Speed rating doesn't raise in some cars

I’m intrigued with something. Some cars even adding parts that raise power the speed rating doesn’t raise. But I know is higher than the speed rating shows. Like, how is it possible a car that is reaching 340km/h have a speed rating of 7.2? It does not make any sense.
Am I missing something or the speed rating is a little bugged?

Check what transmission you have - some cars are quite restricted by their stock transmission, so putting more power in the engine isn’t increasing the speed rating. Swap it out to a street or race transmission and you should see a change.

I’ve already changed to race transmission. The car has a performance from speed rating like 8.0 but on speed rating stats still shows 7.2. That’s why I think it’s bugged.

Aero (wings) could significantly affect the car’s speed… could this be the problem?

Gearing maybe? You can easily take a car with a top speed of 250 km/h and get it over 340. Part of my fun with this game is tuning the cars. Play with the overall and each separate gear or download a ready tune for that car.