Tire pressure Forester - Page 2 - Fiberglass RV


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Old 03-18-2011, 03:07 PM   #15
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I checked the sticker: it is 29-26 for low load, 29-36 for loaded, and 29-41 for towing. I can see the idea of more in front for unloaded (the weight is in front) and more in back for loaded (weight shifts toward back) but my major problem towing if anything is bouncing in back on rough roads; wouldn't higher tire pressure make that even worse? I forgot to look at the tires and will do that soon.
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Old 03-19-2011, 01:20 AM   #16
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Smile over/understeer

Oversteer and understeer are just what they say.

Oversteer: the car turns (steers) more than is expected.

Understeer: the car turns (steers) less than is expected.

To make things more complicated, front wheel drive and rear wheel drive have some opposite handling characteristics, however higher tire pressure adds more steering grip to the axle it is on. That is front axle = oversteer, rear axle = understeer.

YouTube - Car Handling - Grip, Oversteer & Understeer explained by Tiff Needell

Everyone gets used to the handling of the car they drive. If you change the ratio of tire pressure front axle to rear axle, you can affect how the car handles. Front wheel drive and rear wheel drive are discussed in the video. AWD, or All Wheel Drive avoids the power over/understeer of the single axle powered car.

Apparently Subaru desires an understeer condition when towing because of the danger of the TV sliding out and the trailer consequently jackknifing.

I recall hearing a screaming sound and then observing a large white van sliding driver side first sideways down the highway with a utility trailer actually pushing the van down the road. The van had just negotiated a left curve, so I assume he had over compensated for an oversteer condition to the left and caused an oversteer to the right and once the jackknife occurred and the trailer took over, he was helpless to do anything but ride it out.
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Old 03-24-2011, 09:33 AM   #17
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Originally Posted by Greg H View Post
Yes Barrie your right, but car makers put tires on the car at the factory, lets say Detroit, Mi. This week they have a warehouse full of Goodyears, so the cars built this week get Goodyears with the proper size and weight capabilities of the car, next week they have a warehouse full of Generals, those cars are going to get the Generals, the Goodyears and the Generals will both be capable but that doesn't mean they will have the same inflation recommendations. The door tag is good for tire size and weight carrying capabilities but I will always go by the tire makers recommendations not the car makers.
Where do you find the tire manufacturer's recommendation on the inflation for your vehicle? You mean the MAX inflation on the sidewall? Filling to the max inflation (or some given percentage of it) is like always taking an elevator to the top floor. The MAX is the MAX, but not necessarily the proper pressure for the size, weight, and handling characteristics for a given vehicle.
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Old 03-24-2011, 10:17 AM   #18
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I think Subaru is just basing it on where the weight is likely to be. Low load, put more pressure in front where the engine and passenger(s) are. Bigger load, put more in back. Towing, put still more in back.
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Old 03-24-2011, 11:20 AM   #19
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mcbrew, If you look at the door jam on your vehicle you will see the recommended pressure the car maker wants you to use, but remember that was with the original tires. I don't run at the max I run a little below max and at a pressure that rides good. Also remember the pressure stated is at cold tire temp.
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Old 03-27-2011, 11:37 AM   #20
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mcbrew, If you look at the door jam on your vehicle you will see the recommended pressure the car maker wants you to use, but remember that was with the original tires. I don't run at the max I run a little below max and at a pressure that rides good. Also remember the pressure stated is at cold tire temp.
Not what I was asking. Some people mistakenly inflate all tires to the MAX sidewall pressure and disregard the pressure recommendations from the car or trailer manufacturer or the tire manufacturer's weight chart (for trailer tires).
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