toplad said:
Cheburator said:
Curtis said:
I'm glad to hear I'm not the only one who laughs at the " fitted a strut brace and now the ( otherwise standard ) car handles much better " statement!!
Wow - I thought I was in the minority...
The car is stiff, and I mean stupidly stiff, the front end has built in understeer and turn-in is a bit crap as a result of the above... Oh, I know what I am going to do - I will keep the stock suspension settings and supposedly make the front end even stiffer by adding a strut brace. That is definitely, positively, absolutely going to improve handling further
Have you tried the strut brace?
I can only assume you haven't because it makes a noticeable difference to the front end on bumpy roads. Yes the car is stiff, but front end isn't. Yes there's bracing already but adding a brace really does make a tangible difference on rougher roads. It's the effect of linking the two towers together at the top which is the biggest factor. Before I fitted the brace I noticed the wings seemed to move about independently off each other and the car rocked from side to side a bit, link them together and there is noticeable less movement and the front is more settled.
You mention forces acting on the suspension; and how a brace won’t make any difference. On chambered and crowned roads the suspension is being pulled all over the place. Not just in the vertical direction, in theory it should, but in the real world it’s not the case.
Rather than dismissing it, you should actually try it for yourself; you’ll be surprised I guarantee it.
I tried it and it made no noticeable difference whatsoever so I took it off and saved a bit of weight and concentrated on the real problem areas. Once I'd finished building my suspension system I put the strut brace back on and still felt no change so I took it off again. Perhaps if the Z4 didn't already have two diagonal braces fitted then the effects of a tower brace might be more noticeable.
I doubt if the forces a Z4 can generate are enough to move the inner wings towards each other anyway. If you think about it, the bonnet is a separate piece of bodywork that sits between the two inner wings. The gap between my bonnet and inner wings gets as close as 1.5mm in some areas however there it no sign that the two have ever come in contact with each other ie no marked paintwork. This would indicate that the flex inward of the inner wings under the arduous conditions I put the car through never reaches 1.5mm.
I think the main reason why fitting a strut brace and expecting miracles humours me is this.
The whole concept behind stiffening a chassis and increasing torsional rigidity is simply to keep your geometry setting in check and stop them shifting around. It's worth noting that the suspension system won't start functioning until all the flex and freeplay has been taken out of the mounting points and mechanisms within that system.
There are two obvious problem straight away. Firstly most people don't give a s**t about their geometry settings as long as the car seems to drive ok so what is it they are trying to preserve anyway? Secondly, the suspension/steering mounting points are so soft that the geometry is free to move around so much that even if you could make the chassis 100% unmovable your completely wasting your time anyway. That's assuming that a third strut brace will suddenly transform your chassis into an immovable object which of course it won't.
If you look at race cars which are the opposite end of the scale from standard road cars you'll notice that everything about their design revolves around rigidity. Space framed chassis and roll cages have the primary function of being extremely rigid. Each bar is specifically designed and placed at an exact angle for the purpose of distributing and dissipating loads, pressures and stresses throughout that structure. Safety is more of a byproduct. The suspension and steering is bolted directly to this spaceframe and cage using solid mounts and you won't find a single rubber mount or moveable joint on the suspension anywhere. The outcome is that the car is so rigid that no matter what you put it through those precious geometry settings will only waiver fractionally from what you set them to.
Compare that to a typical Z4 and bear in mind that structural rigidity is all about protecting those all important geometry settings.
The owner probably doesn't know what geometry settings he or she has in the first place never mind what settings would be perfect for his or her driving style.
Without spending money on such things as adjustable camber plates you can't achieve these settings anyway.
No matter what geometry settings you come up with they will never stay anywhere near where you want them because the entire suspension system is free to move around on it's mountings as it pleases.
How then do they decide to cure all these fundamental flaws? They fit a third strut brace and announce that it totally transformed the cars handling.
I don't want to sound like I'm belittling people who are of the opinion that adding ANOTHER strut brace will suddenly work miracles but perhaps you can understand why it makes me chuckle.
