Powerflex - urgent advice needed!

B

Blue

Active member
I know this should really go in the Suspension Overhaul thread but I want my own moment in the spotlight for maximum attention!

I've just come back from having Powerflex fitted to my 3.0i with Sport suspension on Eibach springs. Surprisingly the ride quality is still very good, and no nasty noises so far! It's also driving much better around corners :D

Unfortunately on the other hand, the drive quality at speed on the motorway is dreadful. The wheel is now wobbling where before it wasn't, also, it keeps steering itself by tiny amounts requiring constant small corrections. :cry:

Theories so far are that the alignment is out (my wheel now needs to be turned to the right to go in a straight line, before it was dead centre), also a secondary theory that the lack of any tolerance in the control arm bush is making a wheel imbalance obvious where as before it was hidden.

I'm off out in the morning to have the front wheels balanced properly again (even though they were fine before) and have a full four wheel geometry check carried out.

Has anyone else experienced this when fitting Polybushes?

MrWhippy - what is your car like at speed in a straight line now? I know you described "noise" through the wheel, does this translate to the wheel actually changing direction slightly, or just a bit more in the way of vibration?

If the motorway behaviour can't be improved then I'm afraid I will be going back to OEM bushes very quickly on the control arms, the rest can stay though! :D
 
In a straight line on a smooth surface it does just make movements now and again that don't seem to be related to much. They are very subtle though, and I put that down to a steering wheel that isn't straight ahead while the car *is* actually travelling straight ahead (off centre a little bit, was less before the bushes, now it's more)

I think the leccy steering uses the centre position to calculate assistance levels and lots of other things, so I wouldn't be surprised if the wheel is off centre lots, that the car thinks your steering and so is generating assistance variances not in line with what is really going on or needed quite so accurately.


I'm off to BMW to have mine done, just so I know it's done properly by the book and dead-centred with the steering centre reset right etc.

Really I should plug my laptop into the car again via INPA and see what the sensor is reading.



Your problem is likely just balance of a wheel now coming through more clearly, and the alignment/wheel centring...


I'm surprised you've gone with lower springs. Doesn't anyone find their car already bottoms out and scrapes far too much already? Also, the Z4 (not sure on the M) wheel kinematics seem to react badly to lowering :(
Ie, rear camber accelerates harder at back under bump than front, so your getting a really nasty limit understeer problem working it's way in.

Next thing I'd like to do, if I get round to it, is to fit those adjustable dampers that are yellow and about £450... can't remember what they are now :D

Tempted to just save my pennies now and get an M when funds allow :)

Hmmm

Dave
 
Sounds like it could be the problem then, it almost does feel artificial!

Also, did you get 66mm control arm bushes or 60mm?

I got 66mm as per RealOEM.com and the guys at the garage mentioned that the OEM bush had a small gap around the edge and this one has none...

I'm afraid I actually don't understand what you mean by the rear camber accelerating harder under bump?

I've noticed my car does have a very aggressive camber but it's within the factory limits. I didn't personally choose the Eibachs, the car came with them, the advantage in my mind to them seems to be that they don't snap! ;)
 
Woo hoo!! She's working again! :rofl:

The alignment was all over the place, but has been brought into line now and the car isn't hunting all over the road anymore, also, both tyres needed balancing, the wobble has more or less gone too :)

I'm now one very happy bunny, the car has much better body control, roll is greatly reduced, she just feels "right". :D
 
Where did you go for the alignment, BMW?

Did they give you a printout before/after?

Was it a Hunter machine they used? Did they get the wheel dead centre and reset it?


Thanks

Dave
 
Teesdale Tyre and Auto Centre in Thornaby near Middlesbrough. They're the cheapest I've ever found, £36 for a full alignment. :wink:

The machine appeared identical to the one used at Revolution in Gateshead who charge £99 for the same job, although I'm not sure if it's Hunter branded or not, it certainly looks the business, controlled by cameras, with a screen in the waiting area so you can see them working on it and watch the settings come into line.

http://www.teesdaletyreandautocentre.co.uk/teesdale/alignment.php?id=1

I got a before and after print, which now that you mention it when I looked afterwards showed a rear camber a fraction of a degree into the red (was green at first but moved just as they took the guides off) I'll be giving them a call on Monday to ask about having that setting tweaked slightly.

All I know is the car drove like a dog at speed before they touched it but drives brilliantly now :driving:
 
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