tyres 1

[ally89]

Could somebody advice, how to calculate ground preassure area on the truck wheel tyres in depend of the air preassure in the tyres and aplied load on the truck?<br>
How to calculate deflection on the tyre and shape of the tyre before and affter applying a load?

 

[MikeAnderson]

Well, that's a hard one.. It's not so easy to calculate deflection over load. Usually the tyres are specified for a particular pressure for a particular load, up to a max. pressure for a max. load. This gives the same rolling radius for the tyre. By nature deflection is not linear against load for a particular pressure. The manufacturers data sheet will state unloaded Outside dia of tyre, rolling radius (which is the load condition). This can be assessed by experiment if the data sheet is not available. You just have zto measure the distance travelled during one rotation of the *loaded* tyre to find the rolling radius. The O.Dia can obviously be measured, as can the width of the contact patch. The length of the contact patch can be calculated using chord formulas (you could also measure it's length quite easily, if you can drive it onto a glass plate you can get under). If you measure with different loads and pressures, you can build a set of deflection curves for that tyre/load combination.

 

[ally89]

Hi Mike,<br>
Thank you very much for your comment.<br>
Now I'm sure that I hve to conduct particular test.<br>
I thought that the tyre's manufacturers have done<br>
some of the testing and have data I'm looking for,or are there some books I can find formulas to calculate ground preasure area under tyres.<br>
However thank you again.<br>
Sincerely,<br>
ally89

 

[MikeAnderson]

You won't get much more data from a manufacturer, because they don't usually have more than is published.<br>
<br>
Just jack up the wheel and lay a piece of square ruled paper under it and let it back down onto the paper. When you've jacked it back up and got the paper out, you can count the squares, but that will only be for the static condition. Tolerance abot +/- 5%<br>
<br>
When you drive the contact patch gets smaller the faster you go, the slip to the road gets higher. Same if you drive in a corner, brake or accelerate, the lateral and longitudinal loading reduces the contact area. <br>
<br>
The area you've got, the pressure is load through area.<br>
<br>
Why do you want to know this? What are you trying to do?