k value, 40:00 X 57 tire. 1

[bradleyelwood]

I am interested in the K value, (vertical spring constant, kips per inch of deflection) of a 40:00 by 57 bias tire. The tire is inflated to 145 psi and carries 300 kips at very low speed. Does anyone have test data?

The second part of the question is: What happens to the apparent vertical spring constant if the tire moves over a step such as moving over a 6 inch curb?

 

[cibachrome]

Would that be a 68 ply or 76?

 

[bradleyelwood]

cibachrome,

I was beginning to think that nobody read this message, thanks for the responce...the tire is 76 ply.

 

[CapriRacer]

I would think the obvious answer is to ask the tire manufacturer.

 

[bradleyelwood]

We now have the K value from Firestone and Yokohama at somewhat lower pressures, 29 to 40 kips per inch, close enough. We also measured K at 33 kips per inch at 135 psi, good enough for what we need.

Can anyone tell us what happens when a tire goes over a step? I would think that the apparent K value becomes smaller, say 60 per cent. Does anyone have experience to confirm this with smaller tires, even if the tires are highway truck tires or earthmover tires?

 

[GregLocock]

I think you are referring to the enveloping action of the tire?

There is a problem with most analytical tire models in that the tire 'sucks down' onto a step, sadly that is all I know.

you might have some luck with any of pacejka's books, or the ftire's developer

http://www.cosin.eu/prod_FTire

who seems to be a jolly helpful person.

Cheers

Greg Locock


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