I spoke about this briefly in an old suggestion post back in October (Front car loses too much downforce when drafting - #24 by TNR_Blade) but obviously it may have just been covered up by the concerns of the initial post.
This mainly concerns the NASCAR “Next Gen” cars but it does apply to all cars
The main issue at the moment is bump drafting seems to be non existent thanks (in part) to the changes in the collision model from FM7 to FM, but there may also be some aerodynamic changes as well.
At the moment, cars are unable to efficiently transfer momentum from the trailing car to the lead car unless there is a substantial MPH difference (varies depending on speed of all cars, but is still weaker than it should be as a whole.)
The biggest issue because of this is now at all of the oval tracks where drafting can be a factor, (Basically Homestead Miami and larger but Daytona and Sunset Peninsula are the worst offenders), cars essentially race in grid lock because the trailing cars can’t help the lead cars speed up at all. And bumps to the lead car rear bumper only kill the trailing car’s moment instead of boosting the lead car’s.
I’m not suggesting a full 180 where there’s no momentum bleed for the trailing car, but some way to make something like a 5mph closing rate turn into a 3mph boost to the lead car and a 2mph drop to the trailing car would be extremely beneficial for all draft races.