My Tire Hyper-Inflation Story... What's Yours?

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Originally Posted By: Astro14
Here's my recommendation: determine the pressure and then check it cold, at least monthly, to account for leakage and variations in pressure based on seasonal temperature changes...that way, you will always be at/near optimum, instead of way off most of the time. Futher, if you pick up a nail or develop a slow leak, you will catch it before your handling and safety are affected.

And yes, running 38 PSI (sidewall max, 51, manufacturer placard recommended max 38) in the 235/45R17 Fuzion ZRi tires on my T5 Volvo, I wore out the center of the tread before the edges. A difference of nearly 2/32" in tread wear from center to edge. Clearly too high a pressure for my conditions. I now run 36 PSI in the 235/45R17 Conti DWS and they are wearing evenly with 8,000 miles on them...giving me the optimum blend of treadwear, handling and economy (I get EPA or better in the car...if I can resist using all the boost the turbo offers...).

Taking the purchase price of tires into consideration ($500 mounted and balanced), the life that the Fuzions lasted (30K) and the original tread depth (10/32)...the uneven treadwear cut about 20% of the life off the Fuzions...costing me over $100 in premature wear. That alone is enough to make checking frequently a worthwhile maintenance practice...and a tread depth gauge is about $5, while a good pressure gauge is $10...a cheap investment.

For the record, on an airplane, where tires go from -65 degrees C and zero MPH to nearly 200 MPH with several tons of loading in thousandths of a second (and can easily heat up to over 300 degrees C during braking), several orders of magnitude greater strain in load, temperature and speed than car tires, I check the pressure on every flight.


Another Great Story Astro14...

Sorry to hear about the premature wear of your tires.
Did/Do you check your tread depth on a regular basis?
Did you notice any handling issues while traveling overinflated?
Please be careful using all that boost that your turbo has to offer.
(I heard it can become addictive, not to mention unsafe)

Once again Thanks, Jim

PS When I was in the Air Force, We had people for that.
I mean, come on, Making a Pilot check his own tire pressure.
Navy Life is tough...
Oh, and Thanks for your Service for Our Country.
 
Originally Posted By: Astro14
I think this one is very different. For the oil change intervals, the only risk is premature engine failure...the risk of your experimentation is limited to your wallet. Science, analysis and experience can help you avoid that risk...but in the end, a worn engine is a risk limited to the experimenter.

For tire pressure, however, the risk of failure is a loss of vehicle control. That risk is borne by those with whom you share a public road. Engaging in risky practices where vehicle control is concerned is not the same as risking the longevity of your engine.

As an example, what if I wanted to determine the ultimate longevity of tie rod ends by driving my car past the point where I knew they were worn, until they failed? When one finally broke, I would lose control. When I crashed into somebody/something, that person would have every right to sue me for negligence...for knowingly engaging in a practice that subjected them to the excess risk.

I do not accept that anyone has the right to subject others to excess risk...and the law does not accept it either....



I only used the Oil Change Interval analogy as an example of how old thinking is still out there on this topic also.

Stupidity, and carefully measuring different psi volumes in your tires are two separate things. Please do not take offense at what I have just said. It is merely the way this Old Man speaks sometimes.

Good Luck with your new tires, and keep us posted on how they work out for you.

Jim
 
Originally Posted By: dsr70
There is a hefty margin in max inflation pressure ratings. Immediately post the Firestone-Explorer blowout rollover case in the '90s, max inflation pressures were bumped up 10% on a wide range of Michelin truck tires. I remember getting a set with a now 110 psi max and was incredulous, as the max was 100 psi just a few weeks before. Research and confirmation from my shops owner revealed the truth.

Bottom line: max pressure limits are conservative. We are long past the era when engineering decided the spec'd limits on physical items in our society. Now it is overwhelmingly the legal dept that decides. Very sad not to be able to trust the specs.


Perhaps you are confused about the change in pressures. There has been an evolutionary sets of tire specs in truck tires that require more inflation pressure, but take less space to package.

For example, if you change from an old style 11R22.5 Load Range G which has a load carrying capacity of 6175# at 105 psi, to a new style 295/75R22.5 Load Range G which has a load carrying capacity of 6175# at 110 psi, you would need 5 more psi to carry the same load. These tires would be used in the same application.

But both of these tire sizes have had the same pressure specs since they were introduced. Oh, and both of these sizes predate the Explorer incident.
 
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Jim - in answer to your questions:

I do check the tread depth at rotation (as well as checking for damage). So, once every 5-8,000 miles (depending on which car we're talking about). Tires wear so slowly that it's not worth doing more frequently. I do it mainly to determine wear and tread remaining.

I check the pressure monthly, before a road trip, or if the weather has changed considerably (in round numbers, PV=nRT, yields one PSI change for 10 degrees Fahrenheit...so a 30 degree temp change is a big difference in cold inflation measurement...)

I did not over-inflate the tires, they were run at manufacturer placard recommendation for max load of 38 PSI (as opposed to unloaded, which was 29 PSI, or sidewall max, which was 51 PSI). But this is a relatively low profile tire (235/45R17) on a car designed to corner (I know, I know, stop laughing...Volvo really did make a wagon that corners well...) so the optimum handling occured at well below the max pressure for the tires.

Overall, I did not like the Fuzion ZRi tires - they were installed by the PO. They handled very well (at 32 - 38 PSI, the range in which I tried them), but were very noisy and somewhat harsh riding regardless of inflation pressure. It is possible that some of the uneven wear I experienced was caused by the PO. I didn't notice the different depth across the tread until after the tires were rotated twice (now, I check...)...and I was glad to replace them. The new Conti DWS are far superior in ride, noise and wet performance...while still about the same in dry.

My experience with lower profile tires is that they generate far smaller slip angles and have much more stable contact patches at a given inflation pressure than higher profile tires. They are also harder riding and less forgiving. The nearly identical chassis of the XC-70 allows for a good comparison, as the steering response on the XC-70 (215/65R16 tires) is much softer, with greater slip angle and lower cornering limt than the T-5. There is a bit more body roll in the XC - a function of different ride height and swaybar stiffness.

USN vs. USAF is an interesting comparison in philosophies...without getting into a "this service is better than that service" comparison, the Carrier is an extreme operating environment...very, very different than any other...so, practices evolve differently than in shore-based aviation units that have more people, more space, and gentler conditions...

Cheers,
Astro
 
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Astro14,

Thanks for the further clarification.

I have served in two separate branches of the service. None are better. Just different. Just like the People that serve.

Thanks and Take Care, Jim
 
a buddy of mine works at a Walmart TLE, says a Honda Civic came into the shop with 70 PSI in all 4 tires! and no, these weren't "low profile" either.....just standard OEM tires.....lol. Sure, maybe the tires "heated up" a bit on the travel to the TLE, but I don't think they go from even 60-70 PSI in a typical "drive"
smile.gif



Obviously they lowered them to the factory specs (believe it was 36 psi) and the young girl said she was doing it for "hyper miling" lol.
 
Originally Posted By: ahoier
a buddy of mine works at a Walmart TLE, says a Honda Civic came into the shop with 70 PSI in all 4 tires! and no, these weren't "low profile" either.....just standard OEM tires.....lol. Sure, maybe the tires "heated up" a bit on the travel to the TLE, but I don't think they go from even 60-70 PSI in a typical "drive"
smile.gif



Obviously they lowered them to the factory specs (believe it was 36 psi) and the young girl said she was doing it for "hyper miling" lol.


It's insanity. 70 psi on a very hot day while hitting a sharp expansion joint or similar road imperfection greatly increases the chance of a dangerous tire blowout and failure.
 
Originally Posted By: Drew99GT
Originally Posted By: AstroTurf

Wet weather traction has not suffered.
I am not traveling on the center of the tire tread.
My tire operating temperatures are reduced.
My tire impact/ride comfort has not suffered.


Got any objective test results to back that up?


I am with you 100% Drew.

Astroturf, I am not picking on you, but on your statements...so let's look at them:

Wet weather traction? Not tested.
Not traveling on the center of the tread? Not enough mileage to see the wear occur (and it will eventually, I have seen it in several car/tire combos...)
Tire operating temperatures reduced? Really? Since it's not measured (got a pyrometer?) how would you know?
Tire impact/ride comfort? They're not the same. Tire impact hasn't been tested. Ride comfort is subjective.

You have not driven enough to see the tread wear. I am giving you the benefit of the doubt that you did see a mileage increase that was not caused by different factors (weather, road/traffic conditions, fuel quality). So, all of the purported "benefits" of grossly exceeding the tire's limit are subjective and anecdotal save one, you will likely reduce rolling resistance and improve your mileage to some degree (in this case by 5%).

The dangers, however, are real.

I know, and can absolutely prove, than I can improve my gas mileage by over 20% just by driving 5 feet off the bumper of a semi-truck on the highway.

That doesn't make it a smart idea...
 
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Astro14,

How are you? No offense taken. I like to reveal to others what I have done.

Wet weather traction has been tested.
Tire heat reduction can be tested by anyone with a 30 - 50 mile test loop and two mornings at different psi.
Wish I had a pyrometer, thinking of getting a lazer one for now.
But I do think that 70 psi might be a bit much.
As far as center tread wear, I will post up a couple pix of the tires I just took off, and let all see the center wear that they had.

Ya'll Judge as best you can thru this forum, difficult I know.

But, If any leave this table better than when they came, That'll be great.

Small measured steps, different for everyone. Not recommended by me, just My Tire Hyper-Inflation Story.

Jim
 
Personal experience with mildly increased inflation:

2-3 PSI over placard gives me better handling and acceleration response (butt dyno) with harsher ride.

5-7 PSI over placard for about 2 years lead to internal cord separation on all 4 tires, 1 after the other. Tire would get really out of balance and then just leaked on the highway, but not blowout. Still the tire sidewalls were destroyed and it was not something I'd like to repeat. To be fair I commuted between extreme temperature daily (San Francisco and Livermore) and was driving 90mph with a car full of passenger, so the stress / fatigue wear the tires out before the trends are down. It is still well within the sidewall max (36psi vs 44psi) but that doesn't means the increased pressure didn't increase the stress.

I reduce the over inflation down to 3psi over placard and all is perfect.
 
Originally Posted By: PandaBear
Personal experience with mildly increased inflation:

2-3 PSI over placard gives me better handling and acceleration response (butt dyno) with harsher ride.

5-7 PSI over placard for about 2 years lead to internal cord separation on all 4 tires, 1 after the other. Tire would get really out of balance and then just leaked on the highway, but not blowout. Still the tire sidewalls were destroyed and it was not something I'd like to repeat. To be fair I commuted between extreme temperature daily (San Francisco and Livermore) and was driving 90mph with a car full of passenger, so the stress / fatigue wear the tires out before the trends are down. It is still well within the sidewall max (36psi vs 44psi) but that doesn't means the increased pressure didn't increase the stress.

I reduce the over inflation down to 3psi over placard and all is perfect.


Good Story.

Glad it worked out. I was about 3 psi over placard in the first set of tires purchased for my vehicle. Anything higher, and it felt like I was riding on cider blocks.

Again, Thanks for sharing, Jim
 
Originally Posted By: AstroTurf
Astro14,

How are you? No offense taken. I like to reveal to others what I have done.

Wet weather traction has been tested.
Tire heat reduction can be tested by anyone with a 30 - 50 mile test loop and two mornings at different psi.
Wish I had a pyrometer, thinking of getting a lazer one for now.
But I do think that 70 psi might be a bit much.
As far as center tread wear, I will post up a couple pix of the tires I just took off, and let all see the center wear that they had.

Ya'll Judge as best you can thru this forum, difficult I know.

But, If any leave this table better than when they came, That'll be great.

Small measured steps, different for everyone. Not recommended by me, just My Tire Hyper-Inflation Story.

Jim


Jim,

I appreciate the application of the scientific method: systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses...but I don't think that the "butt-dyno" is sufficiently accurate or precise to measure most of what you're trying to test...including wet braking performance. Further, how can you measure temperature without a pyrometer? Once you do measure temperature, your loop doesn't control for weather, load and traffic, among other variables that affect the experiment (temperature) outcome.

If the tires of which you're posting pictures have not been run at the hyper-inflation for more than a few thousand miles, you won't get the abnormal tread wear, and you've only admitted to a few thousand miles of this experiment. You can't "see" the actual loading on each portion of the tread, only the carcase shape. But over time, the wear pattern will reveal the loading as the higher loaded portions wear more quickly. So, without long operation at that pressure, that's not a valid observation.

Tire Rack has done a lot of testing on tires, and published the results: here is one example, showing that underinflation reduces hydroplaning resisitance: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=3 and, in fact, that is true in airplanes as well, where inflation pressure affects hydroplaning (more of a big deal in airplanes because of higher speeds and the load carried by the wing on landing...). But while increased pressure may increase resistance to hydroplaning, it does not necessarily increase wet braking, which is the result of interaction between road surface and tire, because increased pressure reduces that interaction. Without dedicated testing, controlling for all the other variables, you simply can't conclude that on the basis of feel.

Here is a great example of controlled testing, in which they proved that tread depth below 4/32" reduces wet braking traction: http://www.tirerack.com/tires/tests/testDisplay.jsp?ttid=85 In fact - tires at 2/32" (legal minimum) had DOUBLE THE STOPPING DISTANCE vs. the same tires with 4/32" tread depth. You can watch the video, or read the whole report from the link.

That one changed my thinking...and now, I change my tires before the legal minimum, particularly on my wife and kid's cars.

Tire Rack, in fact, has a whole tech article on increasing inflation pressure for higher speeds: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=72 but it includes this important note below the adjustment table:

NOTES: Never exceed the maximum cold inflation pressure branded on the tire's sidewall

There are safety and engineering reasons for that warning...and that's what Capri Racer and others have been saying all along, you can start with the vehicle placard pressure, and adjust up to suit your needs, but NEVER exceed the sidewall pressure...

Cheers,
Astro
 
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Originally Posted By: AstroTurf
PS I like this little safety slogan that I created years ago, for my then current employer...

Safety is, as Safety does.


That's deep, Forrest.
 
Seems like the old ones aren't that bald and should last another 5-10k, 3-4/32 left? I'm riding on something similar and everyone is telling me to throw it out or it is endangering public safety, refusing to flip them, etc.
 
PandaBear,

You are Right. The pictured tires, One was the spare had better than 4/32s, and the other was one of the 4 on the van was about 3/32s.

I like to operate as safely as possible, and had begun my selection of another set of tires. This set happened along at a time and place that I could not pass up.

This was really a Great Tire that I enjoyed very much. It wore very evenly, and was unstoppable in the snow.

Thanks, Jim
 
I'd have ditched those tyres too, I think it a good call, having been a passenger in an R-16 on 155 wide cookie cutters with a similar profile that somehow decided to hydroplane into oncoming traffic...michelins had similar treat pattern also.

In my experience, an average tread depth is less predictable than an even tread depth.

Oz changed the rules from average (match heads) to tread bar ages ago...there was much debate that the closed tread bars reduced water shedding, and became a self fulfilling prophecy.

Personal tyre pressures ?

My vehicles have a high load (ute), and high speed (Caprice) tyre placard rating, and I run them both on their highest sticker rating...have done similar for 25 years...never know when you need the load, or the unexpected 800km trip.
 
Jim - Those Nokian WR G2 are great tires...not cheap...but neither are the Michelins that replaced them.

I am with you 100% on the replacement strategy. Tire Rack's testing shows significant degradation in wet performance below 4/32" tread depth...see my post above...I have about 8,000 miles on the Nokian WR G2s on my wife's XC, they're at 9/32" - how long did yours last on the van?

I can't really tell how they've worn from an internet picture though...I mean, they look OK, but that's pictures. My point still stands, if you did the hyperinflation for only a few thousand miles, you won't see any abnormal wear....

I would hate to see those new Michelins (great choice by the way) worn out prematurely from being over-inflated. At, what, $700-800 for the set mounted and balanced? the cost of replacing them early would negate much of your fuel savings...
 
On the XC, with 215/65R16, for example, placard is 29/29 for light load. 35/38 for full load.

35/35 gives me a good balance of mileage, handling, ride and yields even tread wear. Max on the sidewall is 50 or so...

Same on the T5, with 235/45R17s...placard 29/29 up to 35/38 - and I've found that running 38/38 gave me too much center wear - 36/36 seems to be working about right - good for all conditions...though, if I ever track the car, I would go up from there...
 
Shannow,

We are in total agreement on the wear bars reducing the tires ability to shed water. The Nanny State is Worldwide.
Do your vehicles have two different pressure suggestions? My Wife's Honda had the same.
I like the fact that you have found a standard, and have stuck with it. 25 years, Bravo!!!
Consistency always bears out true results. Whether good or bad.
Keep up the Good Work.

Jim
 
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