Stock Sway Bar Sizes On FRS?

[Racecomp Engineering]

Only the rears swap from Impreza IIRC.

I wouldn't recommend increasing the rear without increasing the front on this car.

- Andy

[wparsons]

Originally Posted by ft_sjo

Don't quit your day job.

You'd rather three wheel around a corner than put power down? Inside rear tire in the air means now power at all unless you have a clutch LSD instead of the stock one.

The absolute last thing these cars need on it's own is a stiffer rear bar. They aren't front biased FWD cars that need help rotating, they're pretty well balanced from the factory.

[eckoflyte]

Originally Posted by wparsons

You'd rather three wheel around a corner than put power down? Inside rear tire in the air means now power at all unless you have a clutch LSD instead of the stock one.

The absolute last thing these cars need on it's own is a stiffer rear bar. They aren't front biased FWD cars that need help rotating, they're pretty well balanced from the factory.

agreed. in FWD situation, you could pull yourself out of a corner in an oversteer situation using the front tyres. in that same situation, it wont happen in an RWD drive car unless there is grip in those rear tyres. hence, when it comes to playing around with rear roll stiffness, you really have to have a baseline on how the car handles at the limit (only possible on a track) and know what you want to do by tuning spring and roll bar and alignment incrementally. Even experimenting with wider grippier tyres can change the handling dynamic immensely without the need for any of the previous mentioned.

i wouldn't just slap on a bigger rear bar and hope for the best, not the safest thing to do.

[2point0]

I played around with a 19mm STi rear bar and it was nuts. TC light was getting really annoying.

This was with 235s (Federal 595SS), I wouldn't have dared on the stock tires. Even then, I was not comfortable pushing the car.

I also have a 22mm bar from the STi that I'm too wussy to even try...what a difference -600# can make!

[ft_sjo]

Originally Posted by wparsons

You'd rather three wheel around a corner than put power down? Inside rear tire in the air means now power at all unless you have a clutch LSD instead of the stock one.

The absolute last thing these cars need on it's own is a stiffer rear bar. They aren't front biased FWD cars that need help rotating, they're pretty well balanced from the factory.

You know there is something between A and Z, right? You also do realise things like tyres play a huge part into bar selection?

I did some track time last night with the 16mm rear bar on stock Michelin tyres. In a tight circle, 1st gear, the rear inside tyre is breaking traction. In a larger, 2nd gear circle it's not. That's probably more to do with the diff than the bar.

With stickier tyres on (i'll re-test with my AD08's) this effect will most likely be less, depending on roll angle.

It really depends on what you're trying to achieve. I've not stated that changing the rear bar is the right thing to do for everyone. But then not everyone in the world is doing 1/2nd gear auto-x events in American parking lots.

[wparsons]

^^ The inside tire is breaking traction in really tight corners because it's an LSD and putting power through it makes both wheels want to spin the same speed. At low speeds and really tight radii the speed difference is enough and the gearing is short enough to cause a bit of scratching at the pavement. At higher speeds and larger radii the forces aren't the same and the speed difference between the wheels isn't as big.

I'm not talking about breaking traction, I'm talking about the inside tire being visibly off the ground because the rear bar is too stiff and the springs aren't stiff enough. Just throwing on stiff sway bars without stiff enough springs does funky things to the handling.

Remember that the way a sway bar works is to couple the sides together, so if the outside spring is compressing the bar is making the inside spring compress too, which takes weight off the inside tire.

Big rear bars can work on FWD cars that need help rotating, but they put power down through the front wheels so it doesn't matter if a rear wheel is in the air.

Putting a bigger rear bar on a RWD car will do nothing but hurt traction when exiting a corner, and since these cars don't need help rotating into a corner it's not helping anywhere.

FWD car, but it paints a picture. Big stiff sway bars, not enough spring rate (I know the owner of the car, and he used this same picture on another forum to prove what I'm saying). Look at the body roll he's getting. If this were a RWD car, how much power do you think that inside tire would put to the pavement?

[ft_sjo]

No doubt that Honda has reduced droop due to some crappy coilovers too.

You can't make blanket statements when it comes to handling. Even the suspension engineers are OEM's and race teams need to do testing, even with complex simulation on a computer.

I'm not sure what point you're trying to get across, you appear to be arguing with blanket statements, where i've clearly explained there is more than just black and white. Hopefully some people reading this will realise it's the grey area that counts.

[Xauterus]

I think the point is clear. Its rear wheel drive. You need the drive wheels on the ground to go fast.

I think the confusion comes from the car being from Subaru, a WRX needs a big rear sway bar cause it likes to understeer.

[wheelhaus]

To add to the clarity, a stiffer rear bar by itself is not recommended. Once other parts change (tires, springs, coilovers, whatever), this is where the gray area exists, but the point remains (as TIC suggested) balance front and rear still needs to be maintained.

[OrbitalEllipses]

Originally Posted by Xauterus

I think the point is clear. Its rear wheel drive. You need the drive wheels on the ground to go fast.

I think the confusion comes from the car being from Subaru, a WRX needs a big rear sway bar cause it likes to understeer.

Even on the Impreza platform adding a stiffer front swaybar will increase performance. Of course balance is key and a rear bar wouldn't hurt, but just because they understeer all day does not mean a front bar doesn't help them.

[wparsons]

Originally Posted by ft_sjo

No doubt that Honda has reduced droop due to some crappy coilovers too.

Hardly, that car (and driver) has the FWD lap record at a local track for both street and unlimited classes (and is fully streetable minus slicks when run in unlimited). At that point it had too soft of spring rates for the weight of the car and amount of grip it generates, but they definitely weren't crappy coilovers. Nice blanket statement though

Originally Posted by ft_sjo

You can't make blanket statements when it comes to handling. Even the suspension engineers are OEM's and race teams need to do testing, even with complex simulation on a computer.

I'm not sure what point you're trying to get across, you appear to be arguing with blanket statements, where i've clearly explained there is more than just black and white. Hopefully some people reading this will realise it's the grey area that counts.

Absolutely, but my point all along is that people shouldn't just throw a stiff rear bar on these cars without having lots of testing data to support that it needs it (which it won't, ever). Too many people are used to FWD cars which need a big rear bar to be fast and assume a neutral RWD car will behave the same. I don't need tons of testing to know that adding nothing but a stiffer rear bar will do nothing but make the car slower and scarier to drive.

[mrk1]

I've always thought sway bars should only be changed after the spring/shock combination has been set up. A way to make a compromise in a suspension, Body roll vs. spring rate.

Bit of an extreme example but check out the "sway bars" in the Mclaren MP4-12C