Z3M Roadster - extra rear downforce please

[marvelharvey]

I've only had my Z3M for a couple of months now and I'm finding that at high speed the rear end feels incredibly light.

Does anyone know of any manufactures who make rear wings for the Z3M which ARE NOT cosmetic?

Of course the simple solution is to drive at the speed limit.

[domster]

You may find lowering the car further than standard settings may stop air from getting beneath it. I'd also do a full alignment check.

I have only driven a Z3M roadster at about 120-125mph but it felt OK at those speeds

You can get aftermarket spoilers that bolt on to the boot, but they may look very strange. Try Hamaan , Schnitzer or Hartge. A phone call to Birds in Uxbridge may help (Hartge agents).

[marvelharvey]

I'm sure it handles perfectly fine, it's just that my last car had a ton of downforce and I liked that feeling of stability. Anyway, I'll give thse guys a call, cheers

[bluesatin]

I took mine to Bruntingthorpe and the car felt fine at 140mph. As dom said check if everything is pointing forward!

[m-five]

domster said:

You may find lowering the car further than standard settings may stop air from getting beneath it. I'd also do a full alignment check. I have only driven a Z3M roadster at about 120-125mph but it felt OK at those speeds You can get aftermarket spoilers that bolt on to the boot, but they may look very strange. Try Hamaan , Schnitzer or Hartge. A phone call to Birds in Uxbridge may help (Hartge agents).

But don't forget you need some airflow underneath otherwise any underside aerodynamic features will not work properly - not that I'm saying it has any - but if you lower a car too much you increase it's drag as more air has to travel further to move around the car!

[marvelharvey]

domster said:

You can get aftermarket spoilers that bolt on to the boot, but they may look very strange. Try Hamaan , Schnitzer or Hartge. A phone call to Birds in Uxbridge may help (Hartge agents).

I've phoned 'Birds' and they said don't bother with a spoiler as they're all cosmetic unless you go for a 'proper' racing type in pylons. He advised me, just like you guys, to just lower the car and stiffen up the springs.

[GreenV8S]

At high speed, small changes to geometry and tyre pressures can make a big difference to how stable the car feels. Also, at very high speed lowering the front of the car and raising the back can cut the lift significantly (although it doesn't usually look very good).

[Webdunk]

One of the members of BMWCC Hong Kong runs a fairly serious looking Z3M. It appears to have a removable 'pylon' type spoiler that he mounts for trackdays and the like. Browse www.bmwclub.org.hk and see if you can snag any details.

[domster]

m-five said:

domster said: You may find lowering the car further than standard settings may stop air from getting beneath it. I'd also do a full alignment check. I have only driven a Z3M roadster at about 120-125mph but it felt OK at those speeds You can get aftermarket spoilers that bolt on to the boot, but they may look very strange. Try Hamaan , Schnitzer or Hartge. A phone call to Birds in Uxbridge may help (Hartge agents). But don't forget you need some airflow underneath otherwise any underside aerodynamic features will not work properly - not that I'm saying it has any - but if you lower a car too much you increase it's drag as more air has to travel further to move around the car!

Not sure the roadster has anything going on underneath it like a Ferrari 360 etc.

And the point is that downforce is designed to cause drag... the opposite of drag is lift and that is what is trying to be avoided here. The top speed may be lowered if drag increases, but downforce should be increased in the process.

[Damo M]

I owned one for a couple of years and had the same problem.

It is not a downforce issue it is a matter of chassis flex which is an inferant problem of the roadster. I improved the matter by fitting a strut brace and uprating the dampers and springs to better quality items with improved (read harder) top bush mounts which have a habit of failing because of the flex.

[marvelharvey]

Damo M said:

I owned one for a couple of years and had the same problem. It is not a downforce issue it is a matter of chassis flex which is an inferant problem of the roadster. I improved the matter by fitting a strut brace and uprating the dampers and springs to better quality items with improved (read harder) top bush mounts which have a habit of failing because of the flex.

I'm sold on that idea, cheers.