[tjswarbrick]

Hi guys (and gals, too!)
Can you stand another one of these "best suspension" threads?
I think I know what I want to get out of it, at least.

I've driven a number of e46 and E90 3'ers, and they just seem to flow over the road. My E88, not so much. It is sublime top-down at speed on the right (curving, smooth) roads. But around town on the unrepaired roads I seem to travel often I get these harsh, jarring hits and sometimes a snap or loud cracking sound. While I do what I can to avoid potholes, these road imperfections go nearly unnoticed in my wife's Pathfinder and were just a minor inconvenience in my previous W203 C230. And the 328's/330's/335's I've driven just take them in stride. I like to drive my wife, friends, and kids around - but a jarring, jostling ride makes it no fun for them. And I fear for the long-term structural integrity of the vehicle the way it sounds. Sometimes it just doesn't seem all that BMW-like to me.

However, I also want to firm up the suspension for those times when the going gets fun. Some body roll is great for feel and progressiveness, but as we all know the stock 135i M-Sport suspension leaves a bit more than necessary on the table.

My 1'er is not a race vehicle, but I hope to take it to CCC, Auto-X, and maybe a couple track days a year. Mostly I want it to feel and perform at the highest level bombing down the awesome but not always meticulously maintained backroads available in my area.

I suspect a great deal of the impact harshness can be laid at the feet of the fun-flat tires. So as soon as they wear out, I'm getting Michelin Pilot Sports. Probably 225/40 up front and 245/35 out back with M3 sway bar, likely Dinan camber plates, and some RSFB's to tame the slop, roll and understeer a bit.

I have 12mm spacers, under the stock 261 wheels, which seem to have helped the tiniest bit. I plan to keep them unless clearance becomes an issue. I'm not looking for huge drop - just 1/2 to 3/4" lower than stock M-Sport seems ideal to me, but the 1" lowering of Swift's springs is right in the ballpark as well. Once I get the damping set to my liking, I really don't plan/expect/want to change it for conditions or environment.

Now, on to my real issue.

How do I improve the handling to something comparable to a 1g-capable E30 M3, while making it ride like an E39 M5 or E90 335i Sport Pack?

I thought I was going to go Koni Yellow's over Swift Springs, but the more I read the more I see that's really a compromise for great handling and acceptable ride at a very competitive price. I want less compromise.

Just received word that I am getting a little bonus this year. Hooray! So I can splurge a little and get a set of $2k-range coilovers.

I read a (single) review here which said that (IP-issues and long-term longevity aside) the CA-Tuned coilovers ride much better than the Yellows/Swifts - so that's got me thinking to go with coilovers.

Fairly common wisdom says that ST XTA's and KW-V1's ride well, but their damping and progressive-rate springs make their on-track handling rather suspect. I once followed a guy with a FBO E82 with ST's, M3 control arms & MPSS on some of our best roads. I could basically keep up with him, but I was working REALLY hard and my passenger got rather motion-sick.

I don't love the idea of the progressive springs on the KW-V2, but otherwise they seem like a good compromise package.

Reading the write-up on the 128i I long for the TC Kline coilover setup. Harold at HP said I should go with 350# front and 600# rear springs for a Cabrio street car.
Swift R-SPec's are 201# front / 502# rear. Will the TCK setup (single-adjust) be able to compete from a ride standpoint? And if I go TCK, which springs are likely to offer the least compromised ride without giving anything away in handling?

Should I look at Ohlins or Bilstein?

What's my best bet to optimize handling (grip, composure, feel, response, progressive breakaway) and driving enjoyment improvement as I can in conjunction with the very best ride in a 135i convertible in an under $2500 springs/shocks or coilover setup?

Thanks!