Dear Car Talk Column about over-inflated tires

General Discussion
41

Please excuse the testing of quote functions interlude, hope you got the chance to use the restroom or go buy some popcorn during that intermission. :rofl:

What I have gleaned here from the over- and under-inflation comments earlier back in this thread, is that because of a combination of lack of knowledge, inconsistent maintenance patterns, cognitive culture, personal preference, or simply feeling that one(a mechanic, tire installer, tech, vehicle operator or owner) knows better than the engineers who designed the da____ned thing(!), new tires, replacement tires, on a newly-bought, or very old vehicle, are being misinflated, both over and under vehicle mfg. specifications or recommendations.

Also, a common, and understandable practice, during the shipping of vehicles en masse, aboard car haulers, and on trains or in ships: Cold tire pressures are pumped up, sometimes 5-10psi over door-frame placard value, to assist in keeping the car steadily lashed down in place and to not shift in transit, and, to prevent flat-spotting of its new OEM tires.

Overinflation might also occur for the long-term residency of inventory for sale on a dealer parking lot. And during something commonly called PDI(Pre-Delivery inspection), the tires might be neglected, beyond just making sure they are shiny and black, and none are missing valve caps.

The grand culmination of all the above likely results in the following scenario:

I could, at any time, drive over to several large supermarket or mall parking lots, one mid morning, one mid afternoon, gauge 50-100 cars in each, and when I plugged the values into a spread sheet by pressure, I would bet the farm I’d end up with something similar to this distribution (just a model mind you, X = one car):

20psi - XXXXXXXXXXX
25psi - XXXXXXXXX
30psi - XXX
35psi - XXXX
40psi - XXXXXXXXXXX
45psi - XXXXXXXXXXXXXX
50psi - XXXXXXXXXX
55psi - XXXXX

etc.

Basically an inverse bell-curve.

That’s right - in America at least, most tires, on non-commercial, private sedans, wagons, crossovers, and light trucks, are in two states of condition: underinflated, and, significantly overinflated. The situation with tires on commercial/ business /govt. agency vehicles, trucks, motor coaches, etc, is emphasized text: hopefully less dire, and more compliant with recommended specs.

With proper availability of, imparting of, and acceptance of, tire knowledge, that hypothetical graph could really ring a bell…!..:

20psi - X
25psi - XXX
30psi - XXXXXXXXXXXXXXXXXXXXXXXX
35psi - XXXXXXXXXXXXXXXXXXXXXXXXX
40psi - XXXX
45psi - XX
50psi - X
55psi - 0!

I could go further, analyzing how closely all four tires are inflated to the same pressure, on this pickup truck or that sedan, etc. And find that the spread is something like this:

Variance/deviation from spec between all tires on the same vehicle:
0-2psi: XXXXXXXXXXX
3-4psi: XXXXXXXXXXXXXXXXXXXXXXXXXX
5-8psi: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
8-12psi: XXXXXX

So in that third category(5 up to 8psi variance between all four tires), a typical late model Honda Accord, requiring
33psi front and rear cold pressures, is most likely to have the following mess:

FL: 27psi
FR: 33
RL: 36
RR: 30

Does this poor Accord’s driver know that they might have a nail in that Front Left, or that possibly the Quick Lube oil place, last week, checked all but the front left’s tire pressure, in their haste to get the customer in and out per some quota?

Again: This is all assumption, driven partly by my own personal skepticism about something as fundamental, basic, and easily routinely maintained, as cold tire pressures, but I think it’s a reasonably objective picture of the situation out there - without actually going out and gauging up to 1,000 individual tires at the mall or the Stop & Shop…!.. and being asked quite often exactly “WHAT do I think I’m doing?!”

So Capri, and anyone else reading this…

What’s the solution???

1 Like
42

Not during shipping, those tires are inflated to transport pressure before the tires reach the assembly line. You can’t expect the transport companies to add air to tires during shipping.

More likely that the vehicles were sold before pre-delivery inspection was performed. If several transporters arrive on a Friday afternoon, the sales staff won’t hesitate to sell those vehicles before they are checked into the service department. Many have claimed they bought the vehicle new with 2 or 3 miles on the odometer, those vehicles were not road tested.

Have you done this?

I inspect 5 to 10 vehicles each day, my observations are nothing like what you fantasize about.

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43

Ok, so maybe I wasn’t perfectly clear. “FOR shipping” - is that better. It’s the point I’m trying to get across.

Of course! PDI usually occurs at some point within several hours before keys and paperwork are handed to the buyer/lessee. Again, forgive me if I was in anyway vague. Now back to the points I was trying to make…

No, but I do look after mine, my wife’s and three of our apartment neighbors’ vehicle tires twice monthly.

And two years ago, when we first moved in here, the situation was not far off: My friend, the one who referred us to the neighboring apartment, was previously driving around with less than 20psi in the tires of his 2001 Toyota Supra - specified cold pressure: 29psi. It’s a wonder his tires didn’t slip off the rims!

The pressures on another neighbors(and a friend of my friend’s wife) Subaru were all 35-36psi cold. Spec is 33 front, 32 rear. Done.

My friend and his wife’s cars, pressures were mixed: 32, 33, 34, 36 on a car that specified they all be 33psi.

Again, my inverse bell model is hypothetical, but I’ll bet it’s not far off from the reality.

How would you say that the checked tires pressures distribute, through your service center or garage?

44

Treat each separately. Quote the first, followed by your 1st comment , then quote the 2nd, followed by your 2nd comment. There may a restriction on this for new members, don’t know. Or it may not work on certain software/hardware platforms. I’ve never been able to successfully download a Best of Cartalk podcast file (to play later) using my cell-phone, but do it all the time using a desktop computer w/Chrome.

45

Thanks, we straightened that out, about 6 or seven posts in back of this one. Does not work on mobile/tablet, just desktop.

Appreciate it!

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46

When I worked at a dealer, the PDI was done at any given point after the vehicles were delivered during a normal M-F workday/workweek… Sometimes the vehicle was checked out an hour, day, week, month before the new owner was handed the keys and paperwork…

They were detailed and gassed up before handing over the keys to the new owner…

47

One day ill tell the story here about the time i put out an incipient brake fire on my '81 Citation with a bottle of seltzer!

48

I am not sure when it started, but it is common for car manufacturers to use about 50 psi in the assembly plant in order to prevent flatspotting on the dealer’s lot. The dealer is supposed to reduce the pressure during the pre-delivery prep, but this is commonly neglected.

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49

In my rather long-winded post a few back, about the causation behind the tire pressure disconnect, I did acknowledge the practice.

Now, I’m trying to reconcile 50psi in an era(30-50 years ago) when 35psi was most often the max cold inflation pressure stamped on a sidewall.

50

Anyone know when they started putting the maximum inflation pressure on tires? I don’t remember it being there in the mid '70s.

51

Yes, that part of the pre-delivery prep was clearly ignored by the Chevy dealership. Perhaps other aspects were also ignored. Quien sabe?

The worst pre-delivery prep that I ever experienced had to do with my brother’s Datsun SPL-310, circa 1967. The incredibly-sleazy Datsun dealership didn’t even have a service department, and they drove cars that needed servicing/warranty-related repairs to a nearby Gulf gas station, where the owner had neither the tools nor the inclination to work on Japanese cars.

The Datsun dealership employed one very elderly man to “prep” cars for delivery to customers, and his prep consisted solely of washing the cars and removing the plastic covering from the upholstery.

52

Yes it does… I just did it on the Android tablet in my hand.

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53

I’m not sure. But once I even proposed leaving that max number OFF.

Too many folks instinctively look there for inflation information.

Instead, just stamp on tire the maximum load, and next to that:

“PLEASE CONSULT VEHICLE LITERATURE FOR CORRECT INFLATION PRESSURES”

54

Several members here have confessed to exceeding the load capacity of their vehicles, maximum load @ XX psi is important information.

Also, I don’t use OE size tires on my vehicles.

55

The problem is, few people understand that ‘mumbo jumbo’(to them).

I do.

I studied the standardized size/load/ inflation pressures.

And as it turns out, if the car mfg did their homework, the OEM-size tires will each support, at the pressure specified, 110-130%(depending on which axle) of gross axle weight(GAWR) as indicated on those certification and tire placards on a vehicle’s door or door pillar.

So no real reason to have to overinflate for driving.

56

I’ll have to trust your research, there are two examples in this thread however I have never seen this happen locally.

We are required to print a vehicle computer scan which includes tire pressure and attach this to the PDI inspection form. Someone is going to notice that the tire pressure has not been adjusted for delivery. Also, some vehicles illuminate the tire pressure warning light if the pressure exceeds a safe pressure limit.

Was the pre-delivery inspection performed? Given that you ordered the vehicle, it wouldn’t have been placed on the sales lot after the PDI, it would remain in the storage area on the rear lot. Did they complete the work before you arrived? Did you receive the PDI certificate?

57

I am referring to loading 3 to 4 thousand pounds into a 1/2 ton/1500 series truck.

Or towing a 3000 pound trailer with a front-wheel-drive car.

58

Setting the pressure to the tire max, or even twice that value, won’t in those cases fix stupid.

Remember, the vehicle itself dictates max load, GVWR, GAWR, etc, not the tires.

It’s all there in those placards, if folks were humble enough to bend over and look.

See? The only info needed on the tire is size, load index, speed rating, and max weight in lbs and kgs - and where the correct inflation pressure is to be found.

59

I don’t know

Nope!
To give you an idea about that dealership’s service department, I complained a couple of times when the car was in for routine service about the passenger door lock slide button ratting while I drove. Nothing was ever done, so I eventually met with the Service Manager over that issue.

His reply was, “It’s supposed to rattle”
Me: Are you SURE that the door lock slide buttons are supposed to rattle?
SM: Yes
Me: Okay, since I want everything to function as it is supposed to, I want you to open up the driver’s door, and make that slide button rattle the same way that the one on the passenger door does.
SM: (speechless)

Clearly, I was taking a bit of a chance, but when I picked it up, the rattle from the passenger door was gone and–obviously–they never opened-up the driver’s door.

That dealership was gone ~2 years later, and I found another Chevy dealership whose service department was a bit better than the first one.

3 Likes
60

I took my car to Toyota dealership for service and my tire pressure reading was 29 on all tires, so, obviously, they needed to be inflated to the correct reading.

Toyota returned the car to me with tire pressure reading at 55 !!!

I was extremely shocked as my tires called for 37 when cold, though Lexus said 35.

I brought the car back to Toyota and while driving, the car felt like a jeep.

Sometimes I wonder if dealers are actually premium places to take your car. :roll_eyes: