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First track day completed at Donington Park yesterday in the Z4. My initial thoughts:

• It still feels bloody good on track

• The noise is lovely but too quiet. Won't help me go any faster, but fitting the exhaust in my garage is next on the list, as is an induction kit

• It feels quite wallowy. I started the dampers on a mid-setting and was shocked at how soft it felt. Ramping up to full hard made it better but still not brilliant - perhaps some higher spring rates need exploring

• Traction control is too officious...even switched "off"

• The brakes need some better cooling...a couple of times they came back in smoking. No fade with the RS29 pads but obviously getting very hot

Overall it was a great day - the car was comfortable to drive the 150 miles each way, and took 250 miles of track work in its stride with no issues.
The rear bumper melted a bit around the exhaust so I'll enlarge the cut-out slightly when I fit the new exhaust.

It'll likely remain in this format for a while and a few track days whilst I research lsd's and summon up the strength to drop the sub-frame and sort that.

Great update, really appreciate you sharing the journey with us all.

Can I ask some stupid questions (understand if you don't want to answer)

1 - What did it cost you to do the day?
2 - Do you wear a helmet?
3 - What do you do for fuel? Fill up before?
4 - Did you take any spares? Wheels etc

Really enjoy updates, keep them coming.

Kind regards

Chris

Congrats Simon!

The car likes to be stiff. Did you adjust your fancy ARBs?

For the traction control, the E86 has a later revision of the MK60 DSC unit. Unlike earlier models, off does not mean off. Try disconnecting the steering angle sensor to kill the DSC while retaining ABS. Pulling any of the ABS fuses will kill both ABS and DSC.

Swampy1982 wrote: ↑Thu Apr 08, 2021 2:10 pm Great update, really appreciate you sharing the journey with us all.

Can I ask some stupid questions (understand if you don't want to answer)

1 - What did it cost you to do the day?
2 - Do you wear a helmet?
3 - What do you do for fuel? Fill up before?
4 - Did you take any spares? Wheels etc

No problem Chris, answers below:

1. I think the day was £250, but I went in a group of 4 with 2 cars between us, and we used an MSV voucher so it won't have cost me anywhere near as much.
2. Yes. I have full race kit, but for a track day just normally use helmet, gloves and boots.
3. I filled up outside the circuit when I got there & Donington has fuel on-site so filled up during the day rather than taking jerry cans.
4. I filled the Z4 up with tools & had the luxury of a friend towing our EnduroKA and put my spare wheels on his tyre rack.

Liam22 wrote: ↑Thu Apr 08, 2021 3:35 pm Congrats Simon!

The car likes to be stiff. Did you adjust your fancy ARBs?

For the traction control, the E86 has a later revision of the MK60 DSC unit. Unlike earlier models, off does not mean off. Try disconnecting the steering angle sensor to kill the DSC while retaining ABS. Pulling any of the ABS fuses will kill both ABS and DSC.

Thanks Liam, it felt good to get it out on track for the first time and that nothing broke having put it all together!

I didn't get to the ARBs, just the damping - I was jumping between the z4 and the KA so didn't really get much time to worry about spannering and setup. Next track day I'll make sure to get to them and the steering angle sensor!

Toppy wrote: ↑Thu Apr 08, 2021 5:28 pm

Swampy1982 wrote: ↑Thu Apr 08, 2021 2:10 pm Great update, really appreciate you sharing the journey with us all.

Can I ask some stupid questions (understand if you don't want to answer)

1 - What did it cost you to do the day?
2 - Do you wear a helmet?
3 - What do you do for fuel? Fill up before?
4 - Did you take any spares? Wheels etc

No problem Chris, answers below:

1. I think the day was £250, but I went in a group of 4 with 2 cars between us, and we used an MSV voucher so it won't have cost me anywhere near as much.
2. Yes. I have full race kit, but for a track day just normally use helmet, gloves and boots.
3. I filled up outside the circuit when I got there & Donington has fuel on-site so filled up during the day rather than taking jerry cans.
4. I filled the Z4 up with tools & had the luxury of a friend towing our EnduroKA and put my spare wheels on his tyre rack.

Top man, thanks a lot.

Time to get my suspension sorted for my first track outing! (Still waiting for dampers, bleeding brexit borders! )

Well, that was a long hiatus since the last post. Since April the car has just sat on my driveway gathering dust, leaves and cobwebs. It seems trying to run a race car whilst building another one is pretty difficult as all my time has gone on the EnduroKa. I've had a new exhaust and parts to sort brake cooling in my garage for months now that haven't seen the light of day.

After mulling over selling the zed, I've decided it's time to crack on and get it going and de-prioritise the EnduroKa otherwise I'll never get there. With that in mind I decided this weekend was time to drop the rear subframe so I can sort all the rear-end bushes, get the diff swapped for an LSD and then put on the new exhaust.

This is definitely the biggest job I've tried myself and was a bit daunting at times. Ultimately it wasn't that hard once I'd figured out that I'd have to disconnect the handbrake at the shoes rather than in the car so I could pull the cables clear of the frame.


Start of disassembly


I used a trolley jack to lower the whole unit in one go


All out


And pulled apart

Next job is to get the blowtorch on the go and remove the bushes and replace them with the superpro ones I have, restore and paint the subframe and then the tough decisions on what LSD to go for.

Wow good job!

I am following this section closely as this is my next job to do and I am not particularly looking forward to it!

I have already decided that I will be going for a Quaife LSD, but still potentially debating a Kaaz 1.5 way LSD.

Hope you get all the bushes out nice and easily!

Cracking build - I'm rather envious of you just getting on with it yourself - kudos!

A couple of questions/comments if I may -

1. with the Traction control - did you press and hold the button for 3-5 secs to fully turn it off, or did you just have it short pressed into DSC mode? I only ask because on my old 3.0si I never felt it intervening at all when I'd long-pressed the button to turn it fully off!

2. I note you're running a true coilover at the rear - have you reinforced the rear mounting points to accommodate this? I've got Intrax coilovers on mine, and these were in some previous specification a true coilover at the rear, however I understand they were rather quickly changed back to divorced spring and damper per the OE set-up as the OE top mount mounting point is quite thin and just isn't designed to be the sole load point for the suspension... I'm happy to be told I'm wrong though (and I somewhat hope I will be, as I'd like to go back to true coilovers myself to be quite frank!)

Also, I'm I was up at Donny on 7th July for an evening session and there was a black coupe going rather well at the end of the 'day session' - I'm guessing it can't have been you if yours hadn't moved off the drive since April thouh?!

Hi Ed,

Yes, I held the TC button down to try and switch it off fully. It was very noticeable that it was still on - mainly holding back power on corner exits. As Liam has pointed out on here, the steering angle sensor needs disconnecting for it to be fully off - fitting a switch is on my list of things to do.

I've not done any re-inforcing of the rear mounts at the moment. I wasn't aware of this as an issue, but when I get a roll cage installed will get them to pick up the rear points to add strength.

It definitely wasn't me at Donny...the car has firmly been sat on my drive!

Toppy wrote: ↑Tue Sep 14, 2021 1:26 pm Hi Ed,

Yes, I held the TC button down to try and switch it off fully. It was very noticeable that it was still on - mainly holding back power on corner exits. As Liam has pointed out on here, the steering angle sensor needs disconnecting for it to be fully off - fitting a switch is on my list of things to do.

I've not done any re-inforcing of the rear mounts at the moment. I wasn't aware of this as an issue, but when I get a roll cage installed will get them to pick up the rear points to add strength.

It definitely wasn't me at Donny...the car has firmly been sat on my drive!

That's very strange! I'll admit (very very quietly) that 'someone' managed to go slidey-slidey round a roundabout a couple of times shortly after I got a Quaife diff installed in my old 3.0si. Also separately the same irresponsible 'someone' managed to spin it in the wet very early one morning on a roundabout. (Note: both of the above somewhere south of the Mexican border...obviously)
More importantly for the purposes of this thread, there was absolutely no intervention from the systems in terms of power being cut - very odd! Mine was a 56-plate car, but I presume that would have made naff-all difference to the engine management installed?

On the subject of reinforcing the rear strut tops, you can get Reinforcement Plates but I presume this is more to reinforce just the damper mounts, not specifically tailored to coilover fitment.

The thing I'm struggling with is very few people have gone for a true coilover in the past - so there's very little in the way of people with direct experience going "yep, screwed my top mounts" or whatever. Makes it awfully difficult to figure out what is best to do! Keep an eye on them and let me know if you spot anything untoward!


you sure the wife didn't nick the car for the day?

my car is the same with a Quaife diff, long press of the traction button and absolutely no interference with the traction control. skids for days

Glad it's not just me then

Just revisiting the subject of true coilovers at the rear - I've been in long discussions with the UK Distributor for Intrax, who supplies multiple race series as well as having direct experience running true rear coilovers on a number of BMWs owned over the years - with no issues at all.

I guess this was the excuse I was looking for, but having also had a really good inspection of my rear top mounts (which are immaculate despite having true coilovers fitted for ages and multiple trackdays & ring trips under previous ownership), I'm going back to true rear coilovers

Ed, I'd give the boys at intrax themselves a call in Holland mate, very cool bunch of guys and extremely knowledgeable, I'd imagine any distributor just wanting to move units mate,your better off getting it from the horses mouth.

Ive had a long good close look at those shock towers at the rear, and there ain't much metal there.. deformation would definitely be on the path with no re-enforcement.

Op, great job tackling that yourself, your well on the way now man, keep at it. Can't wait to see what your plans are and how it comes together.

Vanne wrote: ↑Sat Feb 26, 2022 5:46 pm Ed, I'd give the boys at intrax themselves a call in Holland mate, very cool bunch of guys and extremely knowledgeable, I'd imagine any distributor just wanting to move units mate,your better off getting it from the horses mouth.

Ive had a long good close look at those shock towers at the rear, and there ain't much metal there.. deformation would definitely be on the path with no re-enforcement.

Op, great job tackling that yourself, your well on the way now man, keep at it. Can't wait to see what your plans are and how it comes together.

To be fair Vanne is it a Motorsports company who are the sole distributor for intrax in the UK, and who supply at least one of the UK BMW race series... They did also say its entirely up to me as they can do a divorced spring and damper if I want, but they recommend the true coilover, citing direct experience with various chassis for both trackdays and racing where true rear coilovers for many thousands of miles with no ill effects.
Looking into it as much as I have been able to, I do struggle a bit with the theory the rear towers will deform, they are no thinner than the fronts (which are 'coil over spring', and which have the engine hanging over them too! The only evidence I've seen of failure in the rear strut towers appears to be anecdotal. I'd love some conclusive evidence either way, thus far the only actual first hand experience I have is the fact my car did have true intrax rear coilovers fitted for a period of its life during which it did various ring and spa trips and UK trackdays, apparently with no ill effects. It was then converted back to divorced spring and damper by a subsequent owner for apparently the same anecdotal reasons mentioned above. Rear coilovers would be heaps easier to setup in terms of corner weighting , and a bit lighter too, so definitely my preference if possible!