Tire pressures

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You learn something everyday. I'm pretty anal about tire pressures but never knew that the placard on the door jam were "max" inflations and that the OEMs actually recommended different (lower) settings for other operating conditions.

http://www.automobilemag.com/news/the-inadequate-tire-pressure-sticker/?wc_mid=4035:8240&wc_rid=4035:937951&_wcsid=46612AB0F25A85A50F23ADDAB80697BE477F24FDCE85DE35

My typical habit is to set pressures 1 or 2 psi above the placard to offset seasonal pressure losses and get best mileage on my highway vehicles.
 
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I've seen vehicles state a higher tire pressure in the owners manual for very high speed driving that isn't listed on the door jamb. Like when driving over 100 MPH.
 
Yeah, what I'm seeing in the US is that the vehicle placard shows only the full load PSI, but not half load.

I guess car manufacturers assume that most of us are too lazy and will not adjust our tire pressures as we change loads, so they just tell us to stay at full load pressures at all times.

My old 530i actually shows both full and half load values, but that's an exception...

36403051432_23bec10d7b_o.jpg
 
My Opel have placard with pressure settings for all tyre sizes and light load, full load in comfort and light/full in ECO settings. 2.7 Bar is front ECO settings and even then tyres look under inflated. Nose heavy diesel.
 
Those placards only apply to the tires that came on the vehicle when new. All the tires I've bought since then, have higher pressures then what the card in the door frame says. If I set them to that card, the tires look almost flat. If you have a 10 year old car, you won't be able to find the exact same cheap tire the car came with.,,
 
Originally Posted By: BigCahuna
Those placards only apply to the tires that came on the vehicle when new.

If the replacement tire is the same size and same load rating index as the one on the placard, then the placard PSI still applies.

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All the tires I've bought since then, have higher pressures then what the card in the door frame says.

Just because the replacement tire has a higher max allowable PSI printed on the sidewall does not mean you should be running higher PSI in it.
 
Wife's Koleos pressure sticker rates 2.2 bar in front tires, 2.0 rear. For a correct behavior, many drivers including me sets them at 2.7 front, 2.4 rear. If not, ride seems ok but wear is concentrated on borders of the tread. 10000 kilometers max on stock tire pressure, 40000 at 2.7/2.4
 
Pretty sure the door jamb pressures are wrong for my 99 Ford dually. 45psi. Local tire shop said thats nuts and I agree. Drop on the 5th wheel and things would probably get interesting fairly soon. Front are 65psi with the 7.3 upfront
 
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Max pressure is actually on the tire sidewall,
The door placard is for max ride comfort...

My '02 Saturn came with "T" speed rated, 35 psi max (250 kpa), 185/65R15
I currently have "H" speed rated, 51 psi max (350kpa), 205/60R15's..

Door says 26 psi...

I put 44 in...
 
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FedEx trucks were running the trailer tires at max sidewall and a fleet study showed that they were blowing far more tires than running at just 5lbs under. Now FedEx rarely get a fully loaded truck delivering packages.
 
Originally Posted By: Quattro Pete
Yeah, what I'm seeing in the US is that the vehicle placard shows only the full load PSI, but not half load.

I guess car manufacturers assume that most of us are too lazy and will not adjust our tire pressures as we change loads, so they just tell us to stay at full load pressures at all times.

My old 530i actually shows both full and half load values, but that's an exception...

36403051432_23bec10d7b_o.jpg



My 96 ES300 had a placard like that.
The full load setting was 32 psi (fully loaded to max weight limit)
The half load setting was 26 psi (up to 4 passengers)
 
Originally Posted By: mattwithcats
Max pressure is actually on the tire sidewall,
The door placard is for max ride comfort...

My '02 Saturn came with "T" speed rated, 35 psi max (250 kpa), 185/65R15
I currently have "H" speed rated, 51 psi max (350kpa), 205/60R15's..

Door says 26 psi...

I put 44 in...


This comes up all the time. Search the old threads. Should probably have a thread for common car myths that people believe. The consensus in the other threads is that you go by the what the car manufacturer recommends. Those numbers are for ride comfort and max recommended pressure for the car. I wouldn't exceed it by more than a couple PSI, otherwise the car probably rides like rocks. The car manufacturer knows the design of the car and knows the suspension components that went into it. The tire manufacturer has no idea what car it's going on, the pressure could be higher or lower, they just know that their design is only good for a max of a certain tire pressure, but they have no idea about handling and how the suspension is set up for tire wear.

All you guys have to do is search and you'll find that everyone says to go by vehicle manufacturer recommendation.

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=147
 
Originally Posted By: skyactiv
I've seen vehicles state a higher tire pressure in the owners manual for very high speed driving that isn't listed on the door jamb. Like when driving over 100 MPH.


My Cobalt SS owners manual says this. 32psi normal, 35 for extended periods at 100+
 
Originally Posted By: oilpsi2high
Originally Posted By: skyactiv
I've seen vehicles state a higher tire pressure in the owners manual for very high speed driving that isn't listed on the door jamb. Like when driving over 100 MPH.


My Cobalt SS owners manual says this. 32psi normal, 35 for extended periods at 100+


Same with the Mercedes E-350. It's on the gas door cap, higher number for over 100. The door jam just has the lower number.
 
And what pressure did Ford originally specify for the Explorer?

Drum roll, please....

"After the Explorer rolled over in company tests prior to production Ford decided to lower the suspension and remove air from the tires to 26 psi compared to 35 psi for the same tires on the Ranger."
 
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pressure increases right along with heat, 32 in your garage turns to 40 quickly out on the I.
 
Originally Posted By: mattwithcats
And what pressure did Ford originally specify for the Explorer?

Drum roll, please....

"After the Explorer rolled over in company tests prior to production Ford decided to lower the suspension and remove air from the tires to 26 psi compared to 35 psi for the same tires on the Ranger."


So because of Ford doing something dubious with one vehicle, it negates the validity of the process for the entire industry?

What thoroughly vetted protocol are you offering up as an alternative to what the OEM provides here then? Because your previous post hints at your process basically involving using OEM as a minimum, sidewall as the max and tossing darts to arrive at some intermediate value...
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Maybe something to do with Firestone - I ran a GMC during this mess with 6" of lift and drove like a madman on way oversized BFG's ...
 
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