Z4C front end very light at high speed

[catherinej]

Can someone tell me if there is a cure for the for the front end of a Z4c getting very light at high speed and the stability suffering.

Would the strut brace resolve the issue?

[bmwdrivernigel]

Slow down a bit?

[sixspeed]

Ermm... might be alignment?

Certainly my Z4MC doesn't get "light" until well into illegal figures, and even then I wouldn't call say it was particularly unstable. However the M does have a different front bumper with aero diffusers on the corners, which I'm not sure if the standard Coupe does?

[M5Dave]

Sounds like front splitters or a spoiler maybe the answer, to add some downforce to the front end. There's bound to be an official M Sport one from BMW, or ones from Schnitser or Alpina available through the dealer.

[StuB]

Check the tyre pressures for a start.

[playerone]

It will be the tyres. All the modern BM's (non M) with the exception of the 5 Series dont seem to feel confident at high speed. They seem to skip over small bumps and the steering never has a chance to settle.

The 1 Series is terrifying on a bad road at high speed....well so Ive heard, I have never broken the speed limit myself....

[olf]

This car of yours sounds like no end of hassle. Let me look after it for a while.

[trackdemon]

Have you driven any Z COupe other than your own? I've not witnessed either of the probs you mention on ours.... btw what exactly does 'high speed' mean?

[wrighty78]

Mine only seems light at "high speed" on poorer road surfaces - on smooth roads it has never been a problem - which leads me to think Playerone is right and it's all down to those bloody RFTs.

[youngwill100]

I'd agree I think. My Z4C is fine at 120mph (on a circuit!), front end seems firmly planted. Rough roads do make the RFTs dance around. At 70mph on rough roads the ride is horrible, but I wouldn't describe the front end as light. I'm going to change my tyres for either Gooodyear F1's or possibly Michelin Pilot Sports 2's to fix the ride problem.

[edx]

I have to admit I found this a bit of a problem with mine in the first few weeks (up to perhaps 1000 miles), particularly in high crosswinds and on uneven surfaces. I thought initially it was a bit of aerodynamic lift on the front, it seemed to occur at a very specific speed range - between 75 and 85. Above and below this it went away, feeling very planted well into three figures. It didn't feel unsafe, just a tad light that you had to concentrate a little more on keeping it in check.

I wondered about taking it back to the dealer and having them take a look but decided against it as they would probably have thought I was imagining it or something (my experience of many franchised dealers is not too favourable to be honest), so I decided to live with it and see if it developed or went away, as I also thought other factors such as the new tyres, springs and dampers may also be contributing.

After subjecting the car to some spirited driving on some good testing roads once it was run in to get the tyres nicely scrubbed and give the suspension a thorough bedding in, I can happily report that the problem has seemingly disappeared of its own accord, which I suspected it might. The car now feels well planted at all speeds even at 140 plus (on a circuit of course).

I agree with the general consensus that the RFT's are comprimised when it comes to ride quality and will be changing them for something better when the time comes, but I'll get my moneys worth out of them first.

Sorry you seem to be having a myriad of woes with your new car, hopefully in time things will be better and you can really enjoy it.

Edited by edx on Monday 26th March 11:46

[catherinej]

Well when I get it back I shall have to have a good run in it and see if it does the same again.

At the moment the aircon is foxing them. So far in 2.5 weeks it has been off the road for 5.5 days and at the moment it doesn't look to be returning any time soon.