Have noticed that at around 100mph+ ( private road, naturally ) the front end/steering starts to get fairly light.
Standard suspension, 19" wheels, front brace, tyres - 235/35/zr P7000s, perfect nick and at a recommended pressure of 33 psi
Given my lack of development experience, what's the concensus on this: shockers ? ( not 'bouncy' ) slightly bigger anti-roll bar needed ? anything else I should look at ?
Thanks in anticipation
Z3M: wandering, if you get my drift....
This has been reported as a trait of the Z3 when driving on the autobahns - steering goes very light and car can become rather twitchy.
I would have thought that the lightness is entirely down to the front end lifting with the air going underneath the car, so it is aerodynamics rather than stiffness suspension or roll bars that would have the most effect - they tend to affect handling in corners rather than straight lines.
Cheers R.
I would have thought that the lightness is entirely down to the front end lifting with the air going underneath the car, so it is aerodynamics rather than stiffness suspension or roll bars that would have the most effect - they tend to affect handling in corners rather than straight lines.
Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
Z3M at Speed
I am afraid I cannot provide an answer, except that it is definitely not an inherent problem. The M is normally stable at up to maximum speed - although there is some front end lift above 130mph, it doesn't at any time become a 'white knuckle' ride.
The front end lift, which produces lighter steering, is an aerodynamic issue, and it's difficult to see why your mods have made matters worse.
The obvious checks with any steering issue is play in the joints. I have replaced the front wishbone and ARB bushes recently, and found a significant improvement in steering accuracy generally. Not expensive - probably worth a try.
The front end lift, which produces lighter steering, is an aerodynamic issue, and it's difficult to see why your mods have made matters worse.
The obvious checks with any steering issue is play in the joints. I have replaced the front wishbone and ARB bushes recently, and found a significant improvement in steering accuracy generally. Not expensive - probably worth a try.
I agree with Robert, its almost certainly aerodynamics. Some cars suffer worse than others and also peoples perception of the change can be different.
I think the Z3m is pretty good at high speed compared to a lot I've driven but almost all road cars suffer from this to some extent or another.
In fact my last merc (S series) noticibly dropped its ride height above 50mph so much so that if you came to a quick stop from "cough" high speed you felt like you were on a fun fair ride as the suspension lifted back up. ie in the "electronic age" a lot of manufacturers are using adjustable ride height to counter the problem and change the cars aerodynamics
The solution can only be to create more down force at the front end (ie a rear spoiler could make it worse, forcing the front end up) ie front splitters etc.....(they are not just for show if designed correctly). Also lowering the ride height (permanently for same principle as electronic adjustment described above) can help as well (my car is lowered which will mean I don't perceive as much of a difference).
The problem is a lot of aerodynamic mods have become more cosmetic than functional in peoples eyes ie a 1.2 corsa, lowered with massive spoilers can never benefit from the performance gains and is actually made worse at it normal speeds (ride quality/MPG/even slower).
As with most mods there is always a trade off between "normal" driving and performance driving, BMW must cater for the masses (albiet the boundaries are shifted with ///M cars but they still have to be driven at normal speeds mostly) and so you cannot expect a stock car to be optimal as you push its performance envelope (super cars get over this with adjustable aerodynamics).
The question is do you want to improve high end performance perhaps at some detriment to normal driving (eg ride height/splitters/etc...)
ps I'm no aerodynamics expert, just years of driving lots of different cars, one of the first thing I test on any new car is high speed stability
I think the Z3m is pretty good at high speed compared to a lot I've driven but almost all road cars suffer from this to some extent or another.
In fact my last merc (S series) noticibly dropped its ride height above 50mph so much so that if you came to a quick stop from "cough" high speed you felt like you were on a fun fair ride as the suspension lifted back up. ie in the "electronic age" a lot of manufacturers are using adjustable ride height to counter the problem and change the cars aerodynamics
The solution can only be to create more down force at the front end (ie a rear spoiler could make it worse, forcing the front end up) ie front splitters etc.....(they are not just for show if designed correctly). Also lowering the ride height (permanently for same principle as electronic adjustment described above) can help as well (my car is lowered which will mean I don't perceive as much of a difference).
The problem is a lot of aerodynamic mods have become more cosmetic than functional in peoples eyes ie a 1.2 corsa, lowered with massive spoilers can never benefit from the performance gains and is actually made worse at it normal speeds (ride quality/MPG/even slower).
As with most mods there is always a trade off between "normal" driving and performance driving, BMW must cater for the masses (albiet the boundaries are shifted with ///M cars but they still have to be driven at normal speeds mostly) and so you cannot expect a stock car to be optimal as you push its performance envelope (super cars get over this with adjustable aerodynamics).
The question is do you want to improve high end performance perhaps at some detriment to normal driving (eg ride height/splitters/etc...)
ps I'm no aerodynamics expert, just years of driving lots of different cars, one of the first thing I test on any new car is high speed stability
wandering..
I certainly won't sacrifice the 'lower' speed fun and handling etc for the sake of 'higher' speed stability via mods such as lowering and splitters, and it's good to have one's suspicions clarified by yourselves.
that said, point about steering/suspension component generally is also one well made.
again, thanks for this.
that said, point about steering/suspension component generally is also one well made.
again, thanks for this.
Tyre Sizes
The 235/35/19 tyre is 1/2" larger diameter than the 225/45/17 standard tyre, so there may be a small increase in ride height.uk86ze wrote:19" wheels and have you not lowered it?. That's 2" more of the ground from the factory. This will affect stability not just in high speed but also cornering.
I would be careful about lowering the car with the larger wheels - the ride must already be compromised with the 'rubber band' tyres.
wandering......
Am inclined to agree Mike. Looking at it, any lowering will definitely cause potential rubbing problems.
One thing that lots of owners overlook when lowering their cars is to preserve the "rake angle". The front end must be slightly lower than the rear end when the car is normally loaded to preserve the aerodynamics of the car so that you get lower pressure under the car than the pressure above the car. Also, this preserves the weight balance of the car so that the back end doesn't get heavier relative to the front end.
ACS front flippers will also help.
ACS front flippers will also help.
Last edited by exdos on Tue 27 Jul, 2010 10:03, edited 1 time in total.
Additionally, you are also changing the toe angles.siwilson wrote:Another thing people overlook when lowering a car is that by lowering you are also altering the camber (the angle of the tyre to the road). You might see better grip in tight corners, but the car will not feel as planted on the straight and tyre wear will be increased.
Z3M Handling
I accept that some owners have good reasons to modify cars, but there is a common misconception that there are simple ways to improve on BMW's research and development, often resulting in abortions, or disasters.
I can see that some owners are 'driven' by appearance, perhaps influenced by concept cars and sketches which usually show the largest wheels and lowest suspension, but all become 'normal' by production time.
Others primarily set their cars up for track days and the like, and are happy to sacrifice ride quality and normal road handling to maximise the car's performance on smooth tracks.
I like the standard handling. My S50 has no traction control, and I drive the car almost every day of the year in all weather. Yes, it needs some concentration driving quickly on slippery roads, but once you 'know' the car, it's predictable and responsive, rewarding good driving skills.
It is virtually undrivable in snow and ice, but I'm going to try some winter tyres this year.
The standard cars are not perfect, by any means. The boot floor/ differential bracket issue is unforgivable, and many have needed substantial repair work, so BMW do not always get it right. There are simple upgrades that give immediate improvement - brake pads, rear suspension top joints, braided brake and clutch hoses. It is certainly possible to spend larger sums on brakes and suspension to give even greater benefits, but probably the law of diminishing returns comes into play.
These are my own opinions, after 50k+ miles of intense Z3M driving pleasure.
I can see that some owners are 'driven' by appearance, perhaps influenced by concept cars and sketches which usually show the largest wheels and lowest suspension, but all become 'normal' by production time.
Others primarily set their cars up for track days and the like, and are happy to sacrifice ride quality and normal road handling to maximise the car's performance on smooth tracks.
I like the standard handling. My S50 has no traction control, and I drive the car almost every day of the year in all weather. Yes, it needs some concentration driving quickly on slippery roads, but once you 'know' the car, it's predictable and responsive, rewarding good driving skills.
It is virtually undrivable in snow and ice, but I'm going to try some winter tyres this year.
The standard cars are not perfect, by any means. The boot floor/ differential bracket issue is unforgivable, and many have needed substantial repair work, so BMW do not always get it right. There are simple upgrades that give immediate improvement - brake pads, rear suspension top joints, braided brake and clutch hoses. It is certainly possible to spend larger sums on brakes and suspension to give even greater benefits, but probably the law of diminishing returns comes into play.
These are my own opinions, after 50k+ miles of intense Z3M driving pleasure.
