We'd all like to think we are DONE but we all know that is never the case. Short of a roll bar, I thought my track car was done. Plus I never considered safety items as "modifications", or at least that's how I justify it. But moving on, my car last appeared like this as of mid-March:
Then I found a deal on a used Stoptech ST-40 big brake kit (p/n: 83.148.4600) and the price was too good to pass up. The owner was parting out his E46 330ci track car and was offering the kit for less than half price. Here's the kicker,
the Z4 3.0si shares the same exact front brake setup as the E46 330ci and it's imperative when purchasing brakes you find a kit SPECIFIC to your car. Many kits may "fit" or "bolt-up" but you're really messing with the bias. For example I know some vendors are offering a custom bracket for the 135i caliper but without fitting the matching rear, you may experience more understeer or even worse, lock up the fronts during hard braking. I don't want to offend anyone here who's used those kits and I'm sure they are fine for street but I didn't want to take my chances on track. In any case, I see plenty of big brake kits for sale on M3's but it's RARE you find one from a 330ci (Z4 3.0si) - so I HAD TO HAVE IT :P
Unfortunately though, the wheels above (Apex Arc-8 in 17x9.5 et35) would not clear the calipers due to its concaveness. I could've added a 15mm spacer but the offset would've been way too aggressive for my liking and not safe imo. So I made the hard choice to sell those as well and find a wheel that would a) clear the brakes, b) suitable for track duty and c) wouldn't break the bank
I then stumbled upon the TRM MT1-R wheels. TRM is Tire Rack's in house motorsport brand, but these are basically Enkei wheels made for Tire Rack. I've seen plenty of BMW guys run the MT1 wheels which I actually think looks better because there's no lip and hence the spokes look longer. The MT1-R has a small lip so the spokes don't extend as far out making the wheel look smaller. But the 17x9 et40 was perfect and best of all, Tire Rack threw in 4 free spacers in 5mm.
Couple things on these wheels and brakes
1) TR does NOT offer center caps for these so I just bought replica BMW caps in 68mm off eBay. I had to wrap the center cap tabs with electric tape because it was slightly loose but the tape did the trick. 2) My factory TPMS would NOT fit on these wheels. I know factory-compatible aftermarket senors fit but since these are only track wheels, I didn't see the need for them. Lastly, for those who are curious about these wheels, they will NOT show up if you enter Z4 as your vehicle. TR deems these wheels too aggressive for the Z4 so I had to put in 99 M3 (or any year for E36 M3) for these to show up.
In regards to the brakes, if you're buying a kit used like me, it's probably in your best interest to replace some of the misc. hardware. I purchased new crush washers, oe bolts and jet nuts. The jet nuts were most expensive but you have no choice to buy from Stoptech directly. Regular flange nuts won't work because you need something thin enough to clear the caliper. Also, be sure to read the instructions before, although you think the kit should be a simple bolt-on process, you'll have to a) trim your existing backing plates to fit the larger caliper and b) have access to a die grinder to shave down the steering knuckle in order to let the bracket fit. Lastly, the instruction mentions which parts need loctite and what the torque specs are.
And how she sits now...
