Fill to vehicle spec or tire spec?

[RamFan]

Do you guys fill up your tires to the PSI recommended by the car manufacturer or do you base it on the max tire pressure of the tire and adjust accordingly?

For instance, my Charger doesn't show a recommended PSI anywhere, and I mean ANYWHERE on the vehicle/manual. Online I've seen a lot of people saying 30 psi is recommended. If I chose to go that route I would obviously set my tires at 30 psi.

My current tires, BFGoodrich Advantage T/A, have a max pressure rating of 44, so I fill until 40 psi. The ride is still comfortable and I get a little better MPGs out of it. I've found a set of General tires, Altimax HP, that have a max rating of 51 psi so I would likely set them to 45 psi, if I chose to get them for my next set.

What say you, vehicle spec or adjusted depending on max spec?

 

[Astro14]

Vehicle spec. The max is really for the max load on the tire - an ultimate limit. The Manufacturer spent a lot of time testing, engineering, etc. and the vehicle spec is a set of compromises between ride, handling, fuel economy, etc...and tailored to your vehicle. Most of them have a recommendation for minimum (few passengers) and a maximum (full load) and a recommended high speed setting (a few PSI more). As an example, my Volvo T5 says 29 F 29 R for normal, 35 F 38 R for full load.

Start with the manufacturer recommendation, then adjust for your driving conditions, e.g. lots of high speed/cornering, I would be 4 PSI above the full load max, or what the book recommends for high speed. Keep an eye on tread wear...if you're wearing out the center of the tread, you're too high, if you wearing out the shoulders, you're too low...Again, as an example, I run the car at 36 F 36 R (mostly driven with one or two passenger, mix of highway/city) and have good tread wear, handling and ride. The sidewall max on the 235/45 R 17 tires on car is 51 PSI...way above where I need it to be unless I was tracking the car...

I am hoping one of the real tire experts, like Capri Racer, will weigh in on this...

 

[CharBaby]

I beleive that it is required for a MFG to post their tire PSI card/label somewhere on the vehicle. Either it's on the door jamb, glove box, center console box, trunk area or even fuel filler door...But, Somewhere! Keep looking!

Maybe I'm wrong! I have never had a vehicle that didn't have it somewhere even though I had to search for it.

But, anyway! I use the MFG's spec and then adjust a couple of lbs here and there depending on my personal liking. Usually I like to keep the correct PSI in the rear tires and go up 2-3 PSI in the front tires. Sometimes I'll raise all 4 tires a few lbs...Depends!

 

[Hokiefyd]

On a Charger, it should be on the door jamb label. I wonder if that's missing on your car. 30psi sounds right, maybe 32psi. Most domestic vehicles are in the 30-35psi range. 40psi is likely too much. Remember that you tend to lose contact patch with too high of an inflation pressure.

 

[ARCOgraphite]

Whichever is lower!

 

[eljefino]

This q comes up again and again. +1 on the fuel door idea for the label. I guess it's to nag you to check it every time you get gas!

My benz demanded 2.5 Bar, PSI are good to reach more precise/ significant digits.

 

[440Magnum]

I start with the vehicle spec and then "tweak" up to the tire spec or down just a couple of PSI if I don't like the ride or handling right at the vehicle spec with the particular tires I'm using. The vehicle spec is picked by the manufacturer to optimize handling and ride so its a better starting point than the tire max spec, which is just that. The highest you can safely operate that tire at its maximum loading.

Does your Charger REALLY not have a tire sticker on the end of the driver's side door near the latch mechanism? I thought that was a requirement and had been for years. The stickers are applied by hand on the assembly line, so maybe yours just got left off.

 

[bdcardinal]

I go by the sticker on my Volvo, which is on the fuel filler door, 39PSI cold all around.

 

[HTSS_TR]

Vehicle spec is the minimum cold pressure, you don't want to go below that. It's safe to have cold pressure at 2-6 PSI above vehicle spec, or more if you go on a long trip and your car is fully loaded, but never more than max pressure on tire sidewall.

 

[Chris Meutsch]

I run 4psi over.

 

[crosseyedwx]

Tire sidewall max on all my vehicles.

 

[Astro14]

Originally Posted By: crosseyedwx
Tire sidewall max on all my vehicles.


Which, if substantially over the factory recommendation, reduces the contact patch, increases tread wear, decreases puncture resistance and worsens the ride. In the case of my 4Runner, that would be 50 PSI cold, vs. the factory recommendation of 29 PSI cold...where is the advantage in that? The max number is the design load of the tire itself and reflects only the tire, not the vehicle on which it's installed. The factory recommendation takes into account the application: the vehicle type, intended use, loading, handling, and fuel economy....Unless you're taking the car to the track, go with the factory recommendation.

Adjust intelligently from there based on your driving requirements. More pressure is not necessarily better.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=72

 

[RamFan]

I looked over the car again today and I found the [censored] thing. In deed it was on the door jam, not on the door but on the vehicle frame. It was right in my face and I didn't even see it, hate it when that happens

. Yes the factory spec is 30 psi and judging by the overwhelming majority of responses in favor of the factory spec I will decrease my pressure, not to 30 but to 32. I see it as a 2 psi buffer zone for when I'm in too much of a rush to check and for temperature variability.

 

[crosseyedwx]

My primary vehicle specs 30 psi cold, tires 44 psi cold.

My experience has been quite the opposite... I have better tire wear, no center wear experienced (all tires on my Kia are wearing evenly across the tread and are at 6-7/32 after 25,000 miles, they are 50k mile warrantied Firestone Firehawk GT-H 195/60R15, and the same goes for the Honda). I have had zero punctures, zero blowouts, better cornering feel and steering response, better stopping traction, better hydroplaning resistance, better fuel economy, less rolling resistance all at the expense of a "slightly" noisier and harsher ride. I will also add that I usually drive at or below the speed limit, so I can't attest to highway speeds with as high a degree of experience.

Car companies know how to sell cars, and that is with a nice soft ride, and that is at the expense of the tire. That placard pressure is the absolute MINIMUM tires should be at, and those pressures are for the specified original equipment supplied tire, and should not always be applied to aftermarket tire selections, as every aftermarket tire I have had on my cars have worn on the outer edges at placard pressures. That pressure is simply too low for what I want out of my car and my tires, and I want a larger buffer above that minimum pressure, which gives much less leeway for a slow leak

I have no experience with trucks however, and would tend to run between placard and max due to the lower weight over the bed of a habitually unloaded bed, which could lead to higher center wear if the tires are relatively wide.

 

[rpn453]

Originally Posted By: RamFan
I looked over the car again today and I found the [censored] thing. In deed it was on the door jam, not on the door but on the vehicle frame. It was right in my face and I didn't even see it, hate it when that happens

. Yes the factory spec is 30 psi and judging by the overwhelming majority of responses in favor of the factory spec I will decrease my pressure, not to 30 but to 32. I see it as a 2 psi buffer zone for when I'm in too much of a rush to check and for temperature variability.


Sounds good. I'd try pressures in the 30 to 35 psi range to see what suits your driving style and tire wear best.

 

[HTSS_TR]

Originally Posted By: crosseyedwx
My primary vehicle specs 30 psi cold, tires 44 psi cold.

My experience has been quite the opposite... I have better tire wear, no center wear experienced (all tires on my Kia are wearing evenly across the tread and are at 6-7/32 after 25,000 miles, they are 50k mile warrantied Firestone Firehawk GT-H 195/60R15, and the same goes for the Honda). I have had zero punctures, zero blowouts, better cornering feel and steering response, better stopping traction, better hydroplaning resistance, better fuel economy, less rolling resistance all at the expense of a "slightly" noisier and harsher ride. I will also add that I usually drive at or below the speed limit, so I can't attest to highway speeds with as high a degree of experience.

You can not have both: better stopping traction and less rolling resistance.

 

[Tornado Red]

Originally Posted By: crosseyedwx
Tire sidewall max on all my vehicles.


Typically 85-90% of the tire sidewall max.

 

[sciphi]

A few PSI under sidewall max. The ride is still comfy, the tire handles crisply, and wears evenly. The Pirelli P4's on my Buick have been run at either sidewall or just under for the 70k miles they've been on the car. The edges are still worn more than the center.

 

[CapriRacer]

For a 2007 Dodge Charger, Tire Guides lists a lot of different tire sizes, but the inflation pressure is always 30 psi - EXCEPT - for the SRT8, where it is 32 psi.



Chrysler vehicles, for some reason, do not do a good job of adhereing the vehicle tire placard to the vehicle. Hopefully they will fix this, because not having a placars could result in huge fines - and given their financial situation, they should try to avoid.

 

[SteveSRT8]

I have been to several road course track events in my SRT8, and usually run at about 38 psi cold. Factory does indeed recommend 32, which actually is very nice for the street.

As for running at max sidewall, we do that in 9000 pound service vans, 80 psi.

But for every day driving that seems nuts.