Tire Pressure

Go here and read a bit....http://ecomodder.com/forum/...I run mine at maximum recomended pressure and it gains me 2 to 3 mpg....I also like the ride better...but that's me....I did run 65,000 miles with the tyres ( like the oldtimie spelling.... also aeroplane... ) at 80psi which was the maximum rating....Did not wear the centers out of the tyres , did not hydroplane , and other than what some folks consider a "harder" ride I like it like that..

I did buy a scanguage before the change and got an immediate 2 mpg increase.....try it an if it doesn't work for you.....you can always step back.......

Hobart ( on ecomodder )

Well, you trade off for two things; uneven tire wear and less grip.

However, if you get 65,000 miles on a set of tires, then who cares. I would be happy to get 12,000 miles out of my tires!

On the bad side you will loose some grip, which doesn't really matter until you slam on the brakes and find out that you would only have a brown trouser day except that you stop 12" too long into the next car.

If yiou want to learn more, go to www.tirerack.com and check out their site. You should be able to find the maximum PSI for your tire.

Running with the maximum allowed pressure has only one negative, a slightly harder ride.

All the rest are positives, more petrol and tire mileage, lower wear and tear, better braking, better wet weather road holding.............also fewer punctures I am told, as I have not had puncture for over 20 years, that could be true!

Well, you will probably see a little more wear in the center of the tread.

Although this is splitting hairs, one way to dial in pressure is to measure the temperature of the tires after a good run.

As for nails, come to Florida and try your luck! Like you, I probably haven't had a nail puncture in a tire for 20 years. Move to Florida and I get 3 nails in as many months and $1500 in tire replacements.

I am told that this is normal for Florida, particularly after a heavy storm or hurricane. Due to the roofing damages there is always loose nails lying around.

Running tires at their max pressure versus max - 10% represents little savings. I think it works out for the average driver a savings of $2.00 to $3.00 per month, which is lost in the budget noise (at least around this home).

To get the tyres that I have done this max pressure trick with over the last 40 years or so to wear out in the middle first, you need (in my estimation as I have never had the problem!) at least double the normal pressure - I would hesitate to guess......or maybe even more.......

I feel that its something that you read about in books, never has actually seen....so it is questionable if it really happens......maybe with even older styles of tyres from before Radials?

Radials (almost from my first car onward were radials the best bet) are so stabile in their form (look at F1 racing tyres for example!) that it takes a great deal of pressure to just get them to actually fully contact the road, as they start with the middle "lower" than the rest. To get that middle part to expand further and wear out first is almost impossible with anything like relatively "normal" pressures I feel.......

I would like to state that I have never, ever a) over pressured a tyre so that the problem happens, b) seen another person's tyres with this problem, c) intend to try the experiment out in that direction.....

Well, I run pretty low profile tires and it does not take much pressure ± of optimum to have uneven wear.

However, you tend to feel a performance problem long before any tire wear takes place.

I really have no experience with high profile tires or truck/SUV tires.

Appropriate pressure varies with the tire and the car.

NEVER run higher than the pressure molded in the tire's sidewall.

Your mileage will increase with pressure.

If the pressure is low, the tire wears more at the outside of the tread,

conversely, too high a pressure results in wear at the center of the tread.

I start at rated tire pressure, and may lower it a little based on wear, ride, or handling.

Check your pressure cold, it may rise a little at highway speeds.

Newer cars will have TPMS [tire pressure monitoring system]

You must then run within the manufacturer's parameters.

I had a pair of tires on the back of a Honda Civic for 165,000 mi, the tread was ok, but they were weather cracking by then.

Thanks for the chalk idea. I can't seem to find any information re: increasing tire(tyre) pressure on the web. I realize there are too many variables involved to be able to get a definitive answer. Type of car, front wheel or rear wheel drive, road surface, wheel alignment, air temperature, etc are some of the variables. I would suspect that tire companies use very conservative numbers for safety(read law suit) reasons. This makes me believe that an increase in pressure will indeed raise mpg. Naturally, there is a trade off between tire life, stopping distance and economy, but there should be a compromise point where all variables can be accepted without going to extremes.

G'day Ronseto,

The only reason that mass producers specify the "lowest" pressure they can get away with is give the illusion of comfort. These days, you'll find recommended pressures are somewhat higher but in the seventies, it wasn't uncommon for the recommended pressures to be as low as 22 - 24 psi. To improve handling, braking, cornering power, wet road performance etc., I always increased pressures to at least 30psi. On a Cortina 6 cylinder (nose heavy) I always ran 34 up front and 30 at the rear (205/60R14s). The higher the pressure (to the point where the contact patch is reduced) the greater the grip. I started to get a bit of centre tread heating (wear) at 36psi, probably I only had 690kg (1518lb) on the front wheels (759lb ea).

The critical thing is to maintain the entire contact patch on the road, all else is secondary. Incidentally, never reduce your pressures in the wet, this allows part of the tread shoulder to roll under the contact patch reducing performance due to movement and heat build up and because in effectively increases the contact patch, reduces the contact pressure with the road.

If you can get a cheap and held "laser" type emissive thermometer (AU$50), they work the best. Go for a quick drive (say half a mile) with the tyred at recommended pressures and point this thing at the tread on the shoulders and the centre. Note the readings (a dedicated book preferably). Alter the pressures as you see fit and drive another quarter mile minimum. Take the temps again. You'll know when the pressures are too high as the centre of the tread will be warmer than the shoulders. Always vary the pressures by 2 psi at the first then fine tune by 1 psi variation.

If you find that the inner shoulder and the centre are similar but the outer shoulder is warmer by at least 2 degrees, you have too much toe-in or positive camber. Get an alignment. In fact, get one anyway and start with the proper settings. Always keep meticulous records and alter one thing at a time.

Regards

Royce

GA from me for a well thought out method that basically anyone could follow and do....

Thanks for the chalk line rrvau, it saves me from spinning my wheels to check the rubber left for perfect patch.

Brad

Excellent reply rrvau, I say that cause you stole my idea with the chalk.

I have used this method on many occasions and it work well, especially on low profile tires.

You get a GA from me on this one.

Tire pressure that is given by the car manufacture gives the best ride because the tire is used as part of the suspension system. The tire manufacturer give the best tire life.

I just go with the recommended pressure of the auto maker. Except when carrying heavy load then I concur to the tire people.

That is not a failure, but you would be surprised at the extra length of life the maximum tyre pressure gives.......up to 50% more mileage than usual, is NOT unusual.....

Often (depending upon your way of driving of course!) you can extend the life of the tyres to 3 times longer than what might be considered "normal"!

100,000 (over 150,000 kms) miles or so on a set of tyres is for me nothing new....

GA for that.

I couln't agree more....

I thought the same thing and voiced my thoughts to the old lady.

She said add the damn air and save gas your not driving in a endurance race anytime soon.

She is kind of direct that way.

Pressure should not be increased above car (pickup truck) manuacturer's spec. Nothing is gained except increased tire wear and shortened life as well as poorer braking, handling, wet handling. Running tires at their rated maximums is almost inevitably likely to result in irreparable loss and new tire replacement sooner or later. Rated tire pressure is just that: the pressure beyond which testing has shown that the tire is likely to fail or be permanently damaged. Most ofen such damage shows up as minute, leaking, punctures in the side walls...and sidewalls can never be repaired.

You were not very clear on the point you ranted about, do you mean not more pressure than the max allowed by the car manufacturer?

If yes, I agree as I always use the maximum fully loaded pressure and everything is actually better, mileage, tire life, braking, road holding and traction etc etc.....

No rant was intended, but if rant is what it takes to deter someone from interpreting a tire inflation rating (as embossed on the tire) as an allowable inflation pressure under use than so be it - perhaps someone will also be spared from having to re-buy their own new tires...or worse.

While it is usually true that vehicle manufactures provide tested specs (such as in owner manual or on door pillar) for best/recommended actual tire inflation, it is sometimes also true (I'll grant you) that that mfr specs are not readily available...that a certain amount of quesswork is called for...such as, say, with older or off road vehicles, trailers, and such...and/or when an "Inflate to [range]" statement does not appear on, or is undiscerbible on, a tire's sidewall. The question then becomes, just how to guess.

In addition to the "Inflate to..." statement (that may or may not appear on a tire), there will often, if not usually, also appear a "max inflation" rating figure embossed on a tire...usually near the inner bead. What some may not fully understand, is that the word, (pressure) rating should never be interpreted as a recommended or allowable inflation pressure...but, instead, as a cold pressue which should never be exceeded; or even closely approached. Instead, the tire pressure rating (in absense of tire/vehiclel mfr inflation recommendation) can provide a basis for guestimating (derating) an actual tire inflation range which should prove safe over normal operating conditions. So, for example, a tire with embossed pressure rating of 50 PSI could be safely "derated" to yield an actual inflation range of, say, 25 - 32 PSI, without undue risk of tire failure or damage under most conditions or temp and loading.

From that point, ride experience and treadwear inspection could be applied to refine to an optimum tire pressure. Hope this clarifies what I was trying to impart in previous post... main point being: never cold inflate to a tires pressure "rating"...and always know the difference...

Understood and quite correct of course, the pressures marked on the tyre bear no relationship to the vehicle requirements.

Luckily for us non US Citizens, these "spurious" markings are to be completely ignored if found on our tyres, so the problems you mention are nowhere else to be found other than the Good Old US of A!!! Where they also probably serve just to make the water muddy......

I must admit I had completely forgotten just how dangerous and prehistoric they are, Congress should get rid of them asap as far as I am concerned.....

I actually mentioned (I thought clearly, but maybe not clear enough) that the recommended tyre pressures for the vehicle in question was what I was talking about. I actually wrote previously:-

Running with the maximum allowed pressure has only one negative, a slightly harder ride.

Which is maybe open to incorrect interpretation, but I personally do not see the US pressure rating on the tyre wall as being "Allowed" for a particular vehicle....the car handbook must always take priority. Most garage forecourts have a list of cars and tyre pressures, if you ask them first!!

In Europe the tyre pressures are mentioned in detail in the manual and also usually on a sticker in either the filler cap flap or in the area of the car body covered by the driver's door that you can only see when the door is open.....but mainly on the filler cap flap though......in my limited experience.

These give the front and back pressures for driver+passenger only, to partially loaded and fully loaded. The tyre pressures I use and recommend (with over 40 years experience in variable driving conditions, tyres and vehicles) are the "Fully Loaded Pressures" from either this decal or the handbook....I have not found a single problem to date with using them all the time......other than the fact that you get such tremendous mileages from the tyres, that many people simply think that you are on some amphetamine if you ever mention just how many miles (kms...), as they get nothing like that!!

A Mitsubishi Bus that I once owned from 1989 to 1997 got over 160,000 kms from a set of tyres, that were still completely legal tread wise when they were eventually replaced. This vehicle was noted as having above normal tyre when in the hands of most mortals....so nobody believed me......

Driving style is also a great tyre saver as well, if you are always using your right foot to brake and accelerate heavily, well no tyre, no matter how inflated, is going to last very long!!! I actually drove my Sharan with ABS for OVER 2 YEARS before I ever felt the ABS working!!! I thought it was BROKEN until a mechanic told me that it was working correctly and also an easy method to check that out fully!!!!

I trust that we are now both clear on this point of tyre markings, it was fully correct that you mentioned it in this context.

Have a great day in spite of me!!!

Andy, rrvau,

Thanks for your comments, which are all very informative, and go to show how inflation pressure must adjust to specific driving conditions, vehicle use and springing, and other factors related to driving and driving comfort--there's really no "one way fits all", wouldn't you agree. Andy, you make a very good point suggesting how driring style greatly affects tire durability. You gave one example:

"Driving style is also a great tyre saver as well, if you are always using your right foot to brake and accelerate heavily, well no tyre, no matter how inflated, is going to last very long!!!"

In similar vein, and from personal experience (observing others not myself), I would offer that a major "enemy" of tyre tread is power steering...in that, because most folks (and probably all females) today never encountered unassisted steering, it is not understood the degree to which hydraulically forcing a non-rolling (steering) tyre to turn under the static weight of a car will not only turn the tire but also grind off tread against the pavement quite rapidly, especially in urban cars where frequent parking/backing maneouvers are required. In a large country such as the US where larger, heavier cars have been favored, the derogatory effect of inept application of powered steering becomes even worse. Personally, I always drive a car as if unpowered steering...which is to say, I never force wheels to turn without the car rolling forward of backward. The result: long tyre life between replacement; almost no treadwear differential between front (steered/driven) tyres and rear (driven) tyres. This along with inflation maintenance I would say give the best assurance of long tyre life.

I do the same, I guess its because of that my first 10 cars or so did not have power steering, the habit has stayed......

Any one who runs radial tyres at less than about 30psi needs their head read. The carcass moves about too much, resulting in heat buildup. This can reduce the grip. Radials have little rigidity in the sidewalls, infact, early veith radials had a 2 ply sidewall. This flexibility, combines with a comparatively rigid under tread belt, can allow the tread at the contact patch to be displaced laterally to an extent that the sidewalls are distorted to the extreme. NEVER run radials at less that 30psi.

The late Peter Brock, an Aussie touring car driver and manufacturer of HSV modified Holden Commadore tried a crystal filled box called the Polariser in 1987. The Polariser did nothing and repeated tests with the tyres at the recommended 18psi showed reduced wear, grip, handling, braking and even acceleration compared to the same vehicle with the same tyres pressured to 30, 32 34 & 36 psi. 36 psi produced the best performance with marginal degradation of ride comfort.

I repeat, for safety and wear, DO NOT run radials at less that 30 psi. Not my recommendations re chalk lines and thermometers.

With all due respect, you are not correct. A manufacturer may specify 26 psi and THIS will accelerate wear, increase heat etc. By increasing pressures to ate least 30psi (for radials) there is no downside except comfort (maybe). Handling, roadholding, braking, cornering power and wear are all INCREASED with pressure. Obviously you haven't tried increasing pressures or have suffered a crook alignment.

Read my answers on this subject, ask a tyre expert or talk to a race car driver. Then come back and say I'm wrong.