Poor man's corner weight/tire contact area calculation

[socalsilverRL]

Ok, so I found a cheap way to measure the corner weight of your car. No need for scales, no need for fancy stuff...

What you need:
2 x sheets of 8.5x11 notebook paper
1 x Imperial ruler
1 x Imperial tire pressure gauge

Optional:
1 x square, carpenter's square, or something to help you square the paper to the tire.

First, make sure all 4 tires have the same pressure (i.e. 40psi). You dont have to, but it makes things easier when you make your calculations.

Step 1:
Next, you will be measuring the length of your tire contact patch in inches. So, take your two pieces of paper, and your ruler, and place them on the ground. One piece in the front of the tire and one piece in the rear of the tire (see fig. 1). You want the pieces of paper to be perpendicular to the tire. Make sure the pieces of paper are tucked as far under the front/rear of the tire as possible, then measure the distance between them.
Fig. 1:

Write down the distance on your work sheet. (Optional) Repeat a few times to ensure accuracy.

Step 2:
Now, you will measure the width of your tire contact patch in inches. Take your pieces of paper, and place one on the outside of the tire, and one on the inside of the tire (see fig. 2). Make sure the pieces are perpendicular to the tire. Tuck as far under the tire as allowable, then measure the distance between the pieces of paper.
Fig. 2:

Write down the distance on your worksheet. (Optional) Repeat a few times to ensure accuracy.

Step 3:
Repeat steps 1 & 2 for all 3 remaining tires. Write down the length and width for each tire on your worksheet.

Step 4:
You will be calculating the weight on each tire. Calculate the square inch contact area for each tire:
Length x Width = Area in sq. in.

Now, multiply the area of the contact patch times your tire pressure (i.e. 40psi):
Contact Area (in²) x 40psi = weight on tire

Repeat for 3 remaining tires, and youll have the weight at each corner of your vehicle. If each tire has a different pressure, then use that pressure in the calculation for weight.


Technical:
Now, we all know your tire has tread, and its not a R comp radial. If you want to get very technical, you can determine the actual amount of tread contacting the ground. Take your contact dimensions, and mark off that dimension on your tire with chalk. use your ruler and try to determine the total area of all the gaps in your tread. Take that total gap area, and subtract from the total contact area from your previous calculations:
total area - gap area = actual contact area (in²)

Then you will have a more accurate idea of the weight of your car.

Note:
I did this to my own car, and came up with a crazy value of 4400lbs... so it cant be 100% correct. It will be slightly off due to a few things: human error, actual contact area, the fact that your tire doesnt contact the ground in a perfect rectangle, etc...

[hawlyns711]

well i'll be damned, nice post

[socalsilverRL]

^lol, thanks... got that from a physical science project my GF had to do... she was stoked, i was stoked...it worked out pretty good. she got an A on her project. lol...

ill try and post the actual results from her test later tonight.

[kombi731]

huh
sounds cool but doesn't equate always

[socalsilverRL]

^lol... its not too hard, just follow the instructions, and youll do fine. dont think about it, just follow...lol.