And more updates. The new wheels should finally be showing up next week, so I've been doing tons of research and asking around to figure out what I'm going to do. There are two key issues to contend with; ride quality and traction.
Seeing as I'm not a huge fan of the ride quality with the current 18's, moving up to a 19" wheel is a bit of a challenging proposition. The RE71Rs on the current 513Ms are already ~0.6" taller than stock. Due to wanting traction, I'll likely be looking at tires at least as aggressive as the RE71Rs, which will of course be even stiffer when I start losing sidewall, so I plan to increase tire height as well.
This also brings up another area that I'm unhappy with and can change as well... suspension. The stock suspension felt too much like a boat. When I installed H&R springs, the stock shocks weren't enough to keep up and the ride became too bouncy. My new ST XA coilovers have a lot of issues just in basic design, which I would be fine to look past if they didn't ride so harsh. So while doing research on other coilover spring rates, I ended up finding a coilover setup on ebay with a setup that was just so amazingly cheap I almost couldnt say no. And then when I actually found someone running them that could vouch for the quality, I had to pull the trigger.
Hence, CX Racing coilovers have come into my life at $330 shipped. Now let's compare to the ST XA. Looking at the front struts/springs side by side there are a couple things to note.
Overall height- While CX Racing coilovers look much shorter, they actually just mount lower on the strut body (blue line). When installed, the strut body is very similar to the ST's, although the stock shock mount does add quite a bit of height as well.
Stock shock mount- speaking of the stock shock mount, this requires the use of a spring that has a much larger diameter at the top than the bottom. On the stock setup, the spring seat sits above the tire, so it can be a large diameter with no issue. On coilover setup with an adjustable spring perch, the perch is almost always below the height of the tire, meaning that is needs to be smaller in diameter so as not to actually hit the tire. This became an issue when I originally installed the ST's, as I run a 9" wide tire in front which when the suspension was compressed, would rub against those larger coils toward the stop of the strut. I actually had to run 5mm spacers and raise the height a bit to prevent this from being the issue. Notice that since the CX Racing coilovers come with a 2.5" ID strut mount, it can keep that small 2.5" diameter spring and prevent this issue all together. This also allows you to easily swap in different springs to try out different rates.
Adjustable strut body- One of the things that bothers me the most about the ST's, is the method of adjusting ride height. Since only the spring perch is adjustable, you actually have to change the preload of the spring to change the height. Say goodbye to the soft end of your progressive spring rate. As well, this has the hilarious side effect of actually making the spring effectively softer as you drop the ride height, and stiffer as you raise the car. The is the opposite of what you actually want. The CX Racing coilovers have an adjustable spring perch AND an adjustable strut body. This way you just put the correct preload on the spring and adjust the body of the strut to achieve the ride height you want. But a much bigger benefit comes next.
Riding in the sweet spot- Because the ST's require the spring height be adjusted to change the ride height, this can cause the shock to operate outside of it's optimal range. With the CX Racing coilovers, you simply use the spring perch to align the spring with the very middle of the shock ROM, and adjust the strut body to achieve your ride height. This allows you to actually pick where the spring rides on the shock.
Rear springs- This is another area where KW/ST have had a problem. Thankfully I don't get the dreaded clunking sound generated by the rear coils binding, but I do still have the effect. What's the point in having so many dead coils? By comparison, the CX Racing coils are much shorter and are only made up of 4 coils instead of the 6 that ST uses. I haven't checked for coil bind with the car on the ground, but GUARANTEED it's reduced. And the rear suspension can go at least an inch lower in the rear with the CX Racing setup.
Adjustable rear shocks- CX Racing even took this idea of riding in the sweet spot to the rear suspension, and provided adjustable shock bodies to allow you to shorten/lengthen the overall shock height as needed.
From a practical design standpoint, it's just a much better setup.
In terms of ride, my goal is mainly around comfort, and with adjustments set to full soft all around, the CX Racing coilovers definitely ride softer than the ST's. Truth be told, after a long drive down a shitty road yesterday, it could still be a bit softer for my needs. I've decided I'm going to try one last setup before I make a final decision, and that will be to go back on stock struts and run Eibach springs. My understanding is they basically stock rate but just sit lower. I think with the even taller tires all around, it'll probably reduce wheel gap to pretty much exactly where I want it. If I end up liking the ride quality here I'll then likely have to go with at least a rear swaybar to help with the handling a bit.
I also made a small change after washing the car today, and removed the rear z4 emblem. People already can't figure out what she is, even with the emblem there, so now they're sure to be questioning what just absolutely blew their doors off!
I've got another surprise coming to the door tomorrow, so I'll update when it does. Oh, and I added wheel studs all around. Ugh, they're so much better than stock bolts. EVERYONE should be moving to studs.
