Tire Pressure??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

HotRod929 · 12-11-2002, 09:56 PM

What should the tire pressure be for the front and back tires on my 1970 C/20 lwb?

HotRod

Huck · 12-11-2002, 10:07 PM

Run them at about 32lbs of pressure and that will cover almost every tire size, type and condition. Most important to keep them equal between 28 and 35max. OUtside temp will change the pressure---cold they will drop and warm they can go up 4-6lbs. Also be aware that in the winter, it is common of tires to loose a pound or so a week so keep on them. Huck

HotRod929 · 12-11-2002, 10:20 PM

the sidewall of my tires say something like 65 psi...my tires deffinatly seem low and they are at like 47 psi...32 psi just seems awful low to me but i may be wrong...can anyone else verify this please?

HotRod

71BBK10 · 12-11-2002, 10:22 PM

I would go with what the tires recommend.

4x4 Pray · 12-11-2002, 11:17 PM

the sidewall is recommending the tire pressure for the maximum load. unless you are maxing your truck out on a daily basis, I don't think you need that much pressure. It will just cause you to wear out the middle of your tread. Radials will naturally bulge in the sidewalls, so if that's what's worrying you, I wouldn't let it bother you.

Longhorn Man · 12-12-2002, 12:23 AM

Acording to BFG, good year and michilin, about 10 years ago I did a report on this in high school, and they all said the same thing.
With certian exclusions(Corvair, VW bug) the best way to find the optimum tire pressure is to test and tune it.
Fill all 4 tires to a certian PSI and log it on paper. Drive a few miles down the highway, with out talking any drastic manuvers. Pull over and check the temp across the whole contact area (tread)
What you are looking for is uniform tread temp. A durometer would be the ultimate...but no one has one, and if they do, they won't loan it out. So use your hand to check the temp. If it is warmer in the center...then drop the pressure, if the edges are warmer...raise the temp.
This is directly from the aformentioned companies.
The feds will try to tell you to always go by the manufacturer's recomendations...which I find to be a bunch of crap. In our case, todays tires are light years ahead of the crappy rubber they came with. The technology has gone up a little too. (just a little

)
If you run bigger size than stock, or a high performance tire, this is even more important to look into.
In all reality, almost every time I have done this, my testing comes up within a pound or two of max PSI on the side wall.
I stopped testing them a few years ago, and just pump them up all they way. The only time I have tread problems is on the right rear....I can never seem to keep tread on that one for some reason.

Blackhawkdc · 12-12-2002, 01:06 AM

I've always been told that unless you're hauling a load, to put the tires at about 80% of the maxximum pressure. 35 psi max would be about 32 or so. 50psi, would be about 44, and so forth.

Southpa · 12-12-2002, 04:04 AM

There is also gas mileage and comfort/handling to consider. Max. inflation on my Michelins (31X10.5X15) is 50 psi. but I inflate to 42. I've had the tires 3 years now and there are no signs of irregular wear. Actually, they still look like the day I bought them.

12-11-2002, 09:56 PM	#1
HotRod929 Registered User Join Date: Mar 2002 Location: Bondurant, IA but in Worcester, MA for school Posts: 767	Tire Pressure??? What should the tire pressure be for the front and back tires on my 1970 C/20 lwb? HotRod __________________ 1970 Chevy C-20 350 V-8 Turbo 350 w/ shift kit Dana 60 w/ 4.10 gears AND Powr-Loc POSI New Additions: Summit Headers 135amp alternator Proform HEI Edelbrock 1406 600cfm carb Sunpro Tach Powr-Loc POSI Edelbrock Performer RPM Intake MSD 6A Ignition Box AIM: HotRod929 Visit My Site: http://1970chevy.netfirms.com/

12-11-2002, 10:20 PM	#3
HotRod929 Registered User Join Date: Mar 2002 Location: Bondurant, IA but in Worcester, MA for school Posts: 767	the sidewall of my tires say something like 65 psi...my tires deffinatly seem low and they are at like 47 psi...32 psi just seems awful low to me but i may be wrong...can anyone else verify this please? HotRod __________________ 1970 Chevy C-20 350 V-8 Turbo 350 w/ shift kit Dana 60 w/ 4.10 gears AND Powr-Loc POSI New Additions: Summit Headers 135amp alternator Proform HEI Edelbrock 1406 600cfm carb Sunpro Tach Powr-Loc POSI Edelbrock Performer RPM Intake MSD 6A Ignition Box AIM: HotRod929 Visit My Site: http://1970chevy.netfirms.com/

12-11-2002, 10:22 PM	#4
71BBK10 Teufelhunden Join Date: Oct 2001 Location: Camp Pendelton Ca Posts: 572	I would go with what the tires recommend. __________________ 1971 K10 lwb fleetside 402 T350 205

12-12-2002, 01:06 AM	#7
Blackhawkdc 440 american Horses Join Date: Mar 2001 Location: Anoka, MN USA Posts: 470	I've always been told that unless you're hauling a load, to put the tires at about 80% of the maxximum pressure. 35 psi max would be about 32 or so. 50psi, would be about 44, and so forth. __________________ Seth Petro 1969 Chev Short Step 425hp 350, TH400, big tires, fast truck 1979 Pontiac Trans Am 1991 Saturn SL1 - gas mileage! (and free) 1977 Buick LeSabre - for sale May America bless God, and may God bless America

12-12-2002, 04:04 AM	#8
Southpa Registered User Join Date: May 2000 Location: Victoria, BC, Canada Posts: 2,410	There is also gas mileage and comfort/handling to consider. Max. inflation on my Michelins (31X10.5X15) is 50 psi. but I inflate to 42. I've had the tires 3 years now and there are no signs of irregular wear. Actually, they still look like the day I bought them. __________________ 1970 GMC 1500 Custom Original 350/TH350 Victoria, BC, Canada You can wish in one hand and crap in the other. See which one gets filled first.

12-11-2002, 10:07 PM	#2
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,269	Run them at about 32lbs of pressure and that will cover almost every tire size, type and condition. Most important to keep them equal between 28 and 35max. OUtside temp will change the pressure---cold they will drop and warm they can go up 4-6lbs. Also be aware that in the winter, it is common of tires to loose a pound or so a week so keep on them. Huck

12-11-2002, 11:17 PM	#5
4x4 Pray Registered User Join Date: Apr 2001 Location: San Luis Obispo, CA Posts: 69	the sidewall is recommending the tire pressure for the maximum load. unless you are maxing your truck out on a daily basis, I don't think you need that much pressure. It will just cause you to wear out the middle of your tread. Radials will naturally bulge in the sidewalls, so if that's what's worrying you, I wouldn't let it bother you.

12-12-2002, 12:23 AM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Acording to BFG, good year and michilin, about 10 years ago I did a report on this in high school, and they all said the same thing. With certian exclusions(Corvair, VW bug) the best way to find the optimum tire pressure is to test and tune it. Fill all 4 tires to a certian PSI and log it on paper. Drive a few miles down the highway, with out talking any drastic manuvers. Pull over and check the temp across the whole contact area (tread) What you are looking for is uniform tread temp. A durometer would be the ultimate...but no one has one, and if they do, they won't loan it out. So use your hand to check the temp. If it is warmer in the center...then drop the pressure, if the edges are warmer...raise the temp. This is directly from the aformentioned companies. The feds will try to tell you to always go by the manufacturer's recomendations...which I find to be a bunch of crap. In our case, todays tires are light years ahead of the crappy rubber they came with. The technology has gone up a little too. (just a little ) If you run bigger size than stock, or a high performance tire, this is even more important to look into. In all reality, almost every time I have done this, my testing comes up within a pound or two of max PSI on the side wall. I stopped testing them a few years ago, and just pump them up all they way. The only time I have tread problems is on the right rear....I can never seem to keep tread on that one for some reason.



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