hyper inflation: let's cut to the chase
 

I just burned up about 4 hours of my life trying to sort the facts from the fiction in this thread and other related sites and threads concerning putting more than the placard recommended tire pressure (NOT SIDEWALL MAX) in your tires.

The gist of what I got is this

1. tires are safe to sidewall pressure. But past 44 psi your valve stem might leak pressure.

2. a tire pressurized to max sidewall will likely last longer and not deteriorate at all compared to a tire at OEM recommended pressure for your car (usually 32 psi) but people who sell tires would rather you don't know that.

3. tire mfg companies are in bed with petroleum companies because they both rely on the same raw material. So why would a tire company give you a cheap and easy way to cut into their profits as well as the profits of their partners in the petroleum industry?

4. If I inflate my 50 psi max inflation tires to 50 psi, I should expect a bit more slipping under low traction situations (snow, ice, dirt, rain). But if I'm hypermiling, I wouldn't be pushing that envelope anyway, would I?

5. radial tires will NOT wear out in the middle more than the sides due to inflation to max sidewall psi. Tires on the rear of rear wheel drive vehicles will do this, but due to it being rear wheel drive, not inflation pressure. Front wheel drive tires will likely wear evenly on the front, while the rear tires will harldy wear at all. This also comes from personal experience as a recovering lead foot with many a mile behind me.

6. Don't buy cheap, Korean, or Chinese tires. They have higher failure rates.

The ONE official article I found (and can't find again) indicated that a radial tire will not blow up until it gets to 150 psi, and even then it would require high speed antics to finish the job. So a 50 psi tire set to 50 psi is as safe as you can get. a 44 psi tire to 50 psi is still likely very safe. a 32 psi tire to 50? Meh, you should spend more money on tires mate!

There is much discussion concerning how race car tires deteriorate in these threads. PLEASE, for the love of all things holy, RACE CAR TIRES ARE NOTHING LIKE PASSENGER VEHICLE TIRES!!!!!!!!!!! They use different rubber, different tread (or lack thereof) and are designed with different life expectancies. So there is no comparison. If you drive a car like it's a race car, expect your treadlife to diminish. But having your pressure at sidewall max isn't going to change much. If anything, underinflation is the anti christ, while max sidewall psi is an innocent baby.

While I don't have any technical data to back up these claims, reading as much as I have concerning tires and applying logic to the missing bits, I believe this rant is as balanced a viewpoint as I've seen yet. Put your tires to max sidewall, drive like you want to squeeze every last foot from each drop of petrol, and you'll be fine. But endless debate is only going to confuse the uninitiated. So if you have something to say contrary to this bit of common sense, prepare to prove it immediately!!!!

couple of thoughts:
I have run Kuhmos 255/45/18 Exsta asx on my Infiniti Q45 since 58,000 miles. I now have 195,000. I have never had a problem caused by a poor quality tire. They balance perfectly and I rotate every 5k. I get 40k+ a set. They are also quite.

I think that for true (I don't give a crap about anything but that last 1/10 of a gallon) hypermiling you can pump it up to 90psi.....who cares...the car will drive like and ride like crap. Frankly for real world around town driving 39-44 is just as good. At somepoint your are driving with bricks for tires and the wear on the suspension parts just can't justify the very little gain in mpg. Now if your asbout to hit the highway for the next 4-10 hours.....higher psi might be justified.

But hey, don't mind me......... I was told by someone on this furom that ecomodding a Q45 made me an 'obvious Ugly American' and I should do my part and buy a pos micro,sub-mini-compact w/ no a/c and get rid of the Q.

yeah.....right.......

Don't forget about Nitrogen. They use it in airplanes. That means you really need it.

There is a lot of contradictory information concerning inflation pressure. But rather than go through it all, allow me to select a single subject and present the other side. It's not that this is the only thing that I could take issue with. It's that this is just one that suits me at the moment:

This implies that the tire manufacturers are deliberately under-estimating that load carrying capacity vs inflation pressure characteristics.

Here’s a page from the Tire and Rim Association Yearbook that shows the design standard for some passenger car tires:

http://www.barrystiretech.com/2005traloadtablesmall.jpg

Here it is full size:

http://www.barrystiretech.com/2005traloadtable.jpg

Notice that the pressure operating range is 26 psi to 35 psi.

Vehicle engineers use this book to select the tire size and the pressure that will carry the load of the vehicle, plus a bit more (good engineering practice). They are required by law to put this information on a sticker on every vehicle they make. This means there are going to be severe consequences when they get this wrong - as the recent Explorer controversy demonstrates.

Tire manufacturers, on the other hand, want to produced the least expensive tire that gets the job done - and since they are designing to the same table......

So it becomes a coincidence, rather than a conspiracy, that passenger car tires will burst at pressures well above the maximum sidewall pressure. There must be something else that causes this - and that something is fatigue.

At this point, I could go into a long discussion about fatigue and how it applies to tires, but I don't want to get too far off Point #3. You can look up fatigue on Wikipedia to see where the discussion would go.

There seems to be a point of diminishing efficiency returns on PSI, nobody is advocating 90 PSI that I know of, more like 45-55psi. Lets make sure we keep that much straight.

I'm not wild about the term "hyperinflation" either.

I just think hyperinflation sounds funny myself :D

I agree, 90 psi is crazy hard, and you'd have to replace the whole car after it rattled itself to death. But going to max sidewall ought to be the closest thing to a compromise between OEM over cautiousness and hypermiling lunacy. I've ridden in a truck with tires pressurized to 80 psi, and it's unpleasant to say the least.

So according to that chart, no passenger tire manufacturer even thinks about finding out how a 50 psi tire inflated to 50 psi handles itself? And while I don't think there's a blatant conspiracy going on in the petroleum industry, I suspect the bean counters quietly dismiss anything that could lead to a loss in the quarterly earnings. If I were an executive of a tire company, i would likely do similar things to make sure i still sold a lot of tires. Heck, I'd sponsor tire burnout competitions. But to say that a tire manufacturer doesn't keep certain information to itself (such as longivety of tires at sidewall pressure, and how high they can go without blowing up) would be counter to common sense and ignorant of the issues of capitalism. (No, I'm no proponent of socialism, just there are occasionally bad sides to everything.) And why wouldn't a tire company allow and encourage the myth that tires past the placard pressure are dangerous?

There is simply a lack of evidence that 50 psi in a 50 psi rated tire is a bad thing.

I hope you realize that these so called 50 psi tires could have been labeled 35 psi tires. That's because of the "notes on page 1-34".

I discuss that about 1/3 of the way down:

Barry's Tire Tech

The 50 psi is a permissble usage - and it should be obvious that the intended use for this pressure is high speed operations - and when tires are tested to those conditions, it is in the context of high speed operation.

But when vehicle manufacturers are specifying inflation pressures, they are in the range of 26 to 35 psi - at least in the US. In that context,it doesn't make a lot of sense to test outside that range - particularly given that this is the design standard and not some usage table.

I thought we decided hyperinflation would be used only for ridiculous pressures like 90 psi, or do you still have a problem with it in that context?

that's fine, but not what shadetree meant, based on his sidewall max observations.

I also don't put me running 35 psi tires at 45 in the hyper category, since the 35 psi figure is so conservative to start with.

so there is some grey area certainly, but I would put 90 psi on a ~3000 lb car in the hyper category. and ~50 psi in the higher pressure category.

Main issue IMHO is john Q will think of tires as perfect balloon analogies where more psi will be bad, and anything with the term hyper is reckless.

That Tire and Rim Association paper lists the MINIMUM pressures for each load. MINIMUM. Then in a note on the very next page it states this:

In other words up to max sidewall is perfectly safe. Black and White from the Tire and Rim Association.

I found a report by the NHTSA that in pat concerns tire pressures related to braking distance. While the maximum pressure is 35 psi, there is generally a trend for higher pressures to DECREASE braking distance.

Happy reading.

Is there any manufaturers of passenger vehicles that recommends higher than 35 psi? What about vehicle manufactured for overseas markets? Since many of those cars are extremely similar, we maybe could learn a thing or 2

I have only anecdotal evidence, but that evidence is available to review in the Garage. I have over 39,000 hypermiles between my two cars--with some 44 psi tires pumped to 51 psi and some 51 psi tires pumped up to 51 psi. I've now replaced four of those tires, and all four had perfectly even wear. This is in mountain and freeway driving, in the dry, rain and snow, and from 20 degrees F to 105 degrees F. I've had zero tire failures.

I recently picked up a pair of used 44 psi tires for the Clunker because of finances. They have a lot of tread left, but one was patched because of a nail. Those I keep at 40-42 psi to be safe.

Found another interesting site. Did a search for ford mondeo (contour in the US) tyre inflation pressures and got this page. It lists seperate tire pressures according to whether it is loaded or not. Go figure, the pressures often go well over 35 psi!

Nearly all these cars are available in the US in very similar form, yet why the more informative chart for the UK? Is there the assumption americans are too thick to understand a simple chart?

Sorry, but if you'll read it again you'll see that it says the load limit for various inflation pressures. I think that means for a given inflation pressure, that's the maximum load carrying capacity.

I have found only found 2 situations where the inflation pressure for a passenger car is specified by a vehicle manufacturer over 35 psi (36 in metric units).

1) Extra Load tires

2) European cars, particularly German cars, where they have dual inflation pressure specs and the one over 35 psi is for max load / high speed (I think you found one of those). Obviously they are considering the Autobahn. When these cars come to the US, sometimes the pressure spec changes, sometimes not.

Two ways of saying the exactly the same thing. Maximum load for a given pressure has exactly the same practical meaning as minimum pressure for a given load. The chart then has the note that the tire engineer can increase the pressure up to max psi without increasing the load and this difference is what the engineer has to work with when determining recommended pressure. ie, NVH vs performance, which usually means leaning towards soft and squishy so john Q public does not feel or hear the road.

Please note they call it recommended pressure not required pressure, or some such, because there is no safety issue in going above the recommended pressure. If there was you can bet the NSHTA would have long ago had a placard with that in big bold letters. In fact it could well be that higher than recommended pressure is safer as it gives more crisp steering response and better cornering traction. We already know for a fact that higher pressure means better hydroplaning resistance.

While this may be similar, it's not exactly the same thing. I'll explain that below.

It's the vehicle engineer, not the tire engineer that selects the tire size and the inflation pressure.

The vehicle engineer uses the table, knowing the load that the tire must endure, to select a tire size and inflation pressure combination that not only will carry the load - and knowing that over specifying that combination, a lesson emphasized by the recent Ford /Firestone controversy a few year back - but also have some over-capacity. How he does this depends on the design standards for each vehicle manufacturer. Notice that almost without exception, the pressure specified on the vehicle tire placard is not above 35 psi - and this would include the over capacity (in the form of over-specifying the pressure).

On the other hand, the tire engineer is designing the tire to the table without regard to over specifying by the vehicle engineer. I had a college professor cal this "Over-design / Under-utilize".

The tire engineer generally picks the 35 psi load - for passenger car tires - and uses 35 psi as the test condition.

NVH - for a tire engineer's perspective - is about tread generated noise, since most ride vibration are about "roundness" (a manufacturing issue), and ride quality is more or less controlled by the inflation pressure (which requires a vehicle for testing).

I'm going to call what is written on the vehicle tire placard a specification - which it is - much like oil viscosity and bolt torque are specified.

That's kind of a weak arguement because look how long it took for NHTSA to deal with the issue of inflation pressure BELOW the placard. There weren't any bold letters for that and that was a known quantity for decades. Besides, there isn't a lot of information about what happens in the real world when tires are inflated above the vehicle tire placard - mostly because actual usage inflation pressure information is rarely available from accidents statistics - which is what NHTSA is using to drive what they look at.

Hey..that goes along with an old sube. if it works in an airplane...

the air stuff is simple, max it till its uncomfortbale, you maxxed the tire then for your location.
Yesterday, I puffed back up to 40psi...frosty morning today, now the green leafed
60s of spring approaching mid day. That is as complicated as a tire gets.

the night before the big canuckian sink hole, my tires pounced 3 of my 4 tires to 20psi...and they are the best treads I have ever encountered (nokian 1). My car does this with micronical resonance.. it is hardly a mystery. If the car was squishy failing wiggling (ya know OEM).. the treads would go along for the ride. But no. I am crazy about squeaks creaks rattles moans and groans and a false impression that a car is tough. I welded till it was...by my own standard...and that has expenses. It needs tough everything now. :rolleyes:

The chinese stuff is not true, even my dad goes for those on his rig. I am in rally crazy mig welder realm, so I seek tires from people who give a *hit about making them. CXhinese does have its benefits... remember, they are forced to pass world standards. they cannot get away with much anymore...unless we speak of electronics..but that is another subject.

It's safe to over-inflate, as long as you don't take it to extremes.

Typically my tires are rated at either 28 or 32 PSI and I inflate to about 35. With any more than that the ride becomes too harsh for our bumpy roads.

There are two drawbacks to over-inflation: one is the ride, which will be harder, the more the tires are over-inflated. (If you don't live in pothole land, this may not bother you.) The other is that the car may not handle properly. About 15 years ago I bought a used '89 Celica. The car was very well maintained, but after owning it a few days I noticed the handling was weird; mechanical checks showed nothing wrong. Within the first month I checked the tire pressures and found they were inflated to around 45 PSI. I reduced the pressure to about 35 and then the car handled perfectly. (And I kept the car happily for the next 16 years.)

I know that everyones mind is already made up on this issue already, but I'm going to add my personal experience as well. I have read a lot of claims that running tires at max. pressure or a little higher will not increase tire wear and may reduce it. My experience is just the opposite. I have never had a tire wear the outside edges off from running too soft. I have however had 2 sets of tires wear out in the center on my '93 villager at only 35psi. My work van was wearing the centers out running at recommended tire pressure. I am currently running them 10psi low and getting more even wear. My son put oversize tires on his Ranger and experienced severe center rib wear after only 10k miles at 35psi. I have also seen lots of other cars around with noticeable center rib wear. My Rondo is wearing the inside edges off the tires but that is because of excessive negative camber in the design. I have been running the tires at 40-45psi to help compensate but the ride is terrible, the fuel savings is minimal and I am worried the higher pressure may even be adding to the problem because of less sidewall deflection. I'm sure cars with small, narrow tires will benefit from running a little higher pressure, but many cars today have much larger and wider tires than they need to IMO. I just don't think that it's right to be making blanket statements like "max rated tire pressure is always best" or "will never increase tire wear". There are always exceptions.

Over-inflation may be debatable but under-inflation (by 10 pounds?!) is NOT a good idea. You will not find anyone advocating it.

Generally I would agree with you Thymeclock. I wouldn't recommend it or thought it necessary, but it works for this application. (maybe only this one) I drive a 3500 Savanna van for work that calls for 80psi rear and 65psi front. I simply don't have enough weight in this van to require these pressures and reducing the pressure has not hurt the mileage. Keep in mind that mileage is a non issue for me with this van and it's always bad anyway. The point that I was trying to make is that the ideal tire pressure for max. tire wear and longevity is not ALWAYS going to be max. sidewall pressure like many are saying. It may not be the pressure that gives the best FE either. Even tire wear is going to happen when the pressure is matched to the load on the tire so that all the tread has even contact with the ground. This may not give the best FE on a large tire. I have always run my tires a little over recommend psi on my cars (probably always will) and generally with good results. But, I think it's wrong to say that it will always make the tires last longer.

I have my tires at 54 PSI front and 52 rear. They're Yokohamas rated for 51 max cold.

EDIT: Those pressures are when warm. They're 51 cold on all 4.

I run them all at 50 right now... Once I get lighter rims and put my tires on them, and get heavy duty valve stems, 60-65 sounds better.

Keep in mind, I'm running LRC LT tires on my truck.

On the wife's Saturn, I run the tires at ~40PSI. They're "rated" for 35, I think.

I honestly believe the higher inflation pressure is the only reason I haven't had to change the front two, yet. They've still got about 2/32 on them, and the tire size isn't easy to come by used (in decent condition). I'm thinking about dropping her tire size to 185/65R15 instead of the 195/65s she has now, since those are easier to come by.

First off, I don't work for a tire company and I assure you I have nothing to gain by posting this. I'm a forklift tech running a service van. ( about 20k a year also and probably around 7000 lb) I'm running Nokian Vattiva E rates on my work van which are a very good tire and keep in mind I am still running 60-70psi in them. As for the mileage comment, my customers pay by the hour for my travel, not the mile and I'm not going to hypermile on their $ to save the company a little on gas. Believe me or don't, but it's my personal experience and it's the truth.

I went and checked my tires this morning. 51 PSI all around (sidewall max) and noticed some bubbles on 3 of them. Strangely, there's some going inward. The bubbles are small, but I'm still wondering if I should worry about them or not.

what is the sidewall rating on your tires? Sounds like the steel bands may be slipping. I've had that happen to me before, and the extreme end result is a weak spot in the sidewall that'll cause some shimmy in the short run and a blow out in the long run.

When you say bubbles, is that round bubbles, or enlongated ones?

Ditto on "sounds like belt damage"...
 

Irregularities in the sidewall surely means the internal structure has failed for some reason.

Hit and really bad potholes lately or any panic stops where you had locked up the tires?

I did that one nite at about 2am years ago in Rt 41 South in SC. Thought I was coming upto a fork I had to bear left on at about 70 mph, turns out it was a T-Bone and I locked all 4 wheels like the movies, stopped about 3 ft short of the stop sign and smoke from the tires engulfed the car. Made me chuckle at the time.
Over the next 2-3 months 3 of those tires failed. Belt separation.

One thing I do whenever I stop after driving long hwy distances is a run me hand of the tread surface to feel for high spots or hot spots. Gives great feedback on inflation and/or alignment. The warmest tires are always the ones with a slow leak or impending cord failure. But also the ones on the Sunny side of the car are hotter then the shady side!

Pete

I do my best to avoid potholes, but I regularly drive over railroad crossings. No panic stops.

They're the elongated bubbles. Also, by sidewall rating, do you mean load rating? If so, they're 91.

I should have got the road hazard warranty when I ordered them, even if it could be a defect in the tires.

what brand/model are they?
 

If it looks like belt separation you have a decent chance at "defect" pro-rated replacement.

I mentioned the brake lockup skid because up until I did that my tires were OK.

Back when I had my 91' Toyota 1/2 Ton PU I had Michelin LT's. Expensive but worth it.
One time a local tire dealer talked me into some passenger tires on it as it was "just a toyota pu". About 1 week into the new tires I cranked it into a right turn and almost went off the road. Dealer got reamed by corporate and I got full towards the LT's.

Pete

When did you install the tires on the car?

How much mileage is on them since they were installed?

Nitogen in the tires as in a Airplane, they also do that in Racecar tires ,it keeps the pressure the same even when the tires and inside air in them gets warmed up .

Im wondering about the "donut spare" the small spare tires that say Dont go over 45 on the side and they are good for 60 PSI , has anyone ever ran a set of 4 of these and seem how they handle and what kind of gas mileage improvment they provide? I have 5 or 6 15" donut spares I would like to try out but would like to hear some real life experiance with them Scott

They have about 2500 miles on them, installed a month and a half ago.

There's also 2 inward bubbles on my spare. Only ran 50 miles on it, and it's still at the original 35 PSI.

Curious what brand they were so we all can keep that in mind when hyper-inflating
 

Sorry to hear this happened on your new set of tires.

Well at 2500 miles I would hope you can get them replaced as defective.

Bought my Yokohama's from discount tire direct and right about now I am going to find and fill out that tire registration card I never sent in.

Also going to check my pressure a couple of hrs into my next long trip to confirm the warm/hot tire pressure.

Pete

AeroModder -

Can you post some pictures (does the black rubber make it hard to see)?

CarloSW2

They're very hard to see, and I really only found them by feel. I'll see what I can do, though.

hahaaha I wonder what we're putting in our tires anyway...I typically fill with about 75% nitrogen, 19% oxygen, plus a little water vapor, argon, and some other trace gases - helps the tires warm up faster that way - they're a bit flatter for the first 1/2 mile, then the tires warm up and the vapor expands, fully inflating the tires! :turtle:
Don't get why anyone would pay for what we have about 80% of anyway.

If they're inward dents, it could be where the sidewall belts are joined and overlapped, and not a problem. All 8 tires on my 2 vehicles have these - two depressions that run from the rim out to the tread (like spokes), about 6 inches apart from each other.

Outward bulges are bad.

http://www.tirerack.com/tires/tirete....jsp?techid=32

Some are inward, but there are a few outward ones:

http://i3.photobucket.com/albums/y93...ey/tire005.jpg

http://i3.photobucket.com/albums/y93...ey/tire006.jpg

After reading the link, these are definitely defective. The cords are very poorly lined.

PaleMelanesian -

I have the inward dents too. When I first saw this, I lowered the PSI, but they didn't go away, so I restored the PSI.

CarloSW2

AeroModder -

Ok, I have those too. I only noticed the inward ones, but I will look for the outward ones also. I think I have had them for the life of the tire, but I don't think I noticed them until maybe 10 or 20K miles. Because I already had so many miles on my tires, I (crossed my fingers and) didn't worry about them. I now have 60K miles on my tires. I will also post a picture when I get a chance.

I will also go looking at my wife's and other people's tires while I am at it.

CarloSW2