My tyres were oversized my MPG went down!

[euromodder]

Originally Posted by iskyfly

That doesn't negate the fact that over inflated tires increase tire wear.

Define overinflation.

Over sidewall max set by the tire manufacturer, or over the placard rating by the car manufacturer ?

[euromodder]

Originally Posted by iskyfly

Are there any vehicle engineers here who can say that overinflating a tire past sticker value doesnt;

-decrease safety
-increase expense because of faster tire wear

We got an entire forum running higher pressure than what the car manufacturer decided to put on their tire placards !

It doesn't appear we're losing members by the numbers because their tyres explode


We should really turn the question around :
What / who made you think it is unsafe ?

[car guy]

I’m 62 and my family of 4 kids and wife have owned a lot of cars. Here’s some empirical “truths” I’ve developed over the years.

Measure pressure when COLD, not after driving, but first thing in the morning. There are 2 tire pressure recommendations on any car:
1) Car manufacturer sticker located on the "B" pillar (between front and rear doors on driver side). This is the pressure recommended for the original tire size (e.g. 205x50x16) which is also on this sticker. This is for "best ride characteristics”… suspension is tuned for this setting. My opinion, this doesn’t result in best mileage or wear.
2) Min – Max pressure on the tire sidewall. Tire manufacturer rating based on tire construction.

I set cold pressure exceeding tire max on sidewall by 5%, especially front tires, where all the weight is. Why? When driving, tire sidewall flexes (squashes) between road surface on each revolution, causing heat. More pressure = less squash = less heat. Heat is calories (energy) and all energy comes from gasoline. I believe I get better mileage. I have never had a blow-out. Heat also warms the rubber and therefore accelerates wear.

I’ve never experienced over-inflation, center tread wear to any measureable degree. Tires wear on edges because each turn causes the outside tire to roll under to some degree. More pressure reduces “roll under” and therefore reduces edge wear. I suspect that if I only traveled in a straight line at 70 mpg, center tread wear might become evident.

So I feel the bumps a little more but save cash on tires and gas. In the spring with the new pot-holes, they get a little extra. I've never bent a rim for broken a cast mag.

I only rotate tires front / back on the same side; never changing the rotational direction. In 1979 I had a pull develop in the steering wheel. An old tire guy told me radial tire casings shift under the tread against the direction of the pull. If the tire is placed on the other side of the car the casing has to shift back. Sometimes the tread separates from the casing when this "reverse shift" occurs. I've learned a lot over the years by listening to old car guys. If you do not rotate every 5000 miles, then don't cross-rotate. I'm sure radial design has improved since 1979, but ya can't teach an old dog new tricks.

Just another opinion, if you get my meaning.

[brucepick]

Originally Posted by Ford Man

Most car manufacturers recommend lower tire pressure for comfort (softer ride). I'm running 50 psi in my tires, I think the door placard states either 30 or 32 psi. It does give the car a little bit of harsher ride, but the handling of the car has improved and my tires seem to last longer with the higher pressure.

I do the same, with similar results. Except I pump mine up just a bit more - 58 psi front, 56 rear. I measure when cold, it's a safe bet they go up about 4 psi when driving more than a short distance.

My only regret is that under these conditions, my Kumho tires seem to be lasting approximately forever. I wish they would hurry up and wear out so I can replace them with nice Michelin LRR tires. The Kumho's are supposedly "eco friendly" but I expect Michelin LRRs will be better.

Oh yes - about 1.5 years ago I was rear-ended while driving on um, well-inflated tires. Apparently their braking action was quite good. I've had occasion since then to (very rarely) use the brakes very firmly, with excellent results.

[Mrwassman]

And, back to the topic:

If you put larger diameter tires on your car the odometer is going to read fewer miles that the vehicle actually travels. I don't know if this was said, all I see is a bunch of rubbish.

[mcrews]

iskyfly,
It's just me......but let me know how many of the other "inflation tire pressure" threads you have read here.

I can appreciate a noobie being all excited and wanting to jump into the fray.....
But this is hardly a new topic here.
By a loooonnnnggggggg shot.

There are some VERY smart tire guys here. Read their posts, then get back.

[YeahPete]

@ car_guy:
WOW you set the tire pressure over 5% max when cold? I usually fill it to max cold because when it heats up it will be well over max temp. The greater the cold temp the more pressure when it heats up.

Whats the pressure after the tires are heated?
Anyone else doing this? I was kinda freaked out going over max sidewall pressure because my brother destroyed a tire doing this but he put like 45 psi in a 34psi tire.

[euromodder]

Originally Posted by YeahPete

@ car_guy:
WOW you set the tire pressure over 5% max when cold?

5% over max. sidewall pressure won't kill a tyre

I've run 3.8 bar (55psi) in a 3.5bar(51psi) rated tyre for a while - couldn't attribute any improvement in FE to it , but the car felt a lot bumpier than at 3.5bar (51psi), so that's what I stuck with.

I was kinda freaked out going over max sidewall pressure because my brother destroyed a tire doing this but he put like 45 psi in a 34psi tire.

That's like 33% over ...
What do you mean by "destroyed" ?
Did it blow (due to pressure, not due to wear), or did it wear down the centerline ?