Before you over inflate watch this.

[diamondlarry]

Originally Posted by the_ghost

but in short my point is inflation past sidewall max is bad for tire wear and is dangerous.

Again, I refer you to the tires on Wayne's Accord with over 100K miles on them. They have been at 60 psi the whole time. I guess that shoots the wear and safety issue. Next? I also agree with Delta Flyer that coming here and telling us different than what we already know to be true from 100's of thousands of miles of testing and experience. I would strongly suggest toning it down a notch or two.

Originally Posted by LL3

I don’t think anyone here would question that 160+ PSI for a 44 PSI max is over inflating.

Companies that put the “MAX” on anything are under calculating what the limits actually are. For example, when you see a road sign before a curve that says “Max Speed 35” – It does not mean the curve limits are 35 MPH and you will run off the road if you go over. An engineer for building roads could tell you that the max speed limit for the curve is much higher, but they will post a lower limit for CYA reasons when someone does go off the road at 70 mph.

It is the same for tires. There is a rating so if you’re above their rating and the tire does blow up, you can’t go back to them with a legitimate complaint.

Excellent topic,

LL3

The tires are tested to over 3 times what's on the sidewall. The sidewall max is mainly for legal purposes.

[highwater]

Mr Ghost sir:

I won't even tell you what I'm running in the tires on the Insight.
The last set (original) went 85K+ miles. See my sig for the FE results.

I'm with Chuck, when saying, if this is your first day around here, laying a bit lower in the trench would be a good idea, as the bullets are a flyin'.

Randall

[GrendelKhan]

Originally Posted by diamondlarry

The tires are tested to over 3 times what's on the sidewall. The sidewall max is mainly for legal purposes.

Hi Larry,
Could I get a link for this? For those of us at or slightly over sidewall max who want to go higher, any info like this would really help make us feel better, and let us go higher. Thanks in advance.

[some_other_dave]

Remember, the number one rule for Hypermiling is: BE SAFE! If you don't think something is safe for you to do, then don't do it! As always, you are the best judge of your own circumstances.

I don't think anyone here recommends that othedr people go above the MAX PRESSURE number on the sidewall of their tires. They will tell you that they have, and what their results have been, but I don't recall seeing anyone telling people to go over that number on their car.

I have read the results, and weighed what I feel the risks may be, and have chosen my sidewall pressures appropriately. Please feel free to do the same.

-soD

[bomber991]

Over Inflation - Going above the sidewall maximum pressure.
Proper Inflation - Being lower than the sidewall maximum pressure but being above the driver door placard pressures.
Under Inflation - Being lower than the driver door placard pressure.

Ok, anyways I remember when I told my dad I needed to buy new tires this year since the tires were going to be 6 years old later this year. He was like "What? Those tires are only 4 years old!". I then explained to him that they were already 2 years old when we got the tires "new" from the costco tire shop and that they need to be replaced before they are 6 years old. He said he normally just replaces tires when the tread wears out.

[kwj]

Bomber991, for whatever reason, I tend to do as your dad. Now, tread wearout in my Accord meant when I would slide in the rain in a downhill turn into my town. The tire tread looked okay and wasn't down to the "indicators," but the bite was gone and it was time to get a fresh set.

Otherwise, I wait until they were about shot.

On my Aveo, I hit a curb and knocked the front end out of alignment - but did not get it taken care of. At 44,000 miles, I had to replace the front tires and get an alignment. I put identical tires on the front.

I've driven 15,000 miles since then, at pressures above max sidewall. The original tires are still going strong, as are the new tires. No abnormal wear, not even on the edges.

I drive slowly (Max 55 tops) maintain a good buffer, and watch for any type of road hazards. I am very comfortable with this set up, and am interested in carrying my "test" to a logical conclusion that I'm hoping will show completely even tread wear. So far, so good.

My tires have a treadwear number of 420, a Temperature rating of A, and a Traction rating of A. Based on the treadwear, what kind of total mileage can I expect?

[some_other_dave]

Unknown. The "treadwear" numbers are not consistent from manufacturer to manufacturer, so all you can say is that you will "probably" get longer life from them than from a tire from that same manufacturer with a 380 treadwear rating. (And likely, longer life than any tire with a 100-200 rating, but that's not completely certain....)

-soD

[smartzuuk]

Originally Posted by bomber991

Over Inflation - Going above the sidewall maximum pressure.
Proper Inflation - Being lower than the sidewall maximum pressure but being above the driver door placard pressures.
Under Inflation - Being lower than the driver door placard pressure.

I like that definition, except I would replace 'proper' with 'standard' or 'typical'. If something isn't 'proper', then it may be seens as 'improper'.

'Over-inflation' is a term we have to turn the page on... I'm sure to come across objections to 'higher than car manufacturer suggested PSI' soon.

[kwj]

I hate to be a stickler (no I don't) but some placards are not on the driver's door.

I agree that these terms could resolve our conundrum, and I think they are ours to define, as we are in a grey area, trying to make it as black and white as possible. I agree with smartzuuk about the normal or typical (and vote for "normal") versus "proper.' After all, for us this is typical. We can define things as we please, for our purposes. (Man that sounded so OFFICIAL I almost fooled myself).

So, is this worth a Poll, or should higher powers decide it?

[hobbit]

Awright, I have to chime in with my usual here -- the clarification
I usually offer to the naysayers I run into at all the car and
energy shows who come along and try to pontificate at me about
"overinflation". Consider this: what is "cold"? -5 degrees
with wind chill, or the start of a nice sunny 80+ summer day?
There's an 8 or 9 PSI variation right there. What if I put my
"safe" 44 psi in on a winter morning where I live, and then
drive to Florida? Oops, now I'm north of 50. Also consider all
the transients -- a nice deep sharp-edge chuckhole like we hit
all the time can easily cause pressure spikes pushing toward the
100 PSI mark, *coupled* with significant deformation. High
pressure will better resist said deformation, where severe
underinflation can actually let the rim contact the inside
of the tread. Ever heard of a "snakebite puncture" on a
bicycle tire? Same idea, in a sufficiently underinflated
case, although the car tire doesn't have the inner tube to
put holes in.
.
Modern radials don't bulge in the middle. This is what happens
to tires on a Prius when run at Toyota's recommended pressure.
Now, look at the nice rounded top of that tire. If what is
said about center wear was even remotely true, why do we see
the exact inverse on that underinflated tire?? Time and again
our community has proven that going over the sidewall rating
yields nice even long-term treadwear all the way across.
.
And this guff about "contact patch" is so much bunkum when you
consider the physics. Same downward force applied over a
larger area yields LESS frictional side-force resistance per
unit AREA of tread rubber. It also increases the "plow" area
that gets water underneath during hydroplaning. Small and
narrow is well known to be the optimal shape in many slippery
conditions, where a tire can better bite down through water
or snow and find the real pavement.
.
The only conditions under which a big floppy "footprint" may be
better is loose sand or mud, where there's nothing to bite
down to. Then you *want* less downforce per unit area so the
tire doesn't just dig big ruts for itself and acts more like a
rolling pontoon. But we're not usually out hypermiling in the
sand-pits, are we?
.
_H*