I think people have suggested upgraded sway bars are unnecessary if you have quality coil overs. Only upgrading the rear bar is also not recommended.

 

A bigger front bar will cause more understeer. If you are on soft spring rates (regardless if they are aftermarket coilovers or not), the inside rear wheel will lift with enough body roll, and you'll get massive amounts of oversteer. A rear bar will make this worse. If you are experiencing body roll and too much oversteer, a bigger front bar will help. Those of us who autocross in Street (stock) class use a big front bar to keep the rear end planted with our soft stock spring rates. What spring rates are your coilovers?

 

What spring rates are your coilovers?

It's the DFV from GWR, Street/Track version, 7kg (392lbs) Front / 4kg (224lbs) Rear.

Thanks for the feedback!

- S

 

We all know upgrading the sway bars usually means better handling. You hear people say all the time "I put beefier sway bars on and now my car handles so much better." So I will say the say thing. I installed Karcepts sway bars front and rear and now my car handles a lot better and tracks flatter through the corners.

Now let me quantify it for you. I race on a 0.9 mile track with 13 turns. The turns are tight so it's easy to get oversteer/understeer in the turns. I have Ohlins 8/4 coilovers, 235/40R17 Dunlop Direzza III tires. On March 17, 2019, I ran a fastest lap of 1:05.677, a personal best at the time. I installed the sway bars on March 30 and the next day I was about to cross the finish line with a time of 1:04.5 but I looked at my projected lap time and got too exited and gave it too much gas out of the corner and spun out 30 yards before the finish line. The best for the day was 1:05.118, over half a second faster. Later, I got the sway bars dialed in and did a 1:04.098. That's a massive decrease in time from just coilovers only.

I agree that if you are running quality coilovers, which you are, and not doing track stuff then you don't need to upgrade the sway bars. And with that upgraded rear only sway bar you are risking inducing unexpected snap oversteer in a tight situation. I would not do it.

 

I agree that if you if you running quality coilovers, which you are, and not doing track stuff then you don't need to upgrade the sway bars. And with that upgraded rear only sway bar you are risking inducing unexpected snap oversteer in a tight situation. I would not do it.

Thanks much for the thoughts.

I am a regular at the track, which is the primary motivator for considering the front sway bar upgrade. The rear sway bar is already upgraded (although the track owner called the Progressive bar I have installed a toy =) ), so are you suggesting to revert that? Or that the rear upgrade really should be accompanied by a front bar upgrade?

Thanks again,

- S

 

There are race classes where we are allowed only ONE sway bar upgrade, so we do that one bar. But we do other stuff to fix the understeer that results with just an upgraded front bar. For SCCA CS in our 2019 Miata that means Penske HARD rear bumpstops and full stiff rear shocks to balance the front bar. We can make it work, but unless stuck with rules that limit you to one bar it is a BAD IDEA. Sadly, because cars in classes limited to just one bar upgrade can be made fast, it has become Internet group think that one bar upgrade is a good idea. Video below is me taking top of SCCA CS in our 2019, upgraded KARCEPTs front bar, Koni Sport shocks with rear set full stiff and our Penske hardest rear stops. It works, but that's a compromise we don't like and do it only because that's the best we can do with the rules of SCCA Street class.

Our Fiat 124 has our Karcepts bars FRONT AND REAR. And our Ohlins Coilovers with upgraded Swift Springs. This car races in SSM and other classes that permit coilovers and upgrading both front and rear sways. The suggestion that having good coilovers means you don't upgrade sways is not accurate, but it is true we prefer to start with coilovers and have the customer drive that result and then come back and talk to us about the results with coilovers BEFORE we add the sways. Our Fiat with this setup is faster than our ND Miata by quite a bit, particularly on bigger and more flowing courses like the one below:

With every car we want to add roll resistance to balance the grip. So, the more grip you got, the more rate you need in coilover springs and sways. Today we are at COTA with SuperLap Battle in our Turbo NC and this bad boy has 32mm front Rx8 sway, Rx8 rear sway, 13kg front springs, 9kg rear...and that's still not enough rate for our 17x10 grip package, will be doing new coilovers and more rate for next event.

 

...Video below is me taking top of SCCA CS in our 2019....

Slightly off-topic but the engine in that ND sounds great.