It's BS.

 

and then they accidentally push the trash button and there goes ur evo

 

The tire is not entirely being held up by air. The stiffness of the sidewalls adds pressure. Not to mention that flex in the tire varies the pressure over the contact patch. This method won't even get you in the ballpark.

 

Not to mention different tire designs, wall stiffness, size and elevation you are on, warm tires, cold tires, if surface is bumpy did the paper go as far as it could? "If its within 10% of factory weight, you did a good job" Might as well look up factory weight and do some math with what you put in and taken out.

 

The video is a nice try in estimating a vehicle's weight or technically in engineering term, "mass". The internal tyre pressure does not apply to the actual contact patch's pressure as all the internal pressure in a tyre is cancel out inside due to the prefect symmetry of a circle. The mass of the tyre together with the air inside does accounts on the contact patch area. If I am not mistaken, slightly adjusting tyre pressure to gain or lose tyre grip or contact area is more to do with the property of rubber with other factors and adjusting torque with the tyre's radius. Tyre pressure does affect a contact patch area when the internal pressure is unable make the tyre inflated properly, no longer a good circle.

The measurement of the contact patch areas also ignores the tyre tread. Contact patch changes with other parameters, but those are beyond basic discussion.

 

lol yes, the contact patch will be a perfect rectangle/square.

 

This won't necessarily get you absolute accuracy...but I suppose it could be useful to get relative accuracy between the tires if you are trying to get rough corner weighting done. I'll put this in with the DIY alignment for things that are cool/fun to do at home, but that I enjoy paying my suspension and alignment shop to do.

Where did you get your engineering degree?

 

By the sounds of that comment, elementary school haha

 

Currently, I'm studying at University of Windsor working toward a mechanical engineering degree.

 

I don't know about you guys, but I think that chicks accent is sexy.

 

study harder.

 

I'd consider this proof that it won't work:

A neighborhood brat pulled all the valve stems from a dozen cars parked in the street. But I thought he missed my fiberglass dune buggy. Uhh, no, he didn't miss it...but when he removed the stems the tires didn't go flat due to their stiffness.

So using her method, I'd come up with an area for each tire and multiply by zero. Final answer, the buggy weighs zero. Don't think so.

To be fair, she did say to air the tires up first. But the above demonstrates a big source of error.

-- Bill

 

Actually, you are wrong. The contact patch will be closer to a circle.

Here is your proof:

http://www.rmcbmwcca.org/DrivingScho...ntactPatch.jpg

 

why doesnt someone just try it instead of speculating.

 

haha sorry chief, but #1 those are still closer to rectangles/squares than circles and #2 if you know a little about physics you know that the contact patch between any type of semi rigid tire and a surface is in theory a perfect rectangle/square and in practice a slightly bulging four sided figure of your choice.