Wednesday, Oct 05, 2005 at 10:46
Lots of interesting ideas get put forward about tyre failures on this
forum, some of which seem to have a lot of thought put in.
Have been driving on these round black things for a long time now and have also some thoughts.
A "blowout" is almost without exception a tyre wall failure. They can be of two types; a single hole or the entire wall circle (zipper effect). In my experience the single hole type can be caused by a) staking the wall with either a sharp stone, a sharp stick or the jagged edge of bitumen sealing, or b) by overloading the tyre for the pressure in it and its rating. This failure can also follow sidewall damage at some previous time eg: hitting a curb.
A zipper type blowout is the catastrophic failure of the sidewall most often caused by overloading the tyre for the pressure in it. Most often caused by running half flat and is the result of heat build up in the wall fabric plies due to friction.
Moral; Tyre pressure and load!!!
If the tread cap has seperated from the rest of the tyre, then the heat build up has caused the vulcanised welding of the cap rubber to the tyre carcase to release, causing lots of noise and bits of rubber flying off. Again, heat build up.
Moral; tyre pressure and load!!
tyre carcase construction has little or no effect on which way a tyre should rotate. Tyre tread pattern on the other hand does. If there is an arrow on the side of the tyre wall, then that is the direction of rotation that the tread has been designed for. Some tractor and earthmoving tyres can be the exception, in that they may have two arrows on them, both pointing in opposite directions. this indicates the tread is designed so that they are most efficient in applying drive in one direction, and being non power delivering in the other. Most directional treads are designed to move friction inducing material eg. water, away from the centre of the tread.
Swapping tyres diagonally will usually even out their wear over time, and will pose no danger so long as the tyre is structurally sound.
The difference between radial and crossply construction is rather complex but put simply a radial tyre usually has less fabric plies in the wall than a crossply or bias ply tyre. This reduces the amount of friction caused heat buils up and also allows the tread portion of the tyre to stay in better contact with the road surface.
It seems that some of the science used to reach some of the conclusions here is a bit flawed. If you load up the 4b more than usual, then you drive it faster than usual, maybe, just maybe thats the answer. More load, greater speed equals more heat, equals tyte wall failure.
In thirty years of driving trucks, cars, utes, 4bs and farm machinery on rarely maintained country dirt and gravel roads I have two tyre failures. The first on an inside dual rear truck tyre severely underinflated (thought we might get to a tyre pump, but no), the second due to hitting a rock with a radial tyre some couple of weeks prior.
When you stop and feel the temperature of your tyres and one is too hot to comfortable hold your hand on it, it is going to fail unless you do something about it. Now.
The Bridgestone AT 265/70/R16 tyres on the Patrol have done 90,000, have all five been rotated in all manner of ways and run 29psi front and 26-28 psi rear, and are starting to look a bit worn now.
PS. That tyre you have been saving for a rainy day, either sitting in the shed or on a trailer not getting any use is going to loose its elasticity and the hard rubber will also heat up and fail.
These are some of the lessons I have learned from about fifty years of country driving
Mike
AnswerID:
133124
Follow Up By: Patrol2 - Wednesday, Oct 05, 2005 at 11:07
Wednesday, Oct 05, 2005 at 11:07
One more thing regarding puntures in rear tyres. Ever noticed that nails, sticks and other small sharp objects seem to only spear into the rear tyres. The next time you are following someone on a gravel road, notice how a lot of debris is lifted above the surface level of the road. The front wheels do this also, I think it is the vacumn immediately where the tread lifts of the the surface. Anyhow, if the front wheel debris contains a puncture inducing object, then the rear wheel will arrive before that object has settled back flat on the road. VIola, puncture in rear tyre.
Mike
FollowupID:
387338
Follow Up By: Crackles - Wednesday, Oct 05, 2005 at 21:47
Wednesday, Oct 05, 2005 at 21:47
Thankyou Mike, finally some common sense. I have run 2 sets of tyres (radial & crossply) for the past 22 years swapping & rotating them indiscriminately front to back & left to right with the sole aim of keeping tyre wear even.
Have only had two total tyre blowouts the first a rock in the sidewall then driving a further 5 km as it went down & the 2nd caused by the tyre joint putting an under sized tube in.
I agree also that speed, loading & preasure have far more to do with catastrophic failure than tyre rotation ever would. After watching the distruction of a couple of Firestone tyres on a Ford Exploder, I will conceede that some inferior designed tyres could be susceptible to being spun the other way.....
Cheers Craig.
FollowupID:
387399