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

[StillIC]

~1kg/mm sway bar with ~1kg/mm tension springs as end links. When tension spring preload is overcome the assembly falls from a ~1kg/mm to a ~0.5kg/mm sway bar. This is the equivalent of going from a 12mm to a 10mm bar diameter.

[NitroDann]

Put a gopro on it and do some laps, I need a good laugh.



Dann

[Cus]

My troll-o-meter is going off the scale, but I'll bite anyway:

Wouldn't you be better off with a rising-rate sway bar?

[Magpie]

Why has nobody thought of this yet... Will make blade adjustable sway bars redundant... I want this, does it come in black?

[Okibi]

So that's what they mean by Axle Tramp?

[project.r.racing]

I have subscribed to the thread and have popcorn at the popcorn ready. This is gonna get interesting.

[StanTheMan]

My troll-o-meter is going off the scale, but I'll bite anyway:

Wouldn't you be better off with a rising-rate sway bar?

well from what I recall most of the racers take the rear sway bar out. This could be to compensate that. Bit of spring is better than none....right?

[Purecaboos]

I had to look at the picture in full size to see what was so special. That looks like an old bed spring, should work really well in that application.

[rascal]

well from what I recall some of the racers who fit mismatched spring combos take the rear sway bar out to make up for the mismatched springs.

FTFY

[StillIC]

well from what I recall most of the racers take the rear sway bar out. This could be to compensate that. Bit of spring is better than none....right?

So, firstly, congrats to STM on having some insight as to why I (or anyone) would do such a thing as to create a falling rate sway bar.

My aim was not to create a falling rate bar but to build a softer bar than is available off the shelf. My 12mm bar makes my car too tail happy, and without the bar attached Guran reports that I am cornering on three wheels (picking up the inside front wheel). So I need something stiffer than zero bar, and something softer than a 12mm bar. If I had an 11mm bar I would try it, but it is almost (75%) as stiff as a 12mm bar in any case. So, for ~$10 worth of Century springs I rigged up what I have shown in the photo to halve the bar rate. Problem is that tension springs have some inbuilt preload, about 8kg in the case of the springs I have used, which equates to about 8mm deflection in the sway bar. Not ideal, but for the small price worth experimenting with I reckon.

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.

Having thought about the falling rate sway bar concept I figure that the higher initial rate will keep the car responsive, but the later softer rate will increase grip at that end of the car during hard cornering and restore balance. Time will tell.

[plohl]

Why didn't you just drop the rear, or increase front spring stiffness?
Was it simply because this was a cheap and easy option?

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[pepejesus]

...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.

What kind of set up are you running that requires a softer than 11mm rear bar with A050s? Seems a bit odd.

[StillIC]

Why didn't you just drop the rear, or increase front spring stiffness?
Was it simply because this was a cheap and easy option?

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Partly. I have a mortgage, family, job, hobby...time and cash can both be in short supply sometimes, and swapping out springs is a PITA compared to taking out sway bar links. Plus, I am really fine tuning now...down to plus or minus 0.5kg/mm in roll. Springs are only obtainable in 1kg/mm increments and are more expensive. It only cost me $10 plus an hour or so of time to do this.

[StillIC]

...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.

What kind of set up are you running that requires a softer than 11mm rear bar with A050s? Seems a bit odd.

My springs are nominally 7 kg/mm front and 6kg/mm rear (Teins), which is softer at the front than most racers I know use, but typical to firm for the back. (Edit: I should add that all springs are backed up by tender springs which activate on the inside of the car during roll.)

I have a Racing Beat thin wall hollow front bar, which is as stiff as a one inch solid bar, to compensate the soft front springs in roll. As camber settings have changed, as well as some height adjustment, I have been oscillating between a 12mm rear bar and none at all. I think I have been oscillating around the ideal rear roll rate for all setups and am now finally getting around to doing something about it.

I'd be happy to run no rear bar at all if I wasn't picking up a front wheel. Of interest, Gordon Murray, famed Formula 1 and McLaren F1 designer, didn't run rear sway bars on his cars.

[The American]

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.