Words for the wise: over inflated tires

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jrcowboys

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Guys:

I posted earlier that I had premature tire wear and poor handling due to over inflated tires. Note: I had inflated the tires to 34-35 PSI to improve gas mileage. I dropped them back to 31 PSI (manual says 32, but decided on 31 due to hot temperatures) and found the handling to be much improved. Gas mileage did drop about 1 MPG.

My advice: don't over inflate tires because it can cause accidents (lost the rear end while turning on two occasions) and produce premature tire wear (center tread). Seems to be critical on rear drive cars.

Another topic: got improved performance on Chevron gas vs Shell, both premium. Note: gas mileage a little worse, maybe due to cleaner injectors that provice richer fuel mixture?

Thoughts?

JR

1999 Lexus SC300, 144,000, Mobil EP
 
It depends on the vehicle and tire combo.

In the case of my Mom's 99 Grand Cherokee with P245/70R16 Toyo Open Country A/Ts on it, going over the door plate rating (32 or 33, IIRC) is the only way to get even wear from them. I usually keep them right at the 35 psi sidewall max or just over (36 front, 35 rear).

In my Jeep, the tires wear perfectly evenly inflated to the factory specs (don't recall offhand, but it's either 32 or 36) or pushed to 42 psi (44 sidewall max). It handles fine either way (feels slightly better with more pressure), and I haven't lost the rear end without gassing it way too hard at low speed in the rain.
 
Maybe I'm just ignorant, but I see a lot of people saying they have exactly 33psi in their tires. I wonder if it really matters and if they really are that exact about it. Am I the only one that just tries to keep it between 30-35 and calls it good?
 
Since the advent of TPMS, I find that my OCD wont let me have PSI's of wide variances. If I toggle through and see 32, 35, 38, 30, it'll drive me nuts! I gotta stop and fix it at the next available opportunity.
 
Originally Posted By: nwjones18
Maybe I'm just ignorant, but I see a lot of people saying they have exactly 33psi in their tires. I wonder if it really matters and if they really are that exact about it. Am I the only one that just tries to keep it between 30-35 and calls it good?


Once I figure out what pressure I want to run in my tires on a new car, I inflate them 2 psi over if the seasons are getting cooler and right on if the seasons are getting warmer. On my Corvette I can usually go months without adding air that way.
 
Some car/wheel/tire combinations can be pretty sensitive to tire pressure. My Cougar used to really sing when it had 28-29PSI all around, but lost some cornering stability and bite around 32-33PSI.
 
Most autos are spec. for comfy ride. 30 psi.
High performance/performance oriented autos may call for higher
pressures.
I know of several PU owners that run 40 psi year round. Handling is better and tire life is longer.
My car spec. 30; and I run 35/36 most of the time.
Lately I've gone to 40 for summer trips, etc.
Rides fine, handles good.
Not an agressive driver.

My 2¢
 
I have mine at 44 psi. Handles fine and uneven tire wear . Yes, tracktion is a bit reduced, but unless in snow I am fine.
 
Weird thing I've noticed-on older vehicles that were built when max tire PSI was only 32 pounds, you need to raise the placard pressure by the difference between the new tire maximum & the old max-like on my 300D it recommends only 27 PSI (out of 32 max), but my newer (same size) Kumhos are 44 PSI max, and they seem to ride & handle best at 36-38. Personally, in hot weather & high speed driving, a little too much air is WAY better than not enough!
 
Originally Posted By: jrcowboys
Guys:

I posted earlier that I had premature tire wear and poor handling due to over inflated tires. Note: I had inflated the tires to 34-35 PSI to improve gas mileage. I dropped them back to 31 PSI (manual says 32, but decided on 31 due to hot temperatures) and found the handling to be much improved. Gas mileage did drop about 1 MPG.

My advice: don't over inflate tires because it can cause accidents (lost the rear end while turning on two occasions) and produce premature tire wear (center tread). Seems to be critical on rear drive cars.

Another topic: got improved performance on Chevron gas vs Shell, both premium. Note: gas mileage a little worse, maybe due to cleaner injectors that provice richer fuel mixture?

Thoughts?

JR

1999 Lexus SC300, 144,000, Mobil EP

What tire pressure you run is up to you, but handling gets "sharper" with increased tire pressures. For ultimate performance in autocross you'd probably run your tires above 36psi cold, so they won't roll over onto the sidewall and quicker response.
I think what you are feeling is that your car actually has some negative camber for the stock alignment, so running your tires softer would make the car feel more planted and less likely to follow road irregularities. When I put negative camber on the front of my Neon that is what I noticed, especially with higher tire pressures it will follow truck ruts alot more.
 
Interesting. I have read that over-inflating (to the tune of 7 psi on a 35 psi rated tire) can improve overall performance and cornering in particular. Hyper-milers like to point that out whenever anyone questions the safety of over-inflating (as it also increases mileage).

I have over-inflated my 35 psi tires to 42 psi. In my case, as they claim, my cars overall handling and cornering ability improved. I no longer over-inflate to 42 psi as its too much hassle to maintain. I do still over-inflate by about 2 to 3 psi though. I also dont consider myself a hyper-miler, but I do read their stuff as I have found some of their tips to fit my driving style well or otherwise appealing. And these days, any savings on gas is good savings to me.

Maybe this is something specific to FWD vs. RWD.

-Spyder
 
I overinflate w/o any issue.

Both vehicles get 38PSI year round.

I have a friend who swears on overinflating the fronts and underinflating the rears on his rear wheel drives. To each their own.
 
I've been running 40 psi on all my cars for the past three years or so. All the tires have been doing great with the exception of an incredibly harsh ride with my winter car in the dead of winter. For winter I'll have to back off a bit.
 
Originally Posted By: Spyder7
I have over-inflated my 35 psi tires to 42 psi. In my case, as they claim, my cars overall handling and cornering ability improved. I no longer over-inflate to 42 psi as its too much hassle to maintain.
-Spyder


Put pure Nitrogen in them instead of regular air.
That is what I did in my summer and winter sets, and they don't deflate anymore when stocked waiting to be used.
Summer tires are set at 42 psi.
 
I've run 44-50 PSI in the Pirelli P4's (sidewall 44 PSI) on my Buick LeSabre for the past 48k miles. With regular rotation they're wearing very evenly. I've never come anywhere close to losing the car in the wet. In fresh snow or on slushy roads I'll drop the pressure, and air them back up again when the roads are dry.
 
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