Correlation between ride height and ride quality? (NA Miata + GC/Bilstein HD)

A few of you saw in my build thread that I recently got my Ground Control coilovers (spring rates 440 front 250 rear) installed in my Miata, over a set of new Bilstein HD's. Initially I set the ride height at about stock levels. This was fine. Handled great. Ride was firm, but composed.

Then I lowered it.

It's at this height:

I LOVE the way it looks (well, ok, I'd like it a bit lower but we'll forget that for now). However the ride is just killing the experience. It's harsh. It's bouncy. My ass leaves the seat over good sized but not ridiculous bumps.

So... why? Is lowering it effectively shortening the springs or something and messing with the rates? Or, as suggested in my build thread, am I just bouncing off the bump stops all the time? What gives? Trying to understand this.

If it is a lack of travel/lots of bump stop action... learn my NB top hats? Why shouldn't I use them with NA shocks? Or should I?

Your probably pepetually on the bumpstops. You've not changed the amount the spring is compressed or the actual wheel rate unless you've contacted the bumpstops. You can get NB tophats that give you a bit more travel. Miata experts in 3... 2....

Right. The top of the spring is in the same position, I've moved the bottom of it down by 1.5"+... putting the top of the shock body that much closer to the bump stop. As a result it takes a much smaller bump to cause enough movement to hit it.

I think. I'm a little slow tonight

NB upper mounts (aka "tophats") will not give more travel - that's a myth that doesn't stand up to measurement. Mostly what they'll do is increase the potential for coil bind The Flyin' Miata rear mounts do add significantly more travel as that's what they're designed to do.

But nocones has it right. You're bouncing off the stops. Better bumpstops will help, staying off them will help more.

While Keith is right, the NB mounts do not add travel, they will lower the car about 1/2" compared to na mounts with the same amount of travel. If all you want is the same ride quality you had before but have the body lowered 1/2", the NB mounts will work for you. If you want more travel, get fm mounts or one of te other aftermarket mounts that do increase travel.

mw wrote: While Keith is right, the NB mounts do not add travel, they will lower the car about 1/2" compared to na mounts with the same amount of travel.

So at the same ride height, NB mounts will give you 1/2" extra travel over the NA mounts, correct?

Yes.

So who has used what in the world of these aftermarket mounts? Looks like the popular ones are ISC Racing (cheap!) and FM (pretty - but significantly more expensive).

I have the fancy purple ones in the rear of my Miata. 450/300 GC over Koni Yellows. Paired with the tiny little GC bump stops, all is quite well, and I'm low, a little too low even. Expansion joints and potholes are no fun, but I certainly don't bounce out of my seat.

ninja edit - you may want to ask these guys what the effect of putting the NB tophats in the front and the fancy ones in the rear would be. I only did the rears because the then-common advice was to leave the fronts alone.

I'll triple-check my numbers - but according to my measurements, if you put in the NB mounts on NA shocks you'll get a drop in ride height AND a loss in travel. It's not a popular thing to say though.

The ISC mounts will cause a change in ride height - someting that can be dealt with if you have adjustable perches. The FM ones are the only ones on the market that add travel but will not change ride height.

So the ISC's lower the car (~3/4" apparently) AND increase travel? That sounds about perfect to me. I'm sensing an imminent purchase of ISC mounts and FM bump stops

I appreciate the input peeps.