Normally, the new tires plus rims should not be more than +/- 3% of difference compared with the factory tires+rims. Otherwise, you could be caught by cops for speeding although your speedometer is says legal speed. Conversely, you might drive at <<100 km/h blocking up traffic although your speedometer suggests you are driving at a nice speed of 100 km/h :-) :-)
换小一寸RIM,相应配合适的轮胎,尽量保持外径和宽度和标准一致,可以有两个好处,一是减震感觉会软点,二是RIM外缘离地高了,过高坎低洼不容易损坏rim. ( {# s9 i, J. a" ~6 s) q- C. w% g ; A& M8 D9 P: M G$ p7 F/ U% w1 A关键一点要注意rim小了,是否和刹车部件干涉。
就个人经验,轮胎店和Costco都只推荐原厂尺寸。可以直接打电话给dealer,也可以自己上tire rack 网站查,输入maker, model and year, 选择tire/rim package, 就能看到不同的组合了。我的车原厂是18寸,冬胎就选的17寸,会便宜一点。轮胎直径大了1%,开起来没有区别。