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Old 21-09-19, 12:22 PM   #1
Mark S
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What if? Lowered ZS

so the ZS has been lowered 2" and some say it looks the dogs.

Its been polybushed to buggery and has camber arms all round to correct the geo.
Done right? One would think so.

....

Now on a standard ZS, which is without doubt a great handling car, the rear suspension will always toe in when the wheel goes into bump, or rebound.
Manufacturers do this to keep us safe, generally this creates a bit of understeer and the car is easy enough to keep control of if we have to take avoiding action.

....

Now on the lowered ZS, things are different.
When the wheel goes into bump it toes in, but this time it toes in with a greater rate of gain than before.

BUT, in rebound, or under braking or when the weight is transferred off the rear wheels it toes out, and it toes out quite a bit.

Ever driven a car with rear toe out? They are not stable and likely to snap oversteer if you ever need to take avoiding action.

One option is to stick on a load of toe in, but then we drag the rear like we drag an anchor wasting precious horsepower.
It will still toe to zero or even toe out still, so this really isn't a fix solution.
Another option is to lengthen the toe link, this will reduce the rate of gain but the effects still happen.

Whilst its possible to properly fix the problem (there are people clever enough I'm sure, its not gonna come cheap)

The car will never be put on track, its too nice for that.
In all honesty, polybushing a road car may have been a bit pointless, but its quite impressive to say you have a polybushed car.

Its not even driven fast on the road.

But what if...

What if I have to swerve to avoid an animal at night?
Many years ago I hit an animal that ran into the road, it did a lot of damage to the car, but...

What if I could have swerved to avoid that animal?
Chances are in the same circumstances I'd have ended up in a ditch upside down and totalled my pride and joy.

What if it was a person?
with the toe out that happens there's a fair chance that swerving to avoid would cause loss of control of the car and I could still hit that person having lost control.

What if it was a child?

What if it was my child?

Some things in life don't bear thinking about.

Is my car looking the dogs worth it?
Is vanity worth the price?
The chances may be similar to winning the lottery, but it still happens, but...

What if I never lowered it?

Is it worth it?

What would you do now like me you understand the problem that can't be fixed?

Opinions please.
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Old 21-09-19, 10:48 PM   #2
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Wow...

What if you just never went out?
What if you'd decided to stay and have another coffee before going out so you'd not have been in the position anyway?
What if the thing or person you hit stayed in?I

What if when you reacted the way you did, and the fact that you'd made the change meant that you avoided hurting anyone and now if you change back, you'd be making a change for the worse?

I say whatever you do is the right choice. What will be, will be.
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Old 22-09-19, 07:23 AM   #3
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The opinions will vary. Youíll get those that agree with the geometry understanding and where there is compromise, then youíll get those that only want the static looks to impress and pub/show bragging rights.

The biggest thing for me is whether it is road or track. If a trackway car itíll either be full-on and trailered, so set up accordingly or driven to track and dialled down to make it safe to use but not driven like an asshole.

If road then you will get that typical owner who wants the stance and all the track bits fitted just to brag about, doesnít understand the effects and doesnít care. That will never change.

For me I like the look of a race car, it has a purpose and does what you expect it to do if set up correctly, if that means it sits higher so be it.

Like you said with some clever engineering and understanding you could modify or make new suspension that could control the angular movement, one for the pros I think. The current design works well enough for me for my track use.

I like this topic, makes you think.
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Old 22-09-19, 12:11 PM   #4
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Quote:
Originally Posted by stamford View Post
Like you said with some clever engineering and understanding you could modify or make new suspension that could control the angular movement, one for the pros I think. The current design works well enough for me for my track use.

I like this topic, makes you think.
Thanks, I just put it out there to make people think.

Most people deal with the things you can measure - albeit static, such as castor, camber, toe etc.

That's a little insight to one of the dynamic effects that can't be measured quite so easily, yet it is critical in a race car but rarely entertained at club level with most people saying it can't be done within regs - I disagree!


Back to the original point, I'm not saying its right or wrong, but I am interested in opinions though, would you lower a ZS in the knowledge that you will make the car less safe (induce snap oversteer) if you ever had to take avoiding action?
I think the answer depends on how you think of the consequences.

Thanks for your input

btw. I believe the dynamics can be engineered within club level regs and we will be trialling this theory on a ZS race car which we hope to become the fastest (circuit lap) ZS with the exception of the original BTCC cars.
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Old 23-09-19, 10:32 AM   #5
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Now I may need a lesson in the dark arts of suspension setup; how changing the spring rates will impact the raising/lowering of said setup....

But my car has been lowered with coilovers - it was done by some-one that knew what they were doing rather than "slammed" and uses OEM bushes. It was lowered as much as it could be while still being primarily a road car (the person's judgement was used to find that position front/back & I've not altered it since) - I do get a little wheel arch liner rub on specifically weighted/loaded right turns on the nearside front. Or if there is a bump in the road that causes high compression.

I've been driving since 99 and on the road I've never had to perform a "moose test" type manoeuvre in any of my cars; So it is hard for me to make a comparative type statement on whether the ZS is more/less stable now than it was with these modifications.

What I can say is:
The ZS still feels the most stable car I've driven, and I have the highest confidence with the predictability of the handling and behaviour over any of the cars I've owned; probably more so after the suspension was adjusted.

That said, after the "brembodge" setup was fitted, stability on the rear end under braking was diminished with more extreme loads - nothing too serious, but I am aware it is less forgiving than it was, so have to act accordingly.

The little Mk7 fester I had came very close in terms of predictability and confidence; but with a much softer setup different limits were hit grip wise that ultimately altered how much the suspension was pushed on the road.
I would never attempt as sudden a change of direction in the mustang as I would the ZS at road going speeds & there are corners I go into significantly slower as the car just does not feel settled; off camber downhill bends being the most obvious.

In regards to the swerving aspect itself, I was taught not to swerve unless you can have a reasonably high confidence level you will not lose control and/or the environment is safe to perform said manoeuvre.
Otherwise break as hard as you are able to mitigate the damage as much as possible (braking in a straight line being more effective than at angles etc).

I think a lot of it boils down to awareness/education of the driver of the consequences and circumstances surrounding the car & those that "don't care" won't care regardless of whether the suspension is adjusted. I say adjusted as lifting it would have as large an impact as lowered if gone to the extreme
And I also think that the latter statement is very important.

So to answer the question.

Yes I have lowered the ZS & I'm happy with the change and any associated alterations to the behaviour on extreme directional changes.
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