TSS calculations (TR, TP and Garmin)


#1

I’ve noticed a difference in the TSS calculations on uploaded rides in TR compared to TP, but it’s never been that much or affected anything. However, I set my Garmin head unit to show TSS at the weekend as I was doing an outdoor ride but time was against me so I topped up my weekly TSS up with a shorter harder ride. At the end the Garmin read a TSS of 175. I realised this was probably suspect as the TSS was going up as I freewheeled the last 2km downhill to home. This is compared to a TSS of 93 on TR and 107 on TP.

Is there a fairly solid relationship between Garmin TSS and TR TSS. So if I went out to top up TSS again I’d know that the TR TSS will equal about 1/2, 2/3 etc of what Garmin thinks?


#2

Can’t fully answer your question but I do know for my outdoor rides the TSS is different to TR as my Garmin has a higher FTP set according the Connect ride details on the app, but I can’t figure out how you amend it!


#3

Yeah, definitely check FTP across the platforms. If it’s different that’ll throw TSS way off. They should all be identical as its a propriety calculation from trainingpeaks .

The other thing to check is if one is including zeroes or stopped time while the others are not, that can throw things off too.


#4

+1 check ftp across platforms. Bike FTP formula takes into account your IF and workout duration so that even if the NP reading and duration are the same, if the FTP is different you’ll end with different IFs thus, different TSS.


#5

TSS calcs are different for me between TR and TP because TR syncs from Strava and appears to cut off a few miles of my ride (plus associated TSS). I assume this is due to TR respecting my Strava privacy zone?


#6

That’s just how the equation works, unfortunately. TSS = [(s x NP x IF) / (FTP x 3,600)] x 100 where:

s = length of the workout in seconds
NP = Normalised Power
IF = Intensity Factor (NP/FTP)

If you did a 1 hour time trial with an average power equal to your FTP (Say 300 watts), the Normalised power would be equal to FTP, s would equal 3600 and everything would cancel out to give 100 TSS.

If you did the same 1 hour time trial but coasted for 5 minutes at the end (300 seconds) your normalised power would drop to 294 watts, the intensity factor to 0.98 and s would increase to 3900, giving a TSS of 104.

Obviously the equation has it’s limitations since in this case you’ve done no extra work.

Hope that makes sense,

Mike


Feature request: TSS on screen