Pros & Cons to suspension modification on the 1 series chassis

[Faulal]

I’m struggling to figure out why the 135i with 1M suspension bits have caused such a negative side effect of harsh ride quality in particular from sharp bad road impacts and an over all bouncy ride?

I’ve had this issue for a long while and my best guess is it’s the 1M front control arms with their stiffer bushings?

Over the years I’ve installed:
1M front & rear control arms.
1M front & rear sway bars.
Dinan camber plates, with approximately one degree negative camber for the street.
18 inch apex wheels with Michelin super sport tires.
1M rear sub frame bushings.
Koni single adjustable front struts, factory springs and factory ride height. On full soft setting.
TC Kline single adjustable rear struts, factory springs and factory ride height. On full soft setting.

The last item I installed was the struts this winter and there was a slight reduction in harsh impacts on the full soft setting. Also the over all handling composure improved slightly, with these new struts.

The positives from these suspension mods, is the steering feel/reaction improved and body roll reduced. The car’s cornering speed went up tremendously at the track.
However when the road quality worsens, the chassis composure is borderline bad and I lose confidence at speed. The car definitely feels like it has a way to high spring rate, which is weird since the factory spring rate is soft compared to most coil over set ups.

I have driven E46 M3s and E92 M3s and the ride quality and chassis composure is much better then my car.

Does any one else have a similar setup and what are your experiences?

[titium]

Set tyre pressures to 34psi.

Set the konis to 1 to 1.25 turns from full soft up front and 0.75 turns in the rear. They don't work well on full soft I've found.

I'd then switch back to the stock rear sway if you're still not happy, see how you go, maybe even switch the front sway back (significant loss off front end grip at the limit if you do this).

also I'd be very suprised if you're at 1deg neg camber with dinan plates and m3 arms you're probably closer to -2.

[Ric in RVA]

No independently adjustable rebound and compression? Sounds like more rebound would be good. Maybe as a single adjustable full gives you little to no rebound...when you need more. Adequate controlled rebound is good thing in my book.

[MightyMouseTech]

Originally Posted by titium

also I'd be very suprised if you're at 1deg neg camber with dinan plates and m3 arms you're probably closer to -2.

I have the same, and I am over -2.

To the OP, what tire size are you running? I doubt the M3 you have driven runs 35 series tires.

Also, what tire pressures do you run? I am running 245/265 MPSS on APEX wheels as well and found 35/35 is a good balance for pressures.

[juld0zer]

This will upset a lot of people but i feel the same, although my modlist isn't as long as yours.

It's the M front lower arms. The inner bush that was on the stock arm where it connects to the subframe is now a spherical ball joint. Every impact will be sent through the chassis, undampened. I left the M caster arm in, and refitted the stock lower arms.

I have:
BMW Performance springs
Bilstein B8 all around
Kmac camber/caster front strut mounts (street spec/entry model)
TRW M upper/caster arm (front)
Michelin PSS 245 all round on 4x 261M wheels
10mm spacers up front to accomodate wheels

[Faulal]

Thank you for the tips.

I have the tire pressures at 37psi. I was trying to keep the pressures a little higher, to try and prevent bent wheels from my bad roads. But I'll drop them to 34 and test.

Only single adjustable Konis.

I will adjust the koni's to 1.25 turns from full soft on fronts and 0.75 turns rear and try that.

I want to avoid changing the rear sway bar back if possible, that was a huge pain dropping the rear subframe, the first time.

For street driving I have the front strut pushed out as far as the adjustment allows. To minimize negative camber on the street. Then for the track I loosen the three bolts on the strut tower and shove the strut in.

My street tire setup is 235 wide MPSS on front (40 tall) and 265 rear (35 tall).

[MightyMouseTech]

Originally Posted by Faulal

For street driving I have the front strut pushed out as far as the adjustment allows. To minimize negative camber on the street. Then for the track I loosen the three bolts on the strut tower and shove the strut in.

That is not recommended. When you change the camber, you drastically change the toe. Every time camber is changed, it needs an alignment.

[Faulal]

Originally Posted by MightyMouseTech

That is not recommended. When you change the camber, you drastically change the toe. Every time camber is changed, it needs an alignment.

I was wondering about that. I figured I could get away with it, since about every BMW driver I meet at the track also jacks up their car before going out on the track and loosens the strut top bolts and shifts the strut inward for more negative camber, then they shift it back out before they drive home from the track. I noticed it was a common practice with the CCA club instructors.
I originally had my alignment done for my street setup with the least amount of negative camber.

[MightyMouseTech]

Originally Posted by Faulal

I was wondering about that. I figured I could get away with it, since about every BMW driver I meet at the track also jacks up their car before going out on the track and loosens the strut top bolts and shifts the strut inward for more negative camber, then they shift it back out before they drive home from the track. I noticed it was a common practice with the CCA club instructors.
I originally had my alignment done for my street setup with the least amount of negative camber.

Just because it is common does not mean it is right.

[JEngland]

if everything has been changed and the car still doesn't feel right, change the front wheel bearings. I've replaced everything on my car and was still chasing an unsettled feelings and changed both front wheel bearing this weekend and the car is night and day.

[brytom]

Originally Posted by MightyMouseTech

That is not recommended. When you change the camber, you drastically change the toe. Every time camber is changed, it needs an alignment.

+1 to this. This is why when an alignment is done, the camber is adjusted first. When adjusting toe, the camber changes minimally if at all.

[titium]

Originally Posted by brytompkins

+1 to this. This is why when an alignment is done, the camber is adjusted first. When adjusting toe, the camber changes minimally if at all.

Interesting info here:

http://www.1addicts.com/forums/showp...2&postcount=23

"This means that a slightly conservative street alignment with a bit of toe in will become a slightly aggressive track alignment with a bit of toe out with a camber change of -1° at the track."

If you know what you're doing it is possible. Problem is most people don't understand what they are doing and just max the camber each way.

[ianc]

Interesting that no one's commented on the factory springs. You want bouncy, that's just what you'll get with those marshmallow boats; they are completely mismatched to the rest of your suspension. You've upgraded everything else but.

Those spaghetti noodle springs are made to work with the hard-as-rock factory runflats; there's no way they can keep up with the rest of your upgrades...

ianc

[nanotech]

Originally Posted by ianc

Interesting that no one's commented on the factory springs. You want bouncy, that's just what you'll get with those marshmallow boats; they are completely mismatched to the rest of your suspension. You've upgraded everything else but.

Those spaghetti noodle springs are made to work with the hard-as-rock factory runflats; there's no way they can keep up with the rest of your upgrades...

This. My setup is similar except for the Eibach/Bilstein B12 pro-kit, and although harsh it is definitely not scary at speed. Just harsh. The stock springs are mushy.

Based on comments on the strut tower adjustments, I bet your toe is quite out of spec, you might be toed way out which will make for a scary handling experience on the street and a very wandery machine.