what is the correct tire PSI - Team Camaro Tech
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post #1 of 12 (permalink) Old Aug 7th, 12, 08:30 AM Thread Starter
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what is the correct tire PSI

I am running modern 17" wheels with Firestone Firehawk Indy 500 tires. Sidewall says Max PSI 50 for the fronts and Max PSI 51 for the rears.

I assume then I should inflate them to the max psi rating (cold) - correct?

Just seems really high but I have no experience with this kind of tire.

Thanks

Randy
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post #2 of 12 (permalink) Old Aug 7th, 12, 08:40 AM
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Re: what is the correct tire PSI

Quote:
Originally Posted by il_randyb View Post
I am running modern 17" wheels with Firestone Firehawk Indy 500 tires. Sidewall says Max PSI 50 for the fronts and Max PSI 51 for the rears.

I assume then I should inflate them to the max psi rating (cold) - correct?

Just seems really high but I have no experience with this kind of tire.

Thanks

Randy
I believe the max pressure is used for full weight loading of the tires.
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post #3 of 12 (permalink) Old Aug 7th, 12, 08:56 AM
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Re: what is the correct tire PSI

No don't inflate them to the max psi! The only time you might do that is if you were hauling bricks in the trunk and sand bags in the back seat. Cars come from the factory with a factory recomendation based on the wheels and tires it came with new. I'm only mentioning this because if you go look at your wifes daily driver you might see a factory recomendation of 32-35psi when the sidewall says 45psi max...

With custom wheels and tires you are kinda on your own to decide where you get the combination of best ride, best handling, best tire wear and best gas mileage. Having more psi will give you better gas mileage but will reduce handling and ride quality. Too low of psi will cause faster tire wear and even tire damage.

I'd start with 35psi cold on all 4 and adjust from there based on your driving habits and the cars handling. You could call a trusted wheel and tire shop and ask them what they fill customers tires with your sam spec's too as well...

...Dennis

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post #4 of 12 (permalink) Old Aug 7th, 12, 10:29 AM Thread Starter
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Re: what is the correct tire PSI

Very helpful guys thanks. I did some more reading learned that the road course guys actually bump pressure up past MAX PSI because they can get better handling. They of course are not concerned about comfort or wear.

I know they were set too low by the tire shop that mounted them, now I just need to find the right balance knowing that 50 psi is the upper bounds and 32 felt pretty squishy and I believe induced a higher speed out-of-balance kind of bounce.

50 PSI felt really good BTW going down the highway and in town driving but I think I am going to lower to 40 and see how that feels.

Randy
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post #5 of 12 (permalink) Old Aug 7th, 12, 11:18 AM
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Re: what is the correct tire PSI

Just keep in mind too high of psi will cause the center of the tire to wear more and too low psi will cause the outsides of the tire to wear more. Set your pressure and pay attention to the tread.

Racers are not worrying about tire wear and should be using tire pressure as another tool to dial in the cars handling, the harder the tire is the sooner it will break traction so if the back end is coming around you lower pressure in the rear and raise the pressure in the front. Just the opposite if the front is pushing or plowing...

...Dennis

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post #6 of 12 (permalink) Old Aug 7th, 12, 12:19 PM
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Re: what is the correct tire PSI

When I up grade I like to keep the balance of the original, for example if the original was 25 c front & 30 c rear(or whatever) I keep that percentage spread.

On one of my older sports cars it was a 6lb spread on originals 14 x 70 x205 when I went to 17x35's I kept the same difference but at a higher pressure & the balance was great. The tire shop put them all the same & the car was a mess of understeer.
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post #7 of 12 (permalink) Old Aug 7th, 12, 02:12 PM Thread Starter
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Re: what is the correct tire PSI

wow good information all, I really appreciate this help. I was worried I was asking a simple question but it seems there is a lot of depth to this subject.
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post #8 of 12 (permalink) Old Aug 7th, 12, 02:49 PM
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Re: what is the correct tire PSI

When put new tyres on I watch the little rubber bits wear...
I start at about 33/34 lbs...if the center ones wear off a bit faster..couple lbs less, and visa versa for the outside bits.
Each batch of tyres are slightly different....and even the front and rear tyres have different weights/stresses on them.
Generally about 32 to 35 range and a couple lbs more in the front.
Alway use the same pressure gauge, doent need to be accruate as one is using compaital readings.

My Spelling is not incorrect...it is creative

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post #9 of 12 (permalink) Old Aug 7th, 12, 05:48 PM
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Re: what is the correct tire PSI

You can use a fat piece of chalk and make a line across the tread, take a short drive and observe the chalk. If the line disappears in the center: over inflated. If it disappears near the sides: under inflated. You want the line to disappear all together but, also make sure you are not driving too long to wear the line away.

I did this on my Jeep with over sized tires.

It's the same concept as Steps mentioned but, more for tires that aren't new.

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post #10 of 12 (permalink) Old Aug 7th, 12, 05:51 PM
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Re: what is the correct tire PSI

I've been getting a good wear pattern with 35 lb cold all the way around on 235/45ZR17 and 275/40ZR17. At 40 lbs cold with the weight of a Camaro you'll wear the middle of the tire out.

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post #11 of 12 (permalink) Old Aug 7th, 12, 07:24 PM
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Re: what is the correct tire PSI

Quote:
You can use a fat piece of chalk and make a line across the tread,
Damn , dont you just hate it when someone comes up with a real clean easy way to do it lol
Talking to the gus down the alignment shop this morning...just after posting....they suggested a tyre crayon...well any marker.. then now read the chalk lol

My Spelling is not incorrect...it is creative

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post #12 of 12 (permalink) Old Aug 8th, 12, 08:17 PM
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Re: what is the correct tire PSI

35.. you can run 45-50 psi if you go road racing or autocrossing and the car likes it better..

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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