The first thing I wanted to do with my Saab 96 was to establish a baseline weight. The cheapest scales used for racing are over $700, so that wasn’t an option. People have used bathroom scales but I’d rather not own sixteen bathroom scales. One idea I thought of was to use the tires themselves. I haven’t searched to see if anyone else has been as genius/dumb enough to think of this. Sometimes it’s more fun to try to answer your own questions.
It made me wonder... how about if you were to ink your tire treads, roll the car onto plain paper, draw a couple of marks at the leading/trailing edge of each tire (so you know what to ignore when rolling the car back off the paper), flat bed scan the results, and work out the contact area based on the number of dark pixels in the image (you could get the image scale from the scan DPI)
Hello. Thanks for the article. Looking for a little clarification.
You wrote "The grooves going around the circumference of the tire were deeper than the ones going across the tire. I redid the calculations only accounting for those grooves"
Which "those" grooves do you mean. The ones ground around the circumference or the ones going across? Also does "only accounting for those grooves" mean you discarded the area modification for "those" grooves, or that you only kept the area modification for those groves and discarded the others?
Any scrap yard will have drive in scales, I've weighed my truck that way before. I called beforehand to make sure they were ok with it, and they said it was fine for a one off use.
Though there's also nothing stopping someone from driving in and immediately driving out the exit without unloading anything
That's a lot less fun than using tire pressure as a scale, though
So sometimes tires are filled to higher pressures. And then there are different size tires both in width and diameter causing different contact patches. This is not a way to measure car weight. I thought you were going to measure tire pressure on jacks. And then remeasure with the car on the tires. Unfortunately i think this will also not work due to the elasticity of the tire
On threads manufacturers provide % tread/space ratio as that to traction on various surfaces and weather conditions. For your purpose the sidewall wouldn't matter as you're dealing with static load, not dynamic.
An enjoyable read!
It made me wonder... how about if you were to ink your tire treads, roll the car onto plain paper, draw a couple of marks at the leading/trailing edge of each tire (so you know what to ignore when rolling the car back off the paper), flat bed scan the results, and work out the contact area based on the number of dark pixels in the image (you could get the image scale from the scan DPI)
For what it's worth, this works on much larger vehicles as well, but the sidewall stiffness becomes more of an issue because of the scale. https://www.komatsuamerica.com/equipment/trucks/electric/980e-5. Great work!
Hello. Thanks for the article. Looking for a little clarification.
You wrote "The grooves going around the circumference of the tire were deeper than the ones going across the tire. I redid the calculations only accounting for those grooves"
Which "those" grooves do you mean. The ones ground around the circumference or the ones going across? Also does "only accounting for those grooves" mean you discarded the area modification for "those" grooves, or that you only kept the area modification for those groves and discarded the others?
Thank you.
Any scrap yard will have drive in scales, I've weighed my truck that way before. I called beforehand to make sure they were ok with it, and they said it was fine for a one off use.
Though there's also nothing stopping someone from driving in and immediately driving out the exit without unloading anything
That's a lot less fun than using tire pressure as a scale, though
So sometimes tires are filled to higher pressures. And then there are different size tires both in width and diameter causing different contact patches. This is not a way to measure car weight. I thought you were going to measure tire pressure on jacks. And then remeasure with the car on the tires. Unfortunately i think this will also not work due to the elasticity of the tire
On threads manufacturers provide % tread/space ratio as that to traction on various surfaces and weather conditions. For your purpose the sidewall wouldn't matter as you're dealing with static load, not dynamic.