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      05-12-2020, 09:34 PM   #9
x233
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Ukraine
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Drives: M2C, M235xi
Join Date: Jun 2015
Location: Ukraine

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Update: I have been able to find a workable setup with these coilovers. Not necessarily a perfect one or the only one possible but the one that suits my handling requirements and looks.

My final drop is 30-31 mm in the front and about 27 mm in the rear, rebound set to +5 harder than the factory default in the front and +3 harder in the rear. This seems to work best of all of the combinations I’ve tried in the past month.

Not sure about the alignment, and will have to re-align this week, but last time before I made a zillion height adjustments the front had stock camber and 0.03 symmetrical toe-in, the rear had -1.35 camber and 0.09 symmetrical toe-in. (pretty sure it’s off now, but I’m only going to do minor adjustments and straighten the steering wheel).

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If I had to do it all again, I’d do the following:

I’d re-index all the bolts and nuts just like BMW suggests, to be on the safe side. I’d also use new front and rear top mounts, gaskets and rear spring seats.

As for the height adjustment:

I’d start with the rear, set the rear 10 turns of the spring perch from 0 which would be about 10 mm on the perch (that’s the minimum recommended by Sachs and which I exceed on my setup) and about 20 mm drop in the rear.

Only then would I start working on the front. As it comes from the factory the front is lower than it needs to be and I’d work it gradually until I got about a flat ride, maybe about 2 mm more drop in the front.

Let the car sit overnight, do an initial alignment to get the factory values.

Then drive it back and forth a couple of days just because, probably set the rebound a couple of clicks harder right away since the settings it comes with from the factory are too sloppy for my taste.

Then I would switch off the aids and start taking turns, start pushing it to see how the car handles, and would incrementally either lower or raise the front (without messing with the rear)
until it resolved the understeer/oversteer.

If the drop in the front was getting 4 mm more than the rear would I start stiffening the rebound of the fronts vs the rears to remove understeer.

If at that point I’d get either oversteer or understeer I’d come back to lowering/raising the front by 1/6 of a turn of the spring perch to make it just right balance-wise.

Do the final wheel alignment.

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In my experience getting the front drop more had a negative impact on traction, not just in turns but in straight line also. It’s not noticeable at 2 mm difference but at 5 mm it already is.

Having a flat ride and equal rebound settings, say +3 front and rear, gets you excellent traction, even with all the nannies off you can literally floor it and it would just grip and go. The problem, though, is that with the flat ride and equal rebound settings you get a lot of understeer, especially in fast tight turns. Hence, I had to both drop the front a bit and stiffen the front vs the rear. Only stiffening the rebound of the front shocks, even +3 vs the rears, didn’t completely eliminate understeer at corner entry in fast turns, especially obvious on wet pavement.

Having the front drop more than a few of mm I noticed the braking performance wasn’t as great as on the stock car as too much weight was moving toward the front off the rear. At about 4 mm difference on my setup I find it acceptable, though. Same thing with too soft shock settings.

I think my setup is probably a bit lower that it should be, some 5-7 mm lower, and there could be rubbing issues with winter tires (PA4) in the front which are bit wider and taller but I’ll worry about it if that happens. I don’t think the front bottoms out but I am afraid the rear is close to the bump stops and I don’t know how it’ll behave if I load it with adult passengers and some bags. With just me and 2 kids it’s fine, though.

I was honestly getting frustrated trying to get the handling I liked, with how long it took me. So, even though I realize it probably should be a bit higher than my setup I am just not ready to do it all over again. For now, I would just like to enjoy what I’ve got.

As it is, it’s tight, noticeably tighter than stock, but also nimbler, sharp as a scalpel, there’s hardly any understeer at all while the rear is reasonably planted, more so than the stock, I can push it hard without losing my rear, the ride is stiffer than the stock but not crashy. My kids sitting in the back do complain, though, that it’s more bouncy on back roads but that could also be because I am now pushing it a lot harder.
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