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ButtDyno said:
Re-reading this on the hope that it will start to sink in better.
Does that mean "ever" or "at rest" or something else?
We were, at that point, discussing ride height and roll axis. So that assumes static ride height. The control arms will pass horizontal in roll and bump compression, but you don't ever really want the control arm past 90 degrees with the strut axis in roll travel.

-Steve
 

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mtbmr2 said:
I'm "guessing" that his testing shows the car handles most neutrally when the (total) front spring rates are 150% of the rear spring rates.

change "spring rates" to "roll rates" and I think you are right.


I'm running a Spyder in CSP. Right now I have my total roll rates in the front at about 160% of rear and the car is still a little too tail happy for me. Just a hair. I'd rather have it like this than a hair too understeer biased, but obviously I want to fix it. My next choice of ratios with just one component change and low $ takes me to 190%.... probably way too much stiffer.....
 

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Installment #5

Remember this number: 150%

So now is easy to see why one might choose, as I have, not to use any swaybars at all. I have spent more than 10 years working on this setup theory and testing the various permutations. Somebody else may not like the setup but I know its effective. The above method is exactly how I got to the point I am now. I came to this method by first using a spread sheet to aid in computing wheel rates and roll ratios accurately. I have since transitioned to a more scientific application of this theory using Susprog3d. I can now figure total roll based on lateral grip, ride height, CG height, roll axis and spring rates very accurately. I can also figure camber curves and roll center movement dynamically. A very powerful tool. But there is no substitute for testing and it is through testing that I have tailored my setup to suite my personal tastes. Now I will throw out much of what we have covered to this point.

I prefer a car that has slight understeer and is VERY stable in transition. I DO NOT want the car to feel loose in a slalom or fast transition. I know that a car with a significant rear weight bias, that is loose in transition, is slow. So my car has a lot of front roll stiffness to achieve my preference. So lets throw out all of the theory above and look at some simple data gathered from testing. Pulling off the swaybars and just sticking springs under the car, what works?

I decided I needed an objective comparison. I wondered if I could I derive a better, faster setup by pure testing alone, ignoring my theory. A number of test days at my favorite venue (Hunt Stage Field in Ozark, Alabama)

http://maps.google.com/maps?f=q&hl=en&geocode=&q=Hunt+Stage+Field,+Ozark,+AL&ie=UTF8&mrt=kmlkmz&ll=31.381925,-85.578947&spn=0.03356,0.052872&t=k&z=14

where Wire Grass Region events are run and you can make all of the runs you want, when you want, enabled a lot of valuable data to be gathered. The basics can?t be ignored so the ride height must be set so the roll centers are close, as noted previously, and the camber curves have to be in a reasonable range. So those two elements determine ride height. What about springs? We need the car flat and we determined a total roll based on the weight of the car and potential grip. From installment #2:

2200 lbs car / 2 = 1100 lbs of total roll rate

So pulling data from my test notes. We need 1100 lbs of total roll stiffness less 20% for STS legal tires.

1100 x 80% = 880 lbs

So out came the box of springs and I started making runs. I have a spring inventory that covers a range from 300 lbs/in to 700 lbs/in in 50 lbs increments. I quickly start narrowing down the spring rate combination that produces the best balance. Once the spring rates are close, I start on roll center locations, ride height and camber curves. Then back to spring changes to further refine the balance and confirm the data. Final balance and dynamics are tuned with toe settings and tire pressure.

The testing results tell me that, for most mid-engined cars, making the front roll rate 150% of the rear is a good target. Therefore, given the above data:

350 lbs/in rear springs x 150% = 525 lbs front springs.

and

350 lbs/in rear springs + 525 lbs/in front springs = 875 lbs of total roll rate.

Close enough.

The next installment will cover shocks and dynamics.

-Steve
 

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Discussion Starter #44
Cool so I was very close with my calculations then...no testing yet.

2500 with me in the car
2500/2 = 1250
1250 x .8 = 1000
400(Rear) * 1.5 = 600 front
400(rear) + 600(Front) = 1000
 

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One thing to remember in testing, I/we made an assumption as to the grip and resulting body roll of the STS legal tires. I don't have a lot of relevant data for such tires. So you get to be the guinea pig.

-Steve
 

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Discussion Starter #46
It's a damn good starting point for me though.

Do my above numbers looks good for a starting point?

I would almost assume that the grip level of the street tires now are about as good as R-Comps from the early 90's.
 

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Yeah, the rates look like a good starting point.

I know the new Bridgestones have a lot of grip. early 90s vintage grip might be pretty close. I should note that in my testing, I never really ever found the upper limit for spring/wheel rates. In testing, I kept going up until I had nothing stiffer. I found the car was a little more difficult to drive at the higher rates because there was less margin for error. The reason I came back down on rates was so the car would work better on rougher surfaces.

-Steve
 

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MicaCeli said:
Now the bagilion dollar question....can Koni yellows handle 600lb springs?
Yes.

See my DP suspension thread 'round these parts. Gordon Benson @ Koni feels they can, as you will not have the rebound damping set all the way firm on the front.

I'm not just saying "yes" I'm actually running 600# springs around Koni Yellows (my pbase photo-diary-blog-ma-job shows it)
 

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I started with Red Konis on my X1/9 and at full stiff rebound, they were at the limit of what they could live with at 600 lbs/in.

Of course they were not the same strut at the MR2 so there is no direct comparison. However, it has been my experience that most Konis can work in that range.

Because my car has Ledas on it I can't comment directly on the use of Konis on the Mk1.

-Steve
 

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Discussion Starter #53
XHead said:
Because my car has Ledas on it I can't comment directly on the use of Konis on the Mk1.

-Steve
Did you get those custom built?

I might see if www.resuspension.com would want to put something together for me. They mostly due dirt stuff but carry some top name brand shocks. Not much experience with struts though.

600 Fronts will be here at the end of the week from Hypercoils :)
 

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Discussion Starter #55
Mine were regular. There are no special valved yellows for the MR2. You were special with your grocery car. I guess if I had a Camry I would be able to get me some special koni's :)
 

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The Konis on my X1/9 started out as just plain Konis. They worked pretty good like that. After a few years of developement and testing I decided that I wanted more rebound range of adjustment as I was maxed out with the stock setting. By then I also had decided on a change to the compression so I had Koni revalve them to my specifications.

I don't know anything about RESuspensions, they might be fine, but I would have either TriPoint engineering or Koni revalve your units if you decided to have something done.

The Ledas are not custom made. Leda make an off-the-shelf mk1 strut. However, I wasn't happy with the compression and rebound dampening stragtegy so I sent them back to Leda and had them revalved to my specs.

-Steve
 

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Discussion Starter #57
XHead said:
The Konis on my X1/9 started out as just plain Konis. They worked pretty good like that. After a few years of developement and testing I decided that I wanted more rebound range of adjustment as I was maxed out with the stock setting. By then I also had decided on a change to the compression so I had Koni revalve them to my specifications.

I don't know anything about RESuspensions, they might be fine, but I would have either TriPoint engineering or Koni revalve your units if you decided to have something done.

The Ledas are not custom made. Leda make an off-the-shelf mk1 strut. However, I wasn't happy with the compression and rebound dampening stragtegy so I sent them back to Leda and had them revalved to my specs.

-Steve

RE doesn't do Koni's. And I don't think that the MK1 Koni's can be rebuilt as they might be closed units, from what I've been hearing anyway.

I will run what I have at the moment and make adjustments as I go. This is a good starting point for me right now though.

I would love some top mount camber plates for the front though. Gotta find someone to make em for me.
 

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I had briefly forgotten that the konis can't be rebuilt. That's why I ended up with Ledas, there were no OTS konis to be had. They can certainly build you up a set of customs.

I think most of the standard camber plates could be mounted atop a spacer to sit above the OE center hole.

-Steve
 

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Discussion Starter #59
XHead said:
I had briefly forgotten that the konis can't be rebuilt. That's why I ended up with Ledas, there were no OTS konis to be had. They can certainly build you up a set of customs.

I think most of the standard camber plates could be mounted atop a spacer to sit above the OE center hole.

-Steve
Yes they could I'm just wondering if how far up they will need to sit and clear the hood. Since most of them have a block on the bottom that might not clear the opening if it sits too low.

I will figure it out. I like the design that you have for the X1/9 and might get some made.
 

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That's easy. Pull the strut, close the hood, from the under side of the strut tower, stick a tape meaure through the hole and mark the tape. That's how much clearance you need.

The X had lots of room in the rear, less in the front. I had to trim the tops of the rod for clearance in the front.

-Steve
 
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