New tire pressures!!!

robert graham

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I just put a new set of 235-70-15 tires on my Roadmaster......on sidewall it says 51 PSI max load.....my old set said 44 PSI max load. I generally ran about 36 PSI for a smooth ride. If I run 36 in these new ones I'll be 15 Lbs. below max.....What's with the new/higher pressure and what PSI should I run for everyday smooth ride?....Any of you tire experts/gurus have any ides on this???
 

GA_Boater

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You are talking trailer tires, not tires for a Buick? Are both sets of tires the same load range?
 

GA_Boater

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Max pressure for car tires doesn't mean anything as it is a safety warning, not the recommended pressure.

Are the tires the same manufacturer and model?
 

charleso

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There is a label in the drivers door frame. Go with whatever the GM rated spec is. Especially if this is a newer vehicle with TPMS.
 

GA_Boater

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TPMS only checks for a minimum pressure, not over-pressure.
 

robert graham

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So you think my old 35 lb. pressure is O.K. for these, for the sake of a smooth ride?.....51PSI just seems sorta high for a passenger car tire?...
 

GA_Boater

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You never use the max pressure. For one thing the center tread will be bald and the outer tread will be like brand new from over inflation.

Use the max GM recommended pressure for heavy load or high speed driving. 36 PSI sounds a tad high.
 

WIMUSKY

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So you think my old 35 lb. pressure is O.K. for these, for the sake of a smooth ride?.....51PSI just seems sorta high for a passenger car tire?...

Yes.

My wife has 235/40-19s max load 1566. Max air pressure 50psi

Recommended air pressure on the door is 38psi. That number is for the proper wear of tires. It takes into account the weight of the car. A softer ride is just the product of calculation manufacturers use..... Not the other way around.

I saw Kuhmo sells passenger tires in your size and they to have a max pressure of 51psi. I believe they were rated for 18xx.....

Just keep an eye on them so they wear properly......
 

MTboatguy

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34-36 lbs will be fine, they will deliver a good ride and you should get a good tire wear life out of them, you need realize they are talking about cold inflation pounds. When the tire heats up, it will actually build a couple of pounds of pressure, 51 lbs is the max cold inflation temp, which will grow to between 54 to 57 pounds after it warms up, and is only used for carrying heavier loads. Is there a minimum inflation rating on your tires? Many of the new tires come with a minimum and maximum rating, the new ones I just put on one of my trucks has a minimum rating of 24 lbs and a max of 65 pounds, most tire manufactures list their max and min on their website for that particular tire you purchased.
 

robert graham

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No minimum pressure on sidewall, just the maximum 51 PSI.....guess I'll just run about 35 PSI and see how they ride and wear...
 

JoLin

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Max pressure for car tires doesn't mean anything as it is a safety warning, not the recommended pressure

What GA Boater said, Robert. Use the recommended pressure on the door tag. Long as you're still using stock-sized tires (doesn't matter what brand) you'll be fine.
 

WIMUSKY

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The TPMS on my Jeep shows actual pressure in each tire. Does a minimum pressure thing on the spare.

My spare has the same thing. I saw the light come on, I thought "really"? Too much, imo..... Once the air temp warmed some it was fine..
 

GA_Boater

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The TPMS on my Jeep shows actual pressure in each tire. Does a minimum pressure thing on the spare.

My spare has the same thing. I saw the light come on, I thought "really"? Too much, imo..... Once the air temp warmed some it was fine..

I should have been clearer. The last Roadmaster was for the 1998 model year and TPMS wasn't very sophisticated back then. And most aren't working anymore and the low pressure light on the dash is glowing.
 

jimmbo

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The Inflation spec for the 235/70/R15 on your Roadmaster is 30 PSI on all tires. Should be on a label on the drivers door
 
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jimmbo

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I should have been clearer. The last Roadmaster was for the 1998 model year and TPMS wasn't very sophisticated back then. And most aren't working anymore and the low pressure light on the dash is glowing.

1996 was the last year for the Roadmaster, and for the Rear drive Impala SS, Caprice, and Cadillac Fleetwood

There was no TMPS on the Roadmaster, or the others.

The TPMS on my Cadillac STS reads the pressure of each wheel in PSI or Kilopascals, and warns of over and under inflation too. Real pain to reset it when swapping summer and winter tires. Costco resets it for free.
 

robert graham

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These new tires are made by Nexen in South Korea....look just like all the others, Michelin, Goodyear, etc.....price put on/out the door for all 4 was $579.....I looked on the tire pressure sticker on inside of drivers door and it said 30 PSI....so maybe the lower pressure is fine, but it's a long way from 30PSI to 51 PSI....seems to me?
 

jimmbo

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Well, the more air in the tire the more load it can carry. So the max load is listed on the tire and so is the max pressure. You say the rating is 1950@51psi, well four tires would be 8800lbs. Your Roadmaster is just about 1/2 of that. Even at 30 psi, my the tires on my Roadmaster show wear of over inflation(center wearing faster). My Fleetwood is about 450lbs heavier than the Roadmaster and is speced for 235/70/R15 too, and 30 psi seems about perfect on it. The STS uses 235/50/R17@30 psi and it rides like it is on wooden wheels, horribly harsh ride. Its heavier than the Roadmaster and its tires wear as slightly under inflated. But the ride is so hard I keep it at 28psi, just to be easier on my kidneys. Too bad a 15, or better yet a 14 inch wheel can't fit the STS, a 70 or 75 series tire would ride so much nicer

Those 'Nexens' you are buying/bought are they passenger car tires, or Light truck tires? That might explain the high(51psi) max pressure. When I search online for tires for the Roadmaster and the Fleetwood, Tires for trucks are often in the search results
 
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bassman284

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I should have been clearer. The last Roadmaster was for the 1998 model year and TPMS wasn't very sophisticated back then. And most aren't working anymore and the low pressure light on the dash is glowing.
Mine kind of drives me a little crazy. I'm pretty particular about tire pressure and it's almost impossible to get all 4 reading the same on the TPMS.
 
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