Over-inflating... how much is to much?

[McPatrick]

Well, this subject comes up from time to time and it is really something only you can decide. Personally I run just over 50 psi in tires whose side walls say 35 psi and haven't seen any strange side effects, unless you call saving gas a strange side effect

[rgathright]

I guess I'll just put some cash aside and fill my tires.

[dkjones96]

Originally Posted by McPatrick

Well, this subject comes up from time to time and it is really something only you can decide. Personally I run just over 50 psi in tires whose side walls say 35 psi and haven't seen any strange side effects, unless you call saving gas a strange side effect

You guys are pretty daring, call me what you will but I think if you're doing highway speeds anything over 25% above rated is just crazy. You have the added pressure of the air plus centrifugal forces working to rip that tire to shreds, I wouldn't be worried about the tread area since that's steel belted, it's the nylon reinforced side walls that would worry me.

Don't be doing that on the cheap tires or tires that show any signs of aging. That's just me tho I don't run anything over the side wall rating. Safety first, you lose a tire and cause an accident the cars sitting on the freeway backed up will pollute way more than any reduction you get from increased pressure, plus your cost of replacing a car or your insurance rates getting raised because you were at fault for 3 other cars crashing. (worst case of course)

[GasSavers_RoadWarrior]

I am @ 40 psi on all my 35psi tires, but I had them at 32psi for the snow. Did try 50 psi once, lost 60% of the traction, thing skittered all over the road, 40psi seems just right, seem to keep the traction, get very crisp, predictable and responsive handling.

[basjoos]

A year or two ago, someone posted a link to an article about a police driving school where police officers learn the extreme driving techniques they sometimes need to use in their jobs. Things like high speed manuevers, riding on 2 wheels, etc. The cars in that school keep their tires inflated at 100psi.

[theholycow]

Originally Posted by dkjones96

You guys are pretty daring, call me what you will but I think if you're doing highway speeds anything over 25% above rated is just crazy. You have the added pressure of the air plus centrifugal forces working to rip that tire to shreds

That's not the sort of think that's likely to happen. Tires (well, common modern automotive pneumatic tubeless radials) are very overbuilt against that sort of thing, because there's other things that are much harder on them. Mainly, when you hit a bump hard with the tire inflated far past its maximum rating, you have an increased risk of the bead breaking loose. Since highways tend to be pretty smooth, this is a city driving issue.

These tires don't pop like a bicycle tire, and they don't fly apart unless they're underinflated and overheated. It's funny, this is the ONLY forum where I've ever had to take this side of the tire pressure argument. There was a "Poor man's mods" thread on golfmkv.com where I tried to explain the advantages of inflating past the car's recommendation but not beyond the tire's maximum, and the FUD was just awful, so I finally gave up.

Originally Posted by basjoos

A year or two ago, someone posted a link to an article about a police driving school where police officers learn the extreme driving techniques they sometimes need to use in their jobs. Things like high speed manuevers, riding on 2 wheels, etc. The cars in that school keep their tires inflated at 100psi.

That's fine for controlled conditions and limited time/mileage. If they were operating IRL at 100psi on tires rated for a maximum 50, they'd blow them on potholes and bumps. Riding on 2 wheels would necessitate high pressure, considering the extra weight and the sidewall forces. J-turns would need high pressure to reduce the contact patch.

[GasSavers_RoadWarrior]

Yeah I'd think the 100psi in the training cars would be so that you can practice breaking traction at much lower speeds than needed in real life.

[GasSavers_JoeBob]

I seem to remember reading a Tom McCahill article in Mechanix Illustrated back before most people on here were even alive (and it was a old magazine even then) suggesting around 45-50 psi in the old nylon cord (no steel belt) bias ply wide-whitewall tires for best mileage and longest tire wear.

Back 35 or so years ago, I drove a Corvair. The sticker specified about 15 psi for the front and 26 psi for the rear. I ran 20 psi in the front and 40 in the rear. Usually had junky used tires...never a problem. BTW, the reason for the pressure differential on that car was to introduce a bit of understeer to keep the car from getting away from you in precarious situations. The problems people had with Corvairs often came from not maintaining that pressure differential...thus the first chapter in Nader's "Unsafe at Any Speed"

[theclencher]

Originally Posted by RoadWarrior

Yeah I'd think the 100psi in the training cars would be so that you can practice breaking traction at much lower speeds than needed in real life.

http://www.officer.com/article/artic...on=19&id=27281

[theholycow]

Originally Posted by theclencher

http://www.officer.com/article/artic...on=19&id=27281

Thank you! That is a more reputable source saying the things I've been saying but people think I'm crazy.

That guy must have been following me around on the internet, reading all my posts that each say part of that (but in few of which I remembered ALL of those things).

http://www.tirerack.com/tires/tirete...e.jsp?techid=1 also says some of that, but also cautions against overinflation (as if there's been many cases of intentional overinflation that caused some consequence!). Even so, here's how the part cautioning against overinflation ends:

However, higher inflation pressures reduce rolling resistance slightly and typically provide a slight improvement in steering response and cornering stability. This is why participants who use street tires in autocrosses, track events and road races run higher than normal inflation pressures.