I did a 60k Surrey Hills loop yesterday on my new 29er Hardtail, same route as I rode on my Cotic Soul with lightweight wheels and tyres 2 weeks ago, and fairly similar conditions – grim, muddy, slow.
I knocked 40 minutes off my time. Set a PB on Barry Knows Best and a few other descents as well as most climbs.
Admittedly I rode very hard yesterday – but I also rode very hard 2 weeks ago.
By comparison – on my CX bike in dry conditions my moving time for that loop was very similar to the 29er, though obviously there I made the time on the climbs and linking road sections.
Astounded at the difference.