The 10/12 setup sounds reasonable. I autocross and roadrace my fully caged Evo 8. I had that 9/11 Swift spring setup on my Ohlin DFVs and it was compliant, but the car still nose dived pretty severely. I stepped it up to 12/14 and the car has minimal body lean and no longer nose dives under braking, but it can be a handful on uneven surfaces and in the wet. It also overwhelms street tires up front at the track, so I had to move to r-comps.

 

Do you have any sway bars? What tires were you running? I would like to do a track day next year if everything goes as planned, but right now it's just mainly auto-x and DD.

 

With my 9/11 setup I had a Works sway bar, but I went back to stock with the 12/14 setup. With my 9/11 setup I used street tires (Direzzas) but after I went to the 12/14 setup I tore up my right front Direzza after 2 days at Watkins Glen (tread blocks were tearing off) - had never happened in 4 years prior to that. Works had warned me that a 12/14 setup was right on the edge of overwhelming a street tire setup, so I went to NT01s for track use.

If you're doing your first track day, I doubt you'll be running hard enough to chew up a decent high performance street tire.

 

Works rear sway? Is 12k good for the rear on street tires? Has anyone ever ran 11k/12k?

 

1) http://store.worksmotorsports.com/WO..._p/231.100.htm

2) "Good" is a relative concept, so you'll have to do more research to figure that out for yourself.

3) There may be. Try a search. Most folks go on the 2k difference theory on fr/rr spring rate difference, but I've seen some argue for different separations in rates.

 

what kind of handling can 12/12 rates give me on stock swaybars ?

 

i am done with my research choosing my spring rate. what i found out is that the spring rate has to be chosen based on the weight distribution on the car( for example if your car 62% in front and 38% in the rear you have to go with 6.2kf/3.8kr)
but for the evo you have to multiple the front by 1.1 and the rear by 0.6, for the example i gave means that the spring rate that you have to buy to get 6.2kf/3.8kr has to be 5.5kf/6.3kr.

i talked to Robi (Robispec) that day and i was asking him about which spring rate to get for my car (note my car has a fully weld-on roll cage and seam weld the chassis with solid bushings, solid engine mounts, TOYO R888 255/40/17 the car is to stiff) he said (Robispec) " will all know that if you stiffen the car and got the grip and lowered the car its faster but for the evo its basically deign for Rally you will get more traction by giving a chance for the body to roll" he told me for your car you have to go with 10kf/11kr, and i made the calculation that i talk about in the beginning it was exactly the weight distribution on my car, also we all know that the evo has a heavy front end and it loves to understeers the stock front sway bar is fine what you have to change is the rear with a 26mm.

what i realized from other evo projects that the maximum that you can go with a evo without a cage is 10kf/11kr

i already bought the JRZ PRO RS 10kf/11kr

i tried to upload a excel file that i created for calculating the sprig rates but couldn't upload it

 

I would like to add to your explanation and add when we corner weigh our cars we get the weight distribution and corner weight BUT in order to get the sprung weight at the corner you have to subtract the un-sprung weight.


Once the actual sprung weight is determined the motion ratio can be calculated by either direct suspension travel measurement or geometry calculation method.


Divide the sprung rate by the motion ratio and that will determine the static load at the corner. From there one must decide how much suspension travel they want. Next, the amount of travel gets divided by the static load. That will give you your spring rate. Then you can calculate the effective wheel rate.


For example, if we roll an Evo on the scales and it weighs 900lbs on the front corners, If the un-sprung on the front is 150lbs per side then the sprung weight is 750lbs. If the motion ratio is 1.05 based on the desired alignment and suspension geometry then the static load is 712lbs.


Where this gets interesting is say I want 2" of spring travel built into the suspension then the desired spring rate at the corner would be 712lbs/2" = 356lbs. The effective wheel rate based on the (motion ratio (x) sprung rate)/spring travel = 396lbs.


If I wanted 1" of spring travel built into the suspension then the desired spring rate at the corner would be 712lbs/1"=712lbs. The effective wheel rate (MR (x) SR)/spring travel = 790lbs.


1/2" of travel... static load of 712lbs/.5"= 1423lbs spring rate and an effective wheel rate of 1582lbs.


As one can see the more shock travel taken away from the suspension the stiffer the ride and the higher the rebound rate on the suspension. When you hit a bump with a 1/2" of travel you get 1500+lbs of feedback back per less inch... if that's a bumpy road or turn, YIKES!


The best suspension setup is the one that keeps all four planted. On a hill climb one might want more droop built into the suspension to push the tires back down on switchbacks to have more tire contact. In addition to more effective grip there will be more tire on the road surface to power out of the corner instead of 3 wheeling (which scrubs speed). In this case 2" of shock travel might be better suited whereas on a flat road course 1" of travel might be better suited.


Where it gets interesting is when we start adding aero, dynamic loading, wedge and so forth. The only way to really know is to hook up strain gauges on the chassi and measure the amount of shock travel at speed and examine the loading.


For the most part the simple rate calculation will work. Make sure to take out the unspring weight.


Cheers.

 

nice writing and yeah you let me aware of other stuff, thank you for your help i will try to choose my next springs base on this accurate calculations

 

Which is the prioirity...hillclimbs or autox? How rough is the road surface for your hillclimbs?

- Andy

 

Auto-X. The surface isn't too bad. I'm either thinking Ohlins or AST's with the front plates.

 

Both are good options. Ohlins have gone down in price this year so they're a tempting deal but we've been pretty happy with both.

I wouldn't really recommend 10/10...10/12 or 8/10 would give you a better balance. Since auto-x is the higher priority the 10/12 would be my choice.

- Andy

 

Sent you a PM

 

I originally sent this to Andrew, but thought it would be better to discuss it in here and to also revive this thread.

I'm currently sourcing parts for my Evolution 3 rebuild, and upgraded coilovers are definitely on the list. I'm currently in between fortune 500's series and BC RM series. I'm leaning more to the fortunes just because of the testing that's been done with them vs BC.

My Evo 3 from factory is 2,777lbs. Given the fact that I've removed the carpet, roof liner, most of the interior plastic panels, back seats and spear tire, I'd say the car is somewhere around 2690 +/- lbs.

My car is right hand drive and I also have the battery on the left rear side in the trunk (Odyssey PC680). The car also has a whiteline 20mm rear sway bar.

So... With all of that being said, I'm asking for guidance. Should I go with 8k front and 10k rear OR 10k front and 12k rear. Maybe 9k front and 11k rear to be in the middle (so it doesn't eat street tires).

Also, which brand coilovers would you guys recommend.

The car will be a daily driver for majority of it's use (street tires), and the occasional auto cross event about every 6 weeks. There's also the possibility that I'll be using R compounds on a daily basis. Not 100% sure as yet. So I'm keeping that option in mind.

Looking forward to your replies.


Thanks in advance.

Gabe

 

Current set up. Tein Gravel Spec at their stiffest with a meager 6k front 5k rear. Good amount of roll.





This event was done on 205/50/R15 R888's. When I'm done rebuilding the car, it should be on 17x8's with 235 or 245/45/R17's