Suggestions needed: Spring rates/no swaybars for E30 318is

[BrandC]

I'm doing a bit of probing before I buy the Ground Control/Koni coilover kit. I do NOT want to run aftermarket swaybars, I want to control bodyroll with high spring rates. This setup is meant for track-duty, but it will see street time too.

What rates do you guys suggest? I've seen 600f/650r for a track setup and the owner really liked it at his first track day (I forget your SN, I'm new on here!). TIA, cheers!

-Brandon

[Skafrog]

Call GC and ask. If you have only been to one track day and have only run on one set of springs, you cant pass judgement on suspensions.
GC will give you rates that you need. Just let them know that you wont be running a rear bar, and give them your weight and intended duty.

[2002maniac]

I have slightly upgraded swaybars on my car (Vert front/M3 rear) and run 400/650 on my 318is

I think somewhere along the lines of 500/700 would be a good starting point.

[325is///M-tech]

I am running 375lb front and 475lb rear with stock sways and my car has very little roll. In our race car we run 600lb font 650lb rear with a ST front bar and NO rear bar at all and it is planted.

[BrandC]

325is///m-tech: What car are you using that runs 600f/650r rates?

2002maniac: Thanks for the starting point, I think 500/700 will keep it pretty planted. Do you know if this setup is closer to oversteer or neutral steer?

[e9nine]

Dunno if it's me you're referring to but shock and spring combos are somewhat of a personal choice. It also depends on your driving style etc after a certain point. Some don't push their cars hard - others brake late - some left foot brake - others over-do everything....

Some people assume they can daily these rates. Many variables come to play and I don't claim to be the guru of suspension set up. I think Alex S even runs 500/500 or so depending on the surface he's on.

I went through about 3 different rates before settling with 600/650 and then did the swaybar delete and liked it. You cannot totally eliminate body roll on a car that you will drive on the street. You might think your set up is roll-free till you see pics of your car being driven hard or see someone else driving your car.

Personal prefence :D

Here's pics of 600/650 under different turning conditions with 205-50-15 Falken tires in a 318iS. If you're interested I'll send you the other pics of my car from the HPDE when I get the CD in. Send me a PM

[bmwm3n528]

OT, that last shot is super cool.

[BrandC]

e9nine: Yes, you were who I was talking about! Pics look awesome too. Do you drive the 318is to the track/auto-x events? I'd probably daily the car with the coils on and just run 65-series tires.

[matt]

McCoy riding shotgun, right? :)

[325is///M-tech]

It is our 90 325is race car. It is pretty nuetral. We had softer springs in it but we were getting coil bind in it. we upped the rates then the car had ALOT ov oversteer so we softened the shocks a little, then softened the sway bar a little, then took the rear bar out all together. A team mate of our runs even softer springs with no rear sway.

[Driver1]

please forgive my ignorance

why wouldn't you want a rear sway bar?

[Jean]

500front/650rear, no rear sway yet but will install one later on

[Fidhle007]

please forgive my ignorance

why wouldn't you want a rear sway bar?

I'm in the process of reworking my car's suspension and have been wondering the same thing.

[matt]

Start by thinking about how a rear sway bar works. It links the rear wheels with what amounts to an extra spring. So for example, when you hit a bump with the right wheel, the left wheel is pulled upward by the sway bar.

With me?

Now think about what happens when you're cornering and your car rolls to the outside of the corner (centripetal force). The same effect applies... the inside wheel will be... LIFTED. Two tires have the most grip when they share their load evenly... when one is totally unloaded it's not doing its part, and if you have an open diff, that wheel is hanging in the air spinning.

The bottom line is that sway bars are used to tune the balance of a car's suspension (notice that most cars have thick fronts and skinny rears stock... understeer) at the expense of grip. Exchange the swaybars for stiffer springs (which will also reduce roll, but won't effect weight transfer in the same way) and you can pick up grip.

Ever see a VW lift its inside rear tire? Too much rear sway bar to overcompensate for a FWD car's natural tendency to understeer.

[JRKOUPE]

It is our 90 325is race car. It is pretty nuetral. We had softer springs in it but we were getting coil bind in it. we upped the rates then the car had ALOT ov oversteer so we softened the shocks a little, then softened the sway bar a little, then took the rear bar out all together. A team mate of our runs even softer springs with no rear sway.

what were the rates of the soft set?.......and the stiffer set?... coil vers?..............tia!