Suspension tuning

I'm noticing a bit of understeer on my recently purchased 328is (97). In the old days, if I remember right, we'd stiffen up the rear sway bar to get the back to come out sooner, i.e. oversteer. Does this hold true for the E36's?

Just got off the phone with H&R springs and they told me the opposite...stiffen up the front to reduce understeer?!?

So, I've tried the following to mitigate or preferrably eliminate the understeer:
- Camber shims - around -2 camber up front: made the most notable difference but front is still plowing at limits of traction.
- Alignment - 1/8th rear toe; 1mm front toe; -1 rear camber: made a mild improvment.
- Added rear HR sway bar: Difficult to say whether or not it improved it. Just feels different.
- Adjusted rear HR bar to stiffer setting: Seems to have slightly reduced the understeer.
- Added front HR sway bar: Reduces roll, car stays flatter thru turns, but understeers earlier and worse now.
- Tried 'backwards' tire pressure, i.e. lower front/higher rear: Made steering heavy and front plowed harder, longer, and sooner.
- Went back to conventional tire pressure logic, 42psi front/36psi rear: delayed understeer somewhat.

Next I think I'll try the following:
- Replace missing crossover brace which prior owner forgot to put back on after doing clutch job appearantly.
- Newer struts. Bilstein can't seem to find a cross-reference part number for the struts that on there to verify they are indeed the correct ones for the application. (current model #'s: Right=F4-V36-4008 HO / Left=F4-V36-4007 HO) Bilstein has no idea what these models are or are for?!?
- New front tires. My front and rear tire brands are different with different tread patterns, albiet the same speed rating (ZR).

Yikes those are some high pressures.


try like 34psi all around.

The speed rating on a tire is not indicative of handling characteristics, but treadwear rating is. Longer tread wear tires have a harder, less sticky compound and tend to break loose at lower forces. What is the tread wear rating on your front and rear tires? You want the lower tread wear, sticker tires up front.

Heres the info I found on them....

Rear tires: SN3800
Brand: SUNNY
Part #: 24875008
Size: 215/40-17
Speed Rating: W
Type: High Performance
Load Index: 87
Load Range:
Sidewall: BSW
UTQG: 280AA


Front tires: YS618
Brand: SUNEW
Part #: 2154017SUNEW
Size: 215/40-17
Speed Rating: W
Type: -
Load Index: 87
Load Range:
Sidewall: BSW
UTQG:

UTQG is the tread wear rating. Those are some pretty cheap tires! I'd try switching front with the rears for now and then look at getting some known quality tires in the long run.

The only reason I haven't tried changing them front-to-rear is because the previous owner ran way too much negative camber in the rear and chewed up the insides of the rear tires - which I later rotated so the bald/thread showing strip of tire is now on the outside.
I fear attempting to run these up front might result in a blow in a turn resulting in terminal understeer. Oddly, that has happened to me some 20 years ago while canyon racing. Landed me in intensive care. LOL!

understeer = my-arch-enemy!

Glad your "terminal understeer" wasn't "terminal"! Seriously though, a blown tire in hard turn puts you off the road either way. Just depends which end of the car goes first. Your Sunew tires are made by a Chinese startup company.
The SUNNY tires have a little bit better geneology.
I think I'd be looking for something with a little better known rep.

http://www.sunewtyre.com/About/

http://www.sunnytire.com/background.aspx

I grew up doing alot of drifting, be it cars, bikes, skateboards, big wheels, etc....
So, the back end going is far more comforting for me than the front. I would rather have oversteer than understeer any day.

The tires were on the car when I got it. I've been thinking about the Falken 428's I think they were called. They seem reasonably priced and with good reviews.

I'm running Falken 912's and I'm pretty happy with them. Good performance all around including wet weather. They do make some higher performance oriented tires like the 452 or the 615K.

Changes made the last couple days:
- Replaced missing crossover brace: Didn't appear to make any difference in understeer issue.
- Replaced front Bilstein HD's with Bilstein sports: May actually understeer even worse now. LOL!!!

Seem to be going backwards somehow?!?

I say at this point take it to a race shop and see what they can do. I have the same car with the same suspension and my car is very neutral with throttle-on oversteer easily available.

I have a couple more mods before I consider conceding! LOL!
I have yet to try new tires up front and complete bushing overhaul.

What are all the chassis/suspension mods you've done to yours?

- Bilstein Sport struts/shocks
- H&R Sport springs
- BimmerWorld solid-mount FCABs (M3 offset)
- '95 M3 upper strut mounts
- Rogue Engineering Black RTABs
- Rogue Engineering Black RSMs

I'd say it's more than likely your tires. Simple fix.

Or: Next time you're understeering, let off the throttle. Instant oversteer!

I've tried off power, on power, steady power, trail braking, downshifting, chop steering.....it still steadily understeers! LOL!
The only time it doesn't understeer is if I dump the clutch as I'm rolling into the turn. Then I can drift the turn very nicely.

Going to put on new rear Bilstein sport shocks in the rear to compliment the new front sports and then get the tires. That way everything will be a matched set, i.e. HR sport springs and sway bars, Bilstein sport struts and shocks.

I think FenderBender is right regarding the tires. Its the only thing I have really messed with. And being that the fronts are different brand than the rears, it definatly makes sense that they could be the culprit.

Do you have a bunch of crap in your trunk weighing it all down?

I have Bilstein sport/ H&R Sport springs on all 4 and LOVE it. I don't think I have understeer, but I don't know for sure.

What tires do you have on it NOW (size, i.e. diameter, width, apect ratio) (not what you want to get but what's on it) and what air pressure are you running in them?

Originally Posted by Tidan

Heres the info I found on them....

Rear tires: SN3800
Brand: SUNNY
Part #: 24875008
Size: 215/40-17
Speed Rating: W
Type: High Performance
Load Index: 87
Load Range:
Sidewall: BSW
UTQG: 280AA


Front tires: YS618
Brand: SUNEW
Part #: 2154017SUNEW
Size: 215/40-17
Speed Rating: W
Type: -
Load Index: 87
Load Range:
Sidewall: BSW
UTQG:

From a previous post in this thread.
I've tried a few different tire pressures including higher in the front lower in the rear and lower in the front and higher in the rear. An earlier post in this thread details what I've tried and the result.

Sorry, I read that and thought those were the tires you were considering, not what you have.

I agree with the others opinions....those are some pretty poor tires for a performance vehicle. Get some decent tires on there and the understeer will be minimized.