fredswain- Got a quick question. I built a spring pressure test rig. Positive stops adjusted to compress spring down 3/4 of height. I took measurements on 4 pair of AE big bore springs; 2 fronts & 2 rears. Here are the results:
Front white: 3.24/3.46, blue: 3.84/3.73
Rear white: 3.09/3.06, black: 2.80/2.80
Only one pair of the lot are matched. How critical is it to have matched pairs left and right?

I'm not Fred, but balance is good. .10 of a pound isn't much, I personally wouldn't be concerned about it. Are the springs new? If yes, then run them for a couple races and re-measure the spring resistance, I bet they weaken up a lot. Remember, spring return rate (speed of return) and spring resistance (in lbs) are two totally different things.

Yes I measured the springs straight out of the package.

Hideeho
Considering the front whites are off by .22 & the jump from one grade to the next is only .1, I'd call that pretty significant. With that kind of deviation, I would think it would be a good idea to measure & try to match springs.

This is a measure of spring resistance & I understand how it is measured, but how do you measure return rate? would that be a formula involving the spring resistance, density & diameter, among other factors?

Return rate would be done as explained in this thread...complete shocks minus oil, mounted and cycled. My concern was if small spring pressure differences are acceptable prior to return rate testing or should you test a ton of springs to get a perfectly matched set first.

I'm about 40 pages through this thread (reading every one, not something I do very often).

By page 2 I had my rig on the bench and torn apart.

Had it out on the track today and whoa, what a difference. I thought I had it setup good before, now its way, way better. It still needs some fine tuning, but it's like a completely different truck.

A huge thank you to everyone who has contributed to this thread.

You might want to do a guage study on your test jig. Fixturing of the spring and differences in the measurement process could also lead to the results you are seeing.

Congratulations. Iv'e been doing this forever and I am just smart enough to cut and paste the good stuff as I read page after page... then print it for the notebook. Between theory and practice some of us just luck out.

What exactly do you mean by "gauge study" ?

It's a component of a proper measurement system analysis. Verifying the measurement fixtures ability to repeat and reproduce a measurement. We're obviously just "playing with toys" here so I would guess that you would simply want to fixture repeatedly the same spring and take measurements off of it. If your results vary by a ton you obviously have something wrong with the fixture. I've never checked spring rates before so I can't speak from experience but the results above showed what I would consider to be a LARGE variation that we would not want in our application on small vehicles.

I'm such a geek....

The spring test rig I built is pretty accurate with repeatability. I did have one pair that were matched, but the others were off. Now how far off can they be from each other without creating suspension imbalance...I have no idea. Unless someone is paying me to race, im certainly not going to buy $200 worth of springs just so I can get dead accurate matched pairs.

I've had a lot of suspension tech rolling around in my head for a long time, but have always had a hard time making everything click and actually applying it. Once I ditched the old way of "tuning", and thanks to Fred for giving us an actual working method, its all starting to come together.

Now don't go beating up on the locals too badly, they won't want to play with you anymore.

I don't think that is going to be a problem. Good tuning doesn't fix poor driving.

I'm trying to tune my car for a very bumpy track, and I'm confused about the camber link locations.

The Hudy offroad setup guide says :
But I read on http://www.rctech.net/forum/electric...ber-links.html :
So HUDY says low camber link for high grip conditions, this thread says low camber link for bumpy/slippery tracks.

Which one is it ?