Suspension quesion
 

Will these springs lower my car too much? How about ride quality? This is my daily driver.

"King Springs Super Low coil springs from Australia. They will lower your car 1.5" to 2"

measure the distance down on your car. if it gives you a problem there is a write up on how to roll the lips on your fenders without damaging anything. baseball bat method i believe.

King Springs offer a great handling ride but a bit of a harsh one at that.. :)

1.5 to 2 inchs is no problem.

I had those
 

I had those springs on my 79 back when I was living in Aus. (~5 years ago) I was very happy with them, though the ride was a bit harsh. I suspect that the koni shocks had something to do with that too :)

The 79 hada partially stripped interior and felt like a go-kart. The GSL-SE I have now has racing beat springs with tockico blues and feels a lot more like a car. The extra weight in the GSL-SE really changes the handling.

Stock height is too low. Raising the suspension an inch or two made worlds of difference in handling. :)

Really!! I've always found lowering the car with performance shocks makes it handle better.

PJ is Old Skool. Remember, he still hates those newfangled 13B's, and 5 speed transmissions. :D

That might be true for some cars but the RX-7s suspension is... quirky. There are two problems at work here: Insufficient front compression travel (which lowering makes worse) and a rear suspension that in many respects is Simply All Wrong. The rear suspension is a four link, with upper links about half the length of the lowers, and the upper links are angled. Any four link that has non-parallel (as viewed from the top) and non-equal length links will have a tendency to bind when the car rolls. The quirks of the geometry in our design make this tendency worse when the suspension is lowered (axle raised into chassis). Additionally, a four link with non-parallel links is, by nature, self-centering, but Mazda saw fit to include a Watts linkage, probably because the links are *close* to parallel and they used gooey soft bushings to help eliminate the bind caused by problem #1. (An RX-7 will drive around just fine with no Watts linkage hooked up, about the same as an old single-leaf rear suspension) The Watts has a defined roll center (the center about which the rear suspension wants to pivot) and this fights the roll center defined by the 4-link's non-parallelity (which is by nature always moving around). ADDITIONALLY, the rear roll center (as defined by the Watts) is very close to the rear CG, which means the roll stiffness of the suspension is rather high for a given spring rate, *and* the roll stiffness is quite variable as the suspension changes position as you accelerate/brake/go over bumps. This causes somewhat unpredictable handling.

So basically in stock form the front suspension doesn't move much because it doesn't have enough travel, and the rear suspension doesn't *want* to move because the geometry is all out of whack. And LOWERING MAKES ALL OF THIS WORSE unless you stiffen the suspension up SO tight that it doesn't move at all, and that is fine IF you drive only on perfectly smooth roads (like racetracks or big parking lots full of cones). In the real world where there are bumps and stuff, you want the suspension to be able to move around, because the suspension's #1 job is maintaining tire contact with the ground. So raising the front makes things better by increasing the amount of travel available, and raising the rear makes things better by eliminating two of the three problems (poor linkage placement and poor CG/roll center relationship).

Of course, you can have good handling while lowered on the street, but it rather involves reengineering the rear suspension, which sveral firms (notable G-Force Engineering here in Ohio) will be glad to assist you with.

Very interesting. I always knew about the inherit problems with the rear suspension but I never thought of raising the rear to correct it. Have you tried this? What are you're impressions? Wouldn't the higher CG make it a little worst?

Tried it? I drive it every day.

The higher CG makes more a little less rear roll stiffness. Raising the front raises the front roll center (which is an imaginary point defined by the relation of the strut/control arm/contact patch) faster than it raises the CG so front roll stiffness goes up. You would think this would cause more understeer, which it does to a *small* extent. But there's no more plowy understeer in fast corners due to riding on the front bumpstop, and since the rear suspension actually follows the road instead of trying to lift the inside tire off the ground due to poor geometry, you can put power down more effectively, and the roll stiffness changes aren't as radical when the suspension moves.

Basically, it understeers a bit going into a corner unless you brake deep, which is a good thing, and it goes neutral-to-slight-oversteer when you power out of the corner. Very nice.

I am planning on some stiffer front springs (have 'em, just need to install 'em, they're about the same as Eibachs only a few inches taller) to eliminate the bottoming out over bigger bumps, which it still does.

so what is the ride height and where can you purchase that kind of setup???

^Yeah...what he said.^

Maybe I am agreeing or disagreeing with the analysis...

I thought that the Watt's linkage was in place to avoid the rear axel lateral swing that is not seen in a leaf suspension (that has a mounting point in front and behind the axel). Since the long-short arm suspension (which handles better in acceleration) only has mounting points in front of the rear axl, Watt's linkage is almost necessary for the RX-7.

Regardless, I think that the rear Maybe I am agreeing or disagreeing with the analysis...

I thought that the Watt's linkage was in place to avoid the rear axel lateral swing that is not seen in a leaf suspension (that has a mounting point in front and behind the axel). Since the long-short arm suspension (which handles better in acceleration) only has mounting points in front of the rear axle, Watt's linkage is almost necessary for the RX-7.

Regardless, I think that the rear suspension height plays less a part in the handling than the front suspension. I have less experience than PJ. Listen to him before me!!!!

ddwtrash.
suspension height plays less a part in the handling than the front suspension. But I have less experience than PJ. Listen to him before me!!!!

ddwtrash.

Man, the cut an past is killing me.... I am new to this.

Basically, listen to PJ first. me later.

ddwtrash.