** Tire Pressure Poll **

[RidingOnRailz]

To which do you set your car's tire pressure?

[shorod]

I assume you're asking about daily drivers, not special track use cars, tow rigs, etc.


-Rod

[RidingOnRailz]

Originally Posted by shorod

I assume you're asking about daily drivers, not special track use cars, tow rigs, etc.


-Rod

Correct. A common-sense assumption.

[RidingOnRailz]

BTW I'm not the one embedding those ads in my posts, lol!

[RidingOnRailz]

Reminder: Three more days to vote!

[RidingOnRailz]

So, according to the responses to my poll, the vast majority would inflate their tires to the recommended cold pressures decaled somewhere on their vehicle, or approximately.

Well, I asked the mechanic who recently did my brakes, and he stated that those stickers were "a joke" - his exact words, not mine! He suggests setting tires to the max cold on the tires, or no more than 5psi below. For a tire with 51psi max cold stamped on it, that means 46psi.

And he is hardly the only mechanic or service tech who suggest going off the values stamped on that rubber.

So what changed in 10-20 years - when tires were inflated to or slightly above what the vehicle manuf. specified?

[shorod]

My guess is laziness. It's easier to inflate the tires to what's stamped on them versus looking around the car to find the appropriate value. You may get slightly better fuel economy by inflating the tires to their maximum safe inflation, but it could sacrifice tire wear and vehicle handling.

The manufacturer recommended inflation is based on the vehicle weight distribution as well as, to some extent, alignment specifications. Very few tires are designed specifically for an individual vehicle which is why what's on the sidewall typically differs from what's on the placard.

If you happen to know what the vehicle weight distribution is front to rear and do the math you'll likely find that the recommended front and rear inflation values in psi (pounds per square inch) calculate out such that approximately the same contact patch for the front tires is similar to the contact patch for the rear tires. It might be slightly biased toward the front to account for cornering and braking load differences since the front tires carry more of each of those loads.

-Rod

[shorod]

It would be interesting to ask those same technicians what they torque lugnuts to when reinstalling wheels. I bet they spit out a value of something like '85 ft-lbs" instead of stating that "it varies from vehicle to vehicle." Again, that would demonstrate a decision out of convenience/laziness. The wheel stud torque specifications are another item that can vary significantly from one vehicle to the next, yet determining the correct manufacture's recommended value is not always trivial to find and therefore few technicians likely get it right.

[Stealthee]

I was the solo "personal preference" voter. I definitely don't inflate to max psi, or any where near it. Anyone who does is uneducated, whether they call themselves a technician or not.

The whole reason I go with personal preference is I like my tires around 35 psi, even though my Lancer suggests 32 on all corners. Max psi on my DSW06's is something like 51 psi. 46 psi is WAY too high and will provide for an uncomfortable ride.

As for varying psi my Stealth says 35 psi front and 32 psi rear on the placard.

[CapriRacer]

I've always puzzled why mechanics and even tire shop personnel haven't gotten the message that the vehicle tire placard is at least a good starting point, and the max pressure written on the sidewall is not. Having been a tire engineer for over 40 years, I know where those 2 values come from and the sheer arbitrariness of the sidewall pressure renders that value unconnected with anything technical, where the placard value was at least looked at by the engineers designing the vehicle.

[RidingOnRailz]

Originally Posted by CapriRacer

I've always puzzled why mechanics and even tire shop personnel haven't gotten the message that the vehicle tire placard is at least a good starting point, and the max pressure written on the sidewall is not. Having been a tire engineer for over 40 years, I know where those 2 values come from and the sheer arbitrariness of the sidewall pressure renders that value unconnected with anything technical, where the placard value was at least looked at by the engineers designing the vehicle.

I will set tire pressures to -5psi from what's on the tire only in circumstances where the vehicle mfg load decal is missing or illegible, if it will get the car to a place where I can find out the correct recommended settings. And that's for a 44psi tire. For a 51psi max cold stamped tire, I'll set to -10psi below that, again until I can get to a place where I can get the correct info.

With sites like tirepressure.com, that should not take long!

As for mechanics, they should know better than the general public. But even the public go mostly by what's stamped on the tires, and never get to experience the true comfort & handling potentials for their vehicular investment. Sad!