Tire Pressure
 

What is the proper tire pressure for a 4.50 x 21 tire?

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I use 35 psi for 19's

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I use 35 for my 4.50 x 21. :)

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I only use digital gauges on everything even my lawnmower . With the TPMS now on most cars it's a must have to be precise.. The old school pop sickle sticks are a thing of the past

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Mitch, I wish someone would explain this to the gorilla's that work at the tire shops. Maybe explain torque wrenches and anti-seize for the screws on some of the newer and custom aluminum to them also. Rod

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I hear ya Rod,,and I bet those monkeys don't know that if you look in the door jamb on any car it gives you the reccommended PSI for that particular application. Every car we look to see before airing...

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So, doesn't the TPMS read half as much on 6v ? :)

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I never thought of it that way:confused: ;)

What does your Model A state in the door jamb for tire pressure:D

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That must have fallen off a few years ago. :D

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Mitch, I get the TP (tire pressure) but what is the MS. I have always gone by the max pressure on the tire wall and kept it a few Lbs under. The door jamb pressures are too low and the tires wear out at the edge of the treads, AND your gas mileage suffers!
Terry

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That seems to be the case with tire pressure specs since the Ford Explorer rollover recall in the late 90's. Most was attributed to tire pressure specs being high. I was working for Monroe shocks OE. Our shock valving specs for Ford changed somewhat in the aftermath of this as tire pressure and shocks work together for a smoother ride. Also with the investigations several lawsuits were filed against Tenneco the parent company of Monroe shocks. All were dropped at some point, but still caused undue stress at work as we were under intense scrutiny from Ford as they looked to point the blame in any direction but their own. Rod

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Terry, the MS stands for Monitoring System. This system is calibrated to the pressure stated in the door jamb, with a tolerance of three or four pounds over or under, and if you set the pressure much higher than recommended you will trigger the monitor warning, regardless of the max pressure stated on the sidewall.

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Terry each particular vehicle manufactured is tested with a certain tire, vehicle weight and other parameters etc etc.. The recommended pressure is on the sticker... the TPMS is then set with its parameters which will usually turn the light on at about 6 PSI below the door spec... That being said yes I agree I see certain vehicles that wear tires improperly at the recommended pressure. Compensating for that is ok but as a main setting use the door spec and not the sidewall on most cars. The sidewall spec is max pressure cold for any given tire. Example the new GMC 2500 HD's ---3500 HD's has a door spec of 65 frt and 80 rear.. At those pressures the tires will wear the centers badly because I am not usually carrying a load or trailer most of the time. They recommend that assuming your always loaded. Pretty ass nine system on certain applications I agree.. I run 55 PSI in the frt and 50 PSI in the rear unloaded until I put a load or trailer on then I put the rear up to 80 PSI. It rides like a rock unloaded at the higher spec also. Lowering the pressure to these specs turns on the TPMS light cause it's more than 6 PSI lower than the factory spec. What I did is recalibrate the system with my scanner so it recognizes the lower threshold and stays off...

My 1930 Model A,
I have yet to have a TPMS light activate for over inflation. What type of vehicle does that happen on? And how much over the spec are we talking?

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I see some explorers coming in with a door spec of 26 PSI mostly newer ones since the roll over production era. To low IMO...I usually go 33-35 in those....I bet that's why.. Their scared shitless for it to happen again

Rod thanks for the info

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Not many Explorers were sold here. I was told that the problem was the load rating was dropped for a better ride. The authorities here are strict on load ratings, not so much speed rating.

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Presumably, My 2013 Ford Transit! It had a soft tire when I first got (brandy New!) and I filled the tire and pushed the pressure up to my specs, not their specs. This seemed to have triggered the sensor from the low side to the high side of it's range. Now the light is permanently on and can't be turned off. I ignore it! I never wanted it in the first place! I've never needed one in the past.
Terry

My 1930 Model A,
I have yet to have a TPMS light activate for over inflation. What type of vehicle does that happen on? And how much over the spec are we talking?[/QUOTE]

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Here is some good info, also about over inflation and the TPMS ....
http://www.tpmsmadesimple.com/faq.php

Terry,, on the fords you just need to relearn the system with a hand held remote which is available on eBay for around 10.00.. I can help you do that if you get it..

Over inflation warnings are not mandated by the federal TPMS act ...
But as mentioned by My ModelA::: some may do that... Learned Tire position is also critical on some of the systems

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I run 30 psi in my 4.50 x 21 tires. The car doesn't wander near as much as when I was running 35 psi. Someone on this site recommended the 30 psi to me. I use a good quality 0-60 psi gauge that correlates well with the TPMS system on my new F150

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I usually run 2 lbs less in the left side tires so the crown in the road doesnt make it pull to the right as much. I usually run 33 and 35 if the weather is colder, but drop it to 32 and 30 in the summer when the road is hot because it will build up more pressure as you drive. I always check the pressure cold, before the car is driven for the day.
Good Luck.