QuestionQUESTION: I drive an '02 Honda CRV with 38000 miles, 2WD. The owner's manual specifies 26psi, which I followed. I replaced original tires at 31,000m because the outer edges were wearing, indicating under-inflation. I now ride on Michelins and inflate at 30psi and the tires seem to wear correctly. I think the factory specified 26psi in order to give a softer ride since the CRV is built on a truck chassis and ordinarily rides a bit hard. What is your opinion in this matter, Barry?..............My second queston is, "what are directional tires and non-directional tires, and which am I using?" My manual calls for different rotations but doesn't specify which I have...Thanks again.
ANSWER: Mark,
It is fairly common for vehicle manufacturers to write tire specifications that are all encompassing. They are trying to balance the tradeoffs. For example, ride and handling are 2 of the many things that in opposition. Put another way a great riding tire generally doesn't handle well - and vice versa. It is true that ride quality and inflation pressure are closely linked - and, of course, the vehicle manufacturer carefully chooses inflation pressures that aren't going to give poor ride qualities.
Among the other tradeoffs is rolling resistance (fuel economy), traction, and wear. It is fairly common for the vehicle manufacturer's spec is be a bit aggressive (sometimes a lot aggressive) towards rolling resistance - and that means sacrificing either traction or wear (or both). Since traction is something that has some safety issues associated with it, wear is generally the item.
One of the tricks that tire manufacturers do is to design the tread area of the tire such that the shoulders of the tire are not as engaged as the center of the tread. This results in better rolling resistance while minimizing the impact this would normally have on the wear rate. Unfortunately, this results, in some cases, in more rapid wear in the shoulders - which makes it appear the vehicle pressure specification is too low.
Regular replacement tires - tires designed solely for sale in stores - do not have these types of restrictions - and, in fact, are judged by the buyer almost solely on wear. The result is that replacement tires almost never have these sorts of issues.
Bottomline - while the inflation pressure specified by the vehicle manufacturer is certainly geared towards a good ride, you can't use the wear pattern of the OE tire to judge whether or not the pressure is too low. This is a case of too many variables.
Directional tires will have an arrow on the sidewall indicating the direction of travel. If the tires do not have an arrow on the sidewall, then they are non-directional tires - and it doesn't matter how they are rotated.
---------- FOLLOW-UP ----------
QUESTION: Barry: I still don't know if I'm doing the right thing by inflating to 30psi.
AnswerMark,
Inflating a bit over the placard pressure is going to change a few things - many of which are desirable.
Fuel economy, hydroplaning resistance, steering responsiveness, wear rate, snow traction, and tire durability are all improved, while ride, wear evenness, and impact resistance are degraded.
Personally I use 3 to 5 above the placard, mainly because I like a vehicle that is responsive and am willing to put up with the ride.
