Buying a Z4 to use on track - A few 'pre-purchase' questions...

[DaveP]

Hi folks

After much procrastination/deliberation, I've decided that I'm going to buy a Z4 in the coming months (looking for a winter bargain) to convert to a fast-road/track toy. For context, it needs to be fun on track without being the last word in uncompromising ride and comfort on the road (e.g. I'll be using 17s).

I've done my due diligence in most respects, but I'm struggling a bit with a few last questions. Hopefully the collective wisdom will be able to help...

* I'm likely to get into an earlier 3.0 (which I'm fine with), but the model derivations/options seem to be confusing. Is there a de facto source?
* Looking at suspension upgrades, I really won't get much benefit from uber-adjustable coilovers. Are there any decent fixed-rate or adjustable kits out there?
* What other chassis upgrades (e.g. ARBs, bushes) are recommended to tighten up the handling a little (without ruining it on the road)?
* Are there any easy brake upgrades? I'd planned on fluid, pads, discs and hoses - but I'd be happy to raid the BMW parts bin for more stopping power.
* I want to replace the driver's seat with a lower, fixed bucket, but I'm on the larger side (~100kg/6ft3). Do any of the larger buckets (e.g. Corbeau Sprint XL, Sparco Evo III) fit? Is there an accepted maximum width for the base and shoulders?
* I'd ideally like to run a square tyre setup on track, hence slightly favouring the 17s. Has anyone attempted to run a square 225 setup on the staggered 18s (because I much prefer the way they look, but 255s are massive overkill)?
* Has anyone added a shift-light to their Z4? Google isn't suggesting much...
* Is there any way to replace the (hideous) standard stereo in a way that doesn't look like it was fitted by a Blue Peter presenter?

Cheers in advance!

 

[Marius]

here's what i got ,all parts waiting in the garage :lol:
fully adjustable coilover (must for the track)
6 pot brake upgrade
eibach anti roll bars
extra strut brace at the front
18x8.5 245 semi slicks all round .
powerflex bushes

had similar set up my old z4 and it was proper fun on the track .

 

[DaveP]

Cheers for the reply! But, I feel like we might be coming at this from slightly different angle/budgets...
Keen to hear how you arrived at your decisions, though - as it may help me refine my approach.

Do you think the standard brakes are weak enough to justify the upgrade? I assume they are the same kit I've got on my 330ci, which stop 1500kg absolutely fine, but struggle with fade.
Did you consider any non-coilover kits? What sort of setup changes will you be making to require coilovers? Will you be substantially changing geometry between track/road? This isn't a daily for me (I go to work on the Tube), and I don't think it would need to be 'slammed' to run well on track (in fact, I'd rather something more 'pliant').
Do you think that 245 might be over-tyred for a 1300kg car with 220bhp? I've run much more powerful road cars on 225s without too much issue.

 

[ga41]

Are you that dead-set on a Z4? There's not THAT much of an aftermarket scene for our cars sadly. Especially if you're on a budget. A Honda S2000 is lighter and with about the same power, if not more, than an early 3.0 Z4, with less torque though and is very track worthy out the box. The parts scene is miles better than the Z4's as well.

If you're decided on a Z4 though i'm sure plenty of users will come along shortly to offer advice! Perhaps have a browse at the Z4 section on www.turnermotorsport.com for inspiration on parts availability?

 

[DaveP]

To tell you the truth, the decision was fairly drawn-out. The S2000 was considered, along with a plethora of alternatives. The S2000 was ruled out on the basis of cost. There just doesn't seem to be the same choice available at the bottom end of the market (where I'd be buying). And, for better or worse, I didn't love the S2000 enough to chuck an extra couple of grand at it.

 

[Marius]

Standard brakes fine on short tracks. I'm building mine for the ring. Standards brakes only good enaugh for half a lap witch not ideal lol. 245's because it's widest I can fit to 8.5's

 

[DaveP]

That's really interesting.

I'm coming at this from the other end, I think. I'm purposely going with slightly narrower tyres in the hope that I can generate a bit of 'play' and compliance in the chassis, rather than looking for outright grip (I had an MX5 a long time ago, and loved being able to overcome the grip with the throttle). Although, I suppose if I was hunting Nurburgring times, rather than thrashing around Snetterton, I might well be looking for more grip. Having said that, I recall reading about a chap setting up his E36 M3 for the Ring, and he was advised that a square 225 setup might be best for him. Horses for courses, I suppose.

Braking is a really interesting one. If you're significantly (+50%) increasing the swept area (larger discs, bigger pad coverage), that will definitely have a big impact on their ability to stop consistently and repeatedly. However, even upgrading the stock kit to a decent friction compound (DS2500/3000) and cross-drilled discs should give you a massive improvement. I think I'm going to go down the latter road, and give the former some consideration at a later date - what setup did you go with?

 

[Artful-Bodger]

Just how "fast road/track" are talking here?
Is it going to be used as a day to day car at all or a weekend funster?

 

[Number5]

If it was for the track only, I'd consider starting with a CAT D car and saving yourself a fair bit, which would then allow you more for the enhancements. There are loads for sale on the internet.

There's nothing wrong structurally with a CAT D car, and if its then been modded for track use, re-sale value will never be a concern to you anyway

 

[Yorkie Z]

First and foremost if you want to enjoy the car properly fit an LSD. Then start on the rest of the mods.

 

[Brian H]

* Has anyone added a shift-light to their Z4? Google isn't suggesting much...

Not a Z4 but have a shift light on my Z3 with a M54 engine (which I believe the early Z4s had), the shift lights wire into the coil pack harness and you can set the rev range, limits etc for your car.

The kit I bought was one of these.



https://ecliptech.com.au/shift-i/

Cheers

Brian

 

[Ed Doe]

Can I ask a question first and foremost; how many trackdays have you done before?

I'm not quite in the same boat, but doing my first trackday in the zed in a couple of weeks. Aside from e46 csl geo set-up, my current spec is as per my sig below.

I reckon my next mod will be an lsd and depending on how I get on with the brakes they'll possibly follow on afterwards...

The general advice I've had so far though is to get on track with the car as is first and foremost - don't mod/change/spend money on anything else, and actually see how the car feels, and what you think needs doing. No point in spending thousands on an epic brake set-up if you spend the first 5trackdays learning the car and yourself and therefore not finding the limits of the stock set-up.

I do have to echo the comments of others too - the S2000 is a friggin amazing car for track work out straight out of the box, and something I still have a hankering for....

 

[ga41]

...The general advice I've had so far though is to get on track with the car as is first and foremost - don't mod/change/spend money on anything else, and actually see how the car feels, and what you think needs doing. No point in spending thousands on an epic brake set-up if you spend the first 5trackdays learning the car and yourself and therefore not finding the limits of the stock set-up..

I agree with this! Try and do some track-time with the car stock, ideally with some proper tuition if you're not an experienced track driver. Thinking back to my experiences when I started tracking it, a lot, if not most of my brake woes would be sorted with improvements in my driving technique instead of upgrading brake lines, pads and fluid which I went ahead with.

 

[DaveP]

Hi guys

Thanks so much for all the replies. For context, I should probably explain that I've already got a dedicated track car alongside my 330ci - a stripped, bucketed/harnessed, tuned 206 gti.
After driving 3hrs back from the track (Woodbridge) on Saturday evening, I decided that I need something that's a bit less extreme. I can't accommodate a trailer (I live in central London), and am realistic about the fact that I'm a long way from most tracks, so the choice of a Z4 is a compromise and an upgrade. I think I'm going to have a bash at sprinting the 206 next year, so I want something i can use for a few trackdays (hoping to do Spa next year - I couldn't bear driving the 206 there/back).
I don't drive much, as I take the tube to work and my OH has a sensible company Mercedes, so having a sightly stiffer/louder car is no real hardship.

On the specific subject of the LSD, where is the best place to source one? Is it possible to salvage from the BMW parts bin?

Cheers all!

 

[ga41]

Not sure about sourcing from another BMW... the only recent BMW LSD's have been in M cars, the Z4M/E46 M3's would require the whole rear subframe to be transferred if im not mistaken. Not worth the trouble and cost. From earlier cars like the E36 M3? Honestly I have no idea... Hopefully others will have more experience. Otherwise it's straight to aftermarket.

There are a few members on the board with aftermarket diffs, a quick search should provide more information. Maybe this? http://www.birdsauto.com/quaife/search?m=bmw&s=34027&mi=Z4+3.0i

 

[Ed Doe]

M factory and Quaife are what people tend to go for diff wise. I'm looking at Mfactory at the moment...

 

[bony_13]

1) Powerflex Rear Trailing Arm Bushes (RTAB's) have built in limiters which really help reduce lateral movement out back.
2) Powerflex Front Lower Wishbone Bushes (lollipops) will tighten up the front end and help feel.

Two of the best value modifications you can do in my opinion, I run both on my Z4 and no diference in ride quality but noitcable improvemnt in handling. Consider that you are buying a car that is 12+ years old with a fair amount of use and abuse, the bushes will (all over the car not just the two above) have developed a fair amount of play and will be passed their best for your intended use.

 

[DaveP]

Thanks guys.

On the subject of the Mfactory diff, am I right in assuming this would be an import-only job? I can't seem to find a UK distributor.

The bush input is exactly what I was looking for. The car is definitely going to have seen a fair bit of use before I get it, so rather than swapping every single bush in one hit, it's good to know which will have the biggest impact on driveability. Are Powerflex the only supplier of these bushes?

 

[Artful-Bodger]

I made a list up of possible rear bushes and balljoints for the Z4 here - http://www.z4-forum.com/forum/viewtopic.php?f=2&t=90109

It's a contentious issue but Polyurethane is not the ideal material for RTAB locations due to the multiple load axes, new stock bush with limiters is recommend by many race prep companies unless you fancy going down the balljoint route, I will be ordering a set of these for my own car - http://www.bimmerworld.com/Suspension-Steering/E46-E36-3-Series-and-Z4-Rear-Trailing-Arm-Bearing-Kit.html

At the front there are a number of possibilities, right now I am looking at the Z4M offset FCAB, this bush adds more castor which benefits camber change under lock, polyurethane can work in this location as it's working under compression and rotation only, but as my car is mostly used on the road I am keeping rubber for NVH protection.

 

[Yorkie Z]

Thanks guys.

On the subject of the Mfactory diff, am I right in assuming this would be an import-only job? I can't seem to find a UK distributor.

The bush input is exactly what I was looking for. The car is definitely going to have seen a fair bit of use before I get it, so rather than swapping every single bush in one hit, it's good to know which will have the biggest impact on driveability. Are Powerflex the only supplier of these bushes?

I fitted an M factory to my old 3.0 and it transformed the car. All the info you need should be here mate http://www.z4-forum.com/forum/viewtopic.php?t=59340