THSCC Forums

Need some help here understanding my car would be affected. I am basically a suspension idiot.

My rear sway bar has three positions on it. Let's say position 1 is closest to the end, the bar is currently set at the middle, number 2, position. How will my car handle with it switched to the #1 or #3 positions, or even disconnected all together.

Can anyone help me understand how this works?

Thanks
Todd

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Todd Breakey
STS 42 - 1992 Sunburst Miata
Dammit!
"You souldn't play leap frog with a porcupine. You might get hurt." - Eliza

Todd,

Look at it this way: A sway bar works (primarily) by twisting the main part of the bar. The arms are literally "lever arms". The further out the links are on the arms, the more leverage there is to twist the bar. This makes the bar softer as far as its effect at the connected wheels. Disconnecting either of the arm links totally removes the bar from suspension stiffness. The closer the links are to the bar, the more effect the bar has. Stiffer normally makes that end of the car likely to "slide" sooner. That is, stiffer front means more understeer or less oversteer. Stiffer rear means more oversteer or less understeer. Note that I said normally. There are tons of variables involved, especially with Stock or close to Stock cars. Many autocross cars actually work better with a stiffer front bar than stock, even if they understeer to begin with. Cars like stock Miatas tend to oversteer on R tires and a bigger front bar tames the oversteer, helps put power down, and/or improves transient response.

Edit to add: You might want to budget for some books on handling. If so, start with "How to Make Your Car Handle" by Fred Puhn and "Tune to Win" by Carroll Smith. Most info is "correct" other than Shocks have come a LONG way since the books were written plus autocrossers in Stock classes can do some things with shocks that a racer with normal suspension tuning options would not be "forced" to do.

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Dick Rasmussen

FS 50 2018 Mustang GT

And now for some Miata-specific advice...

Depending on your shock/spring setup, you may want to consider returning to the stock (pencil-thin) rear bar.

On stock shocks and springs, I ran a JR hollow bar up front (stiffest setting), and the JR solid rear bar (softest setting). Very nice setup on stock springs - neutral and controllable. After I switched to adjustable coilovers, I kept the same sway bar setup until VIR-S this year. The back end did not like to stay planted on some of the quicker transitions, so I switched back to the stock rear bar. The back end of the car is much more planted, and I seemed to have quite a bit more grip. The car still rotates nicely when I want it to rotate, but behaves otherwise.

Lots of very fast people in Miatas (locally and nationally) auto-x with this setup. YMMV.

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Tom Freeman
'98 M3/4/5 | '93 Spec3 325i | '12 TSX sport wagon | '03 Tahoe
Team Silver Bullets '91 240SX

Hi Todd,

More Miata input to confuse you...

Running stock class, I have a Racing Beat 15/16" front sway bar, stock rear. I have adjustable Konis that I run full hard all the way around. The front bar makes the car very stiff. I have yet to get it to rotate or throttle steer. However, it doesn't push (that I can detect).

I got a Racing Beat 5/8" 2 hole adjustable for the rear of the car for HPDE. At a soft setting (hole at the end) with the rear shocks full hard, it was a bit too loose for my taste. After tweaking with the rear shocks, I wound up with them set at full soft. I had a car that I felt was handling pretty nicely for Roebling Road. It was ever so slightly drifting through turn 5B, which my instructor and I both felt very comfortable with.

Hope this helps a little.

KB

_________________
“I feel safer on a racetrack than I do on Houston's freeways.” - A.J. Foyt

Kevin Butler
Mobetta Autosport Spec E30 #612
2003 C5 Z06 Corvette
AFR Miata, SM2 61, '93 w/200 SC'd RWHP - soon to be resurrected
Waaaay too many other projects....

Thanks guys. Good information there. I think I understand what everything does now.

Unfortunately I don't know what i have under the car. My brother bought some package several years ago. I know I have the blue Tokiko shocks, but as for springs or bars, I've got no clue.

Maybe this is telling me I should upgrade the package.

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Todd Breakey
STS 42 - 1992 Sunburst Miata
Dammit!
"You souldn't play leap frog with a porcupine. You might get hurt." - Eliza

Or you could measure the thickness of the bars that are currently on the car, and someone here might be able to help you figure out which ones you have.

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In need of car.

That makes sense. :slaps head: Cheaper too. Time to break out the tape measure. Thanks Jason.

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Todd Breakey
STS 42 - 1992 Sunburst Miata
Dammit!
"You souldn't play leap frog with a porcupine. You might get hurt." - Eliza

What he says. I have the same front bar and the same shocks. I have had mine full stiff, but it rides funny, especially when I leave them on full stiff and drive to Virginia Beach.

I have played with the shock settings so much, I can't remember where they are now. I think the are about 1/2 turn off stiff in the back, and 1 turn or so off in the front. I adjust tire pressures to make the car a little loose. (I hate understeer). I can get the car to rotate with a little throttle lift with that set-up.

All these settings may go out the window with the new Avons, tire pressures different.

good Luck