Anonymous
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I am running BF Goodrich All Terrain T/A K/Os, size 265 75R16. Everyone I talk to suggests a different tire pressure. THe side wall states you can run them up to 65psi, whereas Toyota suggests 32psi for the stock 265 70R16. Any suggestions? Am I doing damage to run them at around 50psi?
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Anonymous
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Set the pressure so the tires wear evenly. A good test is to find some level ground - newly paved parking lots are a good choice. Take some chalk and draw a line across the width of your tread. Make sure the line is easy to see... that there is plenty of chalk on the tire. Do this for all 4 tires. Then drive in a straight line, approx 50 feet. Get out and look at the chalk line. If the chalk is worn away more in the middle of the tire, you are running too much air (PSI is too high).
You'll want the PSI such that the tire doesn't look flat (i.e. there isn't a big bulge at the bottom where it contacts the ground), but so that the chalk line wears away evenly. For me, this is generally around 30-33 PSI, but it can vary depending on your rig.
I would bet dollars to donuts that 50PSI is too much. Are you doing damage... not really. But you are cause the tread to wear faster than it normally would, thus shortening the life of your tires.
Edited by jacksonpt (08/17/04 12:01 PM)
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larsdennert
Body Damage is Cool
Reged: 01/06/01
Posts: 1656
Loc: Pasadena, CA USA
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How much air you need is generally based on how big the tire is and how heavy the vehicle is.
The tire has to support the vehicle. If the vehicle weighs 4000lb and there's say 1000 on each tire, then the surface area on the ground and how much psi is in the tires determines how much the tire can carry. 50psi divided into 1000 is 20 square inches minimum of tire area to support the vehicle. That's a two inch strip across the face of the tire. Not much at 50psi. Drop it to 25psi and you need a 4" strip. If the pressure isn't high enough for the weight of the vehicle, the tire will bulge and flatten to increase the surface area on the ground and thereby equalizing. The problem with not enough pressure is that a tire that "bulges" too much will overheat from the increased friction. Obviously you want to do more than just support the weight with the minimum pressure needed to support the vehicle. Handling comes into play too.
In any case, the tire's max load capacity rating comes at it's max pressure. That doesn't mean you need to run them there. BFG has no idea what vehicle they will be mounted on so their figure doesn't really apply. Also the type of tire, the number of belts, the age, the suspension geometry and other factors can all play into it. Overinflated, the tire kind of bulges the other way. It doesn't sit flat on the road causing uneven wear and poor handling.
Having said that, I run that size tire and it rides/wears the best for me at 35psi. 
--------------------
Lars,
Gold Coast Cruisers |My 4Runner
Edited by larsdennert (08/18/04 11:47 AM)
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Anonymous
Unregistered
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Thank you both for your responses. I called both Toyota and BFG to ask their opinion and since the 265 75R16 is not a "recommended" tire from Toyota, BFG can't make a suggestion??? Toyota, likewise, said they couldn't make a recommendation for the same reason, that they did not "sanction" using that size tire on the Runner. Oh well, so much for an answer from the corporate climate. Thanks for your input and I think I will run them at 35psi and see how it rides.
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