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Mazda6 / Atenza > Technical / Performance / Model > Mazda6 1st Generation (2002-2008) > Wheels / Tires
H15A5H1
I recently changed my stock michelin pilots for some falken ziex 912s. The recommended psi for my michellins were 32psi. Should i set the falkens to the same specs?
posttosh
QUOTE (H15A5H1 @ Sep 19 2009, 08:54 PM) *
I recently changed my stock michelin pilots for some falken ziex 912s. The recommended psi for my michellins were 32psi. Should i set the falkens to the same specs?

Depends. How's that for a helpful answer?

The door sticker recommended inflation pressure is really a minimum pressure for the stock Michelin Pilot HX MXM4 tire, which -- IIRC -- has a load index of 93XL in the 215/50R17 size. That tire has a load capacity at 32 psi of 1268 lb. However, your Falken Ziex 912 tires, if we are not mistaken, have a load index of 91SL. At 32 psi, a 91SL tire has a load capacity of only 1224 lb; you need to inflate the tire to 33 lb just to get to the 1268 lb load capacity of the stock 93XL tires. Provisionally, then, your minimum inflation pressure should be 33 psi.

Many of us inflate our tires to a bit higher pressure than the door sticker pressure. For the short period we ran on the OEM Michelins, we had them inflated to 35 psi. That gives a little bit crisper handling at the expense of a little less cushy ride. More importantly, however, it gives a margin for the fact that all tires leak a little air, some more than others, and need to be topped off from time to time to bring them up to proper pressure. Because tires never inflate spontaneously (the inflation pressure increases with heat, but the quantity of the air inside the tire remains the same), if you inflate just up to the recommended pressure, and if you do not check your inflation frequently, chances are you will end up doing most of your driving on slightly underinflated tires.

Finally, allow us to put in a plug for a good, high quality tire pressure gauge. The pencil-style gauges in use at most service stations are accurate to about +/- 3 psi, which is not sufficiently accurate. The ubiquitous AccuTire/Monkey Grip/Ace Hardware digital tire gauges are more accurate than a pencil gauge, but are very fussy about positioning on the valve stem to get a reading and (because of the ensuing "operator error") give bad readings a high percentage of the time. Invest in a good G. H. Meiser (clickable link) tire gauge (Accu-Gage, do not confuse with the undesirable AccuTire), and you will have confidence that a "33 psi" reading reflects 33 psi inside the tire rather than a random number on a screen. Good gauges are not all that expensive, and will repay their cost very quickly.
H15A5H1
Thanks for the great writeup. It was most helpful
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