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Not that I am suffering the slings and arrows of outrageous fortune, or taking arms… blah blah…
I am not looking for secrets, but honestly - how many of you are running rear sway bars?
I know for Autocross a rear bar is a waste of time. But for road racing I always thought that there was a difference in opinion.
Opinions/Musings?
In the absence of a rear sway bar, 2 things are going to happen.
Increase in body roll. The consequence of this is that the tires will roll beyond neutral in hard corners and the tire’s foot print will suck. This will mean less traction both front and rear, and it will mean that you wear out the outer edge of your tires.
Center of roll resistance all the way forward. With only a front sway bar to resist roll the front sway will be maxed out even at moderate lat g’s. So there’s a bar lifting the inside front tire but not the inside rear tire. The unweighted inside tire caused a reduction of front traction…that is to say, understeer.
The Miata was a full second faster sans rear bar - though rolled more and had more front end scrub without it.
The benefit was an earlier transition to throttle and slightly higher entry speed. Which is where the speed came from.
The downsides was in hairpins where the transitional characteristics that sways offer wasn’t present.
Please - more musings - this is helpful.
I’ve run with and without the rear. I liked the way the rear of the car sticks with the rear sway disconnected, but the understeer that results is aggravating. If I had my druthers I’d use a rear sway that was a bit less stiff than the mandated 19mm bar.
All I can guess is that the setup was completely screwed BEFORE you unhooked the rear bar… One second faster than…?
I try to make this pretty simple. I watch what the fast guys are doing and I do that. I don’t know anyone who runs without a rear sway bar in the dry.
Tire wear will suffer, grip will suffer.
I run the bar on full soft almost all the time. Once you are full soft, the only way to make it softer is by playing with the hubs. 
Fortunately, the same works for the front axle.
I ran with and without last weekend at VIR and I was 1.5 sec faster without. I found myself getting on the gas earlier to keep the car from pushing.
On a side note, my front sway bushings are the factory set up and they are torn to bits. I plan on replacing soon so that might have a huge impact.
Jason
Interesting. I find that the push gets worse when I go to gas because I am transferring weight rearward. If, however, going to the gas mid-corner causes the rear tires to lose a little grip, that will rotate the car and maybe make it feel like the push went away.
I believe you’re right. The car was rotating well. I’m sure I was leaving a lot of tire money on the track, but it was good fun. Definitely something I’m trying to fix now.
Worn swaybar bushings in the front will make the car roll and rotate very nicely, but will hurt your lap times. I had my front swaybar links fail once and the added ~1 inch of slop was very apparent (and scary) entering a corner.
I’m not seeing how the absence of a rear swaybar could have any benefit in the dry. Easier to driver, perhaps, but it will certainly unsettle the balance of the car and result in understeer. I guess removal of the rear bar might help if your rear tires suck and your car oversteers every time you turn the steering wheel…
Then again, Billy Jack Ethridge (A good CCA racer from Birmingham) told me that he doesn’t run a rear bar. He does run Koni adjustables on all four corners so a comparison of his setup to ours is probably not valid.
I installed the SpecE30 sway bars from UUC and left the bar in the middle of 3 adjustment points for the rear bar. I took it to CMP, and I felt like I had ZERO rear grip. I then went home and moved it to the softest hole and went to Road Atlanta and the car felt like it had TONS of rear grip. So I gotta agree with Steve and say run the rear bar at full soft. I know disconnecting it will be like it is even softer, but I would imagine that it would push like crazy.
Re: the Miata, it’s now recognized that enough rear spring negates the need for the rear bar, this frees the rear control arms to move with the car more independently and allows for more grip over all and earlier throttle. Though some might still run the OEM bar.
For Autocross with the nature of the driving style - no rear bar was the way to go in an E30 - or the OEM bar.
It’s my understanding - though the last time I was involved in E36’s was in 2001 - that they run sans rear bar also.
Maybe this is a viable tuning option and not an absolute. It may also depend on driving style.
I’m going to spend the time and effort and test this out.
[quote=“kgobey” post=55988]For Autocross with the nature of the driving style - no rear bar was the way to go in an E30 - or the OEM bar.
[/quote] The OEM bar is not an option for us. Disconnected or connected, 19mm it must be.
[quote]Maybe this is a viable tuning option and not an absolute. It may also depend on driving style.[/quote]And tires, and spring rate, and weight distribution.
When I drove Hoosiers at the 8 hour in December I found the car needed to have the rear bar unhooked (but we never did). With the added grip, the body roll was worse. “Add more bar” you say? Counter-intuitively, that would have made the bigger problem worse, which was the car lifting the inside rear on every slow turn (7 and 10b at Road Atlanta).
In SpecE30 trim, a little rear bar seems to be the trick. But let us know what your testing proves out.
Definately maybe.
Ireland rear bar.
So running without the bar was fine - alot of push but easy power delivery… Running with the rear bar on semi-stiff was nasty and running on the rear bar with it at full soft was fastest…
Loose is fast in an E30 at BWRP, at least right now…
This research is void though. The car is in terrible shape, I need to re-do all the suspension and I need to replace the ETA with an I motor ASAP.
I won’t forget this thread though.
But the bar is definately an optional item - no doubt.
Having a bar with only a couple discreet adjustment points is a problem. Some bars are continuously adjustable. I can feel 2mm of adjustment and 4mm is very noticeable.
If I can feel 2mm, anyone can.
Forgive my science ignorance. Is the softest setting towards the rear of the car or the front of the car?
Full soft has the attachment points at the very end of the bar. Some of the fastest guys here have their rear sway bar at full soft. Mine is currently 10mm from full soft.
Everyone’s car is bound to handle a little differently. I found 14mm from full soft to be tail-happy, and 4mm to be too much understeer. But once I got into small changes it becomes hard to isolate bar changes from other factors like tire pressure and tire state of wear.
It’s kind of an experience thing. Last Summer I had a 3 day weekend at CMP where I was having a helova time with oversteer. I kept loosening up the rear sway in small increments to dial the problem out. But ultimately I grew suspicious that the real problem was that my rear tires were more worn (and therefore harder) then my front tires, but I didn’t have my durometer along with me to confirm it. Moving tires around seemed to help the problem, but I didn’t get enough sessions to really confirm it.
A pro team goes to the track with sticker tires and makes good air pressure predictions. A grassroots guy goes to the track with tires with dissimilar wear patters from 3 previous race weekends, and occasionally sees air pressure do things he didn’t predict. So the grassroots guy, due to budget and inexperience, ends up trying to understand the car’s behavior in an inconsistant environment. Of course he’s trying to make it consistant, but inevitably it’s not.
Then the grassroots guy’s inexperience strikes again when he starts changing the wrong thing…the rear sway…because he doesn’t have the confidence to say to himself “no, 10mm of rear sway is known good, so it is not the problem. It has to be something else.”
I don’t know that there is a moral to this story. Read a book on handling. Experiment with your setup and gain confidence that you can change the behavior of your car. Keep good notes. Try to keep the state of wear of your tires equal. Don’t screw up air pressure.
Also keep in mind that the two sides do not have to be adjusted the same. As long as there is no pre-load one side can be in the center hole and one side in the last hole. Or if like Rangers’s one side 10 mm and one side 0 mm.
And, if you want to disable it you only have to disconnect one side as well.
HTH
[quote=“Ranger” post=56269]Having a bar with only a couple discreet adjustment points is a problem. Some bars are continuously adjustable. I can feel 2mm of adjustment and 4mm is very noticeable.
If I can feel 2mm, anyone can.[/quote]Can you feel 2 mm with someone else adjusting the bar and not telling you if/what change they made?
I’ll bet you the entry fee for Friday test day at CMP that you can’t tell 4 mm. :laugh:
[quote=“kgobey” post=56266]So running without the bar was fine - alot of push but easy power delivery… [/quote]I’ll take this to mean that the back end never stepped out? Sure, that will be the case with no rear bar. But if the car is pushing so much that you have to wait to get to gas…
[quote]Running with the rear bar on semi-stiff was nasty…[/quote]Lots of wheel spin and tail wagging? Yup. At the semi-stiff point, you are really just taking grip away from the rear to balance out a low-grip condition in the front.
[quote]… and running on the rear bar with it at full soft was fastest… [/quote]Isn’t that all that matters?