Liam's Z4C race car project

[JonLeeper]

Great thread... looking forward to hear how you’ll get on... trust you know to poly the RTAB’s & maybe even add RTAL’s

Definitely DON'T poly the RTABS would be my advice! Ruins the handling imo.
Limiters on oem rtabs yes.
I've done both back to back.
GuidoK will be along shortly to tell me I'm wrong no doubt....
But really since #racecar the correct thing is to monoball it.

Another topic almost as divisive as Whippy vs Stubby or Couoe vs Roadster... polying the RTA’s change the way the @rse handles, some love, some loathe & some creak

I've just had all of the bushes replaced on my Z4C with poly. . Mainly the purple road spec but I got Rogue Engineering RTABs. I also had the Rogue rear strut mounts, a b12 kit and new anti-roll bars at the same time. I'm not 100% sure which has made the lost difference ebut the car is transformed.

[Jembo]

Definitely DON'T poly the RTABS would be my advice! Ruins the handling imo.
Limiters on oem rtabs yes.
I've done both back to back.
GuidoK will be along shortly to tell me I'm wrong no doubt....
But really since #racecar the correct thing is to monoball it.

Another topic almost as divisive as Whippy vs Stubby or Couoe vs Roadster... polying the RTA’s change the way the @rse handles, some love, some loathe & some creak

I've just had all of the bushes replaced on my Z4C with poly. . Mainly the purple road spec but I got Rogue Engineering RTABs. I also had the Rogue rear strut mounts, a b12 kit and new anti-roll bars at the same time. I'm not 100% sure which has made the lost difference ebut the car is transformed.

Doing that is about 80% of the way there, the other 20% being the geo & what you’ve done with the front.

Suggest u Check your drop links, especially the rears as they take a lot of abuse, though other than the tie rod ends think ur a long way there

One last suggestion is to consider removing the tailgate in its entirety, replacing it with a fibreglass replica& a monster spoiler - if u remove one of the grass struts you’ll see just how much weight is in it

[Liam22]

Interesting discussion about rear trailing arm options. I've ordered Strongflex sport bushes to replace most of the rear end. PowerFlex black series for the front control arm. Rear control arms will be replaced with adjustable items with spherical bearings.

Started to disassemble the rear today. I'm sure I'm doing things in the wrong order, but I'm slowly getting there. Couldn't believe how much of the boot needed to come out just to get to the damper top mounts. Currently debating whether I can keep the drive shafts attached to the trailing arms when they come off the car. Any guides for this? As usual, the TIS leaves me frustrated.

[Liam22]

Slowly getting to know how the rear corners fit together.

I *am* going to try to keep the driveshafts connected to the trailing arms. Any tips on detaching the cables that route through the trailing arm? Other than that it's about ready to drop.

Still haven't figured out how the rear wheel alignment is adjusted...

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[JDavis21]

Still haven't figured out how the rear wheel alignment is adjusted...

That should become quite obvious once you have the trailing arms and brackets off

Whereabouts in Cambs are you? Happy to lend a hand if there's any two man jobs as I'm quite interested to see the end result!

As for bushes, I'd recommend the Millway Motorsports kit over anything poly - although poly arb bushes will have to do.

Below is my R53 MINI Challenge car that I ran for three years, spherical mountings all round improved predictability no end.

[Jembo]

Some cut the plastic cone head off... especially if u decide to run adjustables on the rear top mounts that I assume you are also replacing.

From watching the guys adjust my rear tracking, seem to remember there’s a bolt directly underneath the hub that does the adjustment

[TomK]

Still haven't figured out how the rear wheel alignment is adjusted...

20190226_161050_HDR.jpg

To adjust the toe loosen the 3 18 mm bolts of the RTAB carrier and then move the wheel. There is a specific BMW tool for this but it's not necessary.
Camber is adjusted on the stock arms via an ecenctric bolt at the hub end of the lca. If you're lowering the car much you may find this range of adjustment is not enough in which case you'll need aftermarket adjustable arms.

[Liam22]

Whereabouts in Cambs are you? Happy to lend a hand if there's any two man jobs as I'm quite interested to see the end result!

As for bushes, I'd recommend the Millway Motorsports kit over anything poly - although poly arb bushes will have to do.

I'm just north of Royston (near Wimpole). Very much hoping that I won't come across two-person jobs, but you're welcome to pop round at any point.

Thanks for the pointer on the Millway Motorsport kit - very nice indeed. I'm on a budget (dictated by the sale of the RX8) so I'll stick the the Strongflex yellow bushes for now and see how I get on with them. The rear control arms will have spherical bearings at the inboard pivot.

Some cut the plastic cone head off...

What plastic cone? For what purpose? I'll wait and see what comes with the coilover/damper kit before deciding what to do with the rear damper top mounts.

To adjust the toe loosen the 3 18 mm bolts of the RTAB carrier and then move the wheel. There is a specific BMW tool for this but it's not necessary.

Ah, thanks - makes sense now.

I won't make any friends saying this, but the suspension design is disappointingly archaic. It's only half a step forwards from my 1989 E30. Especially when compared to the RX8, which has double, unequal length wishbones up front, and proper 5 link setup at the rear. All fully adjustable from the factory. Looks like it's going to be difficult to adjust the rear wheel alignment at home (without a ramp).

But the proof is in the driving, so I'll reserve judgement on that until I get it on track

[JDavis21]

I'm just north of Royston (near Wimpole). Very much hoping that I won't come across two-person jobs, but you're welcome to pop round at any point.

Thanks for the pointer on the Millway Motorsport kit - very nice indeed. I'm on a budget (dictated by the sale of the RX8) so I'll stick the the Strongflex yellow bushes for now and see how I get on with them. The rear control arms will have spherical bearings at the inboard pivot.

Only 10 miles away, I may have to pop over.

I'd prioritise a spherical on the trailing arm front bush, as the polybushes all tend to bind at this point.

I won't make any friends saying this, but the suspension design is disappointingly archaic. It's only half a step forwards from my 1989 E30. Especially when compared to the RX8, which has double, unequal length wishbones up front, and proper 5 link setup at the rear. All fully adjustable from the factory. Looks like it's going to be difficult to adjust the rear wheel alignment at home (without a ramp).

But the proof is in the driving, so I'll reserve judgement on that until I get it on track

You're not wrong, I ran an E36 Compact Cup car for two years which shares the rear axle with the E30's. I'd argue the rear is quite different, but the front is near identical. Certainly way behind the double wishbone setups on the likes of an S2000 or the RX8, but then it still works well!

The toe adjustment is the same as the Mini, which is manageable on the floor with some strings and turn plates

[Beedub]

oh yes... best thead ive seen in a while!! this will be a corker!

[Liam22]

Lots of deliveries today:

Water pump
Thermostat
Front brake discs (Brembo Max grooved)
Big box of bushes!

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[Jembo]

Lots of deliveries today:

Water pump
Thermostat
Front brake discs (Brembo Max grooved)
Big box of bushes!
20190227_193405_HDR.jpg

You could have run a competition of ‘guess the bits’... u never know there could be a market for some of the old parts you’re throwing away

[Liam22]

Made my first purchasing mistake and bought an E46 M3 rear ARB (21mm) not realising that it won't fit. Ho, hum - it'll go straight back on eBay...

I already purchased 21mm rear ARB bushes so thankfully the Ultra Racing rear ARB is the same size. Ordered!

BTW, this will match the E46 M3 cab front ARB (27mm) that I have ready to go on. Shame that BMW has skimped on the ARBs and used solid instead of lighter/stiffer hollow tube.

[TomK]

Shame that BMW has skimped on the ARBs and used solid instead of lighter/stiffer hollow tube.

Indeed. The front e46m3CSL arb is hollow and 31mm or so I think, not sure they fit on a standard Z4 chassis though? Otherwise there's a bunch of hollow aftermarket stuff I'm sure.
What are the restrictions placed for things like this on the series you're entering?

[Liam22]

On the whole, suspension tends to be "free" so long as you are using the factory mounting points. In general I'll start with as much OEM stuff as possible and then optimize it once I get to know the car, how competitive it is, and where to focus my energy (and budget).

Speaking of which…

Got the front control arm bushes removed last night, and prep'd the lollipops for the new control arms.

Pressing out the old arms:

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This 1 13/16" socket (bought from Halfords clearance shelf for 99p) has come in handy more times than I can remember. Turns out it's just about perfect for pressing out 66mm bushes. Still hard work, though - needed 8t of pressure to move them.

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Eccentric aluminium shells for the Poweflex black series bushes. This will push the outboard ball joint further forward in the wheelarch, adding more castor for better braking feel (and quicker self-centre steering).

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