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Discussion Starter #1
I thought I'd make this thread here since i am not fond of the 240 forums. I understand I can't ask specific questions, but I was hoping to get suspension tuning suggestions

I've been trying to figure out how to make my car balance between drifting and grip (specifically mountain driving).

I have PBM Coilovers with 10kg springs up front and 8kg springs in the rear. They are STIFF. I've under-steered on on-ramps after hitting a small bump. I've also played with the rebound dampening on them and it only helps to a certain extent.

I was going to put the 8kg spring up front and order 6kg springs for the rear but Im wondering if that will still be too bouncy.

It also has a welded diff if that makes a difference...
 

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id go softer a bit. thats i beleive is like race stiff. check all the bushings obviously make sure they are all good. go max caster and maybe ad a little more front camber. obviously is depends on tires and suspension. but with ****ty tires i had to run 3.8* of negative camber for max grip. but on my re71r tires i ran 2.9* but ill be going to 2.6. i feel like normal cruising tires may need a little more camber them usual. then get a good alighment. slight toe in on front, and rear idk maybe completly straight til you feel out how the car handles.

also i forgot, you can adjust the struts. thats the cheapest option
 

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also remember if you lower or raise a car on good alignment, it completely destroys the settings and you need another one
 

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Okay, this is in my area of expertise. Those spring rates are super stiff for the street. The spring rates always have to be balanced out with available shock damping capability. These rates are almost directly the rates I use on my race RX7. I use 600 lb/in on the front (about 10.7 kg/mm) and 450 lb on the rear (about 8 kg/mm). I also use a railroad beam for a sway bar on the front and no to a small bar on the rear.

What happens to your car when you get up that high in springrate and sway bar diameter, is that for most minor bumps the primary thing working to absorb the bump is the sidewall movement of the tire. On the front, that means when you hit a bump with one tire, the other tire will deflect the sidewall first and then try to move the strut. The strut isn't going to move much with those springs (that's why the rebound adjustment didn't help, you actually need to soften the low speed compression instead), so the wheels will both be trying to come off the ground. You combine that with the welded diff (that is always trying to push the car straight unless you are spinning both rears or sliding an inside tire), the car is going to want to go straight all the time. That's why you really don't want to be using a welded diff on the street and very few race cars use them as well. On race tracks, we mostly use some form of limited slip to allow the rear tires to track around the corner at different rates. This all becomes even more of an issue when you have sticky tires as the rear will keep pushing.

What I would do is test things out first. Take 4 smaller tie wraps and wrap them around your shock and strut shafts. Push them into contact with the body and then go out for a normal drive. See how far up the strut they get pushed. That shows you the working range of the struts or shocks. They should be moving almost all the way up to the bumpstop if you have hit a few bumps. That is the way its supposed to work. The bumpstop is actually used as a rapidly rising rate elastomer spring to prevent metal to metal contact. If the shafts are moving all the way (I seriously doubt that), then its damping control you need to look at. If the tie wrap has barely moved or has moved about an inch, then you need to soften the springs. If there is a substantial difference between the front and rear, this will tell you which spring set to soften first.

My guess is that you need to come down to about a 6 on the front, a 4 on the rear, soften up the front bar some and put a proper diff in the back like a plate style posi. This will work great on lapping days and then if you want to go drifting, put 8's on the back, crank your rear shocks right up, add a big rear bar and hang on.

Eric
 

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Discussion Starter #8
Thanks a bunch. Is a "plate style posi" diff another term for "clutch type"? I was pretty set on getting a 1.5 way clutch type diff, but I recently heard that they also have a problem with low speed sharp turns...

So I searched some more and found out about Nismo Mechanical 1.5 way diffs. Is a mechanical diff my answer? I'm steering clear from Helical diffs because I read that you cant drift with them.
 

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i run 600 front and 400 rear springs in the coug and honestly i was gonna go stiffer. theyre stiff, but not racecar stiff
 

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Discussion Starter #10
Got my alignment....WHAT A DIFFERENCE! I was running +2 degrees of toe and -4 degrees of camber on the drivers side rear wheel... Everything else was decent.

The welded diff actually feels good. It doesn't wheel hop at all in slow sharp turns anymore, and the car is more predictable, until I hit a bump and under-steer. Excited to go do some spirited driving!
 

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Discussion Starter #11
Heres some pictures of the car.

Bumper was saggin because I didnt have a bash bar yet.




Before alignment. Only this side had this much camber.


Tree jumped out infront of me.
 

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Discussion Starter #13
Its fine now :). Bent the metal back and reattached the corner light. Drivers side headlight just needs adjusting. Street Faction makes good bash bars.

This is from today. Always something wrong...haha
 

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I don't think I would ever expect a car with that much camber, particularly on just one wheel to ever handle correctly. Make sure to always have the basic stuff right before wasting money on parts.

On a cosmetic note, I'm a fan of the kouki front end.
 

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ah. well everyone prefers that one. lol. i love the s13s front end both of them. and the zenki is terrible in my opinion lol
 
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