mx5cartalk.com

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.

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.

CT wrote: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

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 wrote: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.

manga_blue wrote: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 wrote: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.

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.

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).

Interesting question Pumpn'Go, have a chat to Steve at Fulcrum Marooka, Fulcrum did a lot of testing early in the piece to help develop Tein suspensions for Australian roads, I think they're be more equipt to answer suspension Qs than most of us. From memory, I think 325/330 (F/R) was their recommended height for optimum handling for the NA. Definitely lower than stock but not riding on bump stop low....

see my sample photo below for 325/330 setup...

http://picasaweb.google.com/s363134/MX5 ... 3167537810

Pumpn'Go wrote:So your saying that in your opinion that for a duel purpose car you would still recomend standard ride height .

Not quite, anyway "standard" depends on which model/year you refer to. the 325/330 advised above is pretty good.

I might run larger rims and lower profile rubber but I keep the overall circumference as close to stock as possible...

go here to see how far you are from stock....
http://www.miata.net/garage/tirecalc.html

As an indication I run 215/40R16...this has a 3mm larger circumference compare to stock (185/60R14)...not much difference at all. Whereas yours is a good ~20mm larger...but again relatively small difference.

As for re-mount the steering rack, or use tie rod spacers, for bump steer. Use adjustable arms for camber,or move pivot mounts for caster and toe on the rear etc....personally I think the MX5 is pretty well design as is, I wouldn't bother with any of that...unless your a serious fulltime racer then maybe...

Hello, may i ask, for 325/330, what is that measurement and how is that measured? ie, is that the finger gap between tyres and fender or ?? do you have a clear picture of it to share please? the above links do not work anymore.

For stock height, it seems that the rear is lower than front. is that true? If this is true, is there any reason why most mod takes the front lower than rear if they are not leveled? and why would we do that?

Thanks

Plenty of good info in this thread, maybe not such a bad thing that it got resurrected.

It would be referring to the distance between the hub centre (centre of the wheel) and the top of the wheel arch, in mm of course.

That measurement is from centre of wheel to fender.