My Ram 1500 quad cab (work truck) specs 40 psi, but I run 32 - 35 psi. Makes a noticeable difference in ride quality, and tire wear is even. For the rare long distance higher speed trip, I air them back up, and also for the rare heavy load.
Vehicle Manufacturers Tire Pressure Recommendation
- Thread starter BlueOvalFitter
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I have an 06 F150 with a long bed. Ford specs 38psi. The truck bounces around all over the place with that tire pressure so much to the point that I deem it unsafe and not stable. I run the front tires at 35 and the rear at 33-34. Drives like a different truck. I seldom carry much weight. If I load it up then I increase the tire pressure. Ford sets the tire pressure requirement for full load capacity which is fine with a load. So yes. You are right on the mark by lowering your pressure to 35.
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My Mazda recommends 26 in the front and 32 in the back lol I always ride on 35 all the way around it’s old so back then that was probably a standard lol
Most of my vehicles have been front heavy FWD hatchbacks.
Most of my driving is on rough city streets with 1-2 passengers and no more than a few bags of groceries (or sometimes a saxophone) in the back.
I run the placard pressure in front and 2-4 psi under in the back.
If I'm carrying a heavy load or going on a road trip I raise the back to placard.
Most of my driving is on rough city streets with 1-2 passengers and no more than a few bags of groceries (or sometimes a saxophone) in the back.
I run the placard pressure in front and 2-4 psi under in the back.
If I'm carrying a heavy load or going on a road trip I raise the back to placard.
I consider the door pressures to be a starting place for the OEM tires only, and only if you strongly prefer heavy understeer over neutral handling in tight corners.
Umm, it's a truck. Were you expecting it to ride like a Town Car? Try adding 1,000 pounds to bed and see if that improves the ride. Or can you convert to air springs?
I’ve always gone with what the door sticker said or maybe 1psi above. Just had General Altimax RT43 tires installed today on my 17 Accord Sport , in the morning I will check the pressure and see how bad they are off from town fair tire
I can accept that the manufacturers specify tyre pressures for sound technical reasons but I suspect that one part of it these days is to eke out the best headline fuel consumption and emissions figures. While that may be a sound technical reason to them the gain is miniscule in the order of 0.5%. I've driven a Mercedes C class for 26 years and my current W204 model has the highest specified pressures yet. Not surprisingly it also has the firmest ride. I drop them by 0.1 bar or approx. 5 % and I can tell the difference in ride and don't worry about the 0.5 % extra fuel used.
1000 kg front axle, 600 kg rear axle, 240 kph, tyres 235/45R17 XL 97Y.
1100 kg front and 740 kg rear with full load
Would appreciate your input
Strange weightdivision front/rear, but OK.
For max 160kmph
Fr 1000kg/2.1 bar/31psi.
Rr 600kg / 1.2 bar/18psi.
For 240 kmph , I subsract forvevery 10 kmph higher one LI step so 240-160= 80/10=8 steps gives 97-8=89 loadindex.
This filled in in my made spreadsheet gives Fr 2.8bar/40 psi ,
Rr 1.6bar/ 23 psi.
Same for fully loaded,
Axle/weight/160kmph/ 240kmph.
Front/1100kg/2.4bar-35psi / 3.1bar-45psi
Rear/ 740kg/1.6bar- 22psi/ 2.0bar-29psi.
Disclaimer: you are responcible for that the given weights are right.
In the official formulasheet , I once got hold of , they write not to go lower then 1.5 bar=21psi, and was believed by most to prevent tire coming loose from rimm in situations. Todays rimms have 2 humps to prevent that.
For max 160kmph
Fr 1000kg/2.1 bar/31psi.
Rr 600kg / 1.2 bar/18psi.
For 240 kmph , I subsract forvevery 10 kmph higher one LI step so 240-160= 80/10=8 steps gives 97-8=89 loadindex.
This filled in in my made spreadsheet gives Fr 2.8bar/40 psi ,
Rr 1.6bar/ 23 psi.
Same for fully loaded,
Axle/weight/160kmph/ 240kmph.
Front/1100kg/2.4bar-35psi / 3.1bar-45psi
Rear/ 740kg/1.6bar- 22psi/ 2.0bar-29psi.
Disclaimer: you are responcible for that the given weights are right.
In the official formulasheet , I once got hold of , they write not to go lower then 1.5 bar=21psi, and was believed by most to prevent tire coming loose from rimm in situations. Todays rimms have 2 humps to prevent that.
Now the official European calculation , only for fully loaded , and 240kmph.
Front 1100kg
Up to 220kmph for Y speedrated the reference-pressure of 2.9bar/42 psi can be used ( not to my opinion)
Would give for 1100kg next
( 1100kg/ ( 2x 730kg) ) ^1.25 x 290kPa= 203kPa rounded up 210kPa is 2.3 bar
29.48 psi rounded up is 30 psi
For 240 kmph you have to highen up the reference-pressure in the official system with 1 kPa for every kmph gives 20 kPa higher then reference of 290kPa is 310kPa
Gives 217kPa is 220 rounded up is 220kPa us 2.2 bar .
My calc came to 3.1 bar wich is much higher.
Will leave it at this calc for front fully loaded.
If you find a 235/45R17 tire with V speedrated the maxload is also 730kg/LI 97 but then you may only drive 160kmph with 730kg on tire and pressure 290kPa, and the Y speedrated suddenly 220 kmph.
Draw your own conclusions about what is right to laws of nature.
Front 1100kg
Up to 220kmph for Y speedrated the reference-pressure of 2.9bar/42 psi can be used ( not to my opinion)
Would give for 1100kg next
( 1100kg/ ( 2x 730kg) ) ^1.25 x 290kPa= 203kPa rounded up 210kPa is 2.3 bar
29.48 psi rounded up is 30 psi
For 240 kmph you have to highen up the reference-pressure in the official system with 1 kPa for every kmph gives 20 kPa higher then reference of 290kPa is 310kPa
Gives 217kPa is 220 rounded up is 220kPa us 2.2 bar .
My calc came to 3.1 bar wich is much higher.
Will leave it at this calc for front fully loaded.
If you find a 235/45R17 tire with V speedrated the maxload is also 730kg/LI 97 but then you may only drive 160kmph with 730kg on tire and pressure 290kPa, and the Y speedrated suddenly 220 kmph.
Draw your own conclusions about what is right to laws of nature.
Forgot to first add 10% to the 1100kg , that is the explanation for the relatively large difference
So new calc (1210kg/ 1460kg)^1.25 x 310kPa = 245kPa rounded 2.5 bar is 36 psi.
For up to 220kmph, wich can be compared to my calc for 160kmph.
Gives 2.3 bar/ 34 psi.
And that is only 1psi/0.1bar lower then my calc.
So new calc (1210kg/ 1460kg)^1.25 x 310kPa = 245kPa rounded 2.5 bar is 36 psi.
For up to 220kmph, wich can be compared to my calc for 160kmph.
Gives 2.3 bar/ 34 psi.
And that is only 1psi/0.1bar lower then my calc.
In the newer BMW G series models, the tire pressures are getting a lot more precise. The pressure in the door jamb is only for the OE tires and for normal driving under 160 km/hr. When winter tires are installed, we have to go into the iDrive and select between summer and winter/all-season, under or over 160 km/hr, and the exact tire size, load and speed rating. Only optional OE sizes are listed. It will also compensate for tire temps, from the TPMS sensors. The pressures can vary wildly. Just the other day, switched an M340 from stock 19’s which call for 36/36, to OE 18” winter tires, and now the recommended pressures went to 32/38.
Unfortunately, using any tire that is not OE and we have to select “other tire size”, and then just use door jamb pressures.
Unfortunately, using any tire that is not OE and we have to select “other tire size”, and then just use door jamb pressures.
Some people have a better sense of feel. I've heard of Nascar drivers being able to feel 1/2 psi difference in tire pressure in a race.
Heavy diesel engine and auto box over the front, front passangers sit halfway towards the rear axle, no rear overhang.... around 65/35 weight distribution without driver.
2.3 is i believe the manufacturers recommendation. 2.1 rear though
Yes they can, but not because of comfort like we would road tyres. Grip drops off when pressures are too high or too low during race.
Especially when you are driving the same corner over, and over, and over, and over again.
yes, takes alot of guesswork out of what your speed was there last time around...
Not a 1/2 or even 1 psi. But my late W126 Mercedes definitely had a different feel on the same smooth CO roads at 35-36 psi vs. 32-33. It seemed livelier, somehow.
I run the '16 LaCrosse at 35-36, 2-3 over the door jamb pressures. Despite the awful roads here, the Buick rides very well at the higher pressures. And if the weather should suddenly turn colder (ha! Tell me another one), there is some safety factor. The tires will not suddenly be at a flabby 30 when they were properly aired during the warmth of the previous day.
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