So how slow is "extremely slow"?

I have a Kurt road machine, don't have the speed/power option, so I just moved my bike computer pickup to the rear wheel. I can average about 19MPH on the road(if it's relatively flat), but usually only average about 16 on the trainer.

i'm lucky to maintain a 17.5 speed (supposedly about 175 watts) indoors and stay below 156bpm.

Speed is meaningless measurement on a trainer.

What is your suggestion on sticking to training plan that is laid out by miles, if you don't pay attention to speed how can you accurately measure if you are putting in too little (in this case too much) time?

speedy_dave,

I also have the Kurt Kinetic, with the 6lb flywheel. It is a 2005 model.

I have a Powertap as well.

My speed is much reduced for the same power when compared to road.

For instance, my Tuesday 2x20 intervals which I'm doing at 250W right now only get me about 20mph on the trainer. I did 6x5 today at 300W and that only got me 21.5mph on the trainer. On a flat road, with no wind, 300W is good for about 26-27mph for me. A 1 hour TT ridden at 250W average gets me 24-25mph on the road (in other words, 250W is the 1 hour 40k point for me, in perfect conditions)

So, yes, your speed will be slower...but the point is that you ride, for instance, 2x20 at your tested threshold wattage range...NOT that you ride at a particular mph. I pretty much don't pay attention to the speed on the trainer. Measured watts, cadence, and time...forget about mph on the trainer...

Just go on level of effort or power.

The "speed" you're going on the trainer is slower than outside. 2-3x the power is required to turn the wheel the same speed on the trainer as outside. For example to go 25 mph outside requires 250-300 watts( depending on drag, grade, wind. etc), but to go 25 mph on the trainer requires 570 watts (for a Cyclops fluid trainer). Keep your tire pressure and roller pressure constant to maintain consistency. The rate of change is also steeper on a trainer. To go from 22 to 25 mph on the trainer requires 170 more watts, outside requires about half that increase.

good deal. does the unit need to be calibrated though? the power still seems low compared to my energy exerted.

No, no calibration needed. Remember, there are no breaks on the trainer, and no occasional respite provided by a tailwind...if you want it to go...you have to work...it will seem harder on the trainer...also...make sure you are riding on the trainer at the same cadence you do on the road...I find a lot of folks will ride at a slower cadence on the trainer. My guess is that since the effort is steady (no bumps, hills, wind, etc) folks just get comfortable at a slower cadence. If you do 90 on the road, make sure you do 90 on the trainer, unless, of course, you are doing cadence specific work like low cadence/high power reps or high cadence spin-ups.

i meant on the power output device. i know the trainer doesn't need calibrating.

i have no problem maintaining intensity (as displayed on screen or heart rate monitor). my question is whether or not the power number on the screen is correct and how that changes depending upon placement of the magnet/wheel size/etc.

thanks!

The resistance (wattage) curve on a trainer is set by the factory to correspond to the wattage output of a theoretical cyclist on thoretical terrain.

For that theoretical cyclist, the manufacturer of the trainer assumes:

A given rider mass

A given rider Cda (aero drag)

For that theortical course, the manufacturer assumes:

A given slope

A given coefficient of friction with the ground

If any of these assumptions do not happen to coincide with your reality, the speedometer reading will be useless; meter wattage instead, as this is much more the significant training variable, and is much less subject to the variance obvious from the above.

My understanding is that the PM on the Kinetic derives wattage from a speed(rpm)/resistance calculation; this will be subject to tire slippage and change in resistance over time due to thermal variation in the resistance unit, but this is probably orders of magnitude less innaccurate than the speed calculation.



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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
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The Kurt power meter requires no calibration. It does not matter where on the wheel you put the magnet - it will take the same amount of time for the magnet to make 1 revolution wherever you put it -- it just travels faster farther away from the hub. Your tire pressure and how hard you screw down the flywheel will have only a small effect on your speed/wattage (according to Kurt). There is a thread from a couple of months ago where a Kurt rep discussed this. Don't get caught up in comparing your indoor numbers to your outdoor numbers. It can be useful to compare your indorr numbers to your indoor numbers, though.

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What a drag it is getting old. -- Stones

<< It can be useful to compare your indoor numbers to your indoor numbers, though. >>

No doubt. I find that the effort/speed is very well correlated to itself over time, and therefore repeatable.



Yes - 21.5mph ='s 300W on the Kinetic. However, I'd compare that to 21.5mph riding up a hill of say, (total guess) 2-4% grade, NOT flat. So, the 300W may or may not be accurate, but the "speed" at 300W is way low (compared to how fast yer 300W would propel you on flat ground on the road) Pretend that you are riding into a constant headwind, or up a constant low grade, and it's all good.

Just be happy that when you get outside, your seemingly pedestrian "speed" on the trainer will likely increase by a good 15-25% on the road in real-world riding conditions.

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float , hammer , and jog