Sway Bar question.
 

I'm looking for a recommendation on which stiffer bar selection (front and rear) for a MY13 FRS would keep the balance the same but stiffening things up a bit. When I lowered and went to sticky tires the roll increased which was expected.
Thanks in advance

What spring rate are you running?


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Are you on standard springs?
I had the Eibach set on my car with 6k/6k springs. Yeah, the car kept quite flat cornering but I could feel the cross talk at the front through bumpy corners. I ended up taking them off and not using any sways.

Because compromise.

H&R not sure of the numbers

I have Hotchkis adjustable bars, which I like, because you can tune with them.

Keep the stock sway bars and upgrade the springs to reduce body roll. It’ll allow each corner of the car to operate independently of the other.

What rates are you running now?

When I was in CS (a class in autocross ) I had the TRD springs that I *think* increased rates front and rear by the same amount. (So they would not have changed the balance)

When I went with the TRD sway bars, the car's balance tilted heavy toward understeer. I ended up going with a an ST front bar on the softest setting and kept the rear TRD bar. This got me back to stock-ish balance.

Springs or coilovers? Which kit...that'll tell others what you have?

I have the Eibach Pro Kit (1'' drop) and larger, stickier tires, so extra roll like you described is there. I have been considering a thicker front sway bar too, especially after adding front weight with my supercharger. From everything I read people have said to leave the rear alone and just slightly increase the front, yet everyone also says that a sway bar is a BandAid that would be better fixed with some good coilovers. I haven't decided if I will do a sway bar because coilovers are not on my budget at this time.

Right however I'm inquiring about front rear bars that keep the handling basically balanced. Front bar stiffer then you increase push. Need thicknesses for front rear that keep things the same but just less roll. Probably will just increase both in equal thickness percentages

But the more you stiffen the rear, the more the suspension moves away from an independent rear suspension behavior to a solid rear axle behavior, which isn't good for any car that is a RWD track car. If you want to drag the car then stiffen up the rear. Now, to what extent you will be three-wheeling around the autocross track based on a two millimeter diameter increase in the size of the sway bar is speculative at best; you will probably be fine with small changes, but just in case, you could get an adjustable bar. It is more expensive, but if you decide you overdid it then you can at least make adjustments instead of being SOL.

20/16 will slide more than stock but 21/16 will push more than stock. I don’t think anything can replicate the 18/14 exactly.

I've got MCA coils with stock bars, the car is on rails.

Spring rates are 6kg front 4.5kg rear.

Point of note is that MCA recommendations are to keep the OEM bars as the suspension is designed to give best performance with the OEM bars.

You really need to look at your handling package as a whole, otherwise you end up chasing your tail and may end up sacrificing grip.

7k/6k.

I will argue this point.
The stock bars were developed with the stock suspension. As soon as you alter the spring rates the original design parameters no longer apply.

Josh was somewhat surprised when I told him I was running their suspension without sways.

You are running 6k/4.5k (which to me looks like you have too soft a spring at the rear for those front rates. That's only about 2.5k at the wheel). My Reds were originally 6k/6k. At Josh's suggestion when I had the Reds serviced I went with non-inverted and 7k/6k.

Which is better? None of the above. Because compromise.

I have the street performance (purple), from my understanding they are more compliant and street orientated.

In the end I just do what he recommended, I'm just a punter, he is the man with the plan.

As for how the car handles now, it's brilliant, chalk and cheese from OEM.

You had me second guessing myself, I do that alot now, LOL.

On the setup sheet (took me a while to find it) they provide, there is a note: MCA does not recommend roll centre adjusters, aftermarket larger swaybars and polyurethane bushes with these.

Albeit I asked for something better than the OEM Sachs/Spring combo for mainly street with a few khanas and a couple of track days, I believe thrashing the car around the Nasho was also used.

For a more track/khana setup they might suggest something else.

But for me the car is in a very happy place handling wise, maybe a better link between the controls could pick some faults, not me though.

What's your local?

Local track, I assume Wakie.

The Nasho = The Royal National Park

I head down to Wakie a few times a year to pit for some mates on occasion, and by pit I mean take the piss when they DNF and maybe take a pressure or 2, I did alot of laps there years ago, now, not so much.

I don't like calling swaybars band-aids...they're part of a system. OEM uses them for a reason and designed the OEM bars for the OEM system. Doesn't necessarily mean don't use OEM bars if you change other things, but just be aware of the complete system.

Good to remember that the motion ratio of the rear bar is quite a bit different than the motion ratio of the front bar, so going up 2mm on both may shift overall roll stiffness forward (depending on the bar and adjustments). But roll stiffness isn't the only thing that affects handling balance.

IMO...if you have really good shocks and can run stiff springs (or don't need a lot of roll stiffness), you can put together a system that uses stock bars. If you have to compromise on your springs/shocks OR just want a bit more roll stiffness (tire choice comes into play here), larger bars can be a positive. Adjustable bars of any size is a big positive IMO. Adjust overall handling balance relatively quickly and easily.

20/16 is a good option for many, and 22/16 (our RCE hollow bars are about that in terms of effectiveness) is a good choice for some autocrossers and those that need a bit more front roll stiffness. For example, 7 kg/mm springs + 20/16 adjustable bars is a reasonable choice for r-comp tires at the track and will give you some control over balance with the adjustability.

- Andrew

If by "BandAid", you mean "tuning device", then I agree, if not, then "everyone" does not say that " :).

ARB's are a tuning device, to dial in the balance of the car. That's why race cars will use driver adjustable ARB's when rules permit.