Determine Ride Height on a Frame Up Build?

[LateNight72]

It really depends on the tire, pressures, etc. For instance, I will be running 30 series tires on the front suspension I am building (the one with a thread a couple down), and 35 series on the back, whenever I get around to designing an IRS.

The tire "squish" is negligible in a 30/5 series that's properly inflated.

[BBShark]

Originally Posted by LateNight72

It really depends on the tire, pressures, etc. For instance, I will be running 30 series tires on the front suspension I am building (the one with a thread a couple down), and 35 series on the back, whenever I get around to designing an IRS.

The tire "squish" is negligible in a 30/5 series that's properly inflated.

Even if it's a 1/2 inch, it's not "negligable". Take a look at what it does to your IC calculation in your thread. Seems like if you are doing these layouts for geometry, you want to start with the most accurate information.

So, do the tire manufacturers give you this info or................?

[LateNight72]

To add to your question,

I redimensioned, taking 1" away from the bottom half of the tires. Mind you 1" of "squish" is very generous for track tires.

Anyhow, the only thing it changed was my rollcenter. It increased my rollcenter by a total of 0.054"

So yes, my notion of it being negligible is sufficient.

[mmliljoker]

if you build everything to function properly at ride hight that you want i don't think that the tire squish is going to be a problem. Think of it like this the tire is squishing, the suspension is not moving. As long as your front lower control arms a as close to parallel with the ground at ride hight during fabrication you will be fine. you will have enough adjustment in the suspension to fix any tire squish woes. There is no possible way on a project like that to know the exact total finished weight of the car and that would make a lot bigger diff on ride hight geometry then tire squish. Don't over think it. set every thing up at ride hight and adjust out. One more thing put the calculator away and have fun its only metal.

[B_Alley]

if you wanted to get really fancy...

in a race setup, you want the vehicle as low to the ground as possible, and you can find that once you know the vehicle's wheel rates (a function of the tire spring rate and the spring rate of the suspension, effected by motion ratio) and know how much lateral acceleration and longitudinal acceleration the car will see...

Also, the tire will compress under static loading because it is a spring itself. If at a certain inflation, the tire spring rate is 2,500 lbs/in and you have a 3300 lb vehicle w/ 50/50 weight distribution, thats almost 3/8" of compression, just in the tire alone...