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# Tyre load pressure / bearing effect

## Tyre load pressure / bearing effect

(OP)
Guys,
Need your help here if possible. I am currently working for a transportation company doing platform trailers or so called heavy haulage.

Currently i am studying on the ground pressure effect from tyres and i have been searching the net for some info but can never find a solid one on this. can anybody help me?

how do i calculate the bearing pressure effect from the laden load to the tyres and finally to the ground? Also what is an accurate tyre-contact-area technically?

is it true that the bearing load from the tyre is equivalent to the tyre inflation pressure? or is there any other co-efficients involved. I don't quite understand this actually.

Can anybody kindly help me or lead me to the right path? have been searcing in and out but to no avail. Maybe i searched wrongly. Anyway hoping for some light from the many 'sifus' here..thanks in advance.

### RE: Tyre load pressure / bearing effect

Tires have a loaded radius (at recommended inflation values) and a nominal radius, as well as a width.  Knowing the nominal radius, the loaded radius, and the width, and doing some arc/chord math, you can come up with a footprint area.

rmw

### RE: Tyre load pressure / bearing effect

(OP)
thanks for your reply but could you imagine me being a dummie and explain / elaborate more on even the terms? :)

### RE: Tyre load pressure / bearing effect

The specific contact pressure of a tire is almost exactly the same as the air pressure inside the tire.  Variations are due to whatever stiffness exists in the tire structure, but those values are small.  Tread pattern figures in little for a street-tire, but the purpose of a tractor tire is to put a lot of weight on rigid lugs to force them into mechanical engagement with the earth.

If the tire pressure is 2 kg/cm2, and the weight on the tire is 500 KG, look for a contact patch of 500/2, or 125 square CM.

Adding more weight compresses the air slightly but flattens the contact patch to put more area on the road surface.

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