'Falling rate' rear sway bar.....

[Magpie]

Still trying to debate is this is a serious post. Your signature has SMPGP: 1.53.256 on 165/75 R13 Supercats this is impressive to say the least.

I'm with others, just disconnect the rear sway instead of using a 'spring' or have a custom made sway bar that allows the lever point to be very close to center of the bar http://www.mako.com.au/

How have you calculated the weight transfer that the sway bar manages? What level of grip do you have in a corner? Is the issue driver or mechanical? Why is it so important to remove any roll "own to plus or minus 0.5kg/mm in roll"? Be interested to see the mathematics/data/logic used to reach your solution.

This is what you should be using, not a coil spring...

[smy0003]

If you hit a bump (rumble strip) mid corner with the unloaded wheel, wouldn't the spring momentarily bind giving an instant change in sway properties?

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[sailaholic]

Why run such a soft spring rate? Increasing front and rear spring rate would allow a bigger variation between front and rear without custom spring rates.

Ie drop the front sway bar back to standard and get it balanced on springs first. Then tweak with sways.


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[Magpie]

Rough guess is the trend in the US to go soft springs big bars??

Where the big bar soft spring set up works better:
• Experienced drivers and successful teams
• Flat tracks seem more conducive to the principles but it can help anywhere
• On tracks with reasonable grip
• With tires that can take some punishment

http://www.longacreracing.com/userfiles/articles/text/SoftSetup.pdf

[pepejesus]

This is what you should be using, not a coil spring...

I think maybe some shocks with suitable spring rates for the tyres (like 14/8 kg/mm) would be worth trying before custom three piece sways!

[rascal]

Your signature has SMPGP: 1.53.256 on 165/75 R13 Supercats this is impressive to say the least.

I haven't tried them on the track, but on the road it is difficult to tell the difference between the 12mm bar and the above assembly. Probably because my 165/75 R13 Supercats can't generate enough lateral grip to really roll the car enough to engage the secondary springs by a significant amount. But warm A050s certainly will.

The above suggest the supercats are his road tyres, with A050s used for the laptimes..

[rascal]

Rough guess is the trend in the US to go soft springs big bars??

Where the big bar soft spring set up works better:
• Experienced drivers and successful teams
• Flat tracks seem more conducive to the principles but it can help anywhere
• On tracks with reasonable grip
• With tires that can take some punishment

Soft springs and big bars on track means you can get excessive dive under brakes and squat under acceleration.

I'd suggest the above applies to the good ol boys affection with running around and around in a circle where they hardly ever brake...

[pepejesus]

Rough guess is the trend in the US to go soft springs big bars??

Not the case with the MX5s in the US, people have been going for firmer and firmer springs over the last few years, to the point that 800/500 lbs/in (~14/9 kg/mm) is the generally recommended starting point for the track when using proper tyres.

[project.r.racing]

I think you'll find the stiff rear springs (compared to the fronts) that is making the tail slide. Not the sway bar.

[StillIC]

If the left and right were not connected and reliant on each other , this might work a little. However, I don't think it would take much for the side under compression (the inside) to simply bulge and pop out, leaving the bar to suddenly change tension mid corner.

Indeed!

That's why I have a 12mm diameter aluminium tube up the middle of each spring, which can't be seen in the photo.

[StillIC]

Why run such a soft spring rate? Increasing front and rear spring rate would allow a bigger variation between front and rear without custom spring rates.

Ie drop the front sway bar back to standard and get it balanced on springs first. Then tweak with sways.

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This is good logic, but it's too late. I have what I have and I am fine tuning it. Plus, I don't like a stiff rear bar and it is a road car as well as a track car. Springs are more than stiff enough for the road I think.

[StillIC]

....or have a custom made sway bar that allows the lever point to be very close to center of the bar http://www.mako.com.au/

How have you calculated the weight transfer that the sway bar manages? What level of grip do you have in a corner? Is the issue driver or mechanical? Why is it so important to remove any roll "own to plus or minus 0.5kg/mm in roll"? Be interested to see the mathematics/data/logic used to reach your solution.

This is what you should be using, not a coil spring...

Custom sway bar...sounds expensive. And I'll have to wait a while. But thanks for the link, I do appreciate this.

No, why do I need to do weight transfer calcs or mathematics? 12mm is too stiff (1 kg/mm bar rate) causing mild oversteer. 0mm (0 kg/mm bar rate) is too soft causing wheel lifting and a touch of understeer. I need something inbetween. It's very simple.

Define should!

[plohl]

I actually priced some custom bars a while ago, and it wasn't that much more expensive than other aftermarket ones. $20- 30 more I think.

General rule is to get away with the softest springs you can...

na8s came with an 11mm rear bar iirc

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[StillIC]

I actually priced some custom bars a while ago, and it wasn't that much more expensive than other aftermarket ones. $20- 30 more I think.

General rule is to get away with the softest springs you can...

na8s came with an 11mm rear bar iirc

The few spring makers I knew have disappeared over the years. Who did you contact for custom bars? I would try a 10mm to start with.

No argument from me...

You are correct re the NA8's 11mm bar. If anyone who has one spare is reading this I would be happy to try it.

[Code4]

Has this seriously gone to two pages !!