[Red Ryder]

As i have posted in some other threads here, i have new tires on my Bu. Yokohama Avid TRZ's and found that they are a much better tire than the stock LS2's the car came with. But, i have been messing around with the tire pressure, up and down, trying to find that sweet spot that works well for this car. I have done some searching on the net for advice on this subject and came across this web page= http://www.modified.com/tech/0208scc_tire_pressure_guide/index.html and have applied the info there in and have to say it has helped a great deal. I'm now running 38psi up front and 36psi in the rear cold psi. (The yoko's have a max psi at 50.) My 2Lt has a curb weight at 3600. Anyway, I'm throwing this out as food for thought. Hope this may help some of you out there looking for info on this subject.

 

[Silver LTZ]

So your running 38 cold? That's gonna go over 40 warm and cause the tire to cup. That will not be good for handling or tire wear though. I wouldn't run anymore then 35 hot.

 

[E_Net_Rider]

It might depend on tire. I've had some Michelins that over a wide range of pressures they always looked low on air (70 series). Because they road and handled so well I kept the pressure a couple of pounds higher than suggested and had no problem.

 

[Malibu Glow]

Sorry but most tire manufacturers don't suggest running tires at pressure more than 10 PSI under maximum. Irregular wear can occur on under inflated tires. Plus rolling resistance increases as you decrease the air pressure, which hurts MPG's. Firestone is a classic example from all the so called failed tires on Ford Explorers, since Ford RECOMMENDED tire pressures of 28 PSI on the LT tires equipped on the Explorer, whereas the maximum pressure rating was 45 PSI, this caused these tires to fail and not imperfections from manufacturing. On all my vehicles I run my tires within 10 PSI of maximum, and closer to 5 PSI from maximum.

 

[E_Net_Rider]

Sorry but most tire manufacturers don't suggest running tires at pressure more than 10 PSI under maximum. Irregular wear can occur on under inflated tires. Plus rolling resistance increases as you decrease the air pressure, which hurts MPG's. Firestone is a classic example from all the so called failed tires on Ford Explorers, since Ford RECOMMENDED tire pressures of 28 PSI on the LT tires equipped on the Explorer, whereas the maximum pressure rating was 45 PSI, this caused these tires to fail and not imperfections from manufacturing. On all my vehicles I run my tires within 10 PSI of maximum, and closer to 5 PSI from maximum.

I agree that it should have been Ford that got sued, not Firestone. But how about some data showing inflation recommendation within 10# of max?

For fifty years my Dad had farm 3/4 ton pickups equipped with bigger option tires having 60/65 max inflation. At that pressure and heavy duty springs they would have ridden like steel tires. He inflated to door sticker or mid/upper 30's. I'd seen those tires squat many times when a load was on the truck, or I should say overload. Often it hauled loads of lime over 4000#. You had to watch your speed because of pot holes. Nose up, but sure road smooth. It is very hard to estimate weight of a pile of lime because it is very dense. I overshot and had 6200# on one occaison. I rode home on the axle, tires squatting. Tires never blew, just wore out.

 

[Malibu Glow]

Check with each tire manufacturer on that, Firestone/Bridgestone does not recommend following the tire placard on the vehicle.

Oh those tires on that 3/4 ton truck are either 6-ply or possibly 8-ply, the sidwall are stiffer than most passenger tires and more than likely Bias ply tires.

 

[08chevymalibultz]

I agree with SilverLTZ. With my 08 Malibu LTZ, I follow the 30PSI on the door. When warm the tires are at least 2+ PSI higher. So I am running them at 32+ PSI when tires are warm. I have the Goodyear Tripletred's on my car and find that this tire is more of a heavy duty tire. The ride is more stiffer and rides too hard anything above recommended tire pressure with this suspension. I know if I run them a little bit higher I woud save on MPG but the ride would be awful. I am sure that GM had recommended
30 PSI for a reason. Car design, ect.

 

[E_Net_Rider]

Sorry but most tire manufacturers don't suggest running tires at pressure more than 10 PSI under maximum. Irregular wear can occur on under inflated tires. Plus rolling resistance increases as you decrease the air pressure, which hurts MPG's. Firestone is a classic example from all the so called failed tires on Ford Explorers, since Ford RECOMMENDED tire pressures of 28 PSI on the LT tires equipped on the Explorer, whereas the maximum pressure rating was 45 PSI, this caused these tires to fail and not imperfections from manufacturing. On all my vehicles I run my tires within 10 PSI of maximum, and closer to 5 PSI from maximum.

If what you say about max 45psi tires is true, then running such tires on the Malibu would be the wrong tire.
Part of the problem with those separating tires was that they were not being kept up to the Ford recommended pressure. On the low side they would build more heat and separate. I never had one of those vehicles, but often, info on the placard or in the manual would tell you to add 3 pounds for sustained highway or heavy loads.
And Firestone was not the only one. Vehicles equipped with Michelin CHX(that model I think) had a notorious problem of separating and causing deadly crashes. There were a number of really bad ones because these were often used on 9 passenger or more vans that were often used by churches and schools for class trips. Those boxes often rolled over killing many onboard. My daughter was about to embark on a class trip on such a vehicle. I noticed the tires and asked the driver if they were properly inflated because of the problem. Upon returning he told me the other van lost two tires on the return trip. What we had here was that more than likely the tires had been run low at some previous time and the damage was waiting for the next time they were stressed a bit.

 

[DrivenDaily]

I read the information on the link that Red Ryder provided. It seems like a very good place to start and an intelligent way to determine an approximate starting point for tire pressures.

I have neither a skid pad nor a temperature probe. What I DO have is what everyone else does, a sense of when the vehicle is taking more steering wheel input to make a turn, or when it's starting to slide in a turn, or when it seems to wander on a straight road.

When I got my car in December '08 and for about a year after, I ran the recommended cold inflation pressure (CIP) of 30 psi in all 4 tires. I was constantly amazed at how quickly it started to slide in a corner when it was dry out, and how unsafe I felt when it was even damp, plus how imprecise the track was when on a straight and level road. On top of that, I watched as the edges of the tread continually scrubbed away. Now I'm no engineer but I'm intelligent enough to observe the difference between these tires and the new ones that I put on my previous car. I saw these (Goodyear Eagle LS2) wearing out way faster than the old ones (Big O Touring), both of which are rated at 44 psi max CIP.

Finally I decided to change the CIP from 30 to 40. I posted about it earlier. When the dealer service dept rotated them and put them down to 30 again I pumped them back up, but this time went to only 38. At 40 the ride was very harsh but cornering improved greatly. At 38 the ride is slightly better (maybe just my imagination since I know I dropped the CIP) and the cornering is about the same. I'm still in flux with what CIP I'm going to use, and 36 will be my next test. But I can definitely tell you that 30 is just too low for my car. I'll probably test using 34 as well.

The biggest thing I took away from that article is that the proper CIP for any tire has to take into account the tire construction, the outside temperature, the load on each tire, and the way that you're intending to use it. What you're trying to accomplish by adjusting the inflation pressure is a uniform contact patch, one that spreads the load and wear across the entire surface of the tire rather than impacting the center more than the edges or vice versa. If your driving is what most of us do (driving on public roads with the occasional fun blast here and there) then that's different from taking it to a road course where you're gonna be constantly throwing it around a lot of corners. I honestly don't know if you should increase or decrease the CIP for a road course, but the article tells you how to determine it, if that is what you need to do.

 

[Sandhopper]

I am running 35 psi cold in my stock LTZ tires and the handling has improved as well as the milage. The tires warm up to around 38 psi right now. Once summer hits and the temps start to climb I will drop my pressure down to 33ish to give me some room as to not go over 40 psi. With a little more air in the tires I have found that the car handles better on rutted pavement. I have not seen any adverse wear issues with the tires at this pressure.

 

[TMoneyR523]

I have them put 32PSI nitrogen in my tyres.

 

[Kranium31]

this is a heated discussion that always has two answers. I remember asking a few instructors back when i went to NEIT and one said go by what the door says no matter what the max on the tire says and the other said go by what the tire says. Ive always went by the tire though.

 

[E_Net_Rider]

I've noticed that most tires at tirerack have increased their maximum pressure during the last few months, at least the ones sized for the bu. I have to wonder what the reason for that is? My thinking was that maybe some suspensions are designed for harder tires as part of increasing EPA requirements for mileage. I had noticed a few months back that several tires were available in lower and higher max pressure versions of the same tire. At that time I would have said that you are running the wrong tire if you had the higher because it would make sense that the tire might have been designed so that it required the larger pressure to make it stand up properly. In the past I ran a couple of sets of Michelin Weatherwise and those tires always looked like they were near flat on the Regal w/ 3.0 when run at the recommended 33psi. I never had a problem with them being like that, they wore properly and handled very well and on that 95 they got 28mpg highway which was very good for its time. I did notice that despite the weight of the carcass, unmounted you could tell they had a very pliable sidewall. They were perhaps just slightly slower to respond to a hard fast move of the wheel, but in every other aspect they were superior to other tires I had with stiffer sidewalls. Obviously they were designed that way. And that allowed the tread to lay flat on the road surface without it deforming the tread mostly at the point of contact, but rather spreading it around the tire.
Also think of the old days of bicycles where the common tire was what later referred to as baloon tires. Aproximately 2.75 inches wide with inflation of about 35psi. Later they moved to tires less than 2 inches wide with higher pressures and in bicycles designed for speed they used a tire of about 1.25 inches with pressures of 60psi. That older style bike road much smoother without bone jarring effects. The bike designed for speed had much lower rolling resistance but very harsh. Despite tire advances this still holds true for ride smoothness. The vehicle suspension has improvements but if it is not designed for the harder tire and will suffer the consequences. Lightening the vehicle, using minimum steel, much lighter components than a truck where they are designed for such use, likely early failures will occur.
Valving in struts has improved for handling some of the extreme and on luxury versions they seem to have started using fluids that change molecular state via electrical input from ride control computer. Until they start using some fancy design where the camber is actively adjusted while driving, we shall have to depend on conventional methods of keeping the rubber flat on the road. And because nearly all vehicles have some camber at zero steer it is up to the tire to have enough flex in the sidewall to allow the tread to lay flat and even more flex when cornering. But not so much that it allows the tire to rollover the point of flat contact. If roads were perfect, we might all be riding on the tires that tried a flat band of steel under the tread.
Finding what is called the sweet spot (inflation pressure) certainly has advantages. With todays tire technologies it is doubtful you will see more than 1 or 2 tenths of a MPG improvement. Only significant when viewed from national consumption figures. Hopefully the industry will catch up with suspensions that match higher pressures.
The Japs used to joke that the reason American trains were slower and less efficient was because of our old wheels. The top half was always moving in the wrong direction. ( you have to think of it in comparison to maglev trains, no wheels.)

 

[E_Net_Rider]

I have them put 32PSI nitrogen in my tyres.

There was an article circulating about the relevance of nitrogen versus air. In theory it is better, especially at extremes. Military and probably commercial use nitrogen in aircraft tires. I don't know that it started in the tire but may have been a convenience since it was needed in the struts where oxygen could be corrosive.
Tires have a thin membrane inside to nullify the deteriortive effects of oxygen. It is quite important that whatever you put inside is dry, water vapor free. If the tire gets hot enough to boil water you have explosive consequences, but unlikely to happen with a tire properly inflated since pressure raises the boiling point. Most likely a problem when the tire is very underinflated causing extreme heat generation and easier to boil with lower pressure. And at such temperature the tire was likely to fail anyway.

The bottom line was that it really was not worth the extra effort and expense of nitrogen.
It reminds me of an uncle that many years ago ran a garage. Ocaisonally someone would come in wanting to sell a mounted tire for a few dollars. After agreeing on a price, Bob would offer them a few more dollars if they changed all that old, bad air out and put in new air. Some were obviously not very knowledgeable or desparate for money. Part of it was for Bob's amusement as he watched them jumping up and down on the tire to get every bit of the old air out.
Point: Just because someone says so, it is not necessarily true.

 

[DrivenDaily]

Not an engineer here, but what I've read about nitrogen in tires suggests it's a good thing if you don't mind paying for it.

Nitrogen is dry so there's no extra moisture being introduced to the inside of the tire. That's not to say that there isn't already some from the air already in there.

Nitrogen molecules are larger which means it doesn't migrate through the rubber and other materials as easily.

Nitrogen is more stable as far as temperature goes so the swings in cold inflation pressure (CIP) are reduced.

Nitrogen costs money, air is free with my pump, and it's only a quarter or two if you pay for it at a convenience station.

Nitrogen is available only at specified locations, convenience stations are all over, and I can pump up my tires anywhere I can pop the trunk lid.

Choices, choices. Can't make 'em with rumors so this oughtta help some. If you want or need more take advantage of the web, then come back and share it.

 

[Starship]

Then, there's the matter of the accuracy of the tire gauge. I finally broke down and bought a Moroso 89560 Tire Pressure Gauge ($36 from Amazon,http://www.amazon.com/gp/product/B000COS8FI). Checking my two old digital tire gauges against the new one, I find that one is off by .5 PSI whereas the other, by 3 PSI. I won't be carrying the Moroso gauge around due to its hefty size but it's going to come in handy to sanity-check the ones do I keep in the glove box.

 

[Silver LTZ]

Then, there's the matter of the accuracy of the tire gauge. I finally broke down and bought a Moroso 89560 Tire Pressure Gauge ($36 from Amazon,http://www.amazon.com/gp/product/B000COS8FI). Checking my two old digital tire gauges against the new one, I find that one is off by .5 PSI whereas the other, by 3 PSI. I won't be carrying the Moroso gauge around due to its hefty size but it's going to come in handy to sanity-check the ones do I keep in the glove box.

I have one of those. I have been using it for years when I go to the track with my other car. It is super accurate.

 

[Starship]

I have one of those. I have been using it for years when I go to the track with my other car. It is super accurate.

Ah, thanks for the info. I understand that it's individually calibrated. I think I saw one on the "How It's Made" show. I hope it stays accurate (you never know with all the engineering, *cough*cost-cutting*cough*, that's going on constantly). I was getting tired of looking at different readouts on the DIC vs. tire gauges. They were all within 3-4 PSIs of each other but that represents over 10% of the nominal 30 PSI.

 

[Silver LTZ]

Ah, thanks for the info. I understand that it's individually calibrated. I think I saw one on the "How It's Made" show. I hope it stays accurate (you never know with all the engineering, *cough*cost-cutting*cough*, that's going on constantly). I was getting tired of looking at different readouts on the DIC vs. tire gauges. They were all within 3-4 PSIs of each other but that represents over 10% of the nominal 30 PSI.

They are made very well, just don't drop it. That could mess up the calibration.

 

[E_Net_Rider]

I've been watching for a good guage that I'd be willing to shell a few extra bucks on. The issue I'd have with that one is that the range causes the numbers to be compacted too much. I don't need one that will read 100PSI. And maybe a little larger dial so that I know I'm within a half pound easily.
It might not be that critical on this vehicle, but a 73 Mazda rotary I had showed handling changes if I was more than a pound off on the same axle.