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Old 09-06-2019, 11:13 PM   #1
basketcase
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20 Inch Tire Pressures

I have this '84 in my shop that a friend bought last weekend at the RM Sotheby's Fall Auburn auction. I'm fixing a few items on it, just some odds and ends that didn't get finished during the repaint. It's a low mile rust free Georgia truck with all the options. Engine is a 305 4bbl and it is a real nice truck. No mods to the driveline.They said it's lowered 5 and 7. Wheels are American Racing 20x8 and 20x10 as best I can measure on the width with 245/45 on the front and 275/45 on the rear.

I haven't been able to find the recommended tire pressures for these tires. Maximum pressure is 49psi. I'd like to know what pressure members with these tires run.

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Old 09-06-2019, 11:51 PM   #2
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Re: 20 Inch Tire Pressures

I would probably run 45 if it was mine...but id put 45 in and see how it rides...might try 40 just to compare...sometimes 5lbs makes a big difference in ride quality...but with those short sidewalls its may not be great anyway
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Old 09-08-2019, 01:03 AM   #3
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Post Discerning Tire Pressures For _ANY_ Tire

I agree you're going to want near 40 ~ 45 PSI but as mentioned, 3 to 5 PSI can make a HUGE difference in ride and more importantly handling and traction ~

Use chalk or some white paint across the tread from one side to the other then go drive it and see if the chalk / paint wears of faster in the middle or edges,if in the middle you need less pressure, if on the edges you need more pressure .

Remember : only add one or two pounds at a time and do both tires on each axle to the *exact* same pressure .

Do the rears first then the fronts, the Customer will think you're a genius and you can then make more $ setting up the proper tires pressures on anything .

Try it on your own tires and discover how much faster, er, SAFER (right) you can drive along with far longer tire life .
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Old 09-08-2019, 09:01 AM   #4
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Re: 20 Inch Tire Pressures

Too much pressure!
I ran 245 45 20 all around on my Daytona r/t at 34 psi. They were good for 40,000 miles.
The wider back tires on the truck I’d run a couple psi less.
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Old 09-08-2019, 06:51 PM   #5
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Re: 20 Inch Tire Pressures

I run 28-30 in mine.
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Old 09-09-2019, 10:55 AM   #6
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Re: Discerning Tire Pressures For _ANY_ Tire

Quote:
Originally Posted by VWNate1 View Post
I agree you're going to want near 40 ~ 45 PSI but as mentioned, 3 to 5 PSI can make a HUGE difference in ride and more importantly handling and traction ~

Use chalk or some white paint across the tread from one side to the other then go drive it and see if the chalk / paint wears of faster in the middle or edges,if in the middle you need less pressure, if on the edges you need more pressure .

Remember : only add one or two pounds at a time and do both tires on each axle to the *exact* same pressure .

Do the rears first then the fronts, the Customer will think you're a genius and you can then make more $ setting up the proper tires pressures on anything .

Try it on your own tires and discover how much faster, er, SAFER (right) you can drive along with far longer tire life .
I'm quoting this, because this is the correct way to make sure any aftermarket tire/rim package is set up correctly. with so many different tires, and pressure ratings, it is almost impossible to say what will work best. typically you should find you want the rear tires a few PSI lower then the front.

In this case, I believe Stock(GM) Manufacture recommended pressures for C/K10 trucks was 32 front, 28 rear. that would be a good place to start the chalk test, a lot of people worry about the bottom "bulge" and think a tire is under-inflated, but this is not always the case, only the tire wear can tell you if it is under or over inflated.
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Old 09-09-2019, 12:39 PM   #7
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Re: 20 Inch Tire Pressures

Good advice. These tires are new but don't ride the best. I think the owner is going to change to a smaller grey painted center American TTII, Probably 17 or 18 with more side wall. He wants it to match his Americans he has on his mid engine 383 1966 Corvair. I just want to make sure his tires are properly inflated and safe in the meantime. I found some 17s listed with the same width and backspacing as the 20s so I'll recommend those to him. I have 17s on my daily driver and have always been happy with the ride.

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Old 09-09-2019, 01:23 PM   #8
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Post Correct Tire Pressures

The ride should have nothing to do with it .

Traction = SAFETY and that is also going to be the best driving pleasure you get out of it .

The soft ride is what caused all those Fords S.U.V.'s to roll over and kill children and innocents ~ the dealers deliberately underinflated the tires, this made the trucks ride like cars and also overheated the tires to their failure point due to excessive sidewall flexing .

Corvairs are well known for spinning out easily and also rolling over in average driving, this too was because no one bothered to accept the front tires required different pressures than the rear tires .

Think about this before you carry your beloved family and friends in your vehicles with cool looking tires .

Most of the original tire pressures were specified for bias ply tires that are thankfully no longer available ~ radial tires always require higher pressures than do bias ply .
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Old 09-12-2019, 01:45 AM   #9
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Re: 20 Inch Tire Pressures

I would put 32-25 psi.
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Old 09-12-2019, 01:30 PM   #10
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Post Re: 20 Inch Tire Pressures

And there you have it :

A ten pound spread on tire pressure is HUGE and can be unsafe .
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Old 10-09-2019, 06:39 AM   #11
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Re: 20 Inch Tire Pressures

I have 275 40/R20 160's on my 71 C10 long bed, i hve 32 in the front and 34 in the back. I live in Seattle so i get a lot of spin in the rain on take off ,manual, any suggestions?
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Old 10-10-2019, 05:33 PM   #12
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Post Re: 20 Inch Tire Pressures

Pix of the actual tires so discern the actual width, wider tires look nice but loose traction in rain / snow very quickly .

Feathering the clutch might help, I don't know many who still know how to do it .
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Old 10-12-2019, 01:42 AM   #13
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Re: 20 Inch Tire Pressures

I appreciate the reply bro, the clutch is feathered that's how I bought the truck from this young kid, he was a wizard and only 23yrs old. what I did tonight was I put some chalk on the tires to to see where it was wearing. so I have the tires inflated properly. So I'm going to load up the German Shepherd go for a drive see how it drives hopefully problem solved I can't lose any sleep over the traction in the rain due to the fact I live in Seattle it is my every day Runner but it is what it is I would rather have my tires properly inflated . so they're 34 in the front and 30 in the back and I threw three tires in the rear of the bed. Thanks again brother love these forums. God bless
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Old 10-12-2019, 07:59 AM   #14
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Re: 20 Inch Tire Pressures

Every vehicle I've owned with 18"-20" wheels and 45-50 series tires called for 32-35 psi cold. And that was anywhere from a 3600 lb. Mustang to a 5200 lb. F150.

I'd start with 34 psi and then have your customer use a tread depth gauge to measure across the tread every 1000 miles or so.
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Old 10-12-2019, 09:31 AM   #15
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Re: 20 Inch Tire Pressures

Quote:
Originally Posted by tino0217 View Post
I appreciate the reply bro, the clutch is feathered that's how I bought the truck from this young kid, he was a wizard and only 23yrs old. what I did tonight was I put some chalk on the tires to to see where it was wearing. so I have the tires inflated properly. So I'm going to load up the German Shepherd go for a drive see how it drives hopefully problem solved I can't lose any sleep over the traction in the rain due to the fact I live in Seattle it is my every day Runner but it is what it is I would rather have my tires properly inflated . so they're 34 in the front and 30 in the back and I threw three tires in the rear of the bed. Thanks again brother love these forums. God bless
Doesnít matter what or how you drive in the right conditions youíll spin the tires.
A little oil residue with moisture at our normal winter temps makes for slippery conditions.
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Old 10-12-2019, 09:00 PM   #16
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Post Re: 20 Inch Tire Pressures

You're welcome .

I've driven in Seattle and yes, it's slippery there most of the time . (try rural Western Wa. state for some hair raising fun) .

An old snow season trick we did in the 1960's was to buy a BIG scrap 1/4" thick iron plate that fir the length of the bed and barely between the inner fender wells so it didn't slide around, that'll work wonders as will a few bags of sand etc....
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Old 10-13-2019, 01:12 PM   #17
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Re: 20 Inch Tire Pressures

Too high of psi and you’ll wear the center on the tread down too quick. I’ve been running 28 psi in all my staggered 20s on many trucks for years and they wear evenly. The rating on the sidewalk is max psi for max load, not what is recommended for all applications
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Old 10-13-2019, 01:17 PM   #18
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Post Proper Pressures

Good trying to get the great unwashed to grasp this simple concept .

It's why chalking or paint striping the tires works best .

-Nate

"Too high of psi and youíll wear the center on the tread down too quick. Iíve been running 28 psi in all my staggered 20s on many trucks for years and they wear evenly. The rating on the sidewalk is max psi for max load, not what is recommended for all applications "
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Old 10-13-2019, 03:34 PM   #19
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Re: 20 Inch Tire Pressures

Yeah, i have 3 fully inflated tires on the eear of the bed
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Old 10-13-2019, 03:39 PM   #20
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Re: Proper Pressures

Like i said i chalked a line across the tires which shows if they're wearing in the middle or outside part of the tire. I don't have staggered tires but ended up with 30psi intge back and 34 in front. That was at cold temperature. I'm gonna check again today
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