Q: I recently replaced one tire due to a puncture. Now the tire pressure monitor light sometimes comes on and goes off while driving. I think it is due to the difference in the new tire circumference. The other tires are three years old and have 15,000 to 20,000 miles of wear. Will this difference in tire circumference harm the transaxle when the unmatched pair of tires is being used on the front?
D.B., Chicago
A: Yes, it could cause problems, especially if your vehicle has four-wheel drive or all-wheel drive. A viscous coupling or a differential comes into play whenever the vehicle turns. But it is not designed to run continuously, which happens if the wheels are different diameters. Carmakers usually state in the owner's manual that all tires should be replaced simultaneously. If you rotated your tires religiously, they will all wear out at the same time. But if you only need one tire, you may be able to have the new one shaved down to the same diameter as the ones in use.
Q: I have been noticing more cars for which, when a turn signal is on, the headlight turns off on the side of the car on which the signal is blinking. I cannot understand what the purpose would be. I suppose someone could argue that when the car turns, opposing traffic will not be blinded by that particular headlight. Thank you for any illumination.
H.K., Inverness, Ill.
A: It probably was not the headlights, but the daytime running lights that were extinguished. The reasoning is to make the turn signals more noticeable when activated. Some manufacturers switch the LED daytime running lights from white to amber.
Q: I have a 2005 Chrysler Pacifica with about 140,000 miles. After a recent oil change at a reliable local shop, I was advised that the car has "cradle rot." Repair involves engine removal and part replacement. Cost was estimated at about $4,000. Do you have any information? I assume there wasn't a recall, and if there was I wasn't notified.
J.W., Elkhorn, Wis.
