this is different to what I'd been going by. an old suspension book said to compare rates of different sway bars you use the cube of their diameters. But this chart gives different results than that does. Whiteline chart added to my modification bible - thanks Benny. That actually changes what I though I needed for a front swaybar though....

My dad is a big believer of stiffening the car and using softer springs and valving, he doesn't like the way I have set my car up at all. I say go for it, doesn't hurt to try these things, but (you have konis don't you?) I'd set the valving softer and maybe look at trying some 200lb springs.

What are your alignment settings?

Here is a very handy chart on sway bar sizing and percentage difference. [chart sourced from whiteline suspension]

from the chart, going from a 18mm to 25mm sway bar is a increase in stiffness of 272%




cheers
Benny

Yeah the rear is a real unknown quantity. It's beyond any gut feeling to know what size bar is appropriate for this kind of configuration. The reference mount on the spring will move with the diff but to a lesser extent but that point can also flex when loaded up which further decreases the torsional rigidity.

most of those points were for the benefit of people interested in your EOI suggestion.

I'm not real sure what the effective rate of that rear bar will be compared to a conventionally mounted bar.

looks like the front bar came up pretty good, you wouldnt have a pic of it out of the car would you?

1. It's not a street car
2. It's not on street tyres
3. The rear bar is very adjustable - the clamps on the springs can be adjusted as well as the mounts on the diff can be moved inwards.
4. I have a CA18DET - heavier than L banger
5. It has a minispooled diff

I appreciate the input and I too agree that they are probably too big but it is an experiment - hence the use of the work madness in the title. Both bars installed cost me about $10 all up because I had the bits lying around.

I will give an honest report on their performance once I get a chance to try them out.

I think they're too big - certainly for street applications.

I had problems with a 16mm rear bar on a street 1200 - it would easily lift the inside completely off the ground when cornering moderately hard. The 20mm rear bar is about double the rate of a 16mm bar, but as its mounted to the spring instead of the chassis may not actually work as effectively. But even if its only half as effective in that position, I still think its too stiff.

Anyone who has upgraded to a 120Y front bar on their 1200 will tell you it makes a huge difference to the car, and that's only a 63% increase in anti-roll rate over standard. A 25mm bar is 2.5times greater than the increase in anti-roll you'd get by going to a 120Y bar!!! I don't think any street tyre is going to be able to handle that - you'll simply overcome their grip co-efficient, unless you drop back to almost standard 1200 spring rates. In which case you'll get alot of pitching under brakes unless you set up some anti-dive geometry in the front end.

I think we've got a case of "if big is good, bigger must be better" going on here.

For comparison, I used 20mm front and 16mm rear bars (both of which are about half the rate of 25 and 20mm) on my previous track car, which handled like this:
Bathurst
MtCotton
and that's with a big heavy L series in the front, and a locked diff so it didn't matter if the inside rear got light (it was actually a bonus). The same is not true for an LSD, let alone an open diff. Lift an inside wheel in one of them and you have basically no drive. You have to remember the sway bar lifts the inside wheel with as much force as is resists roll on the outside wheel. Do you need stiffer sway bars than this? particularly ones that are twice as stiff?

I recently picked up a whiteline rear bar 2nd hand which is 18mm, and would need something like a 22mm front bar to balance that out. And I'm very hesitant to try those bars on my race car, let alone a road car! These are massive changes we're talking about here.

i hope they work for you, but from my experience I think its totally overboard.

i really like the look of them, but know that they've been heated up hasn't that changed the springyness of them? i think that a techical term

The rear rubbers are standard R31 rear swaybar rubbers. They worked well because the R31 rear bar is about 17mm so with a 20mm bar through them they are a bit tighter. The front ones are nolothane and are indeed fairly thin. I unfortunately have no idea where they came from, I had them lying around. I'll have to work out what they are if I replace them one day.