CornUponCob

So I've been riding with power for about 2 years now. Over the past few years, I've noticed I can really lay down the power while going downhill. For example. Doing the gaps up here in GA, I'd be about 320 - 360 watts up every climb (I'm 200 LBS), but descend unicoi gap towards Helen I was averaging 400 watts downhill (FTP is 400), yet it felt easier.

I'm thinking I'm not actually pushing more watts going downhill, rather it's just an error in the math of the power tap unit. While I'd like to believe their math is simply torque x RPM = power, I'm willing to bet there's more to it than that to get these kinds of numbers.

The reason I bring this thread up now is because from my ride today going DOWN a 5% grade trying to catch the draft of a car it said I had a 5 second burst averaging 1200 watts, yet I sprinted up a lot of little hills today and none of them were my 5 second best for the day.

So have you all noticed your power taps reporting suspiciously high numbers while going downhill?

jwible

How high was your cadence? Sounds like something is out of whack to me.

is zero averaging turned on or off? What kind of head unit?

jcpups608

Can't say if there is anything wrong with your PT, but I can definitely put down the same power with a lower RPE if I've got a tailwind or on a slight downhill.

I've chalked it up to the ability to have a smoother, more circular(more efficient?) pedal stroke with the wind or gravity assistance.

That said, my HR will be the same it just doesn't hurt quite as much when I can spin at high speed as apposed to grinding up a climb or against a headwind.

As mentioned above, is the PT zeroing out? Have you ever done a stomp test to check calibration? Those are the two things I'd check first.

CornUponCob

Climbing I tend to be around 90 (unless I'm already in my easiest gear), motoring downhill, even if I haven't spun out the cassette, about 110. Flats around 100 - 105. I've been using an Edge 705 as my head unit and have it set to auto-calibrate. I've been getting pretty consistent numbers out of this power tap at moderate power outputs. 250 watts has felt "the same" over the last 2 years (250 watts has become easier to produce, but it still produces roughly the same speed on the flats).

I have had a lot of people tell me I descend like a mack truck (but what 200 pound cyclist doesn't?), and I've ridden away from people a lot, but as somebody else said, the RPE to produce the same power downhill vs up is much easier. I guess cooling could have something to do with it as well.

gregf83 

I suspect your RPE feels lower (for an equivalent power) going downhill for the same reason riding outdoors feels better than riding on a trainer: intertial load. Riding downhill the inertial load seen at your crank is very high and generally pedalling against higher interial loads feels better.

Your sprint downhill was probably higher due to cadence. Experiment with gearing on your uphill sprints and you can probably get them to match.

Also, you spend less time going downhill, so it's easier to have a higher average power than the uphill portion.