前几天到 ＮＴＢ 去换机油，看到  Michelin 有 manufacturer rebate。正好另一台车轮胎两个轮胎已经磨到了林肯的头顶，该换了。另外两个也磨到了华盛顿的头顶，也可以换了。

Place a penny into several tread grooves across the tire. If part of Lincoln's head is always covered by the tread, you have more than 2/32" of tread depth remaining.		2/32" remaining tread depth
Place a quarter into several tread grooves across the tire. If part of Washington's head is always covered by the tread, you have more than 4/32" of tread depth remaining.		4/32" remaining tread depth

磨得厉害的两个是领导平行停车上了马路牙子刮了一个，先换了。轮胎要一次换一对，当时花了７００ 多大洋。这回想干脆４个一起换。问NTB OEM 轮胎的价钱，说是 4 x 250 = $1000, 包上胎（mounting），平圈（balancing）， 但不包车轮定位（4-wheel alignment)。这个价钱在意料之中。因为前不久敌乐给过价：四个轮胎 $1350 + alignment $179。

等换油的时候，俺掏出聪明手机，上网查了一下找到一个最低价，总共便宜 200 大洋左右。以前俺在这个店换过轮胎，刹车等，花过好几千大洋，是常客。跟店长商量，店长说：行，我给你这个价。于是第二天下班后把轮胎换了。不过，没有时间做 wheel alignment。太晚了，他们要下班。换轮胎的时候，俺注意到后车轮不是想象中的 |----|  位置，而是像下图右边一样。当时很纳闷。于是引出另外一段故事。（待续）




（下一篇： 换轮胎与车轮定位 (2) ）

Tire tips:

(1) Tire markings



(2) When were my new tires manufactured?

Since 2000, the week and year the tire was produced has been provided by the last four digits of the Tire Identification Number with the 2 digits being used to identify the week immediately preceding the 2 digits used to identify the year.

Example of a tire manufactured since 2000 with the current Tire Identification Number format: