garrett376

I weighed my car following race impound - when I looked at the numbers I got scared - how is this possible...?

garrett376

Yeah... the scales were in the wrong spot, under the incorrect wheel!! But it took me about 20 minutes to come to that conclusion! I figured there's no way my front end could weigh more than my rear!!!

But, I am curious how my weights are so far off from before... almost like a spring was mis-mounted in its perch...

Colin 90 C2

Were the scales zero'd.
did you have the same weight in the car, ie fluids

garrett376

I didn't see the scales, so I assume they were zeroed - but the car did have the same amount of fluids as it had previously...

I think I'll have to borrow some scales and re-check things...

springer3

Garrett:

The spring constant is about 300 lb/in, so your change could be due to a 1/8 inch discrepancy in the floor. It is possible the 2 nd set of scales has a very small floor elevation discrepancy opposite the direction of a very small discrepancy in the floor under the original set of scales.

Can you get back to the original scales in the original location? That is the only way to know if there was a change in the car. My bet is this is mostly measurement uncertainty due to change in location and change in the instruments used.

Cupcar

This is something I have wondered about, since if you examine a typical concrete slab with a laser level it is not even and smooth.

For the purposes of obtaining the total weight of the car with corner weight scales, a concrete slab works, but for obtaining the corner weights, a bump in the surface is the same as a spring collar adjustment, so it has to be a "dead flat" surface.

Look at the flat table set ups pro teams use, particlularly Formula One.

I think they set up there stuff using laser levels to check flatness, maybe a laser level could be used to shim a corner weight scale set to be flat on a concrete slab or other uneven surface if necessary.

garrett376

I bet you're right, Springer. The club uses the same set of scales - and at Buttonwillow in december my weights were almost the same as I had measured at my house even with a different set of scales. This weekend at WSIR they picked a spot on the asphalt which was likely not level.

Good thinking, guys! I guess I won't bother my friend borrowing his scales... although it is a good workout doing the procedure, and it's kinda fun fine tuning the beast!

chris walrod

Technical inspection doesnt really care what your corner weights are, just total car weight per class specifics. This is why -level- is not important to them.

Cupcar

It just needs to be both level and flat, doable with a laser level.