fatbillybob

Anyone ever make a rig to test leaf spring rates?

coffey

I haven't but I would. Should be pretty easy. Make it as an add on to a standard spring checker.

davidfarmer

I just did it using the car. I strapped the car down on the lift, put my digital scale underneath, and used a 4x4 to connect the two. Measure deflection vs load at several loads, then average them out. Of course you need to correct actual rate vs wheel rate to have a usefull measurement.

I started just using the weight of the car, but found I needed some weight and/or straps to pull down to get adequate deflection. You need a reliable point of reference for your measurements also, but it's not hard.

fatbillybob

That's a good idea Dave.

ghoffman

That is a really good idea because how you mount and load it is critical to getting accurate results. On each side, the spring is a cantilever beam and the deflection goes as the length cubed! So if the spring is say 20 inches long, a 1/4 inch difference in where the load goes equates to almost 4% difference. So, judging from your previous posts, if you are trying to see a degradation in rate over time, 4% error or scatter in the data, is very relevant. So, just do whatever you decide to do the same way every time. It would be very interesting to see how much the opposite side moves as well when you load the spring to confirm/deny the leaf spring "crosstalk" theory.

fatbillybob

Very true! The leaf will deflect to an "s" to a certain degree and act like a coil spring and a sway bar at he same time. So I suspect there is crosstalk by design. I like your idea of checking the other side to measure deflection if any. I got these rear stock '04 Z06 springs and T1 springs. The T1's are flatter and have 2mm more material on them but when I jump on them they feel exactly the same. I figured the T1 would be noticably stiffer but maybe they are when put in the proper positions. The Z06 spring larger arch would provide more droop which I think would be a benefit. I'm thinking the arch difference is like number of coils on a coilover altering rate. Basically I'm fumbling around with a number of things just to see if I can gather any useful info.

0Randy@DRM

The funny thing is I was just thinking about doing this again. We have a chassis on the lay out table and I'm going to have my suspension apart, and have some pin top testing that should be done. Now with video cameras, digital cameras and etc this would be a good thing to show the forum. We have done it in the past but for our own good.

During the Corvette challenge we tested hundreds of springs.

We know the answers, but that doesn't work anymore. Now we have to show the customers more to make a few sales....

Crosstalk is one of things on the list of things to test again.

Now how to find more time in the day....

Randy

fatbillybob

I'd love to see what a pro does. Frankly I'm trying to find my A$$ with both hands. I guess one of the things I would like to find out is if the Z06 spring is truely lower rate than the T1 spring as advertised. In the rear springs are easy to change. So I'm thinking things like whats better to soften up the rear in the rain by a spring change or a sway bar disconnect or both? Without testing I don't know the wheel rate of the T1, Z06 or the sways. If you got numbers I'm all ears.