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      03-17-2013, 09:24 AM   #1
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Psi question for aftermarket tires

I just got a new set of tires and wheels and I'm not sure what pressure to set the tires at(previous owner didn't know). The tires are 255/35 on 9.5x19 and 305/30 on 11x19.
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      03-17-2013, 10:23 AM   #2
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It may say on the tires I think
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      03-17-2013, 10:24 AM   #3
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I think it says max pressure on the tires, not optimal pressure.
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      03-17-2013, 11:01 AM   #4
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Quote:
Originally Posted by Trip3's
I just got a new set of tires and wheels and I'm not sure what pressure to set the tires at(previous owner didn't know). The tires are 255/35 on 9.5x19 and 305/30 on 11x19.
The recommended pressure set by factory would be the same regardless of tire or size used. Thats why its pressure per square inch. Not quantity of air used. Check your door. Sticker on edge shows recommended psi, which is about 35 for our cars if i remember correctly.
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      03-17-2013, 02:02 PM   #5
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Originally Posted by Da M3nace View Post
The recommended pressure set by factory would be the same regardless of tire or size used. Thats why its pressure per square inch. Not quantity of air used. Check your door. Sticker on edge shows recommended psi, which is about 35 for our cars if i remember correctly.
Thanks, I never thought of it that way.
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      03-17-2013, 02:06 PM   #6
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OEM recommended tire pressure are for OEM sized tires

I would test and adjust the pressure to see where you feel the tires have the best balance of handling and comfort
agree and will also have to follow your tread wear as you go to see if they are over or underinflated.
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      03-18-2013, 07:20 AM   #7
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Quote:
Originally Posted by Da M3nace View Post
The recommended pressure set by factory would be the same regardless of tire or size used. Thats why its pressure per square inch. Not quantity of air used. Check your door. Sticker on edge shows recommended psi, which is about 35 for our cars if i remember correctly.
^This
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      03-18-2013, 11:10 AM   #8
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Originally Posted by 1MOREMOD View Post
agree and will also have to follow your tread wear as you go to see if they are over or underinflated.
I would have to say this. Larger tires need less pressure to carry the same load. Try to see it from the extreams; imagine mini tires trying to carry the load, then with tractor tires same load.
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      03-18-2013, 04:54 PM   #9
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Quote:
Originally Posted by Trip3's View Post
I think it says max pressure on the tires, not optimal pressure.
This is an excellent point. Everyone please remember this. I get lots of calls from people who think that the max pressure limit stated on the tire is in some way a recommendation.

For the OP: in your case, since the tires are slightly bigger than the originals, the original pressure should be fine. The recommended pressures have to ensure proper load bearing capacity, and beyond that are set to give the manufacturer's desired handling balance and ride feel. If you don't need to add more pressure to carry the weight, I would start with keeping the same pressure.

For general tire pressure tuning: To test if you are over- or under-inflated, you can put some chalk stripes across your tires' tread and drive around a parking lot a little bit. Is the chalk wearing off evenly across the large majority of the molded tread? If yes, you're OK. If the middle 1/3rd or so is going away first, take out some pressure. If the edges are going away first, add some pressure.
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      03-18-2013, 07:07 PM   #10
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Quote:
Originally Posted by ben@tirerack View Post
This is an excellent point. Everyone please remember this. I get lots of calls from people who think that the max pressure limit stated on the tire is in some way a recommendation.

For the OP: in your case, since the tires are slightly bigger than the originals, the original pressure should be fine. The recommended pressures have to ensure proper load bearing capacity, and beyond that are set to give the manufacturer's desired handling balance and ride feel. If you don't need to add more pressure to carry the weight, I would start with keeping the same pressure.

For general tire pressure tuning: To test if you are over- or under-inflated, you can put some chalk stripes across your tires' tread and drive around a parking lot a little bit. Is the chalk wearing off evenly across the large majority of the molded tread? If yes, you're OK. If the middle 1/3rd or so is going away first, take out some pressure. If the edges are going away first, add some pressure.
This is the kind of answer I was looking for and will definitely be calling you when I need tires.
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