Tires and Top speed.

[A Tanga in the woods]

So I got a sultan RS, performance is good, looks good everything is good however something is bugging me when it comes to its top speed. You see, at first I had competition suspension on it and I noticed the car kinda spins sometimes in cornering. I changed the suspension to race suspension and it's a bit better.

Now here's the thing, I used to have tuner wheels on it and I changed it to off-road cause I wanted it to have a nice rally look. The car no longer spins what so ever at all however, I have this feeling when I'm driving it that its top speed is less with offroad wheels on.... Do we know if there's actually a correlation between the tires and the top speed of cars in the game? or I having a placebo effect and the top speed is the same? :/

[Caped Crusader]

Far as I know (my favorite activity in GTA Online being racing) tires don't impact top speed. However, the type can have a slight impact in terms of how they deal with bumps - fatter tires, such as offroad and muscle, being better since apparently those are allowed to clip a bit and thus drive a bit smoother on rough road/surfaces. There have been occasional reports of the devs trying to address this behavior, as well as curb boosting, through the use of advanced handling flags applied to most vehicles released since IIRC the Doomsday DLC, but with very mixed results.

This video by Broughy1322 talks about optimal car upgrading for max performance:
https://www.youtube.com/watch?v=5I-vYo1GUpc
Just for the record, I personally feel like having offroad (or other similarly thick tires) offers only a tiny benefit in races and I don't add those universally the same way I did when I was first getting into the racing scene. If you're doing the Premium Races, I would say go for the best setup possible since competition can be strong there, but otherwise I doubt the tires alone will make the difference between a win and loss.

Edit: The open wheel race cars are different and I do believe the harder tires offer a slight boost to top speed compared to medium/soft ones, but those 4 cars have had special programming applied where modifications have more pronounced performance impact, code that isn't active for the other vehicles in GTA Online.