Another thing, the wider wheels DO affect performance.
GTL checks the rubber patch to the road, as a resuklt of the wider wheels you'll have more grip.
But also you'll be slightly slower going to top speed.
The effect was such that on Gamers-Crib the wide wheels aere not allowed in Mini-League.
However, added lights, no-bumpers, cabrios, and other shenanigans are allowed (they do not affect performance).
For hotlapping I'd just stick to the default cars though.