Yeah GPS can be a bit variable, particularly on twisty single track where the pings might not be close enough together to collect every twist and turn of every metre of track, or where dense tree cover disrupts the satellite connection etc... Also Strava will take your data and reconcile it against other users and their basemap etc to identify segments and so on so there can be some unpredictability in outcomes. Could be that the other guy's Wahoo collected/calculates data differently - or just that he forgot to press "start" until halfway up the first climb...I also used my phone. And ours were pretty close.
The Derby Tunnel is a weird one. In November 2019 I got a KOM on that of 3 seconds!!! Fricken Time Warp through the tunnel.Followed the other half through Derby tunnel, both using the same garmins linked to the same phones. She was 13s, I was 2min+.
Most rides where I follow her, so our times should be identical, there are differences.
I almost always end up doing more km, and more elevation too.
Identical set ups.
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