Here are the values I come up with using the FT kit setup:
Red springs front #2 hole on tower, inner on arm = @3.6
Gray springs rear #1 hole on tower, inner on arm = @3.34

I didn't have a protractor handy nor take the time to calculate the shock angles but rather guessed.

It doesn't matter where you start. Pick a spot. Any spot. Any spring. Any location. If it doesn't balance, start moving things around until it does. We've already stated the guild lines of what changes what in regards to rate and shock location. If you can't make them balance no matter what you do, change a spring on one end and try again. Repeat as often as necessary.

Only YOU can determine what works. This is not a thread full of answers. This is not a thread with posted setups to copy. I am dead set against those anyways. This is a thread talking about a technique that people can learn for themselves that will allow them, potentially through a whole lot of time and effort (that's the bad news), to arrive at a nice setup that works well for them.

That's great, but what happens when you change to springs of a different manufactuer? The Losi springs reported rates are consistent with one another, but they aren't equivalent to how they are rated by AE, or Kyosho, or Yokomo. How do you handle that?

I believe you misunderstood what I wrote. What I'm suggesting you do is actually rate your own springs on your own car, which is what Fred is suggesting, but I'm taking it a step further. This will require you to do your own work and create your own data. So, let's go back a couple of steps and recap.

Fred is suggesting you find a set of springs with matched frequency by observing their frequency during testing.

I am advocating you find a set of springs with matched frequency by measuring wheel rate, and then doing the calculations to figure out the frequency (which is related to shock mounting position, spring selection, and the amount of dead weight you have on the axle you are measuring) and then verify your data by using Fred's method to ground truth your work.

When I attempted to use Fred's method, I realized it would work but it didn't give me any empirical data that I could refer back to. Lets say I got four sets of matched springs at different stiffnesses. While I know which is softest and which is stiffest, how do I how how soft and stiff they really are? And how big are the steps in between?

Now we can start asking other useful questions while we're at it, like how much does moving a mounting hole over really change things? Did I make a mistake in measuring because I find an inconsistency in the data, or is there something else going on? And then it occurs to you that once you figure out how to measure your chassis, you can go out and measure any other chassis of any other manufacturer and bring that setup over to your totally different chassis - and with your data book, you can do it right now.

The downside is it requires a significant amount of testing and data collection on the bench. My first dataset took about 30 hours to measure. These guys are using the same method to measure the stiffness of sway bars, but how you would figure out the wheel rate is exactly the same way.

http://www.circletrack.com/chassiste...s/viewall.html

What I'm doing now is calculating how adding/subtracting weight or moving it changes wheel rate and frequency. We commonly refer to that as moving the battery. If you need a chassis to 'cut' harder entering the corner (like a hairpin), you move the weight back. If you need it to have more constant arc grip (like a sweeper) you move it forward. But that also changes the spring frequency - if you can measure it, you can account for it, and make changes accordingly.

If I change springs then I'll test them to see if the manufacturer was close when they spec'd them.

Regarding wheel rate you are correct! My numbers were based on the wheel rates of my SC10 using my electronics & my battery mounted all the way forward. Moving/changing any of these can & most likely will change wheel rate.

Here is what is weird. According to the formulas I found the wheel rate went up when the shock was angled more. This in turn increased the spring frequency using the calculation I found to determine that. I'm scratching my head trying to figure that one out. Must be something I'm doing wrong.

In an ideal world we can measure things, put them into cookie cutter formulas and model an expected result. I think Fred is trying to tell us not to do that but to 'bench test'. Being I'm totally left brained and analytical I'm always searching for a mathematical equation.

This is an interesting thread!

I'm sure the mfg's specs on the springs are fine. But the way they rate them is different between mfg's. Let me be more blunt:

The only thing the manufactures ratings are good for is figuring out which spring is stiffer or softer in their product offering. Associated truck rear greens are rated at 1.9 ICRC. Losi big bore rears in red are rated at 2.6 and they measure SOFTER when mounted on the same vehicle and checked for wheel rate.

The whole reason I started reading this thread, and doing these measurements, is I wanted to convert from the AE springs to big bores, but I couldn't figure out what the equivalents are, and I didn't trust the spring charts. Turns out I had good reason to be skeptical.

If you look at the article I linked, they are doing exactly that.

Fred and I have discussed this extensively, he and I do not disagree. The method I am advocating is in addition to what Fred has suggested. It is imperative that you preform Fred's method after you do it my way to ground truth that your calcs are right. I read this thread in its entirety before it occurred to me there was a way to measure and catalog what Fred is suggesting.

I farm for a living, but I'm trained as an accountant. To me, farming with living things is simply an extension of cost accounting. I take this "management by numbers" very seriously in both work and play - you should see my home theater.

Indeed.

I find it difficult to understand how wheel rate could go up as the shock is laid over further. Here's an example of why. Let's say you have a shock standing straight up and down. We know it's going to have full leverage over the suspension arm. Now lay the shock completely over on it's side 90 degrees but don't give the arm a way to transfer motion 90 degrees to it. The full laid over shock now has zero leverage on the arm. It has no wheel rate. If you lay the shock over 45 degrees it too has less leverage on the arm than a vertical shock and hence a lower wheel rate.

Shock mount location on the arm has a larger effect than shock mount location on the shock tower. If you move a shock outwards on an arm, it has more leverage. This is a higher wheel rate. If you move the bottom of the shock inwards, your wheel rate goes down since leverage on the arm goes down. By moving the top of the shock and slightly changing it's angle, you are fine tuning the wheel rate. Let's say one location on the bottom is very close to where you need it and the other location is very far off. Obviously you use the closer one. Now you fine tune the upper position until you get it where you want it. Your frame of reference is the other end of the vehicle. That's what you are trying to match.

Again, don't over think this. Pick an end and work at it until you find a match. If you don't fine one, play with the other end to see if you can find a match. If you can't, change springs at one end and against keep trying.

It is very possible to figure out a formula to help you predict what spring rates will match at each end based on location and vehicle center of gravity. Craig has done that but at a considerable amount of his own time. At the very least he'll get close since advertised spring rates aren't always what they truly are in reality. They should be close though.

What I did on my old RC10 is to find a shock mounting location and spring combination that balanced. I'm not going to get into where the shocks were mounted since my suspension isn't even the same geometry that it was when stock anyways. In my case it was AE blue rear springs (2.55 lb) and AE green front springs (3.5 lb). The ratio between them is a spring rate that is 1.37 X more in front than rear. Weight different front and rear and shock leverage over the arms is the reason why these aren't the same or why a higher spring rate isn't used in the rear. Keep in mind this is using these exact same mounting locations and the exact same vehicle weight and distribution. If I want to change spring rates and use the exact same mounting locations, I already know that whatever springs I choose must also use a 1.37 or near ratio for balance. Let's take this further.

What if I want a lower wheel rate. Let's say instead of the AE blue rear springs that I want to go down a spring rate from them. That means I'd be running AE gray rears which have a rate of 2.33 lbs. I need to take that 2.33 and multiply it times 1.37 to see what fronts balance them. 2.33 x 1.37 is 3.19. AE black front springs are 3.2. Bingo. I just lowered my wheel rate and didn't have to change shock mounting locations at all. Coincidentally it just so happened to be going down to the next lighter spring offered by AE for both the front and rear but this isn't always going to happen. It will happen less often than more. Now keep in mind since the given spring rates and the actual spring rates may be a little off, I may have to move the top of a shock over a hole to get true balance again but this is close enough.

Keep in mind I am only using 1 shock mounting point as an example. I haven't figured out every possible combination on that car yet. There are tons of other springs that fit my shocks too so I'm sure there are many other combos out there. I've just shown you 2 that work out on one of my personal cars.

Craig, let me take a stab at something. You and I both think alike. We like to see quantitative data and formulas to back up the things we observe in the real world. I assumed you were looking for a way to back up what Fred is describing. Funny thing is, the same thought went thru my head but I didn't know where to start. When you prompted me to google spring frequency much to my amazement there was actually something out there. You farm for a living? Oh my! You have my utmost respect! Things aren't what they used to be.

By the way, the 'sprung weights' I used were 13 ounces on the front corners & 21 ounces on the rear. I also found moving the lower shock mount location increases the spring frequency by about 10%. Do you have a way to measure your springs? Years ago I used a drill press to compress springs on a scale. Rather crude, but I only wanted to match left & right.

Fred, I agree with you on laying the shock over at the tower. My information came from the first source I google'd. Obviously there is an error someplace. I will keep searching. Maybe it's the way the formulas were put into Excel.

It doesn't. As you lay the shock over, you calculate a correction factor that is a decimel that reduces the spring rate.

http://performancetrends.com/Definitions/Wheel-Rate.htm

Like Fred said, don't over think this. Be aware that the angle changes things and how it does, but remember on an RC car with significant amount of wheel travel the angle between the spring and the arm doesn't remain constant throughout the travel, so the rate changes.

That's where things really start to get complex since one spring/shock mounting location and another spring rate/shock mounting location that arrive at the same wheel rate in the bounce test may result in slightly different handling characteristics since the leverage of the shock is a bit different through suspension travel. That's where real fine tuning is done and it's the part that is hardest to put into words.

My general guideline for what I'm personally looking for is for my shocks to be at exactly 90 degrees to the arm when the suspension is fully compressed. I try to shoot for the same angle front and rear. That's my goal. I get as closed to it as possible. I prefer not to have a situation where the front shocks are vertical but the rears are laid over or vice versa. If you guys haven't figure it out yet, I like things pretty well balanced.

Since your here...
I have done a partial on the method and I am very happy with the way the springs turned out, but I've lost track of droop. When changing upper and lower shock positions the droop changes quite a bit. Is there a rule of thumb when it comes to measuring droop? Do you try to keep that balanced?
I've done the search, read the thread about two months ago, and had bad luck finding the info.

This is a great thread, while I haven't finished the setup method entirely it has encouraged me to think logically about setup. Helped me to understand why adjustments are made.
Thank you.

Well balanced is good. I like to start by setting everything in the 'middle'. That way if something needs adjusted there is 'wiggle room'. Logic would tell me if you are extremely one way up front and another on the rear something isn't right. Same would go for left & right. Oval races might disagree because they mostly go left.

I need some more time to play with springs.

So how you apply this setup method to nitro where the weight of the vehicle is not constant throughout the run? Do you tune at 1/2 a tank of fuel? Tune light, tune heavy? Go by driver preference?

How do you account for differences in the tires? Density and stiffness of foam is going to change your results between the table and the track. Indeed they will also provide some level of damping. And then once you change tires... My head is spinning.

Tires is another aspect of tuning. It is separate from everything else. One thing at a time. There are many things that affect handling.

In regards to nitro/gas cars, I'd use the average or middle fuel level. The worst case scenario is that your imbalance is off by half the weight of the tank. If you tune to either full or empty, the worst scenario is that the weight of the entire tank is the amount you are off. Location of tank will affect things too. I have only ever run electric. Keep in mind that on a real car, if the vehicle weighs 2500 lbs and a tank of gas is 18 gallons, that's only a little over 100 lbs difference full to empty which is only a few percent.

I got the springs balanced.


Using green rear and silver fronts on an SC10RS. All as close to the center of the truck as they go top and bottom. Battery in the middle. Running bones level on the rear and a bit higher than arms level on the front.


I've chosen to start with 30W all around as I have 25, 30 and 35 to try out.


I haven't driven it yet. I have batteries charging as I type.


The drop test after balancing the springs and putting oil in just "looks right" if maybe a little stiff.


I'll let you all know what I find.

I just pulled the trigger and did my T4, and I ened up with the same springs as you. I went with Losi 25wt rear, and AE 40wt front. And I, like you, thought it felt good with the drop test, all seemed pretty flat, but yet it feels stiff. Much stiffer than it has ever been before. But it wont be till Friday at the track till I can test it out and see how it really feels.