Thread: B13 with Progress rear sway, twitchy. Advice.

Hey folks.

I am creating this thread in this section because I am hoping someone with a little experience or perhaps the same problem will be able to help me out.

Setup:

1991 B13

Front:
CSK Top adjustable (yellows?), with GC Coilovers (unsure of springrate). Stock front swaybar with Polyurethane bushings with the thicker endlink washers. Cusco strut tower brace. Caster bushings (heaviest durometer avail).

Rear:
AGX's in decent shape (no squeeks, no leaks) set at 4 out of 8, with GC Coilovers (Unsure of springrate). Progress rear sway, set to medium, used supplied polyurethane bushings.

15'' Konig Countersteers, with 205/50/15 RT615's I have my ride height set to about 1'' gap front and rear. Tire pressure I believe is 35 F&R.

Now, the car has always felt pretty good to me, I have autocrossed it the past 4 years and after adding the progress rear sway it really rotated nicely, always kicking the back around if I needed to under throttle lift. However I never had to worry about too much oversteer as I pushed it as hard as I could and was always able to keep it in control.

Now aside from this I have only done street driving. I never really noticed an issue until recently when I was able to take my car for two laps on VIR.

After this I noticed my problem allot on highway off ramps. The car will handle like crazy in parking lots or autocross conditions. However the second I am in a highspeed turn (55mph+) I find the back end feels extremely sketchy.

I would describe it as too twitchy for my taste, if i lift throttle the car will feel like it is about to spin.

The reason i take issue is many folks say they set thier bars to medium or heavy, and they just have to learn to drive with it (implied that as your skill increases you can have it set heavier).

I want the car to feel more balanced around highspeed turns, however I would hate to lose my lower speed turn in. And under extreme situations the ability to induce a comfortable amount of oversteer.

Thanks for any advice.

Dudeman

GT wing lol.

Are you yanking your foot off the throttle, or slowly letting off the gas? You can also left foot brake a little so there isn't as much weight transfer when slowing down.
That is all just for driving on the street.

You could also try lowering your tire pressure in the rear when you're on the street.

I don't think you're alone with the problem Dudeman. And as funny as Dan's suggestion is, aerodynamics are the problem and possible solution here. Not sure if you're willing to go down that road though.

I too had the same problem with great low speed rotation but unnerving high speed instability in the rear. I have the XE bar up front and Progress set in the middle on the rear and had a staggered tire setup (225 front/205 rear). I was about to change the progress to a softer setting but had my rear end aligned to factory specs and got my high speed confidence back with what seemed to be little change in the low speed corners. You might give an alignment a try if it's been a long while.

i was accussed of having the driving skills of a drunken yak when I wrecked my SE-R with a recent alignment and hypercoils and CSK's on all four corners.. the kicker is an active tuning RSTB and progress rear sway bar.. with nothing similar done up front. This reduced understeer drastically.

I have never claimed to be a good driver...nor do I have any formal track training or experience.. I was in a turn at 70+ and grip was lost and I started to slide when I hit a patch of sand and I overcorrected (because of the oversteer induced from stiffening up the rear and doing nothing to the front) and lost control... I spun out and hit a stone retaining wall..

pics are here: vqman | MySpace

sad times..

So improved areodynamics can fix this issue??

Yes. Basically you need GT wing and or rear diffuser to get some nice downforce to keep your low speed rotation and high speed stability.

I had a hair of (accidental) positive camber in the rear of my VE B13 at the Chicago convention. (setup: Tiens, Progress bar, and RSTB..and an eBay STB in the front)

The car was sketchy and squirrely. I roughly adjusted it to negative camber in the back, and my car felt surefooted again on the little Autobahn.

Is that tire pressure hot or cold? If it's cold, then it's higher than I'd want. Are the tires old? Get a top notch alignment by someone you know sets up cars for track situations. Get the car corner weighted. Find out what spring rate you have. For the front - add some offset bushings for greater castor.
Two laps is just a beginning. Get a school or two under your belt. That will help a lot.
Just a couple of cents worth - hope it's helpful.

Have you cheacked the condition of the rear bushings? We have really high spring rates and custom bigger rear bars on the back of our Sentra race cars and I think that sometimes they still understeer too much.

All your modifications are fine. I have similar stuff - rear Progress on medium, even - and the car drives great at lapdays.

Eibach Racing Springs for coilovers have a code stamped on them that you can look up. If you bought them from someone on the forums, they're probably in the 3xx/2xx lb F/R range.

Get an alignment. Do not pass Go. Go straight to a good shop that does alignments beyond factory spec and find your settings. This is everything. If you have adjusted the ride height on the coilovers, you have changed the static alignment.

Guys: fixing with aero parts? On a 20-year-old Sentra? For occasional lap day? Seriously?