Bad tires---front or back

[clare]

A driver with a brain in his head KNOWS to slow down when there is water on the road, before he feels either the front or rear tires coming loose. Can't remember the last time hydroplaning caught me by surprise - gotta be over 40 years ago.

As for what FWD car I drove in 1969 - I started with an Austin Mini. I also drove 204 Peugot (1961 and 1967 respectively) as well as a 1967 Renault R12 (which I rallyed successfully for 3 years) ,1981 Pontiac Phoenix XJ, and 1980 Tercel(all before 1984)

Chrysler Lebaron, Chrysler New Yorker (E-Class) Colt 100, Neon, Pontiac TransSport, Mercury Mystique(Mondeo), VW Rabbit, MagicWagon, and the current PT Cruiser since.

It's likely been over 30 years since I replaced anything other (less) than 4 tires at a time.

[clare]

And the fact he was able to drive it untill it was that bad before noticing proves the rear tire is not nearly as important for stability as many on the list believe. If it had been the front tire, he'd have known about it a lot sooner - and had a lot more "fun" controlling it.

Not as bad on new cars with negative scrub radius as it was on the older stuff - but still not a walk in the park (unless that's where the car deposits you when the tire fails)

[HeyBub]

Driving home at night a couple of weeks ago, I heard a slight thump.

Looking in the rear view mirror I saw a black lump under the street light in the middle of my lane. Curious, and not being in a hurry, I did a U-turn to investigate.

IT WAS MY SPARE TIRE! which has been stored under the bed of my pickup.

I retrieved the tire and sorted through the detritus on the roadway capturing anything that looked like it may be related.

Turns out, the cable holding the tire in place broke.

But, following your advice and not being curious and not just moseying along, I could have lost a GOOD tire.

[HeyBub]

You went through all that to save eight dollars on a Walmart tire?

[HeyBub]

When I went throught the Texas Department of Pulic Safety Pursuit Driving School, we saw a video produced by NASA investigating what kind of tires were appropriate for the space shuttle.

They used a ratty sedan with regular tires traveling at 50 mph. With a tire pressure of 60psi on a wet runway, the measured the stopping distance.

They let 10 pounds of air out of the tires and repeated the experiment. The stopping distance increased slightly.

Continuing to reduce the air pressure - down to ten pounds per square inch - uniformly increased the stopping distance. The final results were the 10psi tires almost DOUBLED the stopping distance of the 60psi tires.

Here's why:

As the air pressure drops, the width of the tire increases. On a wet surface, the wider the tire the more hydroplaning it does until it acts more like a surfboard than a tire. As the tire hydroplanes, very little of the rubber (i.e., none) is in contact with the road.

Bottom line:

Wide tires do not increase traction. In some cases they actually PREVENT traction.

And before anybody gets all exercised, here's a law of physics

Friction force = (coefficient of friction between the surfaces) x (weigh perpendicular to direction of movement)

Note that surface area is NOT involved in determining frictional force.

Probably.

[DerbyDad03]

re: "And the fact he was able to drive it untill it was that bad before noticing proves the rear tire is not nearly as important for stability as many on the list believe".

Apples and oranges.

Stability while driving with a flat and the propensity of a tire to skid or hydroplane due to worn tread are 2 very different things.

The fact he was able to drive it until it was that bad before noticing proves only that the driver wasn't in tune with his vehicle.

[keith]

Same issue; loss of friction due to surface conditions.

[keith]

The spare mounting hardware is so rusted on my truck it'll never come off. A garage tried a few weeks ago.

[keith]

Ok, now rerun the experiment and measure cornering Gs. ...though this isn't really fair because an under-inflated tire will roll excessively, causing the tread to lose contact with the pavement.

[clare]

Last time I used my spare was sometime back before 1975.

[clare]

True on just about anything but clean dry pavement

But the surface area can have a lot of influence ofer the co-efficient or friction when there is water on the road!!!

[clare]

You have obviously never been involved in performance driving of any sort, nor do you have any REAL knowlege of handling - what it is, and what affects it.

You are also, it seems, one of the many that will believe anything a tire salesman tells you.

You likely believe used car salesmen as well.

[clare]

But totally DIFFERENT conditions.

8 inches of snow is a whole lot easier to drive in than 1/2 inch of slop. - assuming you have the required ground clearance.

[clare]

I've lost 4 spares over the years on Toyota, Ford Aerostars, and Pontiac TranSport

[Jules Richardson]

I'm not sure where I gave that advice... [I know you didn't type that, keith - just condensing two replies into one!]

Mine's mounted vertically on the side of the load-bed.

cheers

Jules

[Jules Richardson]

I've needed a couple in the last decade - one on a 1970s car due to internal corrosion of the alloy wheels (I was staying at a friend's house and came out the next morning to find I had a flat - the garage fixed it by tubing it) and once on a truck in the middle of the Australian outback (changing a tire in 140 degree heat is really not fun!)

cheers

Jules

[Larry W]

The experiment described may prove that reduced air pressure increases stopping distance. It does not conclusively prove that the reason is because the tires are wider. To prove that, they should have mounted progressively wider tires and tested stopping distance at the SAME air pressure. (I'm not saying I disagree with the results or even the explanation, just disagreeing with the application of scientific method)

[aemeijers]

I hate those under-bed mounts on trucks and vans with a passion. No way to get it out without getting filthy, and as you noted, the hanging hardware is very prone to failure.

[krw]

So WHAT? The issues are *exactly* the same.

...and until you bottom out, the issues with slop are the *same* as hydroplaning.

[krw]

Mine's under the bed; hanging for seven years in VT salt. It's now nine years-old, but it's never been off the truck.