Performance: How do anti roll bars and spring rates affect car handling?

Originally by TaviaRS!

Righty ho, I've been asked loads of suspension questions via PMs so I'll try to get them all in a couple of posts for general benefit. Please accept my apologies for not answering your PMs, I keep forgetting

Anti Roll bars

Ride height and spring stiffness should be set before uprating and anti-roll bar. The reason is that the lower the front of the car, and the stiffer the front suspension, the less weight transfer there will be and therefore less work for the ARB to do.

ARB are rated on thickness, which is expressed in either mm or inches (or fractions thereof). Watch out though as a few mm or 16th of an inch can double the stiffness of the bar. Reason is that stiffness increases as a fourth power of change in diameter ie you multiply the diameter 4 times to get the stiffness. Best to work it out in mm. eg a 22mm bar gives an end value of 234256 while a 26mm bar gives 456976 (26x26x26x26) basically nearly twice as stiff!

General handling

Below are links to 2 flow charts which will help in the setup of your car. They are very simplistic, but they are correct and the info does help.

Understeer removal

Oversteer removal

Spring Rates

Ah ha, now this one is a good one! Its very hard to uprate when you don't know the starting point (does anyone know the spring rates for a standard RS? All I do know on this is that "uprated" springs aren't! Well, they are uprated for a standard Octavia, not the RS. They also have a lowering effect and are usually progressive rather than linear. I found that the motorsport Golf IV runs 550lb at the front and 650lb at the rear and just scaled down from this (400/475 f/r). Spring rate changes are similar in their logarithmic change to anti-roll bars. I have not tried "my" uprated springs yet. What I am doing is using standard RS springs and then putting in coil inserts, effectively removing coils to make them shorter and stiffer. Due to my high road mileage this means that I can keep some suppleness on the road then firm up on the track. For people who want their RS to be softer (due to really bad local roads) how about some adjustable dampers matched to some springs from an estate. I would have suggested 4x4 springs, which although stiffer than standard Octavia springs, would be too long and make your RS look very strange (without the 21" wheel conversion). Another possibility would be to drop down a wheel size (giving you taller profile tyres to keep the same rolling diameter) which would give additional "cushioning"

Hope all of the above helps in some way.