I was informed that there are some modifications that affect the vehicle performance, about hidraulics and nitros is quite evident, but there is another one. The offroads wheels modification, available on Transfender garage, when applyed to a vehicle, it will acquire a flag called Offroad Ability 1 (useless on vehicles that already have this flag enabled, like a Landstalker for example). There are 2 missions that the player is given a vehicle with offroad wheels, Life`s a Beach and Farewell my Love (Badlands B), maybe with the purpose of helping driving on the sand/dirt/grass? So, have any experienced drivers ever noticed an improvement when using offroads wheels.

This is a list of which vehicles already have Offroad Ability 1 (even without offroad wheels), as well as other flags already available as default, and a still incomplete list of which mods which vehicles can handle without the game crashing: https://docs.google.com/spreadsheets/d/1ySqX6XuPTCjkxlGwsqcX-lT-s0_n8C9CxdvY7eKqsCc/edit#gid=0

I also noticed that Dareka00 has beated Wu Zi Mu in 2:06 without the use of any offroad wheels, I am not sure how Offroad Ability 1 would impact on a Bullet since it already has Offroad Ability 2, but maybe is something very minor, and very hard to notice any difference at all, but I don`t know, what if he can do it in 2:05 using those wheels:

in my experience theres a difference when you drive with offroad wheels, its kinda obvious;you get better handling when you drive on sand or grass ive seen that it has been discussed a while ago somewhere else, though

check the video by "madmax" on this forum,its a comparison of wheels. could be helpful too http://forum.adrenalinex.co.uk/index.php/topic,6744.msg159471.html#msg159471

hope that helped a bit