The repair is to refresh the rigidty on the car. Overtime the car will twist and warp from high speed and torque. When the happens it effects the cars handling a bit and will effect tire wear in an adverse way. Adding the rigidty upgrade will help the car last longer before this happens but it will happen eventually on all cars no matter how careful you are.
The key things I noticed with this are 1: The car will begin to handle a little different and 2 you will start to see a tire on one side wearing faster than another. So let's say with a good rigid car you can get 20 laps on your tires and the front are wearing at the same rate. After the car starts to warp you will begin to see one tire wear out a bit faster and now will only be able to get 19 laps or maybe only 17 laps. One tire will be fine and the other needs changed.
Of course this uneven tire wear is normal on ovals or tracks where all of the hard corners are the same direction but on most tracks right and left tires should wear about the same. If there is a noticeable difference on most tracks between right and left front tire wear then you likely need to refresh the car. So far I have saw that some cars cost up to 500k to do this even if they do not really need it.
