Incorrect Information re: Tire Pressure in Efficiency Mods

[theycallmeebryan]

I run 65-70psi on my Ninja 250 Kenda K671 tires, and 65-70psi in my saturn's cheapo tires. I've never had a problem other than a nail the rear tire of the ninja because i was riding down a road where they were doing new construction... the tire would have been punctured no matter what pressure it was at.

[CapriRacer]

Originally Posted by Frank Lee

What are you waiting for from me?

I think I missed the post about the bursting pressure when I posted

- BUT -

Originally Posted by Sularus

Frank Lee, not to doubt you, I know you are very informed about automotive matters, but I have always wondered about tire burst pressure. Can you guide me where to find that information.

I hope I did not come across as sarcastic. I am not trying to be.

J

I think Sularus was looking for something more definitive. In your post, the one link is an article that doesn't mention burst pressure and the other is a link for a forum basically stating it, but no reference to where that information came from.

[Frank Lee]

Yeah, I didn't feel like googling all night when the asker could do the same.

[CapriRacer]

Originally Posted by Frank Lee

Yeah, I didn't feel like googling all night when the asker could do the same.

I did a quick check (Don't have time, now) and didn't find anything about passenger car tires, but assuming we can - and the value is 200 to 250 psi.....

http://en.wikipedia.org/wiki/Fatigue_(material)

That says that we need to consider the fatigue resistance. The sidewall of a tire goes through a cycle for every revolution. 50,000 miles is something on thee order of 30 million cycles.

S-N curves (Stress vs Number of cycles) are similar for most materials - and they show that after millions cycles the strength is actually 20% of the single event value (like a burst test would be).

So 20% of 200 to 250 psi is 40 to 50 psi. Isn't that about what is written on the sidewall? Perhaps that is what the tire manufacturers are referring to?

[PaleMelanesian]

Does a sidewall undergo more fatigue at higher or lower pressure?

[NeilBlanchard]

My guess is that too low or too high pressure would each have different stresses, and neither would be good for the tire's integrity?

[Arragonis]

Doesn't over-inflating wear the middle quicker and under inflating wears the edges ? The wall only wears if you corner 70s french door-handle style, no ?

[PaleMelanesian]

Originally Posted by Arragonis

Doesn't over-inflating wear the middle quicker and under inflating wears the edges ? The wall only wears if you corner 70s french door-handle style, no ?

In my, and many others', experience, the center wear issue went away when steel belts came in. I have my tires inflated to high pressure, and the wear is dead even across.

I can confirm that low pressure wears the edges. I can also confirm that on my car, this includes 40 psi on 44-max tires, when the car calls for 32.

[euromodder]

Originally Posted by Arragonis

Doesn't over-inflating wear the middle quicker and under inflating wears the edges ?

That's the traditional wisdom.

At the correct inflation - according to Volvo - I've had excessive wear on the shoulders, to the extent that I asked the dealer check the wheel geometry, but apparently, it's a common occurrence on the Volvo P1 platform.

Even at 45psi, I'm still seeing a bit more shoulder wear, though it has been largely reduced.

[Arragonis]

Originally Posted by euromodder

That's the traditional wisdom.

At the correct inflation - according to Volvo - I've had excessive wear on the shoulders, to the extent that I asked the dealer check the wheel geometry, but apparently, it's a common occurrence on the Volvo P1 platform.

Even at 45psi, I'm still seeing a bit more shoulder wear, though it has been largely reduced.

Rant alert.

I know the V50 is a totally different car but tyre wear is where (ahem) I fell out big time with my Volvo dealer and decided never to buy another one although Mrs A loves them. The car was a V70 Diesel (2.5D) which (I now know) is bad for tyre wear due to the extra weight of the Audi TDI 5cyl engine.

They failed its safety check on brakes and wanted 500GBP to fix. I took it somewhere else and they said brakes are fine, tyres are worn, safety check is passed.

This is of course after said Volvo dealers charged us 400+GBP for 4 wheeled alignment, missed getting the car aligned 3-times because their alignment tool (at a BMW dealer) was booked, tried to convince us that the rear wheels could not be aligned because of the live axle (its a front wheel drive car, eh ?...) and then failed to fix it at all.

How do you tell if a Volvo dealer is lying ? Their lips are moving.

Rant Off