I found that the only place it helps to turn it on is the longer races on Nurburgring.
When you set the strength to anything other than off the driver will pit when his strenght drops to this point even if his tires and fuel are still good to go. Result is that in most races especially with lower level drivers is that they will pit to soon.
On Nurburgring 4hr there can be an issue where the tires on the car are pretty worn as the car comes by the pits but not worn enough for him to want to pit just yet. This will result in Bob having a very poor lap as his tires continue to degrade during the lap and then he will pit on the next one. I find that here with my drivers a setting of 30% will have them pit 1 lap sooner and keep them running on good tires. The result was very good as well because now Bob does not get that 1 slow lap drifting the corners and sliding all over before he pits.
Its the strength level the driver pits at. If its set to 90, he pits for a driver change at 90% strength, if its set to 10, he pits at 10%. The best setting is probably 10 or 20 for every race.
If you set it to 10 or 20 in the first races where it shows up he will pit way to early. My advice is to keeo it off except on Nurburgring for the reason I mentioned above.
