Sway bar delete setups for auto-x and canyon runs?

[Bullwings]

I know it's a common practice to disconnect rear sway bars and run only the front sway bar.

However, has anyone removed the front sway bar and run only the rear sway bar? I know our cars are front heavy, and most aftermarket spring/shock setups bias a much higher spring rate in the rear versus the front. Would this effectively achieve similar results, albeit in a mickey mouse sort of way?

I'm asking because one of my front sway bar tabs broke and the other one is bent upward - i'm pretty sure bending it back into place will likely destroy it as well. I'll get some new welded on tabs soon enough.

In an effort not to bias toward too much front traction and making the car overly tail happy, i've removed the rear sway bar as well. So, now I'm running no sway bars.

Current suspension setup is
-refreshed bushings, control arms, tie rods, etc. etc.
-Billy Sports w/ H&R race

I'd like to re-connect the rear sway, but I don't want to be surprised on the street with a super oversteery car. It'll be another month or so before I can get out to an auto-x and really push the limits. This is a project car (isn't every e30???) as well as my DD for now since someone crashed into my other car... sways are stock 325is sizes (on a 325is). I'm not trying to run a 22mm rear bar and no front bar...

So, what's the recommended setup until i can get some new tabs welded on? Run without sways completely, or reconnect the rear and run the front delete?

[george graves]

Weight distribution, F/R: 53%/47%

Hardly what I would call front heavy.

There are some really great book on the subject (some with their first printing back in the 70's (?) - not much has changed since then. As a auto-x guy, you really should pick up one, and read it cover to cover about 4 times. It will really help with things like sway-bars, tire pressure, toe, caster/camber. Totally worth the $15 bucks at amazon.

I'm sure someone will pipe up to recommend their favorite book.

[nrubenstein]

It's not panic inducing, but it won't be good. Either way. Honestly, I wouldn't worry about none vs. just the rear. The reality is that the car relies on the front.

[z31maniac]

You'd need to run outrageously high front spring rates to account for no sway bar.

[Bullwings]

Cool, thanks for the replies. Those are the responses I was looking for. I don't know what the car is "supposed" to feel like, but compared to my S2000 it isn't exactly the amazing handling machine that everyone raves about.

I'm sure the sways will help that out quite a bit (especially the front). Right now it feels like the car takes a little bit of time to "settle," so I'm pretty sure it won't transition well in the slalom sections of an auto-x course. However, once it does set, i can feel the grip. I'm on 15x7 style 10s with 205/50 RE-11A.

Anyway, I'll work on getting some tabs welded on and just run F/R sway bar delete until then. It didn't sound like such a good idea running the rear only, I just needed some verification.

[Mr. Tasty]

You must have something set up wrong if it doesn't drive like god's chariot

[iwantspeed]

I currently run a big sway bar in the front no sway bar in the rear.
My friend talked me into letting him borrow the front sway bar but only if he did the work of removing and reinstalling back on my car.
He wanted to try it out at a track day.
So I drove the car around for a week with no front bar. It was totally drive able.

[LJ851]

... and most aftermarket spring/shock setups bias a much higher spring rate in the rear versus the front. Would this effectively achieve similar results, albeit in a mickey mouse sort of way?

The reason the rear spring rates are higher is because there is a ratio between the rear wheel movement and spring movement on the rear and the front is 1 to 1 (no ratio)

The rear wheel does not see a higher spring rate than the front.

[JeffRR]

The reason the rear spring rates are higher is because there is a ratio between the rear wheel movement and spring movement on the rear and the front is 1 to 1 (no ratio)

The rear wheel does not see a higher spring rate than the front.

Hey, something I can chime in about.

Actually most production cars are sprung so that they're stiffer in the rear. Just looking at spring rate alone won't give the entire picture. Ride frequency is the main factor and is what vehicle dynamics engineers will use to quantify stiffness coming from the springs/tires/bushings etc.

In the simplest form ride frequency is a product of the spring rate at the wheel (wheel rate) and the static load on that corner. Ride frequency is directly proportional to the spring rate and inversely proportional to the load.

Spring rate goes up, then ride Fn goes up
Static load goes up, then ride fn goes down

Based on some rough calcs, an e30 is in the 1.2hz ride Fn at the front and 1.3hz ride Fn rear ballpark. Which are reasonable.

With that ride Fn split, the rear will have a higher % of the roll stiffness distribution, this is tuned out with sta-bars to bring the roll stiffness dist back to something reasonable ~ 53% front.

So without either the front or rear bar, the car will have a tendency to oversteer. Adding the rear bar with no front bar is just pushing it more towards oversteer. There are a number of other factors that come into play when talking steady state OS/US, but that is the run-down when talking about spring & bar stiffness.

I've never had the bars off my e30, so not direct experience but if I were you I might not try and hit my personal best on a canyon run without the bars. Don't want to be chasing the rear with a mountain on one side and a cliff on the other.

Day to day driving, no trouble; just watch the limit canyon runs.

[z31maniac]

Cool, thanks for the replies. Those are the responses I was looking for. I don't know what the car is "supposed" to feel like, but compared to my S2000 it isn't exactly the amazing handling machine that everyone raves about.

That's because most of the 19 year olds have never driven a modern performance car on sticky tires at an Auto-X or HPDE.

Squealing your ZIEX 912s around an off-ramp is not an indication of your awesome skill.

You must have something set up wrong if it doesn't drive like god's chariot

E30s can be fun, no doubt, but they are outclassed by nearly ever car with sporting pretentions since the early 90s. Especially if you're talking about something like an S2000.

[blasphemy101]

Hey bullwings - you might remember me from s2ki...

I know exactly what you're referring to when you talk about the E30 taking a moment to "settle." In relatively stock form, it isn't nearly as sharp as the S2000.

Some thoughts...

a) Worn suspension components/bushings - I know your OP says you have refreshed bushings. Did you take care of all of them? If so, with what kind of bushings? OEM spec E30 bushings may not be as stiff as those on the S2000.

b) Soft springs/sways - The stock sway bars are pretty small, and the stock springs are seriously soft. It looks like you've somewhat addressed the springs issue, but keep in mind the H&R Race springs are not that stiff. Check out some pictures of e30s with that setup on track or at auto-x. They still have quite a bit of body roll...

The stock rear sway bar is pretty small. I'm sure you'd be fine driving without the front, as long as you do so responsibly. I imagine at the limit the car would feel pretty sloppy and eventually lead to oversteer.

[blasphemy101]

That's because most of the 19 year olds have never driven a modern performance car on sticky tires at an Auto-X or HPDE.

Squealing your ZIEX 912s around an off-ramp is not an indication of your awesome skill.

E30s can be fun, no doubt, but they are outclassed by nearly ever car with sporting pretentions since the early 90s. Especially if you're talking about something like an S2000.

This - most people talk about E30s like they're all M3s. Even the "sport" trims ride on very soft suspensions.I know it's becoming a cliche, but a lot of people seem to forget these cars were just sporty yuppie-wagons.

I use these pictures a lot to demonstrate how soft a stock e30 really is...

[z31maniac]

Even the M3s were relatively soft sprung.

[Bullwings]

You must have something set up wrong if it doesn't drive like god's chariot

Yeah... I'm missing both of my sway bars F&R. hahaha

are you associated with garagistic? i'm thinking of taking my car there for the welding repair/re-enforcement tabs. I'm located in Anaheim, so they're pretty close. Can the complete the car in one day if I drop it off in the morning, and have it ready to pick up in the afternoon?

That's because most of the 19 year olds have never driven a modern performance car on sticky tires at an Auto-X or HPDE.

Squealing your ZIEX 912s around an off-ramp is not an indication of your awesome skill.

E30s can be fun, no doubt, but they are outclassed by nearly ever car with sporting pretentions since the early 90s. Especially if you're talking about something like an S2000.

Yeah, my S2000 is my track car. I get about 10-12 days per year running in an S2000 specific TT with four separate classes - it's regional thing just for fun, but we get around 20-30 participants at the events, so there's some decent competition.

I bought the e30 as a fun DD with more utility (from a space standpoint), and as an opportunity to learn more about cars - since I know they all need work and a lot of TLC.

Hey, something I can chime in about.

Actually most production cars are sprung so that they're stiffer in the rear. Just looking at spring rate alone won't give the entire picture. Ride frequency is the main factor and is what vehicle dynamics engineers will use to quantify stiffness coming from the springs/tires/bushings etc.

I'm guessing this is because most production cars (this one included) use some form of trailer arm suspension due to the compact design.

Cars with full a-arm double wish-bone design tend to stagger higher rates front and lower rear for a car that has a tendency to understeer. Most cars are engineered to understeer from the factory. It's a safer design for most drivers since they tend to throttle lift when they notice a loss in traction, which is the exact opposite of what you want when your rear starts stepping out.

Thanks for the explanation though - i'm pretty new to this car and this suspension geometry.

All the aftermarket suspension setups (ohlins, ast, kw, moton, jrz, tein, eibach, etc. etc.) for the s2000 tend to recommend either non-staggered f/r spring rates or stiffer front and softer rear stagger - the dampers are also valved for that sort of setting too.

Hey bullwings - you might remember me from s2ki...

I know exactly what you're referring to when you talk about the E30 taking a moment to "settle." In relatively stock form, it isn't nearly as sharp as the S2000.

Some thoughts...

a) Worn suspension components/bushings - I know your OP says you have refreshed bushings. Did you take care of all of them? If so, with what kind of bushings? OEM spec E30 bushings may not be as stiff as those on the S2000.

b) Soft springs/sways - The stock sway bars are pretty small, and the stock springs are seriously soft. It looks like you've somewhat addressed the springs issue, but keep in mind the H&R Race springs are not that stiff. Check out some pictures of e30s with that setup on track or at auto-x. They still have quite a bit of body roll...

The stock rear sway bar is pretty small. I'm sure you'd be fine driving without the front, as long as you do so responsibly. I imagine at the limit the car would feel pretty sloppy and eventually lead to oversteer.

Yup, definitely remember you on S2Ki. I did powerflex for my CABs, replaced front strut mounts (stock rubber - it's a street car), rear shock tower mounts with the upgraded ones from bimmerworld. The RTABs looked good - not cracked or dried out, so I left them in place (although I do have the parts to replace them). Subframe and diff mounts also looked good compared with the torn up front ball joints and bushings, so i'm guessing one of the last owners did something to them.

Thanks for the responses everyone. I opted to post in this forum rather than the suspension forum since I figured i'd get more mature relevant responses here. The suspension sub forum looks like it's more concerned with going low, riding on bags, going on a budget, and hellaflushing/slamming the car.

[JeffRR]

I'm guessing this is because most production cars (this one included) use some form of trailer arm suspension due to the compact design.

Cars with full a-arm double wish-bone design tend to stagger higher rates front and lower rear for a car that has a tendency to understeer. Most cars are engineered to understeer from the factory. It's a safer design for most drivers since they tend to throttle lift when they notice a loss in traction, which is the exact opposite of what you want when your rear starts stepping out.

Thanks for the explanation though - i'm pretty new to this car and this suspension geometry.

All the aftermarket suspension setups (ohlins, ast, kw, moton, jrz, tein, eibach, etc. etc.) for the s2000 tend to recommend either non-staggered f/r spring rates or stiffer front and softer rear stagger - the dampers are also valved for that sort of setting too.

Production cars are tuned with the rear stiffer than the front to help pitch balance, basically the idea is that as the front hits a input it will start to oscillate at say 1.2 hz (as an e30) once the rear hits that same bump it will start to oscillate, the rear will “catch-up” with the front within about 1 complete cycle. With the rear catching the front it is minimizing pitch and moving towards bounce. Assuming reasonable damping (not over / under damped) the full motion should be decayed at about that one cycle mark. With damper tuning you can reduce pitch as well even with the spring ratio being off, just not ideal. I’m assuming even the S2k stock has a higher rear ride Fn.

I’ve worked with aftermarket springs on my personal cars and work projects, some are tuned with spring balance in mind (h&R sprorts have a ~ 10% bump in the rear like stock) IE stage3’s are about even front to rear. The racers are worried mostly about handling balance so they’ll throw out pitch balance, I’m guessing mostly due to the selection of available sta-bars to balance out the roll-stiffness dist. Really most production based non-aero race cars would benefit from decent pitch balance assuming like I mentioned ealier that a good compromise can be made with the handling balance.

On an e30 you really need to try hard to get decent spring balance on aftermarket / coil-over springs and still run enough front RS to balance it out with available parts.

Just another note on spring rates, its worthless to compare spring rates between various cars, even the same car with large differences in weight. But what can be compared is ride frequency (Fn)