Ride Height For best Handling

[Pumpn'Go]

Hi I am looking for opinions on the best ride height for a na.I race bitumen motorkhana's,spirited road and hope to do some track.
I like the look with very small or no tyre gaps and will be running 15\"Falken 615's.
I am also getting a set of coilovers to help with the tuning,Thinking the tein ss or the Jap ones from Race Supplies.I Would like opinions on their lifespan how many km will they last.
I dont want to run out of travel,but I am happy to fit the lengthened strut tops to get back travel.
Do I need different bump stops?I am thinking of the softer ones that they use in the US.
Any way back to the first question,
How low is too low?
At what hieght does lowering go from improving to worstening handling?
Thanks Col

[Matty]

It's such a grey area that there's no definiteive answers.

Going lower:
a) lets you get more negative camber out of the factory adjusters
b) lowers the CG
c) lowers the roll centre even more than the CG (so the roll couple increases as you go lower)
d) significantly alters the camber pattern
e) reduces bump travel
f) reduces ground clearance (legal and practical implications)
g) decreases aero drag

Somewhere amongst those compromises is a setup that will work well in a particular scenario. The trouble is that the ideal height varies with whatever you're doing...

The other trouble (in asking for advice) is that everyone thinks the solution they have is the best.

Personally I don't like going below the point where the lower control arms are horizontal, for a street dríven car - too many compromises. Personally I'd rather be fast than look fast.

[Pumpn'Go]

Thanks for the input.
At what height are the controll arms horizontal?

[CT]

Actual height depends on lots of things but you must have your lower arms parallel to the ground in the front otherwise bump steer will ruin the handling.

[Juffa]

Actual height depends on lots of things but you must have your lower arms parallel to the ground in the front otherwise bump steer will ruin the handling.

Ah ha....that explains that then....must check my lower arms. The great thing about the threaded body shocks is that it take 15 minutes a side to adjust the ride height. (including wheel removal)

J

[manga_blue]

Nevertheless I've been trying to figure out how Sam can have his so low that the diff almost drags on the ground and the arms point up yet he's so bloody quick.

[Pumpn'Go]

Isn't there an actual height that the arms are horizontal?
With or without coilovers the arm is attached to the body ,so does that not give a specific height?

[Matty]

Isn't there an actual height that the arms are horizontal?
With or without coilovers the arm is attached to the body ,so does that not give a specific height?

You can check yourself pretty quickly (on a flat surface, measure the height of the inner and outer LCA bolts from the ground)

As I recall though, it was about 320 front and 325 rear... (+/- 5mm) on my NA

That height also leaves a good amount of bump travel.

[Matty]

Nevertheless I've been trying to figure out how Sam can have his so low that the diff almost drags on the ground and the arms point up yet he's so bloody quick.

Part of it's the driver.
Part of it is that it's a compromise he's made for the track (I bet with more travel he'd be faster up a bumpy road)
Part of it is that sitting the rear of an MX really low seems to aid rear stability. I don't know if it's due to camber, roll centre or what, but it works. (James Sanderson used to run his NA like that too)

[Pumpn'Go]

Is it the angle of the lower wishbone ,or is it the angle from the steering rack mounting to the outer tie rod end.To my understanding of bumpsteer this can be fixed by lifting the mounting point of the rack by the amount you lower the car,
Please let me know if I am thinking wrong, or you are talking about something else.

[Matty]

Is it the angle of the lower wishbone ,or is it the angle from the steering rack mounting to the outer tie rod end.To my understanding of bumpsteer this can be fixed by lifting the mounting point of the rack by the amount you lower the car,
Please let me know if I am thinking wrong, or you are talking about something else.

Bump steer geometry is pretty hard to explain with double wishbones. As a simplification, you can roughly say that the tie rod should be about parallel with the LCA.

[CT]

Yes - moving the steering rack can help to compensate but if your car is that low with standard suspension pickups, your geometry is so far out of wack you are not going to fix it.

With height adjustable coilovers, the most important things are:
- Travel: you need to have it
- Lower control arms: parallel to the ground
- Droop travel: the fronts match and the backs match at the very least, if possible, all should be the same but it depends on springs rates and free lengths.
- NBs can be lowered and maintain correct geometry moreso than NAs: the front pickup points are slightly different.

[Pumpn'Go]

I'm not looking to slam the car,its just that:
I like the look of, at least having a smaller tyre gap, prefer 10mm or so and all the cars i see racing have this or less . Most of them would be duel purpose and its hard to believe its just for looks with all of them.
Its been many years since I raced, just club level down in sydney. But in those days the cars we started with were tanks , I think I could get round quicker in the mx now than I could in my xu1 Torana.
That said the first thing we did to help with the handling was to lower the car( yes we had bump stop problems but we had diferent ways of beating-minimumising it) stiffen it up with springs and bars.
The mx already handles better than they did so maby I'm just expecting too much.

[Matty]

Like I said in my first post: slamming the car for maximum traction at the track represents a different compromise to setting an MX-5 up for road use (with the occasionaly weekend track day).

[Pumpn'Go]

So your saying that in your opinion that for a duel purpose car you would still recomend standard ride height .