Suspension Voodoo

[gran racing]

First of all, you want the heavier springs in the rear.

See, if only suspension and tuning topics were this easy I'd actually get it. LOL With the suspension design on my car, Koni recommended running higher spring rates in the front. Curently I'm using 750 lbs front, 600 rear with a stock bar and have no problems getting the tail to come loose. My original suspension was running 400 lbs front and 600 lbs rear.

[John Herman]

I did a search, and the 1987 Honda Prelude uses a dual wishbone front suspension. The Ford Escort is using a MacPherson strut. Two completely different animals. Thus, this now gets into the technical difference between wheel rate and spring rate. We buy our springs (and brag about the monster rates we use) using spring rate, but the tire cares about the effective spring rate (aka wheel rate). The suspension is nothing more than levers and springs. Depending on where the spring is placed in the design of the suspension, determines how "hard" it is for the wheel to move up. Do a quick internet search on "wheel rate versus spring rate" to get more. Sorry, just don't have time to go into more details myself.

[Jeremy Billiel]

I am LOLing...This is a great thread of all kinds of various items.

Dan the bottom line is your dollar will determine how fast you can go and how technical you want to be. Greg is 100% in relation to struts. They suck in every possible way and you will need to run high spring rates to make it work which in turn requires expensive shocks.

Dave has a totally different suspension design that is much, much better than struts.

A arm cars can spend less to get the same performance on struts because its a superior design. But even A arm FWD cars need big money shocks and springs when you get to the pointy end of the field.

[wepsbee]

I am LOLing...This is a great thread of all kinds of various items.

Dan the bottom line is your dollar will determine how fast you can go and how technical you want to be. Greg is 100% in relation to struts. They suck in every possible way and you will need to run high spring rates to make it work which in turn requires expensive shocks.

Dave has a totally different suspension design that is much, much better than struts.

A arm cars can spend less to get the same performance on struts because its a superior design. But even A arm FWD cars need big money shocks and springs when you get to the pointy end of the field.

I will be delivering my car to Matt on Sat. I will check with him and have the suspension looked at for suggestions. I am checking with Koni for max springs rates for the struts I have. I imagine stiffer springs are going to result in a car that will have to be learned how to drive.
All, thanks for the input, this forum really helps!!

[rsportvolvo]

Stiff springs on a strut to reduce movement are only required IF it is outside of the operating window. That is dependent on your exact strut layout.

Some struts have a lot of wiggle room within the ITCS. VW's are screwed as are most cars with bolt on struts. Cars with integrated struts have basically a blank check (BMW E30).

For struts:

1. Within the ITCS regulations design a strut to work within it's limited window.
2. If 1. is not feasible then mask the struts deficiencies with stiff springs to limit movement on a lowered car or run a lighter spring and an ARB on a higher ride height car.
3. Buy top notch dampers for item 1. and good enough dampers for option 2.

If you run really stiff springs it's a waste of money to buy high end shocks as they don't move much (dampers only work when moving). Also chassis flex and component stiffness enter into the equation and the benefits will be tough to realize. If you do run a stiff spring get as big a damper piston as you can, like 45mm and up. The stock Bilstein's 36mm won't work as well.

Note: The Pratt & Miller designed GTO-R's and GXP-R's use @ 400 lb/in springs on an SLA (A-arm) suspension with a HUGE ARB (anti-roll bar). That low of a wheel rate seemed to work quite well.

This is just my intellectual masturbation on the subject.

[lateapex911]

John, good point. Reminds me of a funny story. Was in the pits of a Honda team at a world challenge event, and they were swapping springs:
Crew Chief: "Well, lets put some 7s in the rear then"
Crew, "OK"
Me: "700? I would have thought higher"
Chief: '7 THOUSand"
Me: "OH!!!!!!"
Chief: " But that's not really accurate, it's more like 3500 wheel rate"
Me: "Well, that's more like it, LOL"

[Greg Amy]

As an addendum to my above post (yes, I've been thinking about it), unless/until you're ready to go to Hoosiers (or comparable) I'm not convinced significant suspension improvements will do you too much good.

Example: in my original build on the NX2000 (c. 2002) I slapped on KYB AGX shocks and standard-issue street spring rates (350F/200R?) This was during my "listen to the Nissan experts" phase...anyway, key note is that I was running Kumho Victoracers...one of the first tracks I drove was Lime Rock Park, and after some testing I was able to get that car down to the 1:03's.

Soon thereafter we switched to Hoosiers. It didn't take long to recognize we needed more spring rates on the car to both control the geometry and keep it off the bump stops. Of course, as we added more spring rate we needed better shocks. We went from those crappy AGXs to some Advanced Design struts (another one of those "listen to the experts" things) and then later on to Kessler-fabbed 8611-based struts. Strangely enough, even with all those improvements - including a new very stiff cage to replace the old bolt-in Showroom Stock one - it took us until 2006 to get the car down into the low 3's, eventually into the 2's...

This was always one of those things that totally perplexed us. Had we bent something we can't find? Had I suddenly recognized my mortality and was driving worse? Was it true that maybe AGXs were a better package for this car? Nope. What it most likely was was that with the lesser grip of the Kumhos we weren't getting nearly the lateral g-force as from the Hoosiers, and as such simply didn't need to control the suspension geometry nearly as much. In effect, without the lateral forces of the Hoosiers we simply weren't getting into that nasty negative-roll center and suspension-bottoming area that we found ourselves in when we Went Purple.

So, this makes me wonder if maybe it isn't time for some soul-searching on your part. If you're going to hang with your current selection of tires, I'd suggest you need to maybe tune some things around without massive changes. I'd suggest your 8611 are fine as-is and maybe we shouldn't look into seeing how the suspension is working with the current grip levels. Then, once you're ready to make the Jump to Purple we then start delving into significant springs, shock, and bars changes... - GA

[JeffYoung]

The above is very good advice and consistent with our experience in progressively moving to working the suspension harder with lateral gs and travel using Hoosiers and more cornering force.

Edit -- Andy makes an interesting point. We've heard for years that the rates we run on the TR8 (600/300) and Z (500/250) are too high, especially by the Z guys. I don't think so, at all. In fact, I think we could go higher with better shocks. So, Andy, what do you think is too high on a strut based car? Some of it is a structural issue right? How much can the frame rails take? The 8 has some beefy rails, the Z is pretty weedy.

I know most 2nd Gen RX7 guys down here run 400ish front 300ish rear. Lower than us.

[John Herman]

And of course, the setup will change as your driving improves and you start to realize you can go through the corners much faster, which necessitates further changes, which allows greater speeds.........Good stuff.

[wepsbee]

You'all realize I have understood about half of all this. It will take some time and explanation to get it all. What I do have fully understood is that I need to get Hoosiers and setup and test with just them. So it shall be!!!!

[Flyinglizard]

Hey K.
FWIW, Low drag is zero scrub. Zero scrub for 3degrees camber on a 15in wheel is about 3mm out. Not straight ahead.
Zero scrub can also be called camber vector or camber steer. The tilted wheel pushes the car sideways a certain amount, etc.
MM

[Rabbit07]

I have followed a similiar path as some of the others here with my Neon. I recently doubled my spring rate all the way around the car when I was at Sebring in Jan. My wheel rate was not doubled however because I was experimenting with sway bar combinations. The car felt great with more rate upfront, but the laps weren't any better. The conditions kept changing on us the whole weekend, which really was like a week since it was a double. The conditions made it hard to be scientific about the changes. All of this required that I have my already very expensive Dynamic shocks revalved. Fortunatly I have two sets of shocks, so I can have one valved for one spring rate and vise versa. The higher spring rate seems to work very well with mac strut front drivers. I also have lots of experience tuning Mustangs. They have a mac strut front and solid axle rear. They tend to not like lots of spring rate. Moral of the story is to keep an open mind about set up. Try not to get caught up in using half of one guys set up and half of another.

I also agree with many of the others who have steered you towards tires. I tell people all the time that the biggest bang for your buck will come from tires and seat time, in that order. With crap for tires you seat time will mean very little.

[924Guy]

Ah, you think struts are confusing - you should try tuning torsion bars sometime...

[Andy Bettencourt]

See, if only suspension and tuning topics were this easy I'd actually get it. LOL With the suspension design on my car, Koni recommended running higher spring rates in the front. Curently I'm using 750 lbs front, 600 rear with a stock bar and have no problems getting the tail to come loose. My original suspension was running 400 lbs front and 600 lbs rear.

And comparing rates on a DW vs. McS car is not smart. My rates on my DW car would be undrivable on any of our McS ITS RX-7's.