QuestionCan I replace the tires of my car (235/55 R17) by new (225/55 R17) using the same orignal wheels? would there be any impact on the car safety or stability?
My Car Info is:
FORD - Crown Victoria 2004 (LX Sport)
AnswerThis is not a very safe thing to do!
1) Tire size = load capacity, so you are reducing the load capacity of the tires and even though there is some reserve, it becomes more possible to overload the tires. And overloaded tire failures are not pretty sights!
2) This change would also result in saturation of the tire at an earlier stage. Predictable vehicle handling depends a lot on linear relationship between certain paramaters - verticle load vs slip angle, lateral load vs slip angle, etc. Once a parameter gets saturated, then the handling starts to become unpredictable and the more staurated the parameter or the more parameters that get saturated the less predictable the handling behavior.
3) Hopefully you've recognized the speed rating issue and have chosen to stay with the H rated that came on your car. This is important. Not only does the speed rating related to the speed capability of a tire, it is also a gauge on the grip and handling responsiveness of the tire. Your vehicle's springs, shocks and sway bars were selcted for a particular set of tire characteristics and deviating from them might cause some handling issues, particularly during an emergency manuever.
4) Philosphically, engineering a vehicle requires balancing conflicting goals. But one of the things that has been recently uncovered during the recent tire crisis is that the more reserve that is engineered in, the less likely some bit of debris (or a cut or puncture) will cause a tire failure. It's all a matter of statistics. Unfortunately, Ford hasn't gotten around to re-enegineering the Crown Vic, so its tires are smaller than the newer design standards call for.
For the above reasons, I would recommend against going down in size and speed rating.
