smokeyram

I know everyone has there favorites for various reasons. I need to update my profile,I finally broke down and replaced all 6 tires on tuesday.

I went with the Peerless Widetrack AT. 235 85 16

I have to say i am shocked at how well they perform. If anyone else is in the midwest, you know the rain we have had last few weeks. I do all highway driving and with the old bald ones, i had to slow for fear of hydroplaning constantly.

Last night, I was coming south out of Milwaukee, another massive storm.
And even though I know better I put the tires to the test, 75 mph and felt like my sloppy driving truck was on rails. no problems merging, plowing through deep water , perfect tracking all the way.

anyways, they get my vote.

HOHN

I'd consider a tire like this, but most tire makers say that my factory 16x8 wheels are too wide. I think they want 7.5" or narrower for a 235/85 16

patdaly

Hohn, been running 235/85/16's on mine with the stock Dodge chromies since before I got it.

I've had her squatting with firewood on the back and no issues.....

HOHN

I have the factory 02 alloys, which are wider than your chromies.

Your wheels are in the good range for 235/85 because they are only 6.75 inches wide (iirc). Mine are 8" wide-- too wide.

patdaly

Hmm, I had better store that in my memory book, thanks for the info.

LOL, I almost bought a set for when I upgrade to 17" Does the same apply to the chromie 17" wheels?

RowJ

Have heard good things about those!
If I recall correctly from my flying days..... Hydroplaning has nothing to do with tire tread. Simply a function of tire pressure (9 times the Square Root of the pressure).
But below that speed, bald tires will loose some control so .... nevermind.
Everytime I try to be a Hohn lookalike (soundalike), I fall short!

RJ

smokeyram

oh im sure that the tires i took off were not only blad, but under inflated, just shot in general. either way they were toast.

as for the size, i have the factory steel wheels, i looked, I dont know what it would take to make them rub, I have alot of room between the duals.

I just need to get it aligned tommorow, before i thrash the fronts .....again

HOHN

Trust me, you don't want to be anything like me People will question your sanity...

HOHN

Tread does matter for hydroplaning. Plane hydroplaning and road vehicle hydroplaning are different-very different. Tires are shaped differently.

The pilot's "tire pressure" rule is a rule of thumb for flying based on coincidence, and has no bearing at all for hwy tires or hwy vehicles.

Stay tuned for a dissertation later....

Ph4tty

And I thought thats what the avatar was for?

RowJ

I might argue that point. I was taught that formula in a ground school. I have always applied it to my street tires, as a speed to avoid when on water covered roads and it has served me well... but have no test data to verify. I have heard stories from guys of hydroplaning at a speed that did match the formula..... but that could be coincedence?

RJ

Cougsfan

ROWJ, Would you expound on this hydroplaning based on 9 times the square root of the pressure theory? I am curious about how that works. I have changed tire profiles and tread design on rigs before and seen profound differences in hydroplaning tendencies without any significant differences in tire pressure.

HOHN

Nine times sqrt of tire pressure...

Lessee, that means a large dump truck could hydroplane at 18mph? This also means that a large semi should be good to go at 90mph (9 times sqrt of 100psi).

The problem with this rule of thumb is the fallacy that tire pressure supports the weight of the vehicle. It doesn't. The TIRES support the weight of the vehicle, and the pressure inside them gives them support.

What if I made the tires out of metal that needed no air for support? The formula then predicts I should never be able to avoid hydroplaning.

Tires must deflect from their round shape to conform to the flat road surface. This is completely non-linear. Can you make your contact patch half the size by doubling air pressure? Of course not. A change from 40psi to 80 in a CTD will not halve your contact patch-- it will get smaller by a factor of perhaps 15-20%. If you could double the pressure again to 160psi, you'd see an even smaller percentage of change.

A better example is with a more rigid tire like an 18-wheeler tire. The pressure doesn't carry the load. The carcass does, and the pressure reinforces it.

The factors that affect hydroplaning are the viscosity of the fluid (water), The amount of fluid that must be displaced (water depth and tread width),the efficiency with which it is displaced (tread design and wheel load), and the time available to do so (vehicle speed).

If tread design didn't matter for hydroplaning, the boat hull design would have no effect on the speed at which a boat achieves plane, yet we all know that hull design matters greatly, and two boats with identical width can perform very differently.

Also in the same vein, note that some hull designs are greatly affected by the load, and some are relatively unaffected. A deep Vee hull that almost never achieves plane won't be affected by loading, as there's no planing effect to impact. However, your typical duck blind Jon boat gets on plane almost instantly, but is VERY susceptible to different loads, and the same boat that planes out instantly with just you in it can struggle when you add two hunting buddies (and their beer and ammo).

The "9 times sqrt of tire pressure" is taught in ground schools because it approximates the typical hydroplaning speed of a typical aircraft tire (no tread, just grooves) at a typical aviation load ratio.

But the relationship of "9 times sqrt tire pressure" is simply an alignment of numbers, not one of cause and effect.

Applying this "rule of thumb" outside its original intent can be VERY dangerous.

Final thought: Both my bicycle tires and my truck tires are rated to a max of 80psi. I've hydroplaned my truck easily at this tire pressure. Yet there's not a human alive that's hydroplaned a bicycle.

How can this be?

phox_mulder

Because everyone that has hydroplaned a bicycle didn't live to tell about it?


phox

HOHN

Either that or they weren't strong enough to get their pedal bike up to 75mph?

OK, bad example... hehe