Track spring rates - is 628/784 stiff enough?

[Move Over]

Good evening guys, I wanted to get some of your input on if you think a 628F 784R spring is a good enough spread for the track. I see some guys running a 700/1000 on MCS's. I am on 2 way clubsports. It's mainly for 6-8 events per year, but still some street driving.

I currently have a 628F/672 installed (oem clubsport numbers), but have a set of 784's sitting in my garage that I am getting ready to install. Should I go stiffer (896 or 1008 are the next two options up) in the rear? I would rather not change the front spring again, but I could jump up to a 685 or a 742 up front.

Let me know your thoughts. Thank you in advance.

[okusa]

Personally I wouldn't go any stiffer. The whole idea of upgrading the dampers is to primarily rely on the dampers. Go any stiffer and you are robbing the dampers of the chance to do their job.

[MasterP]

Depends on your setup. I run higher rates than that, and dampers were valved to match.

Stickier tires can run more rate, aero? need more rate at the axle your aero is working on. More rate means you can soften the sway bar if you are running them stiff.

My car is more focused than yours likely is but I don't have a trailer and I still drive it back and forth to the track. It's stiff, but not brutal.

[SYT_Shadow]

The stock 2 way CS are a very capable suspension. I believe a later iteration of the CS upped the spring rates

[Move Over]

Originally Posted by SYT_Shadow

The stock 2 way CS are a very capable suspension. I believe a later iteration of the CS upped the spring rates

They upped the fronts, and dropped the rears. They used to be 500/800 and now are 628/682. No idea why.

I purchased a set of 784 rears - which I probably will stay with, just wanted a second opinion

[jakob66]

Originally Posted by Move Over

Good evening guys, I wanted to get some of your input on if you think a 628F 784R spring is a good enough spread for the track. I see some guys running a 700/1000 on MCS's. I am on 2 way clubsports. It's mainly for 6-8 events per year, but still some street driving.

I currently have a 628F/672 installed (oem clubsport numbers), but have a set of 784's sitting in my garage that I am getting ready to install. Should I go stiffer (896 or 1008 are the next two options up) in the rear? I would rather not change the front spring again, but I could jump up to a 685 or a 742 up front.

Let me know your thoughts. Thank you in advance.

The only way to check if your spring rates are sufficient is to check if you have shock travel
left under load. The easiest way is to check if you're riding on your bump stops.
If that's the case your shock can't operate (lets forget the bump stop spring rate for now).
Before you go on track slide your bump stops onto the shock housing.
When you return from track session check the space between upper porch and yellow bump stop. Not easy to do but a good indicator.
I took the plastic tube attached to the pump stop off so its easier to check yet still PITA.
I'm on much higher spring rates 850/1100 but on 295 Hoosiers. It all depends on how much load you apply based on your driving skills and the equipment.
Hope that helps.

[M3 Number 86]

I would just drive them on track first and see how they feel. If they are fine, it doesn't matter. Not sure about pounds but you are talking 11/12kg right?

[ortho281]

I'm running the 500/800 CS with aero and heavier sways. Like said before spring rates depends on tire selection, aero and the tracks you are running. If you upgrade the rears to the 784# springs, you will need to add more compression/rebound to handle the increased rate.

[RickyBobby]

What handling traits are you trying to fix?

[z3papa]

People try to fix handling issues with spring rates when it is a complete package process which is also dependent upon what the dampers can actually handle. My understanding is the Clubsports are much different than the V2's or V3 and will accept higher spring rates to a limit. Looking at what MCS DA's will accept is very much comparing apples to oranges. You don't need sky high spring rates to handle the g load put out by r-comps or full slicks but you do need more than what would be typically used for street driving. Personally, my take on what KW units are valved for is similar to TCKline (Koni based) DA units can take which is limited to 800# whereas MCS, AST, Moton, JRZ may tolerate higher rates if valved correctly. I'd suggest making up some of this with sway bars but understand motion does not solely make a car fast on the track.

[italyix]

You can actually calculate the proper spring rates you need based on the corner weight of your car. Takes the guess work out if choosing proper spring rates and will make you car handle properly.

[warp10]

Originally Posted by italyix

You can actually calculate the proper spring rates you need based on the corner weight of your car. Takes the guess work out if choosing proper spring rates and will make you car handle properly.

can you explain this process?

[M3 Number 86]

Originally Posted by warp10

can you explain this process?

I was curious too so googled it and this is a website I came to with a calculator.

Involves weight of front/back, type of car (weight), motion ratio, coil spring angle, and shock stroke length.

Someone try typing these in and see what it comes out to.

http://www.ridetech.com/tech/spring-rate-calculator/

I just go by feel

[s65m3fan]

I run 600/900 Hypercoils with my MCS 2 way. My M3 is a daily driver. Were it a track car only, I would have gone up to 700/900, but that on the street is a little too harsh for me.