Road Cycling - garmin accuracy on Motion Based?

i got a garmin a few weeks ago, and everytime i upload a ride on motion based, the stats it shows don't seem to be accurate with the stats that the garmin shows. i didn't really notice it until today, because the numbers for todays ride seem way off...

for example, at the end of the ride, the stats on the garmin said:

riding time: 2:49
distance: 44.78
average speed: 15.9
max speed: 34.1
total ascent: 1749 ft.

but when i uploaded it, it shows these stats:

riding time: 3:03
distance: 45.22
average speed: 14.8
max speed: 38.8
total elevation gain: 2520

and those are just a few...

the thing that strikes me as odd is that if you click the laps link, it shows one lap, and all of the stats there are the same exact ones that were on the garmin, so why would everything else show different numbers?

if it matters, i'm using version 3.20.0.0, which as far as i know is the newest version. on the equipment link, it says that the recommended version is 2.90, which i don't understand because there have been 3 updates since then...

any help would be greatly appreciated...

I don't know how your riding time changed, but your numbers should be different on MB due to correction algorithms. My distance always goes up slightly, as does my average speed, generally. Max speed may go up or down. I've never noticed my riding time changing, though.

FWIW, SportTracks almost always reports a lower distance, average speed, etc. after doing its corrections.

so does that mean the stats on the garmin during the ride are wrong? and why are the corrections necessary?

MB takes the data points from the garmin and interprets it differently. same with sportstracks. they both try and correct any errors they think exist in the pure data. the differences should be minor. i have never seen any 10 minute time differences. i would suggest running the latest firmware, software, and chipset garmin has out. i am and have had no issues. you could post a link of the activity for us to look for further thoughts? or not. later.

you could post a link of the activity for us to look for further thoughts?
http://trail.motionbased.com/trail/invitation/email/accept.mb?senderPk.pkValue=135365&unitSystemPkValue=2&episodePk.pkValue=2988589

it has the latest software that garmin has out, and i'm guessing it has the latest everything else too, since i only purchased it about 10 days ago...

I just noticed this too. Lost two miles today. I don't get why if you have the wheel sensor, it just skips estimating with GPS and go with the damn wheel sensor. Same thing for speed.