FTP test and power numbers

[bhattman]

Hi,

I have recently calibrated by power pod and did 20 min FTP test. Surprisingly, the power numbers seems to be on higher side as I know some riders with same FTP much faster than me. Can you check if settings seem to be fine? I have attached calibration ride and FTP test file. FTP test start from 17.1 kms onwards in the file

Thanks
Mandeep

[Velocomp]

Your FTP is 95% 0f 228W, or 217W

I don't see anything unreasonable about your FTP, given bike speed and hill slope. Your wind data is pretty symmetrical, too.

A common rookie mistake is starting out hard and "dying" at the end. You did a nice job of maintaining an even power pace throughout the ride. Congrats!

[bhattman]

Hi John/Team,

Just wanted to check if FTP is 95% of 248 or 228. What my Garmin shows as power for 20 min interval is 248 and I think isaac is also showing 20 min power around same number(245-248). Am i viewing it differently?

Thanks a lot in advance for your response.

[brookside]

If your average power over 20 minutes is 248 then your FTP is 95% of that, by common convention, or 236. If you think the number is too high then check what you have entered in your profile in ISAAC for Crr and CdA. With racing tires (e.g., any 320 tpi tire, Conti Supersonic or TT, Specialized Turbo Cotton, etc) and latex tubes the iBike suggested value of .004 is far too high, try .0030 to .0033 as a better estimate. I also think the suggested CdA values are too high if you have any kind of aero position and are wearing close fitting kit, and especially if you wear an aero road or TT helmet and have aero wheels or a rear disk. Try .31 for a road bike and .25 for a TT setup.

That being said, you might still have power numbers that seem too high. I've used a Newton with a DFPM and the Newton almost always calculates power 10 to 30 watts higher, on average, for an entire ride and can be 60 to 100 watts high on certain segments.

[bhattman]

If your average power over 20 minutes is 248 then your FTP is 95% of that, by common convention, or 236. If you think the number is too high then check what you have entered in your profile in ISAAC for Crr and CdA. With racing tires (e.g., any 320 tpi tire, Conti Supersonic or TT, Specialized Turbo Cotton, etc) and latex tubes the iBike suggested value of .004 is far too high, try .0030 to .0033 as a better estimate. I also think the suggested CdA values are too high if you have any kind of aero position and are wearing close fitting kit, and especially if you wear an aero road or TT helmet and have aero wheels or a rear disk. Try .31 for a road bike and .25 for a TT setup.

That being said, you might still have power numbers that seem too high. I've used a Newton with a DFPM and the Newton almost always calculates power 10 to 30 watts higher, on average, for an entire ride and can be 60 to 100 watts high on certain segments.

My Crr is 0.0053 which I think is high. Though i was totally riding on hoods and was using training wheels only with normal helmet as I wanted to measure power for normal riding conditions. Do you think even then the Crr is on higher side?

[brookside]

Crr (coefficient of rolling resistance) has to do with your tire and tube rolling resistance, n ot aero factors like helmet etc. CdA is the drag factor of you and your bike, including your clothing, helmet, wheels, frame design etc.

A Crr of .0053 is quite high, might be correct if you're using Gatorskins and standard 100g butyl tubes and riding on rough roads. Lots of resources online that have tested tire and tube combos and generated Crr values for each. Since knowing your power zones, including FTP, is really useful only for racing I'd do the test in full race kit with bike configured as such. Then you have apples to apples comparison when using power meter during a race.