Quote:
Originally Posted by ZDan
There are WAY too many variables other than tire size to draw the conclusion: quicker because smaller tires...
Test the same car, same make/model/age/heat-cycles tire, same day, same driver, only difference being tire width, and then you have a valid comparison.
Road and Track did a test like this, but unfortunately didn't test tires of the same diameter (215/45-17 = 24.7", 235/40-18 = 25.4"), so different gearing and c.g. height. If only they'd tested a 245/40-17 vs. 215/45-17...
Car went 6 tenths faster lap time on the 215/45-17 StarSpecs vs. 235/40-18. However pulled slightly more g's and quicker slalom time on the 235s...
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Yes, you need real world testing to determine which is best. But you cannot assume wider is always better. The 215's may well be better on a road course with longer straightaways because of lower wheel/tire weight and less drag. But if you're running a slalom course, the wider tire will always be better because the contact patch is much more square and you are going against much higher lateral G's.
There are many car fanboys who believe that wider is always better. In track testing alternatives, as I have done in the past, there is a sweet spot in width for each car, each track, and each pavement type -- and weather conditions. The trade-offs of wheel/tire weight and number of curves as well as engine hp make this interesting. However, the stock BRZ has only 200 hp, and good 215's, could well be the best performing tire width on the road. Put on a supercharger, and I would never go with 215's on the rear, but may well keep them on the front.
In general, people who spend money on wide tires and wheels, are just trying to justify their purchases. You can tell, because with a stock engine, there is absolutely NO reason to change the fronts, and they do. Changing the fronts make the car less responsive in virtually all cases. The backs are a different matter and there are valid arguments on both sides. But there is no argument that justifies super wide tires on a stock BRZ/86.