Does a 5 degree slope affect front rear reading? If so, the lower side (elevation) would read higher or lower (pressure), vs. flat?
Checking Tire Pressure on a Sloped Driveway
- Thread starter Jonny Z
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One would need to know your vehicle's wheelbase and the height of the CG to give you a quantitative answer, but the short answer is no difference you would see on a normal tire gauge.
I don't think the effect on pressure would be measurable with a tire pressure gauge.
We measured the tire pressures of a vehicle on a lift (tires completely unloaded), and then on the ground, and the pressure increased a maximum of 0.5 psi (we used a very accurate gauge)
I would think a driveway could be as severe as that!
I would think a driveway could be as severe as that!
Only if it was vertical
Did you forget an n't?
It makes no difference pretty much. Just like when you measure the pressure when the wheel is off the car (think: your spare in the trunk), and then you put the wheel on the car - it'll have the same pressure.
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Only if it was vertical
Did you forget an n't?
Yup, that's exactly correct.
Mr. Moderator, could we get an edit function?
NO!!!!
Whatever volume is consumed by the "flat spot" on the bottom caused by vehicle weight will increase the pressure in the rest of the tire.
The lift example is a great one.
Now imagine having 5% different weight on different tires due to the hill, and multiply that by the 2% difference in pressure you get between loaded and COMPLETELY unloaded... 0.1%!
The lift example is a great one.
Now imagine having 5% different weight on different tires due to the hill, and multiply that by the 2% difference in pressure you get between loaded and COMPLETELY unloaded... 0.1%!
Heck check them in the air and on the ground. Never seen a meaningful difference either way. The pressure is their to maintain tire shape not hold up the car.
I measured on a lift and off, and it was about a pound difference? More than I thought even.
Can I delete or edit my first post?
[image]http://www.geocities.com/jason_ettorre/tirepressure/frontupgauge.txt[/image]
[image]http://www.geocities.com/jason_ettorre/tirepressure/frontdowngauge.txt[/image]
[image]http://www.geocities.com/jason_ettorre/tirepressure/frontupgauge.txt[/image]
[image]http://www.geocities.com/jason_ettorre/tirepressure/frontdowngauge.txt[/image]
Kestas
Staff member
The way I find answers to this question (and many others when I studied engineering) is to look at the situation 'in absurdium'.
Let's say you took a tire and put enough weight on it until it looked flat. Would you expect the pressure to rise?... I would. After all, there's plenty of resistance (increased pressure) to push the tire back up. Plus, I don't expect the tire to significantly bulge out to accomodate the displaced air. So it stands to reason that a little extra weight will raise the tire pressure. Whether it's enough to worry about, I'll leave that for you to decide.
It's kinda like the question presented to me once.... "A guy on a lake in a canoe throws a penny overboard. Does the water level go up, down, or stay the same?... and why?"
Let's say you took a tire and put enough weight on it until it looked flat. Would you expect the pressure to rise?... I would. After all, there's plenty of resistance (increased pressure) to push the tire back up. Plus, I don't expect the tire to significantly bulge out to accomodate the displaced air. So it stands to reason that a little extra weight will raise the tire pressure. Whether it's enough to worry about, I'll leave that for you to decide.
It's kinda like the question presented to me once.... "A guy on a lake in a canoe throws a penny overboard. Does the water level go up, down, or stay the same?... and why?"
jje, your .jpg files are mislabeled as .txt files.
I can't link them as jpg files, so renamed them txt files to fool geocities. It looks like this board won't link to a txt.
However, I had the car on the ground, and saw 32psi. Lifted it on a hoist, and saw 33psi. Just to be sure I did it a couple of other times and on the rear axle too, and the same numbers kept repeating.
However, I had the car on the ground, and saw 32psi. Lifted it on a hoist, and saw 33psi. Just to be sure I did it a couple of other times and on the rear axle too, and the same numbers kept repeating.
Aaarg, why can't I edit...
The tire construction looks really good for keeping a stable shape under internal pressure - but maybe not so good keeping that shape under vertical load, so one might think the volume in the tire isn't the same with the car on the ground compared to car on the hoist.
I'm ready for your comments.
The tire construction looks really good for keeping a stable shape under internal pressure - but maybe not so good keeping that shape under vertical load, so one might think the volume in the tire isn't the same with the car on the ground compared to car on the hoist.
I'm ready for your comments.
It will work, but you have to put url tags around it, not image tags...
http://www.geocities.com/jason_ettorre/tirepressure/frontupgauge.txt
http://www.geocities.com/jason_ettorre/tirepressure/frontdowngauge.txt
http://www.geocities.com/jason_ettorre/tirepressure/frontupgauge.txt
http://www.geocities.com/jason_ettorre/tirepressure/frontdowngauge.txt
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