I was wondering, what is the effect of increasing sway bar size in the front relative to the rear? In the rear relative to the front? Too much both ways? Thank you.
I believe that increasing the diameter of the rear sway bar will decrease understeer (or increase oversteer) while increasing the diameter of the front sway bar will increase understeer (or decrease oversteer).
In good old boy-ese, bigger front bar= push. Bigger rear bar=loose. Do you know the difference between push and loose? Push is when you get to see the accident.
Be careful with self diagnosis though. Excessive understeer promotes oversteer. You need to make sure you're in the window. On a road car, there's more to gain from Tyre pressure and type, camber, caster and toe before changing anti roll bars.... but basically, a quick fix for most road Ferrari's is to fit a stiffer rear anti roll bar.
VERY slow to respond to emails and voicemail, but once you get John on the phone, VERY knowledgeable and helpful.
I agree with the above, the rear bar on my 82 308 GTSi is quite small. Question now is - were does one obtain a larger rear bar?? Thanks in advance.
Not sure about that...most road rear engine ferraris are prone to snap oversteer by design ala 911 syndrome even if cars are set up safer with factory understeer there is faulty driver input, the classic let off the gas or brakes on in turn. So becareful with barchanges. A stiffer rear bar will make for more rear oversteer ala the old pre911SC. You need a proper diagnosis on a closed course then adjust the suspension accordingly like Ffixer said then make aftermarket changes to suit your driving style. Many people have messed up their ferrari suspension with new wheel tire combos. Ferraris are very sensitive to chassis changes thats why they feel like ferraris when you drive them.
fatbilly...snap oversteer is exactly what I meant by excessive understeer causing oversteer. You'll find that most rear engine Ferrari DO like a stiffer rear bar, but as I said, proper diagnosis is needed. Most 3*8 models have different size rear bars between GTS/GTB. Also you may find the 348/355 Spiders have different bars to GTS/berlinettas too.....It can be quite easy to "borrow" one to try as a start point.
USA model 1984 308 GTS/QV is 18mm for both front and rear bars. I've gone to 25mm front and 22mm rear on my upgrade (see pics at http://www.ferrarichat.com/forum/showthread.php?p=134561181)
Before you put on those sway bars I noticed you said you had updated the rear sway bar bushings. Where did you get these from? Thanks.
Fisrt off, we're talking about anti-roll bars, not "sway" bars. But before we get there, lets get a better, working picture of what roll bars do and are: A roll bar is a bar of metal that connects two wheels on the same axle to the chassis. It's job is to control the rate of lateral transfer between the two wheels. Lateral transfer of load between occurs under cornering and can has an effect on camber changes and the tire's contact patch. Because roll bars can limit or reduce the body roll and have an effect on the rate of the lateral load changes, they're considered to be an integral part of the overall or total roll resistance of the car's suspension. How it works: as you corner, the outside wheels compress and at the same instant the inside wheels unload, this simultaneous action is body roll. The roll bar limits body roll and lateral load changes becuase of the fact that it's connected to both wheels and the chassis, therefore the only way for this to change would be if the bar twisted - the bar's resistance to twist, therefore defines the increase in roll resistance. So ... if you remove the front bar you reduce the roll resistance of the front suspension and in effect soften the suspension. If you remove the rear roll bar, the same would happen. If you removed the front and kept the rear, the car would be more prone to oversteer and if your removed the rear and kept the front the car would be more prone to understeer. The same pattern as above would apply if you adjusted the bars front to back and back to front; ie., putting too fat a bar on the front will actually induce understeer as the rate of lateral loading is increased significantly and youre overworking the front tires sooner; and if you go too fat on the rear your induce oversteer by the same physical phenonmenon.
Another thing to consider is that spring rates can be played with to have the same affect, so I've read. As an aside, I thought the 911 snap overstear was attributed to suspension geometry coupled with worn bushings, so that while under cornering loads, the rear wheels would have positive toe out. Any truth to that? I find it hard to believe it's all weight distribution...
I once heard the difference as: Oversteer is where the back end comes around and the passenger is scared. Understeer is where the front end goes straight ahead and the driver is scared. hth, chris
Actually I updated the A-Arm bushings with urethane bushings from Energy Suspension. They're also available from Nick's Forza Ferrari and even special order from places like Autozone. The new urethane anti-roll bar bushings came with the bars, courtesy of Saner Performance.
Do you have terminal understeer? I don't know anything about the GT4, but I found my GTS to be a little unsettling for a street car on a drop-throttle freeway entrance. Perhaps it goes back to my theory: "Never set up an autocross car to push and never set up a street car or road race car to oversteer!"