Strength upgrade is only done once and costs bugger all. less than racing soft tires.
Chassis rebuilds I don't even bother with, unlike engine rebuilds that need to be done nearly every 4,000 miles to get the car engine back to top forum are done regular.
(free oil and car wash included).
Use Low cost rebuild cars to get money to rebuild Expensive cars...or Borrow a car as it never gets engine wear. (Resets when you reborrow it)
