Autox Guys on KW V3 Coils

[EvilMS3]

I'm installing my KW V3 coils this weekend paired up with Corksport Camber plates and SPC rear camber arms.

I'm trying to get a feel for what your preferences have been regarding Rebound/Compression settings for F/R after some experience at events. I know the instructions give you a "starting point" but I wanted to get some opinions from you guys with some real world experience for your preferred settings.

Thanks!

 

[ThatRed68]

* I will fully admit to not having enough track time in my car so take the following with a grain of salt*
On paper my car should be very loose with worn factory shock up front, bilstien b8s out back with a CS rear bar on full stiff. I have not gotten the car out on a road course since I made the swap so I really cant speak to the steady state handling characteristics of it. On the autox, it will rotate on demand with a little left foot braking or throttle lift off. It seems that on a vehicle scale, I prefer a tighter rear end to help cut down on understeer.

I would imagine that you should leave the setup as is until the first event, then play with rebound settings. It is my understanding that rebound adjustment has a more noticeable difference on road manners and ride quality while compression helps with weight transfer and body roll. With autox being big on transferring weight between contact patches effectively I would assume that a stiffer compression is preferable but it has to have a point of diminishing returns for each driving style. With that same logic, I would assume that a softer rebound setting let the "inside tire" re establish contact with the road through said transitions.

I'm curious to see how far off my casual observations are from the experienced racers in the group.

 

[VTMongoose]

* I will fully admit to not having enough track time in my car so take the following with a grain of salt*
On paper my car should be very loose with worn factory shock up front, bilstien b8s out back with a CS rear bar on full stiff. I have not gotten the car out on a road course since I made the swap so I really cant speak to the steady state handling characteristics of it. On the autox, it will rotate on demand with a little left foot braking or throttle lift off. It seems that on a vehicle scale, I prefer a tighter rear end to help cut down on understeer.

I would imagine that you should leave the setup as is until the first event, then play with rebound settings. It is my understanding that rebound adjustment has a more noticeable difference on road manners and ride quality while compression helps with weight transfer and body roll. With autox being big on transferring weight between contact patches effectively I would assume that a stiffer compression is preferable but it has to have a point of diminishing returns for each driving style. With that same logic, I would assume that a softer rebound setting let the "inside tire" re establish contact with the road through said transitions.

I'm curious to see how far off my casual observations are from the experienced racers in the group.

So let me get this straight, you don't even own KW V3's, and you're commenting on this thread...why?

Shock tuning only affects the car's behavior during transitions. Shocks can only change the rate of weight transfer, they cannot actually change the amount of weight transferred. The amount of weight on the inside wheel during steady-state cornering is dictated by roll stiffness, not the shocks.

Your car's ability to rotate is determined by roll stiffness bias vs. weight bias (refer to Phate's write-up here). You can tune the shocks to alter this behavior temporarily during quick transitions, but why would you want to when you can easily set up the car to behave the way you want it to all the time by changing bars, and then you don't have to have shocks that are over/underdamped every time you aren't throwing the car into a corner.

Shock tuning is black magic to me. That is why I had a professional valve my shocks. They are nonadjustable.

If I were OP I would start with the procedure outlined in this page on "Autocross to Win". Since you aren't trying to change the shock valving, only alter the forces of the existing valving, you can proceed to datalogging and tuning your shock forces. There's also lots of other reading material on the site for you on this subject.

Keep in mind that the KW V3's use really weird ride frequencies where the rear is actually significantly lower than the front. Pretty much nobody who autocrosses uses a setup like this. Revalving the rear shocks and running stiffer rear springs would solve a lot of problems, but since I imagine you already have your heart set on running these coilovers as-is, what you'll need to do is calculate your roll stiffness bias vs weight bias (the MS3 gets a huge amount from springs vs bars in the rear) because you will likely need an extremely stiff rear sway bar to get the car out of understeer territory which is where you are undoubtedly destined to be out of the box with these coilovers.

 

[EvilMS3]

I appreciate your honesty on my setup. I ended up with the KWs because I got them for all of $900 from KW during a sale. I'm sure there will be a learning curve and they're probably not perfect and I'm ok with that. I've got to start somewhere. I'm not looking to win Nationals or anything, just hoping for a little bit more performance to just keep progressing.

I'll probably just set things to the recommended settings and tweak here and there till I find a sweet spot that works for me.

 

[Mauro_Penguin]

I found my old notes. I do not AutoX, but I've been driving the hell out of my KW v3's for almost 3 years and 28k miles now.

The springs that KW includes in their kit for our cars are 400lb linear springs in the front, and progressive springs in the back (roughly starting at 250lb~to~who the hell knows at max rate.) They use these rates for ride compliance since these are intended for daily use and occasional track time. You sacrifice track ability in order to keep it soft for daily driving, that is the intended selling point of these coilovers. Now that we have that cleared up, here is how I set mine...

It is worth noting that I have both sway bars upgraded, and run 255 40 17 tires.

KW spring rates...
Compression (bottom knob, max stop is 12) Front=7 Rear=6
Rebound (top adjuster, max stop is 16) Front=9 Rear=6

I upgraded to 500lb linear springs on all 4 corners a few months ago, and readjusted them.

500lb settings...
Compression (bottom knob, max stop is 12) Front=7 Rear=7
Rebound (top adjuster, max stop is 16) Front=9 Rear=9

I won't go into detail on how to adjust them unless you need me to. I hope this helps, and good luck!

 

[VTMongoose]

I found my old notes. I do not AutoX, but I've been driving the hell out of my KW v3's for almost 3 years and 28k miles now.

The springs that KW includes in their kit for our cars are 400lb linear springs in the front, and progressive springs in the back (roughly starting at 250lb~to~who the hell knows at max rate.) They use these rates for ride compliance since these are intended for daily use and occasional track time. You sacrifice track ability in order to keep it soft for daily driving, that is the intended selling point of these coilovers. Now that we have that cleared up, here is how I set mine...

It is worth noting that I have both sway bars upgraded, and run 255 40 17 tires.

KW spring rates...
Compression (bottom knob, max stop is 12) Front=7 Rear=6
Rebound (top adjuster, max stop is 16) Front=9 Rear=6

I upgraded to 500lb linear springs on all 4 corners a few months ago, and readjusted them.

500lb settings...
Compression (bottom knob, max stop is 12) Front=7 Rear=7
Rebound (top adjuster, max stop is 16) Front=9 Rear=9

I won't go into detail on how to adjust them unless you need me to. I hope this helps, and good luck!

Why not step up to a 600-650 lb/in spring in the rear so you can have flat ride? I run about a 13% frequency split front-to-rear in my car and it feels just about perfect at autocross speeds.

http://www.optimumg.com/docs/Springs&Dampers_Tech_Tip_1.pdf

 

[Mauro_Penguin]

Why not step up to a 600-650 lb/in spring in the rear so you can have flat ride? I run about a 13% frequency split front-to-rear in my car and it feels just about perfect at autocross speeds.

http://www.optimumg.com/docs/Springs&Dampers_Tech_Tip_1.pdf

500lb springs on my damper settings can be very stiff. The rear is slightly bouncy, but not annoying. I may do all 4 600lb springs when I retire the car to track duty only, but I would worry about it being too much for the KW valving.

As far as flat ride frequency, my understanding was that spring rate was based off of sprung weight to achieve X.X ride frequency. So if I read your post correctly, tossing 600-650lb springs in the rear would actually over spring the rear and put it at a higher frequency than the front. It would make for fast recovery from weight transfer at the rear, and give you some oversteer without beefing up the rear bar, but I don't think it would give you text book flat ride.

 

[VTMongoose]

500lb springs on my damper settings can be very stiff. The rear is slightly bouncy, but not annoying. I may do all 4 600lb springs when I retire the car to track duty only, but I would worry about it being too much for the KW valving.

As far as flat ride frequency, my understanding was that spring rate was based off of sprung weight to achieve X.X ride frequency. So if I read your post correctly, tossing 600-650lb springs in the rear would actually over spring the rear and put it at a higher frequency than the front. It would make for fast recovery from weight transfer at the rear, and give you some oversteer without beefing up the rear bar, but I don't think it would give you text book flat ride.

If you math it out using the sprung weight on each corner and wheel/spring motion ratios (NOTE: MR is expressed as wheel/spring in the equation...invert any "book" motion ratios as needed...most express as spring/wheel) following the equations in the link I posted above (also screenshotted below), you'll find that you need a higher spring rate in the rear than in the front to get the rear ride frequency higher than the front. I am running 600 lb/in in the front and 750 lb/in in the rear which sounds like a huge difference but in reality is only about a 13% split. Mostly because the rear spring/wheel MR is only like 0.72 (spring/wheel).

 

[EvilMS3]

Pardon my ignorance, but replacing springs on this setup.... What size springs are needed and where do you typically go for them.

For future reference.

 

[Mauro_Penguin]

Pardon my ignorance, but replacing springs on this setup.... What size springs are needed and where do you typically go for them.

For future reference.

2.5" ID springs.

The the length can vary on ride height and rate but the KW fronts are roughly 6 1/2".

The rears will require some hardware since the KW weight jack uses the odd OEM size spring. I think it cost me about $350 in hardware from ground control, maybe a little less.

I'm using Hyperco springs from PitStopUSA.com. It cost about $120 for each pair including shipping.

Depending on how you want to go, it may be cheaper or easier for you to get the coilover conversion kit from ground control since it comes with rear hardware and springs for the front and rear.

Don't worry too much about spring swaps. Get familiar with the coilovers first.