New front suspension + old rear suspension -- OK?

[yoda634]

Recently, I redid my entire front suspension. New control arms, E30 M3 CABs, bavauto springs, spring pads, bilstein sports, new tie rod ends, new sway bar links and bushings.

The rear is still the way I got it from the previous owner. The car's driven just fine ever since I got it, but when I pulled the front shocks (OEM replacement), they were absolutely shot -- could compress them with no effort, took them ~30 minutes to fully re-extend when left sitting upright. The shocks were last replaced as a full set, so I'm guessing the rears are pretty well shot too.

So, as it is now, everything up front is brand new and tight, and everything in the back is old and theoretically sloppy, but like I said, never felt particularly bad.

The car hasn't been running since the front suspension was replaced, and I'm wondering what the effects will be of driving it on the worn shocks and old springs in the rear, and the lower/stiffer springs and new shocks up front - is it unsafe to drive it like this? How's the handling going to be affected -- I'd think the stiffer front would make it understeer more? Of course I'll get the front aligned before driving it, but does the back need immediate attention? If I really needed to, I could probably put the springs and new shocks on it, but I'd rather hold off until I've got the money to replace everything back there at once.

[Elephant]

When I redid the suspension on my 740 last spring I did the opposite. I was short on time so I did the rear first (which, ironically, took longer than the front). Refreshed it completely including Bilstein HD's and H&R Sports, all new arms/bushings. I drove it for a week, maybe 2, before I had time to do the front. And believe me, my suspension was absolutely shot, I could compress/rebound the dampers by hand with ease...beyond dead. It certainly was not a joy to drive it that way but unsafe? Well, to me if that is unsafe then that person probably shouldn't be driving a car period, new suspension or otherwise. ; ) Seriously, drive sensibly and do the rear as soon as you can....maybe a couple weeks or something, I wouldn't make it a habit. It's not unsafe, just not ideal.

[yoda634]

I'm not sure how long it'll be. I know there'll be a 600 mile trip right off the bat, but other than that, it'll probably be ~ a month or so. Maybe I need to find a way to get it done now.

Any other opinions on it?

[JGood]

Just don't push it in any corners, the balance is really the only thing that will be affected, and it's not going to be THAT bad, to the point where it's dangerous.

[Elephant]

Well, you can do that trip but it may get annoying depending on the roads. Unmatched front/rear suspension can cause porpoising....the front and rear will not "bounce" at the same rate and it may feel undulating. In bad cases you may actually get a bit nauseated as it is very possible and not out of the ordinary for vehicle bounce modes to couple with internal organ modes.

I wouldn't likely call it dangerous, more annoying than anything.

[yoda634]

Well, you can do that trip but it may get annoying depending on the roads. Unmatched front/rear suspension can cause porpoising....the front and rear will not "bounce" at the same rate and it may feel undulating. In bad cases you may actually get a bit nauseated as it is very possible and not out of the ordinary for vehicle bounce modes to couple with internal organ modes.

I wouldn't likely call it dangerous, more annoying than anything.

If that's all, then I'm fine with it. I just wanted to make sure I wasn't going to be over-stressing any components to the point where they'd fail a hundred miles down the road, or make the car a bitch to control.