Inflating tires

dodge
caravan

#1

I recently purchased new tires for my parents’ 1997 Dodge Plymouth Voyager. The maximum psi for the tires is 44. The recommended psi on the door sticker is 35. Which value should I use to inflate the tires? Thanks for the help. pj


#2

Use the value on the door sticker, which is correct for the vehicle.

The “max” pressure on the sidewall is just that, the maximum to which the tire can safely be inflated. This is not intended for normal use, but as a warning to avoid over-inflation.


#3

44 psi is what I use.

The harder the tire = lower rolling resistance = better gas mileage.

The fuel saved over the life of the tires more than makes up for the very slight greater wear in the middle of the tire tread.


#4

Ignore Robert Gift’s post. This person has no idea what he’s talking about.

I’m sure that when the sun comes up others will back me up on this one.


#5

The harder the tire = lower rolling resistance = better gas mileage.

Yea, but it also makes for less traction (longer stopping distance) and may result if some strange tyre wear.

44 = MAX
35 = RECOMMENDED

MAX does not equal RECOMMENDED

The only reason that 44 psi is on the tyre is as a warning never to use it on a car that recommends over 44 psi as the tyre is not designed to carry that much weight.


#6

If the tire size on the placard is the same as the one you are using, then the pressure listed there is appropriate. If you are using a different size, then the pressure has to be recalculated. It is not hard to do, but requires the use of load tables which aren’t published on the 'net. I have copies and am willing to do the calculation if I know the placard size, the placard pressure, and the new size.

DO NOT use the maximum pressure on the sidewall except as a warning not to exceed that value. It is not a recommendation, or a suggestion. It is exactly what it says - a maximum.


#7

Robert, you may want to reconsider that policy. 44 psi is the maximum pressure the tire had handle without suffering a catastrophic blowout. Of course when you drive the car the heat generated from the tire’s friction with the road will cause the air pressure to increase even further, well above the 44 psi mark. What you are doing is potentially dangerous. Then there’s also the issue of traction, your tires are the only things that connect your vehicle with the road, when you run such high pressures the contact patch is significantly smaller and your traction is compromised. Finally, the pressures listed on the tire are just telling you what the maximum air pressure for the tire is, not what the best air pressure for the car is. For example there are probably a dozen vehicles that can use any given tire. Each vehicle has different weight and weight distribution characteristics. This is why you go by what air pressure the car’s manufacturer suggests and not what’s on the tire.


#8

Do NOT put it as the max…that is a very nice way of getting killed or killing someone else. The car will NOT handle anywhere nearly as well as it would with the optimal tire pressure. The engineers who designed this car and the tires and suspension system know a lot about what the tire pressure should be to give you MAXIMUM comfort and control.


#9

In addition to the other valid posts pointing out that Robert Gift’s tire inflation suggestion is NOT a good idea, I want to add another point:

By overinflating tires as Mr. Gift has suggested, the impact of potholes and other road irregularities is MUCH more damaging to the suspension components of a vehicle. He may well be saving some money on gas, but that saving will be eaten up and exceeded by the money that he will have to spend on replacing ball joints, tie rod ends, shocks, struts, etc.

Mr. Gift’s idea is bogus as it will actually cost more money over time, in addition to exposing the driver to problems resulting from the poor traction of those overinflated tires.


#10

Yep, mcparadise is 100% right and Robert Gift is 100% wrong. Over-inflating might improve your fuel economy, but at the cost of traction, which is important. It also might damage your suspension components and lead to premature wear of your shocks/struts.

The 44 psi pressure for the tires is the maximum (not necessarily recommended) in any application. The 35 psi pressure is the recommended pressure for any tire used on this particular car. The only reason they print “maximum pressure 44 psi” on the tires is so nobody will put them on a vehicle that requires more than 44 psi.


#11

The automobile manufacture recommends a prudent level for OEM or equivalent tires. Use the door sticker level.


#12

The tire size on the door sticker is the same as the one I’m using.


#13

Since I’m big on safety, I will go with the automaker’s psi. Thanks for everybody’s input.


#14

Just make sure you’re checking the pressure with the tires cold (before the car is driven that day) and you’re using a good pressure gauge. Many of the ‘pencil’ gauges aren’t very good, you’re better off with a round dial gauge.


#15

“44 psi is what I use”

That might make some sense on a closed course road rally where you’re skidding around every corner, but not on the street.


#16

Thanks everyone for your advice.

Yes, I am concerned about the effect it may have on suspension components.

Does it really make a difference in footprint?
Between 35 and 44 I see no difference. (Only 9 psi more.)

What about using a narrower tire? They allow a range of sizes.
On our 99 Expedition, (I removed the trailer hitch and third seat) I used P265 75R 16 - the largest in the allowable range.

I ran brand new tires at 44 psi down to their wear bars and they were surprisingly even from center to sides!
If there is a slightly smaller footprint, would not the greater weight/area continue the same traction?

I have not noticed any difference in handling or braking, but I also drive gently and have not panic braked (skidded) so don’t have a comparison.

I suspect vehicle manufacturers would like us to feel a more comfortable ride by lowering the tire pressures. But WE pay for it with higher fuel costs.


#17

I won’t get into the idea of owning a Expedition and being overly concerned about fuel costs. Expeditions aren’t known for their thrift at the pump. But look at it this way, Automakers have to meet CAFE standards, If they could get better mileage without compromising safety, don’t you think they would do it? Also did you adjust your speedometer for the increased tire size? You could be getting better mileage than you realize. Assuming the stock size tire was a P265/70/R16 the P265/75/R16’s are about an inch taller. If you had the 255/70/R16’s then the difference is about two inches, more than enough to throw off the speedometer/odometer.


#18

Contact patches and friction coefficients are not something you can usually perceive with the naked eye. The best way to view the contact patch is from underneath through a clear surface. If you were to do that, you would see the difference between 35 psi and 44 psi.

I am less concerned about your suspension components than I am about tread separation, which is more likely to kill people when it happens to an SUV. Over-inflating your tires can cause tread separation.

The engineers who designed your vehicle factored the vehicle’s weight into their tire pressure recommendations.

This isn’t about ride comfort. Your suspension can compensate for your overinflated tires, at the cost or a shorter life for your suspension components. You won’t notice this now, but you might have to replace something like your shocks/struts at something like 150,000 miles instead of 200,000 miles.

Consider that the manufacturer’s tire pressure rating is based on the cold tire pressure. When your tires heat up as you drive, the actual pressure is higher than 44 psi, which is the maximum rating for your tires. When the cold pressure is the maximum, the actual pressure in everyday driving is above the maximum. How can that be a good idea?

You drive an Expedition and you think you are getting poor fuel economy because of a vast conspiracy perpetrated by Ford? Thanks for the chuckle!


#19

“…Does it really make a difference in footprint?
Between 35 and 44 I see no difference. (Only 9 psi more.)
…”

How about this as an answer:

Not only are the footprints visibly smaller with higher pressures, the pressure distribution in the footprint changes as well!

wwww.BarrysTireTech.com


#20

This is easy - pressure MUST make a difference on footprint. The footprint is directly propotional to the weight, and inversely proportional to the pressure. If a tire has to hold up 1000 lbs, it needs about half the footprint at 40 psi as it does at 20 psi.