Speed in zwift / strava / training peaks


(Allan Watkins) #1

I’m getting variances in speeds from the .fit file on Strava vs training peaks vs my garmin.

fit file from zwift http://tpks.ws/MbS1
on strava http://www.strava.com/activities/220034600/analysis
garmin file on training peaks http://tpks.ws/KmU5

I could provide the two fit files if you let me know how if interested for comparisons.

I’m not sure why the speed on the zwift file uploads to strava shows me going SO slow compared to training peaks.


(Gary Randolph(BTC)) #2

The speeds will be different. Zwift uses power to fit its own speed curve. I believe this is done in order to provide a “level” field for users of various trainers. Keep in mind that all of the “smart” trainers do the same thing. Yes, the wheel is actually turning at the rate given by the smart trainer but that speed is still based on the manufacturer’s power/speed curve.


(Allan Watkins) #3

But why would the SAME file have different speeds on strava versus training peaks?

I also did not use my speed sensor on the zwift .fit file. So it’s even more odd that there are 2 different speeds between strava and training peaks.


(Gary Randolph(BTC)) #4

Sorry Allan, I didn’t realize that it was the same file - that is very odd.


(Allan Watkins) #5

Yeah, It’s pretty strange, and I figured taking the same file on training peaks to strava would result in the same avg speed on strava of 19.4ish mph but nope.


(Jon Mayfield) #6

There’s 2 issues at play here.

  1. Your garmin file is measuring wheel speed, which has no correlation to speed in Zwift. Zwift is totally controlled by watts (in fact, you don’t even need to pair speed if you don’t want to). So Training peaks is showing your wheel spun at 16mph, whereas the speed you went in Zwift is based on a physics model of watts vs various slopes and wind in the game.

  2. Now, in your case the discrepancy is HUGE, and that is because on low end computers (or at least, computers with low end graphics chips) there’s an issue in the current beta where you will not travel the proper distance. The bug has been fixed, but it has not been sent out to the beta testers yet.


(Allan Watkins) #7

Right on! that makes more sense now, appreciate the update. 'm on a laptop and I’ve got a pretty decent chipset / ram / ssd / etc… but the graphics card has been tweaked for all performance settings, I can play quite a lot of other games on good graphics settings without issues but Zwift seems to be quite a beast.

My coach and I were planning on chatting soon and I don’t want to mess with my TSS / time on bike etc… so I just deleted the extraneous zwift file from training peaks so that link broke, but I can upload/email in the .fit files if you’d like for confirmation.


(Allan Watkins) #8

Just following up on this, my computer doesn’t seem to be terribly low end. I looked up the specs, and have no problems playing other games that are modern.

specs that matter:

Dell XPS 17
2nd Generation Intel Core i7-2760QM processor (2.40 GHz, with Turbo Boost 2.0 up to 3.50 GHz)
8GB,DDR3,2 DIMM
17.3in FHD WLED AG (1920x1080)
NVIDIA GeForce GT 555M 3GB graphics with Optimus
(using a samsung evo 840 ssd as the main hdd

I’ve recently played starcraft 2, deus ex human revolution, world of warcraft, rift, all in the past 2 years without any troubles on reasonably high graphics settings, maybe not maxed out settings but these are games with similar system requirements.

Zwift is pretty hefty on resources, and even after exiting the game it’s clear that there is a possible memory leak or something that’s still bogging things down. Is there a diagnostic thing I can do and e-mail in for a closer look at this issue? The game does seem to be a bit laggy when in play at times (but I just thought it’s mostly due to being a beta issue) and I’ve had to set all my graphics settings to performance oriented which aren’t that way for other games.


(Allan Watkins) #9

I had an idea, what if any time a power meter is detected the speed sensor is completely removed from the GUI to eliminate any confusion and replaced with a “speed will be calculated by power” message.


(Jon Mayfield) #10

Allan, the pairing dialog has already been redesigned much like you’ve suggested, we’ve just not had a chance to implement that. Once classic non-smart trainer support goes in you’ll see the new pairing screen.

Your machine doesn’t seem like it’d be low enough spec to have a problem, however I noticed when you ran today your frame rate was double what it was last time. Could it be you ran with the laptop unplugged the first time, and plugged in today?


(Allan Watkins) #11

Believe it or not but I was just doing a little stress testing, my wife pointed out last night “wow your laptop is getting REALLY hot” while we were on the couch and I left it down to grab a drink.

Long story short, I disassembled it and cleaned out the fan and other dusty parts, it wasn’t that bad but it looks like it made a huge difference in the level of throttling cpu my laptop is doing. My coach has had me take it super easy this week but tomorrow I’ll be on for at least a couple hours and so far it seems like it’s fixed that issue.


(Allan Watkins) #12

I should’ve said “GPU throttling”, and I no longer have any problems after zwift exits either.


(Allan Watkins) #13

And 2hrs ride today… What a difference! I was actually pretty competitive this time around and the AI feels like it needs to step up it’s game, that was quite a different experience.