Strut Brace discussion

[gslender]

In my mind the strut brace will have minimal impact on vertical movements as the strut brace 'looks' like it would only be good for horizontal movements.

I'd agree

Hence lifting up one wheel with/without a strut brace I would expect to see a similar vertical movement

Not exactly. Lifting the front driver wheel is similar (in part) to a cornering force. The C shape that is the subframe would have some pressures on it to collapse (think of the C ends moving towards each other - the cornering wheel wants to push up and to the middle. The wishbones are pushing inwards at the top, and pulling outwards at the bottom. These forces can be counteracted (or shared) by closing the box shape of the subframe. Unfortunately the top of the subframe can't be connected (because the engine is in the way) and so this force is counteracted by part due to the subframes inherent rigidity and part by the body chassis and members in the car (and a much lessor degree the engine mounts and the block of the engine).

I'm of the view that tying the top part of the towers together assists the lower subframe in having a body structure that is more rigid.

This is where the issue of double wishbone suspension comes into the equation, that is double wishbone is more efficent in dealing with horizontal loads hence benefits less from a strut brace.

No! There is no increase in efficiency with a wishbone suspension as the forces are the same. The benefit of double wishbone suspension is it gives greater control to the designer of what will happen to the suspension as it moves through its angles of travel. That's all!

Double wishbone suspension applies forces in different areas and they are still the same - and if those joint areas are sufficiently strong/stiff, then you get a good and consistent result in wheel geometry. Equally, if the wishbone is tied to a weak area, or an area not designed to cope with the forces of wider wheels and tyres then the wishbone suspension isn't able to keep everything aligned - eg. the area is it tied to just bends or moves with the forces applied.

[Magpie]

gslender you raise a valid point of people adding additional stress to the suspension by wider wheels and tyres. The car was designed for certain forces, whilst there is a safety factor involved (think duty cycle) no component is designed to run at 100% of it limits 100% of the time.

If the strut brace is added to overcome a design limitation then this would be what I consider dangerous. What should happen is the other components should be modified/replaced to accommodate the new stresses placed on the suspension then a strut brace may not be needed.

With respect to lifting a wheel up I disagree as you have vertical forces and horizontal forces acting simultaneously when a car corners, this cannot be replicated by statically lifting one wheel. I have had the displeasure of sitting in on doing fracture analysis of welding and learnt more things about stress forces than I would have liked. It is a very complicated field of study. The car was designed for certain forces and we upgrade at our own peril, hence a holistic approach is needed.

For example on my NA it does not have any of the orginal NA6 suspension components, however it still has stock damper mounting points, they have all been changed to suit the cars direction so my car will not behave like a typical NA6. The car could take wider wheels/tyres however it is still running 205/15's. If I decide to go to wider tyres then I will revist the whole of the suspension setup to ensure that I do not increase (by too much) the duty cycle.

This is a good discussion!

[KevGoat]

I read the 1st page and figured the following few pages would be people attempting to argue the effects of metal poles with dann.

First line was probably sufficient

[hks_kansei]

I would say that the strut brace on my car made a HUGE difference.

When I open the bonnet there's a shiny thing there which looks cool.

And as far as physical performance goes, massive difference.
My old cold air intake was able to be securely cable tied to the brace, and when I'm working under the bonnet it's a convenient handle to hold onto rather than putting my hand on the hot rocker cover.



As for it making a difference when driving, well the fact that until I opened the bonnet a few days ago I had forgotten that it was removed.

[KevGoat]

I basically fitted one for aesthetic reasons, but I did notice a slight reduction in shake in my NB8A after fitting a later factory brace. Plus as hks_kansei mentioned, with my back, anything I can lean on under the bonnet that doesn't burn me has to be worth it!

Will be interesting to see where any forthcoming "facts" may take this discussion, but the way I drive these days, even perceived performance gain is wasted on me ...

[RS2000]

Why did Mazda go to the trouble of designing & manufacturing a quality tower brace for later NB's ?
Surely not just for show!

Cheers

[NitroDann]

"With full respect, products exist to profit from the sale of them."

[hks_kansei]

Why did Mazda go to the trouble of designing & manufacturing a quality tower brace for later NB's ?
Surely not just for show!

Cheers

Probably the same reason they went with 16inch wheels, and leather interiors, and projector headlights, etc.

Something else to add onto the spec list to make people upgrade from the previous model.

[RS2000]

You may be right, but I'm not convinced a tower brace helps sell new MX5's.
I don't think it was an optional extra, & they'd sell bugger all thru' their spare parts network.

Also, the brace has good 'joint' design - unlike a lot of aftermarket ones.
I'm leaning towards Mazda adding it for engineering reasons.

Cheers

[gslender]

In 92 Mazda added a lower rear brace for similar reasons, so those with 89-91 models either have faster cars due to the unneeded weight, or Mazda engineering is better than a bunch of forum dudes and it actually does something worthwhile too that earlier first models could benefit from adding.


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[NitroDann]

What do you know there might be benefits, but no one in this thread is discussing NVH.

Dann

[davekmoore]

All right then Dann.

Extra stiffness generally increases NVH.

Runs, hides, crouches, puts arms over head.

[sailaholic]

Stiffness can also reduces vibration by changing the natural frequency of the structure. My understand was the rear brace helped the "65 mph shimmy"


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