Spring rates

[Mike-SEiW]

Just as a datapoint to the archives, I just rang Westfield and found out my spring rates on the "stock" / cheapo springs that come on the black dampers.

They are

300lb/in at the front (black coloured with white splash of paint)

160-180lb/in at the rear (white coloured)

The damper adjustment is only for rebound, not compression.

These values seem to vary, because they asked me how old it is. I purchased my kit in June 2003.

Edited to add: it's a VX engine'd car.

[ChrisG]

You need to also state what engine etc you have because they will vary depending on the weight of the car, for example the standard BEC springs will be lower spring rates than for a Vx Car.

Chris

[Blatman]

Springs sound OK to me, although you may want to try 250lb fronts. If you have ARB's, then I'd definitely try 250 fronts, and maybe 140-150 rears....

[Matt Seabrook]

I have 275 front and 160 rears with ARB and a car that is about 590kg and a fat bloke driver

[Mike-SEiW]

Why would I want softer? I was thinking along the lines of harder.

I don't have ARBs and am contemplating whether to go harder springs or anti-roll bars.

I haven't yet worked out the effective rates and the Hz of the suspension, which I'll do first of course. No sense doing any modification if I don't know where I'm at.

Ideally, I think I'd like to get it to about 2Hz which should be a little hard for the road, but "good enough" for a smooth track.

My theory is I won't need ARBs if springs are correctly dimensioned since the CG is so low and quite close to the rollcenter. That's my theory at least.

[Demos]

Hi,

I have worked out in the past the rates and frequencies and I can agree absolutely with Blatman. As my car was 580kg +80kg driver with the CVH engine I worked out that for just less than 2.0Hz first mode then the springs and anti-roll bars should be:

Front : 220lb  + 13mm ARB (for normal, not wide track)

Rear :  150lb   No ARB

However I never tried this setup because now that I have bought the above 'correct' rates, I have also dismantle totally my car due to a new Engine (Vx) change and some other mods. By the way the Westfield ARB seems too stiff too me (although never tried it, only did some calcs), so I made another one in a local machine shop (used appropriate grade steel) as my car will feature wide track as well.

I would say yes up to 250lb front springs for the VX car may be ok with ARB 13-14mm, to be trying both..sometime I hope.

Rebuilding a car from scratch it is such a hard and time consuming job isn't it? But I enjoy it I suppose.

[Blatman]

Why would I want softer?

More grip.

My theory is I won't need ARBs if springs are correctly dimensioned since the CG is so low and quite close to the rollcenter. That's my theory at least.

I had the same theory........

A stiff car will have less grip, plain and simple. Controlling roll with stiff springs and wound up dampers is a poor solution, as my experiments in the Speed Series have proved to me. Softening the springs and adding ARB's is definitely the way to go. It'll take some setting up, but the end result will be well worth the effort.

[Ian Podmore]

Controlling roll with stiff springs and wound up dampers is a poor solution

Can't comment on the spring rates, but I was amazed over the weekend on the effect of front damper adjustments. I've fitted some new AVO's to the front (with 7" 300lb springs for reference) and started at 8 clicks on Saturday.  

Had loads of understeer, so backed off to 6 clicks for first practice on Sunday, loads of front end grip, and top oversteer slide onto main straight (fun but slow...). Then went for 7 clicks and more neutral set up for rest of the day.

Probably should have backed off rear (Spax) dampers and set front at 6, but didn't want to start making any more adjustments during an event.

Must re-read Staniforth to understand what I'm doing......

[Blatman]

Same result as me on Sunday. Not much front end grip at all for practice, and it was the same for the first timed run. I was waiting to see if grip picked up any as the runs progressed. It did a bit, but backing off the fronts a couple of clicks helped a lot. FWIW, even my AVO's have never been set above 6 or 7 clicks, even on the faster tracks...... On Sunday, my fronts were down to about 4 clicks only....

[Mike-SEiW]

Wow. I didn't know it was that hard. It doesn't feel like it on the road.

I know that controlling roll through hard springs vs. ARBs is a little of a "religion" and it works different for different cars. Since I'm new to Westfields, I'll respect Blatmans experience.

Since I can't fit Westfields ARBs due to interference with other things in the front, I'll have to "roll my own" so to speak. If anyone has the dimensions of Westfields ARB (diameter, thickness and length) that gives me a good starting point.

Thanks guys for good tips.