer is if you have a known power curve for your trainer, and you can extrapolate power from speed using the known curve.

I go 0 MPH on my trainer. I'm surprised you can get up to 20 MPH with your wheel of the ground!

I don't have power or a HR monitor. I just go off perceived effort. Seems to work for me, but then I'm no pro!

Lift your rear wheel higher, then you will be going downhill.

I typically get around .03mph. The Garmin will show 200-300 feet distance in an hour trainer session, from margin of error in the GPS.

When I first rode my trainer I had the tension too tight and couldn't go faster than 45kmh which seemed odd.
I loosened the tension against the tire and can hit 53kmh now.
Something to look into if your speeds seem off and it will save your tire too.

Also, switching your computer to read in KPH in stead of MPH will make seem like you are flying.

I used to go through the hassle of turning the GPS off indoors. Then my ratio of laziness to OCD went inverted.

The nice thing about the trainer is that it's consistent: unless you mess with the resistance setting, 20 mph is 20 mph is 20 mph. So, if you can figure out the relationship between speed and power for yours, you don't really need a power meter. You might be able to find the relationship in Google.

If you have a magnetic trainer, it probably has a relatively flat resistance curve. On the road, resistance goes up very quickly with increasing speed. Very roughly speaking, for each additional 5 mph you have to double your power output. Budget bike trainers don't scale nearly as rapidly, they are closer to linear. 20 mph on the road might feel easy compared to 20 mph on the trainer, but 25 mph on the road would feel much, much harder than 25 mph on the trainer.

Kurt Kinetic makes a gadget that converts speed of the roller into wattage, as the power curve from trainer to trainer of their brand is supposed to be consistent.

14 MPH = about 140W. 21 MPH is in the neighborhood of 290W. On flat ground sans headwind I can go faster than 14 MPH from 140W, I think. I don't know for sure because I don't own a power meter, just the gadget for the trainer.

From the manufactor's site: Kinetic Road Machine:
P = (5.244820) * S + (0.019168) * S3
S=speed, S3=speed cubed.

That's about 30% too high.

Not by my results.

I use a KK Road machine with a quarq or PT and ride outside with both. Comparing some trainer and solo road rides with an average speed of ~20 mph I get a power meter reading composite of around 239 watts whether indoor or out. If my math is right the above formula would predict 258w for a error of around 8%. And fwiw, I weigh 175, calibrate or zero before every ride and probably do solo rides at around 70% hoods/25% drops.

5% no handed?

For training purposes, I've heard that you need to do 75% the time on a trainer than you do outside to get the same workout, because outside you are able to coast a bit down hills, etc.

This is my second season spending significant time on the trainer, a Cycleops Fluid 2. For the second time, I noticed about a 3mph drop from the road speed that I was averaging to the trainer for rides of comparable length. That 3mph came back as soon as I hit the road in earnest in March.

I don't use or own a power meter, but just for grins, I ran the power curve calculation using the Cyclopsops formula I've seen published in another thread. On a recent 75 minute trainer ride, the outcome for my 19.1 mph average speed on the trainer was 246 watts. Plugging that wattage into bikecalculator.com for a 160 lb rider on a 16 lb bike, flat, no wind, hands on the hoods, gave an average speed a shade over 22, which is pretty much where I am on solo rides working moderately hard in those conditions.

All in all, I agree with the OP's observation that a difference exists. Riding on the road is the apple. Sitting on the trainer is the rotten orange. Compare only things of like kind.

There is no reason to assume the resistance on a trainer bears any relation to resistance on the road. So speed has absolutely no meaning on the trainer. Fugeddaboutit! Power or heart rate. Dems de cherces.

I practice my victory routine A LOT.

If you listen to the folks at Kurt (and some others), there is. I know it hasn't for everyone, but for me it has bore out. Maybe I'm their model weight and riding form and/or more consistent than others in set up. But as I said above, my Kurt Road Machine has come consistently close to my on road speed/power readings and also consistently close ( but lower) than there chart & published formula.

It's hard because you're weak.

This is taken from DCrainmaker's web site:



In this he is taking wattage derived from the power curve of the trainer and comparing it with the actual measured power from two different meters.

It it seems pretty accurate.

My diddling around speed on the road is 12 MPH because I'm old, fat and slow. My diddling around speed on the trainer is also 12 MPH.

Go figure.

My speed and power output (with a Powertap) are pretty close on the road and on my KK trainer.

I do about 30% of my yearly riding on my trainer. They way to make this useful and to keep my sanity on the trainer is to do interval workouts and not long steady state rides (preferably with some training DVD's). I did a 2 hour interval workout on the trainer today (Spinervals Have Mercy) and enjoyed it. I would go crazy though if I had to spin for 30 min as you mentioned in your opening post.

I used to use my PT wheel on my KKRM before I went back to using my trainer wheel/ tire because it was always within a handful of watts.

OP, all that matters is duration at intensity. Nothing else.

I didn't say a trainer couldn't be engineered to have power on it match power on the road at the same speed. In fact most trainers probably have at least one speed where that accidentally happens. I just said there is no reason to assume it. Think about a trainer with selective resistance. Clearly you can ride that trainer at the same speed but several (five?) different power outputs. A high end, really well engineered trainer could perhaps map the speed vs. power curve of road riding through tuning of the resistance mechanism or maybe even using a composite mechanism (magnet + wind + fluid). With three contributions to resistance it is likely you could develop coefficients for each component that would closely trace the on-road experience. But wait a minute. That would be at only one effective headwind speed, right? Different headwind, different speed/power curve. Oh and at only one slope too. So you see, it really is hard. Unless the whole thing was programmable and you could put in your wind and slope particulars and get a custom resistance. That would be cool, but not likely any time soon. Is it?