# Tire Pressures?



## 1968 Q8 (Jun 9, 2011)

Hey team!

My 68 owners manual says 24 and 26 psi on the tires, seems a little low??? Was that recommended based on ride quality or was it based on the tire construction back then...? 

215/70/14 BFG radial t/a are what i'm on, what's a good pressure to run for regular driving?

Thanks guys.


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## GTO JUDGE (May 14, 2005)

1968 Q8 said:


> Hey team!
> 
> My 68 owners manual says 24 and 26 psi on the tires, seems a little low??? Was that recommended based on ride quality or was it based on the tire construction back then...?
> 
> ...


Was that on bias-ply or radial? I keep it at 35psi on my 14" T/A's.


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## SANDU002 (Oct 13, 2004)

I run 32 psi on 225/60/15's


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## facn8me (Jul 30, 2011)

Actual needed pressure will vary from car to car and tire to tire. Yes the pressures on your car was based on tire technology available when it was built. On the side of the tire will be max pressure and the weight it will handle. Just to put it into perspective. My wifes jeep has 285 75 16's on it. 1 tire will at 60 psi will handle the entire weight of her jeep. With all 4 tires at 60 psi the jeep is very close to undrivable. at 28 pounds in the tires the tire has a full contact patch has a decent ride. Same way on my big chevy. Run 34 pds in it for ride and tire wear. Too much air and you'll wear out the center. Too little and there goes the outside tread. A slightly dirty road and a lil trial and error will show up ground/tire contact. I wish there was some formula (and there probably is) to take weight of car tire load ratings and come up with a suitable air pressure for everybody. If you find it let me know.


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## geeteeohguy (Feb 2, 2008)

I agree.....and I worked for a tire company for 14 years. Disregard the glove box pressures unless you are running repop bias belted tires, and even then, the label is suspect. When I ran bias belted tires in my GTO's (they were still available everywhere) I ran the same pressures I run currently in my radials: 30-32 psi front, 32-34 psi rear, depending on the load and the type of driving. On long cross country hauls with a trunk full of gear, I go higher, into the low 40's.


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## BearGFR (Aug 25, 2008)

Best to follow the advice of the tire manufacturer / tire shop.

Bear


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## facn8me (Jul 30, 2011)

BearGFR said:


> Best to follow the advice of the tire manufacturer / tire shop.
> 
> Bear


 You must have better info than I do or the internet can provide and much better tire shops than around here. Seen many a low profile tire and wheel destroyed because some gave the advice of 32 pounds of air was fine. See many over inflated and underinflated many tires destroyed because jimbo making $9 an hours said the tire say's 80 psi that's what it takes. To many different tires that are different than the factory tires. Case in point. Here are the specs on two different tire. BOTH are 225 75 r15's One will hold 1764 lbs at 44 psi. The other will do 2475 lbs at 65 psi. Either one of those tires set at max pressure will be overinflated and way to rough. BUT either could have pressures played with and perform fine. In most cases manufatures recomendations are at a specific weight and pressure making sure the real world is nowhere in the picture. By taking these two tires below and they were random. Your vehicle would need to weigh min of 7046 lbs for the pressure to be correct. 

600 A B 1764 lbs. 
44 psi 
11/32" 
29 lbs. 6-7.5" 
6.5" 
9" 
NA 
27.4" 
761 




None 2470 lbs. 
65 psi 
12/32" 
31 lbs. 6-7.5" 
6.5" 
9" 
NA 
27.4" 
758


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## 1968 Q8 (Jun 9, 2011)

Thanks for the responses guys!

Great info as always :cheers


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## pontiac (Mar 6, 2011)

the two tire comparison for the same size is suspect. one of those tires is not to be used on a car. The max pressure on the sidewall is based on that tire being used on a vehicle close to design loads. On our cars, those suspensions were based on the original factory supplied tire. Even a switch to radial was not part of the design.


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