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

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Originally Posted By: Volvo_ST1
How does exceeding the maximum sanctioned tire pressure specs affect liability? I am not only talking about the loss of liability insurance, but also personal liability due to negligence.


I guess we would have to first establish...

What is The Maximum Sanctioned Tire Pressure. Do you know what it is?

Thanks, Jim
 
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First, the tire manufacturer puts a maximum pressure on the tire. The presumed and certain safety margin is really irrelevant from a legal perspective. The listed maximum pressure simply states the tire manufacturer does not accept liability claims from exceeding the listed pressure. Now, to whom falls liability, should you exceed the recommended limit? The tire manufacturer will say it's not on their responsibility.

Second, the car manufacturer lists tire pressure recommendations for a vehicle, based on tire size and on vehicle load. Should the operator not stick with the recommendations, do you believe the car manufacturer will accept liability for deviation from the suggested tire pressure, should a claim arise?

You can bet the farm that your insurance company will not want to be liable for the operators (perceived or real) negligence, if they have evidence that the operator grossly disregarded tire and car manufacturer guidelines. By "grossly" I mean exceeding recommendation not by merely a few psi. What constitutes "grossly" is certainly debatable and you may want to ask a lawyer.
 
Volvo_ST1,

I did a quick search and could not find any such lawsuits on Google.

Could you direct us? Or are you just thinking about a defense?

What is your Hyper Inflation Story?

Thanks, Jim
 
Originally Posted By: AstroTurf
Volvo_ST1,

I did a quick search and could not find any such lawsuits on Google.

Could you direct us? Or are you just thinking about a defense?

What is your Hyper Inflation Story?

Thanks, Jim


Your modus operandi of answering question with questions is getting old and rather obvious.

Why should I have to provide you with examples? Just call your insurance company and ask them. Also call your car manufacturer and ask them. Ask a lawyer. I have merely expressed my layman's thoughts and opinion regarding the issues into which you may run. Feel free to dismiss what I wrote. I don't care one way or the other what you do as long as it doesn't affect me. Rest assured, if you were to cause an accident in that I am involved, and if I were to find out about the questionable tire pressure you are running, I would most certainly bring that issue up for close examination.

I do not have a hyper-inflation story, because I have never exceeded the maximum allowed tire pressure stated by the car maker. I would never exceed the limit printed on the tire. Common sense tells me the figure is there for a reason. As previously pointed out, I don't care what the safety margin is.

I run higher pressure than suggested by the car maker for a partially loaded vehicle (gassed up, two people, some cargo), but I do not exceed the limit set for the fully loaded vehicle.
 
Originally Posted By: Volvo_ST1

I do not have a hyper-inflation story, because I have never exceeded the maximum allowed tire pressure stated by the car maker. I would never exceed the limit printed on the tire. Common sense tells me the figure is there for a reason. As previously pointed out, I don't care what the safety margin is.

I run higher pressure than suggested by the car maker for a partially loaded vehicle (gassed up, two people, some cargo), but I do not exceed the limit set for the fully loaded vehicle.


You can't have it both ways...

As you say in your Sig:
Should the rules serve us, or are we to serve the rules?

Thanks for sharing your Hyper Inflation Story, Jim
 
Originally Posted By: AstroTurf
Originally Posted By: Volvo_ST1

I do not have a hyper-inflation story, because I have never exceeded the maximum allowed tire pressure stated by the car maker. I would never exceed the limit printed on the tire. Common sense tells me the figure is there for a reason. As previously pointed out, I don't care what the safety margin is.

I run higher pressure than suggested by the car maker for a partially loaded vehicle (gassed up, two people, some cargo), but I do not exceed the limit set for the fully loaded vehicle.


You can't have it both ways...

As you say in your Sig:
Should the rules serve us, or are we to serve the rules?


The rules (regulations, recommendations, guidelines etc) are supposed to serve us. The guidelines you choose to ignore are in place to prevent laymen from tinkering with that which may affect safety.

I presume you can read, since you highlighted parts of what I posted. However, comprehension skills seem lacking. You should have highlighted the part where I said I have never exceeded the limit that is suggested for the fully loaded vehicle. The range of tire pressure for a particular vehicle has a lower and an upper limit, which denote the safe operational range per the car manufacturer.

It doesn't matter what opinions people here voice, since anything that is not in line with your thinking will be questioned. If you were really interested in anything other than placing yourself in the center of debate, you would ask your questions to the already mentioned sources: car and tire manufacturers, insurance companies, and lawyers.

Originally Posted By: AstroTurf
Thanks for sharing your Hyper Inflation Story, Jim

Thanks for twisting what I posted.

Please stop calling me Jim.

Thanks,
-Volvo
 
Originally Posted By: AstroTurf
Thanks Again for your Story, Jim

PS How was that? Better?


You are still calling me Jim. I do love the random caps, though.
48.gif
 
Well Alrighty Then...

Who's next?

Step right up, and tell us what you did, how you did it, and what kind of results you've had.

Thanks, Jim

PS Don't mind the Doom & Gloomers... We have always had em, and always will.
 
Come on, AstroSmurf, answer a question. Why don't you get your answers regarding the legal implications regarding hyper-inflation and you being a test pilot on public roads straight from the horses' mouth? The horses being the car maker, the tire maker, possibly the DOT, and an auto accident attorney?
 
Originally Posted By: AstroTurf
Capri Racer,

2) An under inflated tire runs hotter, and an overinflated tire runs cooler. So, once again, I started with placard pressure and drove a test loop. Measuring the psi and ambient temps both before and after the test loop. I found that as I increased the tires cold psi, that the tires hot psi increases began to fall. When I reached the point of a drop off in vehicle control. I stopped the psi increases and reverted to the last satisfactory test loop scenario.

I hope this answers your questions, Jim


The above is correct observation, and I guess the tyre you use is having soft sidewall that is why you never encountered uncomfortable ride before traction suffer. That is why the best test should include tyre surface temperature, because when it rains/in cold weather, too high pressure may cause insufficient tread temperature to offer best traction even though the ride quality is ok.

However, if you find the best psi is higher than the one written on the sidewall, I wonder whether at the first place you use correct tyre size and load index. I don't find a norm that different tyre construction give so much difference until you exceed the recommended tyre psi recommended on the sidewall, except the tyre comes with too small load capacity(load index) or you use passenger car tyre on SUV/light truck(which why they recommend to reduce the capacity calculation to 90%) due to higher variation on load due to heavier vehicle weight or too soft of sidewall design/too firm suspension spring rate)
 
Originally Posted By: AstroTurf
My name is Jim. I am not a special person. Just a simple man searching for the best bang for my buck.

On April 25th, I put to rest a set of Nokian WR G2 SUV 215/70 16 tires. They served me well for 64,500 miles. They stood tall at about 41psi throughout their lifetime. I replaced them with a set of Michelin LTX MS 215/70 16.

These were placed on my 2005 Chevrolet Astro 8 passenger van. It has been converted/used for work. It's psi placard calls for this size tire and a psi of 38.

Upon the first day of travels at 38psi, I found the van to be very sloppy. On the second day of operation, I began to measure, monitor, and modify the cold psi as well as the hot operating psi.

Within the first 9 days of operation, I conducted at least 27 recorded psi/temp/time measurements. I also decided on the best cold psi for my van/tire combo. I traveled 600 miles during those 9 days, and my average mpg was 17.3.

During the next/last 30 days of operation at my new cold psi standard, I have traveled over 3,100 miles, achieved an average of 18.4 mpg, and recorded another 60 psi/temp/time measurements.

I will say in closing that...
I am very happy with my results.
This is not for those not willing to put in the work, measurements, and monitoring required to make safe decisions.
I have done this with my past sets of tires also.

I believe that...
Neither the vehicle psi placard, nor the tire sidewall max are absolutes, just guidelines/starting points.
Everyone's results/needs will be different.
There is No Simple Calculation that Applies to Everyone.

Your Mileage May Vary, Jim

PS My operating psi is over both the placard and the sidewall recommendations.


Just did quick search, the Nokian is designed to run on SUV and has LI (load index) 100 and H-rated, the Michelin is a passenger tire with LI 99 and S-rated, definitely the Michelin is much more comfortable and softer. The issue is 38 psi on the original placard is already max level load for that size, so when you change to the tyre with lower LI, definitely it will be out of spec. So as long as the van never been fully loaded, it may be safe to use, but when it is fully loaded, the new tyre may burst.
 
Originally Posted By: Volvo_ST1
Come on, AstroSmurf, answer a question. Why don't you get your answers regarding the legal implications regarding hyper-inflation and you being a test pilot on public roads straight from the horses' mouth? The horses being the car maker, the tire maker, possibly the DOT, and an auto accident attorney?


Volvo_ST1,

Just as I has been honest about my psi findings...

I will share any Legal encounters with you as well. O.K.? Kewl.

Thanks, Jim
 
Originally Posted By: kr_bitog
Originally Posted By: AstroTurf
Capri Racer,

2) An under inflated tire runs hotter, and an overinflated tire runs cooler. So, once again, I started with placard pressure and drove a test loop. Measuring the psi and ambient temps both before and after the test loop. I found that as I increased the tires cold psi, that the tires hot psi increases began to fall. When I reached the point of a drop off in vehicle control. I stopped the psi increases and reverted to the last satisfactory test loop scenario.

I hope this answers your questions, Jim


The above is correct observation, and I guess the tyre you use is having soft sidewall that is why you never encountered uncomfortable ride before traction suffer. That is why the best test should include tyre surface temperature, because when it rains/in cold weather, too high pressure may cause insufficient tread temperature to offer best traction even though the ride quality is ok.


What is the best tread temperature?

Originally Posted By: kr_bitog
However, if you find the best psi is higher than the one written on the sidewall, I wonder whether at the first place you use correct tyre size and load index. I don't find a norm that different tyre construction give so much difference until you exceed the recommended tyre psi recommended on the sidewall, except the tyre comes with too small load capacity(load index) or you use passenger car tyre on SUV/light truck(which why they recommend to reduce the capacity calculation to 90%) due to higher variation on load due to heavier vehicle weight or too soft of sidewall design/too firm suspension spring rate)


Well, First we would have to clarify the three sidewall pressures used on P Rated Tires... 35, 44, and 51. What are they and what do they represent?

The tire I am using is the proper placard size. I also can assure you that this tire is not currently overloaded.

Thanks, Jim
 
Originally Posted By: AstroTurf
Capri Racer,

Sure, I will try.

1) As I progressed through small psi increases, there came a point when the vehicle control was more vague, had more under-steer than I was willing to accept. Understand that I have driven this vehicle for the last 2 1/2 years, logging more than 71,000 miles, so I know what is optimal and what is not. The psi at that level was not acceptable to me. I never reached a point of an uncomfortable ride with this tire.

2) An under inflated tire runs hotter, and an overinflated tire runs cooler. So, once again, I started with placard pressure and drove a test loop. Measuring the psi and ambient temps both before and after the test loop. I found that as I increased the tires cold psi, that the tires hot psi increases began to fall. When I reached the point of a drop off in vehicle control. I stopped the psi increases and reverted to the last satisfactory test loop scenario.

I hope this answers your questions, Jim


Jim,

That's helpful, but I was looking for a bit more detail. So a few more questions, please.

1) How long was the test loop?

2) What was the average speed of the test loop?

- and I could continue to ask questions about the test loop, but that's enough info for because:

3) I am assumimg that the test loop did not involve any sort of limit handling manuevers and the like - that the drive around the loop was pretty stedate.

4) About the pressure: I assume you watched that the pressure build up decrease as you increased pressure - but you stopped adding pressure once you got that vague feeling. What was the pressure build up that you observed?
 
Originally Posted By: kr_bitog
Just did quick search, the Nokian is designed to run on SUV and has LI (load index) 100 and H-rated, the Michelin is a passenger tire with LI 99 and S-rated, definitely the Michelin is much more comfortable and softer. The issue is 38 psi on the original placard is already max level load for that size, so when you change to the tyre with lower LI, definitely it will be out of spec. So as long as the van never been fully loaded, it may be safe to use, but when it is fully loaded, the new tyre may burst.


Both tires are P metric... IE Passenger Tires.
Both tires are within spec, according to the vehicle placard.
The current tire sidewall rated load is 1709 lbs.

But, Even if we reduced the Michelin tire load to 1554 lbs, as is indicated on their website. I can assure you, The weight limit has not been reached. And, Still meets all of the vehicle load parameters as designed by the manufacturer.

Thanks, Jim

PS The Michelin website even allows for increased pressure (for this tire) Based on speed and load.
Look all the way down at the bottom... In the Fine Print. LOLz
http://www.michelinman.com/tire-selector/category/light-truck/ltx-m-s/tire-details/
 
Originally Posted By: CapriRacer
Jim,

That's helpful, but I was looking for a bit more detail. So a few more questions, please.

1) How long was the test loop?

2) What was the average speed of the test loop?

- and I could continue to ask questions about the test loop, but that's enough info for because:

3) I am assumimg that the test loop did not involve any sort of limit handling manuevers and the like - that the drive around the loop was pretty stedate.

4) About the pressure: I assume you watched that the pressure build up decrease as you increased pressure - but you stopped adding pressure once you got that vague feeling. What was the pressure build up that you observed?


Capri Racer,

1) 28 miles, Mixed pavement, No gravel.
2) 65 - 75 mph
3) The loop included a cloverleaf exit, which was used as a turn around point. And, Yes, I am a very sedate driver.
4) The pressure build ups that I observed where as follows...
a) At or slightly above placard pressures, a 4 - 4 1/2 psi increase after completion of the test loop.
b) As I increased the tire inflation levels, I found that the pressures recorded after the loop began to settle in the 2 - 3 1/2 psi increase area.
c) At the point of vague vehicle handling, I then began to be a little less sedate as I reduced my psi to my current operating pressure. Again, making all of the same observations.
d) Keep in mind that these cold psi tests were completed in the early morning hours, and regular business was conducted throughout the day, with further psi observations.

Hope this helps, Jim
 
Originally Posted By: AstroTurf

What is the best tread temperature?

It depends on the tyre, some require 160-220F, some may need higher, and winter tyre may require lower. One way to determine proper pressure is to measure whether the tread temperature is even across the tyre.


Originally Posted By: AstroTurf

Well, First we would have to clarify the three sidewall pressures used on P Rated Tires... 35, 44, and 51. What are they and what do they represent?

The tire I am using is the proper placard size. I also can assure you that this tire is not currently overloaded.

Thanks, Jim

I am not sure how the tyre size is shown on your placard, whether it is with P or without P because those 2 aren't the same. For P-rated, tyres the 35,44 and 51 psi is shown for handling optimization, but there is no load increase beyond 35 psi. For non-P passenger tyre, it shows no load increase capability above 36 psi.
You can read here for more details:
Tyre Safety Manual
Tire Tech
 
Originally Posted By: AstroTurf

PS The Michelin website even allows for increased pressure (for this tire) Based on speed and load.
Look all the way down at the bottom... In the Fine Print. LOLz
http://www.michelinman.com/tire-selector/category/light-truck/ltx-m-s/tire-details/

Here below is the fine print,
they allow increase for higher speed but not for higher loading and not beyond pressure marked on tyre sidewall.

Inflation pressure increase must not exceed the maximumpressure branded on the tire sidewall. Whena customer requests a replacement tire with a lower speed rating than the original equipment tire, you must clearly communicate to him or her that the handlingofthe vehicle may be different, and that its maximum speed capability is limited to that of the lowest speed-rated tire on the vehicle. Exceeding the lawfulspeed limit is neither recommended nor endorsed.

For high-speed driving, additional inflation pressureand possibly reduced tire loading and/or upsizing is required. In the absence of specific recommendations by the vehicle manufacturer, usethe following guidelines based on those in the European Tyre and Rim Technical Organization Standards Manual.

For speeds over 160km/h (100 mph), load and inflation must be adjusted according to the table below.

S-Speed Rated Sizes:

Maximum Speed (mph) 100 106 112

Inflation Increase (psi) 0.0 1.0 2.0

Load Capacity(% of max.) 100 100 100
 
Originally Posted By: kr_bitog
Originally Posted By: AstroTurf

What is the best tread temperature?

It depends on the tyre, some require 160-220F, some may need higher, and winter tyre may require lower. One way to determine proper pressure is to measure whether the tread temperature is even across the tyre.


Originally Posted By: AstroTurf

Well, First we would have to clarify the three sidewall pressures used on P Rated Tires... 35, 44, and 51. What are they and what do they represent?

The tire I am using is the proper placard size. I also can assure you that this tire is not currently overloaded.

Thanks, Jim

I am not sure how the tyre size is shown on your placard, whether it is with P or without P because those 2 aren't the same. For P-rated, tyres the 35,44 and 51 psi is shown for handling optimization, but there is no load increase beyond 35 psi. For non-P passenger tyre, it shows no load increase capability above 36 psi.
You can read here for more details:
Tyre Safety Manual
Tire Tech


Vehicle placard calls for a P Metric Tire.

Thanks for the links, Jim
 
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