Did some mods, did some maintenance, washed the M

[mattfwalters]

Decided to prep the Z4MC for more track time. First important item: dial out that understeer! It seems like the best solution to that problem is to add rubber up front, so I decided on a square setup - 9.5x18" ET35 all around, with 12mm spacers in the rear. Here's a stack of Kumho Ecsta PS91v2 265/35ZR18 rubber on APEX EC7s:


I hate wheel bolts, so I installed APEX 90mm studs on all four corners. They're excessively long, but I've decided that I like the look, so I'm keeping them.

In order to fit those fat tires under the front fenders, I needed more camber. For adding camber, it seemed like camber plates were the right option. If adding camber plates, why keep the 10-year-old stock suspension? Ground Control to the rescue!




Those are 550lb/in springs in the front, and 700lb/in in the rear.

Then, of course, stainless brake lines and brass caliper bushings, and the realization that the rotors were total junk (1.5mm ridges on both sides of the front rotors, ~1mm ridges in the rear). Why replace when you can upgrade?



And stockers for the rear, because damn those ECS 2-piece rotors are expensive for the rear fitment, and Hawk HP+ pads front / rear to round things out.


Out of the garage!


Hmm, that doesn't look right. Good thing it's going in for an alignment / corner balance the next day.

Also, I decided that the "chrome" trim on the grille looked incredibly out of place, so I sanded the trim rings down, primed them, and painted them with some gloss black chassis paint I had left over from another project. They turned out really well for a $0 mod, and if they don't last, I'll buy some black ones to replace.

At least I got the camber set pretty well...



Result!


And then a show and shine. Just my luck that a 1M parks beside me - pretty much the only BMW paint that makes Sepang Bronze look dull and flat in comparison.


It's been a super fun few weeks. Not pictured: engine / trans / diff oil changes, and new accessory / serpentine belts. The undertray is still off so that I can change the coolant tonight... but the track day is tomorrow. So probably I'll button everything back up and change the coolant on Sunday.

So... yeah. Change one thing at a time, right? :evil:

 

[paddy wright]

Looks great!

 

[TomK]

That looks lovely! How are you finding the GC stuff? I'm still trying to make my mind up with regards to suspension. Koni dampers on the rear?
No worries with rubbing at the front with that tyre/wheel setup? Which look lovely by the way, I was torn between those and the ARC-8.
I assume you had some weights in the car for that 3394lbs reading? Mine was a little less than 3100lbs with a half tank I seem to remember.

 

[mattfwalters]

I am loving the GC bits so far, but I've only got ~60 freeway and ~15 surface street km on them. They're 1-way adjustable Koni shocks front and rear, but GC adjusts the valving to your car / target driving conditions at the factory, so they're great value for money in my book - and comfortable to ride on, even with the fuckoff stiff rear springs. The goal is to see if I can run without the rear swaybar, which a bunch of trackrat Z4M drivers have indicated is the ideal way to get the car out of corners quicker.

The wheels rub the smallest titch at full lock - apparently on the inner fender liner - so I'm expecting some more fender liner rubbing at the track. No rubbing at all at the fender lip or the fender area of the liner - but as you can see, I'm running shorter tires (265/35R18 == 231mm tall, vs. 225/40R18 == 241mm tall) along with -2.5 degrees of camber - the outside top edges of the tires are only 2cm further out from the hub than the stock tires, based on my math (yes, I built a huge friggin' spreadsheet to calculate the most aggressive fitment I could do on the car) - and research told me that this is about the limit for these cars. Also APEX confirmed that they had fit a similar setup on a Z4M successfully in the past - camber plates required! - so I pulled the trigger on the 9.5" ET35 square setup. Side note: I am oddly excited about the fact that I can rotate my tires front to rear.

I was also torn between these and the ARC-8 - but the EC-7 group buy started just as I was shopping, and they're slightly less common than the ARC-8s, and I decided that I really like them. Glad I did - I think they really suit the Z4MC.

The car had 185lbs in the driver's seat during corner weighting, and around 2/3rds tank of fuel, yeah, so that would be the difference in weight. Still a bloody respectable power:weight ratio, even with me in it.

I'll be at the track tomorrow, so I'll post an update about (1) how everything performed, (2) how (if!) my lap times improved over last session with the stock bits; and (3) how (if!) lap times changed after disconnecting the rear swaybar. Should be a fun afternoon.

PS thanks for the kind words, both, and Tom, I'm going to pick your brain about the CSL / Alpha-N stuff, because that sound... my god...

 

[Fishy Dave]

That looks superb Matt, will be very interested to hear how you get on. Which track are you driving?

Tom, you're not allowed to upgrade your shocks, I'm struggling to keep up as it is

 

[mr wilks]

Like the looks a lot but I need enlightening here :?
A square set up I can go with to a extent but will 9.5j with 265 rubber on the front not ruin the turn in / handling

 

[mattfwalters]

That looks superb Matt, will be very interested to hear how you get on. Which track are you driving?

Tom, you're not allowed to upgrade your shocks, I'm struggling to keep up as it is

Thanks, Dave. I'll be at The Ridge, which is my local favourite - a great combination of elevation changes, on and off camber corners, tight tricky bits and sweepers... really a modern work of art. Nothing like the local tracks in your neck of the woods, mind, but we new-worlders must make do.

Like the looks a lot but I need enlightening here :?
A square set up I can go with to a extent but will 9.5j with 265 rubber on the front not ruin the turn in / handling

Not necessarily, and certainly not in my case experientially. The wheel / tire combo is something like 8lbs / corner lighter than the stock setup, despite the extra width, and it's a car's alignment characteristics that dictate how it turns in, for the most part. Having more stick up front will (theoretically) keep the car from pushing through tight corners, or on long sweepers under power - the stock stagger is designed to make the car tend to understeer, since the short wheelbase makes oversteer fairly dangerous for the uninitiated.

I'll let you know how it goes in reality on the track, though. Worst-case, I have a spare set of rear wheels / rubber and I'll go to a narrower front.

I don't think that's how it's going to go, though.

 

[Anonymous]

Looking good buddy

 

[mattfwalters]

Trip report:

[youtube]https://www.youtube.com/watch?v=NdrFMwUNLC4[/youtube]

I knocked nearly 10 seconds off of my previous best lap at this track, and as you can see from the video, there's more to be had. Sector times suggest that I was tracking for a 2:04 on the last lap...

Car feels absolutely amazing though. I brought the wrong tools, so wasn't able to disconnect the rear swaybar to see if it improved drive out of the corners, but this video was all done with the DSC off and I'm just floored by how neutrally the car handles now. I'm still going to disconnect the rear sway next time out, should be interesting. It's very responsive, just goes where you ask. The tail will come around slowly if you're heavy with the gas. The brakes modulate really nicely now with the brass bushings / steel lines, and they don't fade at all, and again as you can see they're still locking up the 265 sections, so I don't need any more brake at this point.

I need to get more comfortable with keeping it planted for longer, and I really think the car needs to lose a few hundred pounds / gain a few horsepower. Exhaust system / CSL airbox / Alpha-N next? Ugggghhhhhhhhh :roll:

And there was zero rub. This is the tire package that the car should have had from the factory.

 

[Fishy Dave]

The report sounds great but I can't see the video? Not sure if the embed Youtube option is working at present?

 

[mattfwalters]

The report sounds great but I can't see the video? Not sure if the embed Youtube option is working at present?

Oh, interesting. I can see the video.

Here it is: Video!

 

[buzyg]

Looking very 8) . Sepang beats even 1M orange for me.

 

[Fishy Dave]

Great video, really clear, well driven, nice track too with lots of gradient. I've just bought Harry's lap timer for my new phone, will give it a tray on track in a weeks time.

 

[mattfwalters]

[youtube]https://www.youtube.com/watch?v=1wTzG00CbrA[/youtube]
https://www.youtube.com/watch?v=1wTzG00CbrA

...and then I took another 4 seconds out of that by disconnecting the rear sway (and, obviously, getting a bunch more practice).

2:02.36, damn. The car is a monster. Now I'm going to have to order splitter / wing and build a diffuser for it. :evil:

 

[Viren]

Looks awesome!

 

[RedUn]

Love it