suspension tuning + upgrades: your thoughts?

[xlr8tr]

Hello all, looking for some direction on spring selection. I'm new at playing with these kinds of things, so bear with me.

Current springs are eibach coilovers 275 lbs/inch rears, fronts are 350. The car is too soft: way too much pitching in all directions, major tourquing on launch. I have no sways front or rear, and shocks are koni's with no adjustments. The car does corner at the moment quite balanced at neutral throttle (with the usual fun when throttle added). Rear end is a straight axle 9" with triangulated 4 link. With the soft suspension and the 4 link there is TONS of rear steer with the amount of suspension travel at the moment .

I'd like to start the upgrade process by going to stiffer springs front and rear. How much stiffer would be a good first jump? 25%? 50%? I'm not afraid to try different ones, i was a bit surprised at how reasonable spring costs are. Eventually sways front and rear will be added along with adjustable shocks, but i want to go step by step on this.

Any and all thoughts and comments are appreciated!

[FWB]

with the 460....600# springs.......i have 500 # with a FE and still too soft, i would loose the non adjustable shocks and just buy a set of adjustable coilovers right away.......

[vatdevil]

Need to view the suspension as a whole..not pieces. Both springs and sway bars affect overall spring rate. So, if you plan on sway bars, you need to include their rate into what springs rate you choose.

[xlr8tr]

Originally Posted by vatdevil

Need to view the suspension as a whole..not pieces. Both springs and sway bars affect overall spring rate. So, if you plan on sway bars, you need to include their rate into what springs rate you choose.

Thats what I'm thinking, I need stiffer springs to control the forward/backwards weight transfer and pitching motion that sways wont help with, and sway bars to further control side to side, adjustable shocks to keep it all under control once I arrive at a good spring/sway bar balance.

the 460 is a boat anchor with iron block and heads, it would be nice to drop a bunch of weight off the front end with aluminum heads and block, but thats a project that requires more funds than I have right now.

[bobcowan]

Your fronts are most likely too light. You should increase your front spring rate. But how much depends on how your wheel rate calculates out. My front springs are 750#. But my wheel rate calculates to 240#.

Springs add wheel rate all the time. Sway bars add wheel rate at certain times. There are a couple of different theories about how to balance springs and bars. Personally, I like a medium to heavy spring, and then balance that with a medium to light bar. For a variety or reasons, that seems to work best with a light weight car, with relativly low unsprung weight. But your 9" rear is a bit heavy, so you have a little more leeway there.

Start by calculating your suspension frequency. Get it up around 1.7'ish and see how you like it. You'll get nice handeling without a bone jarring ride. Drive it around for a while before making any other changes.

If you like the ride quality but want better cornering, add bars.

A note about springs. There is a huge difference between a $25 spring and a $75 spring. They may both be rated at 600#, but one will feel considerably different than the other. I highly recommend that you only use an Eibach spring.

I would not recommend an adjustable shock just yet. They are very expensive, and you haven't established your baseline just yet. As long as your current shocks have been valved for your car, leave them alone for now.

[mdross1]

Went through all this with our 460 powered car it still was a handful till finally having the car scaled.Wow what a difference.Sway bars are a good thing as long as they are right for the car.
Keep the ride height in mind when messing with springs.

[xlr8tr]

excellent info thanks everyone: bobcowan, how does one go about calculating the suspension frequency? And funny enough, eibach is what I have on the car now and thats what i was going to go with, glad it is actually a good decision

I'd really like to scale the car as well, that might be soemthing I figure out how to do on my own as i think i will be messing with this (happily) for a while, maybe share the cost of the equipment with some other local gearheads.

[bobcowan]

If you do a web search on suspension frequency, you'll find some good info. I found this site to be especially helpfull: Suspension Worksheet | performance-suspension.eibach.com

I have a spreadsheet I can send you. It's for my car (A Factory Five) so the numbers won't be exact. but it might get you in the ball park, and give you something to play with.

Scaling the car could be very helpful. Some people spend a lot of time getting the ride height just perfect at every corner, but that can actually really mess up the balance - which is much more important. Here's a simple way to get the ride height close, and the balance even closer.

- Unload the suspension, and adjust all 4 spring collars until they are just touching the springs.
- roll the car back and forth a couple of times to settle the suspension.
- you can also set the front tires on folded plastic trash bags and turn the steering wheel
- measure ride height. It will not be exactly the same left and right.
- adjust left and right spring collars exactly the same amount.
- measure ride height again, front and rear.
- Make left and right adjustments EXACTLY the same.
- Left and right ride height will not be exactly the same, and that's OK as long as the springs are adjusted exactly the same. If your goal is 4", shoot for (as an example) 3.9" on the right and 4.1" on the left.

I did my car this way. When I got it on the scales, it was so close to perfect, I didn't adjust anything. I was afraid I'd screw it up.

[xlr8tr]

Thanks Bob- when you did your corner scaling routine, did you put ballast in the drivers seat?

[bobcowan]

Yes, I did. I also had about 1/3 - 1/2 a tank of fuel. I figured that would be when I would be pushing it the hardest on the track.

You also want to disconnect the sway bars if you have them.

[Bobcat]

Bob ... you answered my questions about weight in the seat and sway bars being disconnected , but got another one for you . Does your method work if the chassis/motor is offset to one side . The ERA has the engine offset to the passenger side about 1 " and I am running an IRS .
Your method intrigues me as I`ve not seen it done this way before , and the guy that let me use his scales has moved away .
I just finished a tracK weekend and now have some time to play .... may want to try your way and see what happens .

Bob

[xlr8tr]

hmmm good question. my head is spinning a bit thinking about that... if you had tons of weight on one side, the car would lean heavily and you'd want to raise BOTH front and rear on the low side, and if you adjusted the F+R on the low side the same amount, would that approximate an equal adjustment?

[bobcowan]

The FFR also has the engine offset to the passenger side. Every car is built a little bit different. The only way to get your car exactly right is to put it on the scales. Instead of that, try my suggestion and see what happens. It worked well for me.

[Bobcat]

Curses Bob , there you go making me learn something new . Just like when I had to get into motion ratios , wheel frequencies etc .
Car really handled on the track , but anything I can do to make it better , I will . I`ll try this in a few weeks and then try to find some scales see what the wheel weights are .
I`m still playing and will be trying the car out on the street with the rear bar disconnected just for giggles .
FWIW ... at the track last weekend , I found that the car handled best with the rear tires about 2 psi lower than the front ... COLD . Hot , they were almost equal in pressure .
Question , when you say adjust left and right spring collars , you mean front ( or rear ) left and right or left side front and left side rear and then right side front and right side rear ???

[bobcowan]

Well, you want want the front ride height to be a certain number, say 3.5". So you adjust the front left and front right spring collars the same amount until you get the ride height where you want it to be.

Then you do the same in the rear.