Fitting new parts

after a race i saved the next race part with re fitting the whole car with new parts, double checked before race and all was good, as qual started i went back to check it and all the changes had been made but not to 100%? 

is there a reason for this?

Thanks 

Need to check if you reached engine supply limit  if it were the engines that weren´t replaced at 100%.
Need to check also if you had enough engineers/mechanics hired to replace all parts.
And finally money also.

u used the parts in qualy and in the race -.-

yeah i replace a full car, but there losing loads of % like straight away

Make sure your components are being produced at 100% quality in the manufacturing facilities section

Make sure you are saving after making any changes

It is normal for suspension being completely degraded after the races.