Suspension gurus, help (Update 5/30/04: I found the problem)

[Mystikal]

Here's my setup: GC springs/perches, 300F/475R, Koni SA(F), OE Boge(R)

Now, before we get into the issue of stock rear shocks, I never intended to use them, but the used ones I had waiting were shot when we went to mount them. Besides, the rear really isn't lowered more than an inch in the back, it was low with the stock springs. The front perches are set just about all the way down, though many on this forum with GC's and Konis are much lower. The rears are about an inch from the top of the range.

Here's the current stance:



My problem is the car is riding too damn stiff. On expansion joints and pavement irregularies, you can feel every groove. Over moderate-large potholes the front violently slams down. The rear isn't nearly as painful, and just about never bottoms out. I was messing around with the adjustments on the front shock, and found that they were set to full soft. I decided to start going firmer, which I assume would prevent the bottoming out on huge bumps, but those only made the "better" roads around here even worse. Basically I removed the chance of running out of range, but created an ungodly stiff ride for the rest of the time.

Now I ask, is my poor ride simply because the car is set too low? I can't imagine that, but it's the only possibility. If the springs are longer, the shock has more useable range, but do shocks naturally have a stiffer dampening towards the end of their travel? For example, if my shocks are sitting 50% down their available movement range, are they stiffer than if I started at 10% down, therefore the car being higher?

Any help is appreciated.

[Jon325i]

When you say slamming down harshly, are you implying that your shocks may be bottoming out? Or perhaps your tires are rubbing the wheel wells when the suspension is fully loaded up?

I think your shock set up may have something to do with it. I don't know much about Boge shocks, but I do know that Koni SAs are pretty firm....more than Bilstein Sports. Your spring rates aren't terribly aggressive so I don't think that's the issue here.

Lastly, how low have you set the coilovers? If you've got the car sitting roughly 1.5" lower than stock then you are running an aggressive drop....and that could be part of the bottoming out issue.

That's my speculative

Jon

[Bill 84 318i]

First of all, that picture is a pain in the ass to look at from a technical standpoint.

Your car is too high in the front for being close to full low. Are you sure that the spring perch is welded in the correct spot?

Adjusting the Konis will not affect bottoming out - they are single adjustables and only adjust rebound (and it's compression that would prevent bottoming out). I just installed Konis on a Miata and read (either in their documentation or online) that Konis have the same dampening throughout the entire travel of the shock. I would check to see if the car is bottoming out - did you install bumpstops? Your front isn't super low, but it could happen.

[e304lyfe]

i would say one of two things are happening....

1. your car is bottoming out
2. you have a waffleswaffleswaffleswaffleswaffles

if you fall in category two... dont feel bad, lots of people are in this category... running race springs isnt for everyone. i have absolutely no clue what experience you have with riding on stiff suspensions, or who you are, so take no offense.

from my short experience riding in a car w/ 300/475's, the ride is not overly pleasant, and is a lot stiffer then your run of the mill street spring (read: eibach pro kit, h&r sports, etc.)

if it werent for people like these... i wouldnt have the suspension i bought a few weeks back. (thx alex aka dire if ur reading this)

[e9nine]

What tires are you running and what pressure? You will be surprised how a good suspension points out poor tire setup variables out .... It might solve part of the problem. Now the bottoming out; are you SURE you're bottoming out? If you went from a not too good susp. setup to GCs and Konis you'll be surprised at the difference in ride feel, as mentioned before, its' not for all.


PS: I am not a guru, just posting based on experiences in the past...

[aaron_silva]

You must have some terrible, terrible roads because I love my ride and I have 450's in the front.

You shouldnt be bottoming out in the front. The Koni's are too stiff the compress them all the way down with the GC spring.

Drive around in a parking lot with smooth asphault. You will appriciate the suspension you have. It is always frustrating having a harsh ride when you arent in the right mind set.

Aaron

[Mystikal]

I will try to answer everything you guys posted:

Yes, the fronts are bottoming out over very large potholes. It produces the most violent jarring I have ever felt in a vehicle.

Rubbing is not an issue at all, there is LOTS of clearance.

My front is sitting MUCH lower than it was stock, as I said it's all the way down. It's not nearly as low as some guys on here though, and that's the real point.

I'm sure the welding and install in general is perfect, the guy who did it is a master BMW tech and has done many E30 coilover setups including GC's.

The car IS bottoming out, but I think it's just too stiff in general, before I hit the bumpstop. I feel I will get used to it, but it's STIFF. It's all relative I suppose. I'm not used to riding in cars with such aggressive setups.

I have run 3 different tires since the suspension was installed 2 weeks ago. First the winters, then bald Bridgestone RE930 summers, and since last week 195/60/14 Azenis. I even lowered the pressure on them to BMW's unloaded specs, a waffleswaffleswaffleswaffleswaffles 29/33. It barelyhelped (I was at 36 all around).

We DO have TERRIBLE roads, especially at this time of year, right after the snow cleared. No road repairs have been done yet, and you can randomly find a terribly patched pothole that stands 1.5" above the ground or a 2" vertical drop in the pavement while blasting down the freeway. I've seen stock Accords and Camrys blow sparks at one particular spot of the main highway.

Aaron, the car feels GREAT on new roads. When I'm on those, I understand how you southern guys live with such insane spring rates. I could go on making excuses, but you really have to see it to believe it.


Anyways thanks a lot guys, I've tired what I could. I'll just get used to the new ride, or maybe even try Bilsteins for fun, who knows.

Thanks again.

[BMW BMXER]

Trade ya setups at no cost to you?

You probably just rode on mushy stock suspension for too long. But then again my rates are not stiff at all.. A few potholes will rattle my shit but I can drive over most stuff.

Like always I have no real information to add to your post.

[Bill 84 318i]

Your car will probably feel even stiffer on Bilsteins.

[Brew]

You'll get used to the rougher ride. Sounds like your roads are even worse than the crap over here. Just take it easy driving and keep an eye out for the big potholes. Jarvis and I look like a couple of drunks when we're driving around town cause we swerve so much to avoid shit.

[aaron_silva]

Can you take pics of the completed installation? I would like to see what has been done.

Aaron

[EVOIIIM3]

Get softer front springs, and see if you can get a set of progressive rear springs, and loose the rear shocks.

Due to your rim size, I bet the car is about 3in lower then stock, you might want to move it up just a bit.

Then, get the car corner balanced, and aligned, it will be a LOT nicer after that.

[Mystikal]

I have good news. The waffleswaffleswaffleswaffleswaffles 29/33 setup seems to have paid off nicely. Over everything but LARGE bumps the car is very livable. The sidewalls of the Azenis Sport are stiff enough to provide plenty of control left in the twisties.

And yes, though it doesn't seem it, my car is pretty damn low. It reminds me of boom-monkey's car, and his Kopis are rubbing the fender liner.

I'll take some pics of the setup this weekend if I find time.

[BMW BMXER]

You got new springs?

[808BMW]

Everyone says raising the car up a bit will make the ride MUCH better, it gives the shocks more room to work.

Screw that, I am used to my suspsension, and the front has still never bottomed out. The rear has though, but only with over 600 lbs. in the backseat.