interesting handling characteristic?!

Post Wed Nov 22, 2006 1:08 am

Hello there,
i'd like to pick everyones brains for a minute, i've got a 318is that i'm going to night event/rally and i've got an interesting handling characteristic. i'm finding that the rear of the car seems to wallow around an awful lot under braking/accelerating/cornering. it feels like the rear of the car almost needs to be braced more or something? any ideas what this could be or how to cure?

the mods i have done are...

brand new poly bushes (last week) all except anti roll bars.
front end has 34mm front shocks (unsure of make) and 325 springs.
the rear has oe spec bilsteins and stiffened standard height springs.
rear has aluminium/rose jointed top mounts and a strut brace.
i'm running 14inch wheels all round with yoko 021's at front and a539's at the rear.
the car currently doesn't have a diff (but will have a rebuilt 40% lock up jobbie on the weekend)

any suggestions guys

kevo

Post Wed Nov 22, 2006 3:48 am

Kevo, mine exhibited similar behaviour to yours. Seems like the rear wallows upon hitting dips and bumps, along with other interesting noises. Had no choice but to do front and rear suspension rebuild. I suspect it's the subframe bushes, along with other rear ARB/swaybar bushes that are going off.

I'll enclose more pics with details on what has been done on my car.

Post Wed Nov 22, 2006 3:57 am

These are the things I bought to start the rebuild...Cost me about 154 quid in total.

Post Wed Nov 22, 2006 4:01 am

Short ball joint for the control arm. S/N 31-121-126-254. 2 pcs for front end.

Long ball joint. S/N 31-121-126-253, 2pcs for front end.

Post Wed Nov 22, 2006 4:05 am

Wanted to get the M3 offset control arm bushes, but the local stockist didn't have any and I didn't want to delay. So got the normal ones...

Control arm bush. S/N 31-129-069-035.

Not sure what's the difference between this and the part S/N 31-129-058-815. Anyone with ETK to check for me?

Post Wed Nov 22, 2006 4:09 am

Rear absorber top mounts were due for replacement too, so chose the later version.

S/N 33-521-092-362

Post Wed Nov 22, 2006 4:15 am

Front antiroll bar or swaybar bushes also needed some TLC. S/N 31-351-127-414.

Quite puzzled when first got it - how to fit onto the ARB? 2 minutes later, after prodding the piece - it actually has a split on one side to wrap around the ARB...duhh...

Post Wed Nov 22, 2006 4:17 am

Here's the front ARB linkrod to connect to the control arm. S/N 31-351-091-764.

Post Wed Nov 22, 2006 4:25 am

My biggest headache was the rear rebuild. Since almost all bushes are to be replaced, I knew it'll be a subframe-out job. With not enough tools, smarts nor strength - the car was sent to my mechanic for the hard stuff...

Subframe bushes S/N 33-311-129-144

Trailing arm bushes (4pcs, 2 per side) S/N 33-329-061-945

Post Wed Nov 22, 2006 4:30 am

Received many comments about my 4x4 ride height, so I exposed my credit card to further turmoil by getting these...

35mm drop front and rear. Car looks much better even with 17"x7.5", and the ride is much much better. Dips and bumps move me up and down, instead of up-left-down-right-forward-right....

So kevo, hope you got to the bottom of your wallowing rear end! Good luck!

piperzero

Post Thu Nov 23, 2006 12:52 am

hiya piperzero,
i've done everything you did to yours except that i used poly bushes, non concentric front arms and solid top mounts instead which if anything should make it better again but i'm still getting the dreaded wallow. the only thing different with mine is that i've jacked it up on purpose but have stiffer springs than standard so i suppose it must just be shocks need to be beefier again and springs a little stiffer again? i don't know there's nothing else under there?
kevo

Post Thu Nov 23, 2006 3:50 am

Kevo,
What about antirollbars/swaybars? Perhaps your spring rates do not match the damper/absorber rates? Scratching my head about what else could contribute to the wallowing...

Post Thu Nov 23, 2006 12:55 pm

me too, my anti roll bars are standard but i've been thinking of upgrading the back one to a front one (if tht makes sense), to see the difference? the springs/dampers were sourced individually on the cheap so perhaps they are not suitably matched up properly then?
i dunno
Kev

Post Fri Nov 24, 2006 8:39 pm

woo hoo! found it found it!!!!

when i was fitting my newly rebuilt LSD which is a pleasure by the way ha ha. i found that the old diff was held in with bolts (the top pair) without washers meaning that they were done up tight but they weren't clamping the diff up. job done.
Kevo