Z4C...attempting to go from write-off to race car

[Toppy]

Progress has been slow on the zed, 2 weeks holiday got in the way of doing much more researching. Eventually, I ordered a new ignition switch just to give a cheap fix a try...to no avail.

Decided it must be the starter motor so got one ordered from Germany. Covid seems to have slowed order processing and delivery, so required a 2-week wait. Whilst waiting we decided to tackle the gearbox on the EnduroKA to change for one from an aircon car with a slightly better ratio. Wasn't too tough between 3 of us, but was a grubby day working on a gravel driveway.



Finally, the new starter arrived this week along with a few more tools to help me try and get to the bolts, so got to that this morning with the help of PDB's thread https://z4-forum.com/forum/viewtopic.php?f=3&t=97004&p=1774184&hilit=starter+motor#p1774184. I can confirm it was a pain in the ass to get it out and definitely required some foul language. The new one went in pretty easy which made up for the grazed arms, and hey presto the car now starts.





With that sorted I got an oil change done and took it out for a quick spin round the block. The engine seems to run sweetly, but the next thing to investigate is a clunk coming from the rear suspension going over speed bumps. Hopefully, it'll just be a knackered bush or loose nut somewhere, any suggestions welcome though!

I was hoping to get it out for a first track day at the end of Oct just with some brake upgrades, but that might be a long shot depending on the suspension issue. Either way, I'll be getting a stud conversion sorted soon and finding a second set of wheels, as well as finding a local body shop to straighten the front wing and repair 2 alloys.

 

[TheDan]

With that sorted I got an oil change done and took it out for a quick spin round the block. The engine seems to run sweetly, but the next thing to investigate is a clunk coming from the rear suspension going over speed bumps. Hopefully, it'll just be a knackered bush or loose nut somewhere, any suggestions welcome though!

Typically the most common causes of knocking on the rear are (most common first):

• Rear springs broken

• Play in RTAB

• Damper top mount (only if knackered or changed to versions known to knock)

• Play in stab (drop) link bushes

I have had 3 of these 4 happen to me! :headbang: Let me know if you find it and its something else.

 

[Toppy]

TheDan you are indeed correct. Had a spare 10 mins today to have a look...both rear springs have snapped...





I was going to leave the suspension for now and just get it out on a track day fairly stock, but I guess that plan's over and I'll get some coilovers on order.

Current top of the list is a set of Gaz Golds with adjustable top mounts, but any other recommendations welcome for track use.

 

[Toppy]

Well, that's been a while since the last post. Most of the time in October went on the EnduroKa getting it prepped then racing in the season finale Indy 500 at Brands Hatch. That was a day/night race in cold and damp conditions but was awesome fun and just nice to get out with friends. We qualified poorly in p31 but dragged it up to p10 at the end which felt a pretty decent result and a nice way to end the year.





With that put to bed, the attention could turn back to the zed. Next on the agenda was to sort the front wing and both driver's side wheels which all took a knock when it was written off. The car went off to Kudos Bodyworks http://www.kudosbodyworks.com/ to get them sorted - not bad at £210 for the wing and £50 for each wheel. Anyone in South London needing work doing, I can highly recommend Marcus...they do a good job and are great value.



That saw the zed now back to a roadworthy condition having been written off as a Cat N - all repairs done for sub £400, not bad really.

With the rear springs snapped I decided I'd get on with getting suspension ordered & making a start. Having spoken to Gaz I decided on a set of their monotubes of the same spec as the BMW 330 challenge cars, but with spring rates and adjustable top mounts for the Z4. They're not cheap at just over £2k, but given I plan to race the car felt like the best option and sure look and feel quality.



Whilst on this I decided it was also worth replacing the front control arms as well as upgrading the bushes. For bushes I decided on superpro, with caster offset for the front as they did these in a kit with some of the rears.

Whilst I was waiting for the coilovers to arrive I set on removing the control arms and replacing the bushes. I don't have any experience with bushes, so borrowed a press of a friend, and promptly failed to remove them despite it having a 6 tonne jack. Smashing them with a club hammer didn't do a great deal either. After a weekend of swearing I decided to replace the jack in the press for a 15 tonne version, and low and behold it worked and I could remove the old bushes and press in the new ones.











With that done, the coilovers arrived so I could start on the install of everything. This was all fairly straight forward but I still managed to make a few cock-ups along the way. The most awkward part was getting the nut tightened on the driver's side control arm where the engine mount is directly above it. But nothing a bit of patience, grazed knuckles and swearing couldn't sort.



Whilst doing this I realised the ARB links wouldn't likely fit, so got some adjustable Roadnutz ones ordered from https://www.spring-loaded.co.uk/. Whilst there I spotted they were selling the H&R ARBs about £100 cheaper than I'd seen anywhere else so decided to get these ordered as well.







With that done I decided to change the driver's side steering tie rod as the passenger side had been done as part of the repair and ensure alignment could be done easily. Annoyingly whilst torquing up the arb brackets I managed to snap one of the studs, so need to come up with a gameplan to sort that.

I dropped the car down today - it's in serious need of both alignment and a geo setup - the steering is completely pissed, and the camber is very different on both sides.

That's where it's got to so far, next I'm planning on sorting the rear bushes and coilovers, then it'll be on to brakes before I take it for a full geo-setup, hopefully in time for some track days in Feb.

 

[M340]

Loving the thread and saving this car. Following with interest!

Saw your post about Kudos Bodyworks. How do you rate them? They’ve quoted me for some work and are considerably cheaper than the other two quotes I’ve had, wondered how you found the repair?

Cheers

 

[Toppy]

I've used Kudos twice now and been really impressed. The work hasn't been major - mainly small dents & scratches as well as wheel refurbs but the quality has been excellent and cost low. He used to work on people's driveways but has a unit with spray booth now which can only have helped on quality.

 

[Liam22]

I don't have any experience with bushes, so borrowed a press of a friend, and promptly failed to remove them despite it having a 6 tonne jack.

They're a bugger, aren't they. Mine took 8t of pressure to budge the old bush sleeve.

I'd love to know what the optimum drop link length is for the Gaz monos. I went too short and bent the tabs over.

 

[Toppy]

It's been a frustrating few weeks over Christmas with the weather not playing ball and not having a garage to work in to keep me dry. Finally, it's stopped raining so I've managed to get going with the rear end.

First up, to replace the RTAB for superpro ones. I found the Pelican parts guide the most helpful, but the first side still took me a good while and I managed to break the 12mm bar in my bush kit whilst doing it :x . Despite all the practice I'm getting at doing bushes at the moment I don't think I'll ever really enjoy it.


Bushing kit setup


Nearly there


Apparently it took me this many tools for one bush!


New one finally in

Fortunately having spent a couple of days on and off doing the first side, the other one was done start to finish in about an hour. After that I set about taking the boot trim apart to get to the rear top mounts ahead of installing the rear coilovers. I've decided not to both putting any back as it'll get fully stripped at some point.



With that done I got onto installing the rear coilovers, definitely one of the easier jobs I've done so far, and finally get the broken rear springs off the car.



With that sorted and bit of time left this weekend I decided to get the H&R rear ARB on there. It was a bit of a pain getting the old one off, and of course required removing and replacing bushes on the links, but the install was surprisingly simple.


Old bushes out of links & new ones pressed in


New ARB on

Next up I'm going to need to have my first go at alignment as its completely out, then I'll be needing a couple of sets of tyres. The car came with completely shagged tyres so these will go for Michelin PS4s for road & wet track use, I'm not decided on dry track tyres yet. I've mainly used Toyo R888s in the past but they cost a fortune in these sizes, so any other recommendations much appreciated.

I'm amazed at the weight of the MV2 wheels, but I'm also not keen on spending £1k+ on a set of lightweight wheels just yet. A bit of research showed the MV1s are a kilo lighter, so I picked up a set of these off ebay for £150 over christmas. I'm not keen on the look, but don't really care too much as they'll only be used on track.

I've also got brakes on order - just some new OEM discs, Pagid RS29 pads, HEL lines and some racing fluid, so once that arrives that'll be up next, followed by an MOT and a geo setup. Hopefully that should keep me on track to get it out when track days are allowed again!

 

[Z4C_er]

I may have asked you this before, but if you have subwoofers and are going to strip out the interior, could you let me know when you'd like to sell the grilles please?

 

[Toppy]

I may have asked you this before, but if you have subwoofers and are going to strip out the interior, could you let me know when you'd like to sell the grilles please?

Sure thing. Are there different audio system specs? There are 2 speakers with round grilles behind the seats...does that sound like what you're after? If so, I reckon I'll be doing full interior strip in 3 - 6 months depending on how the year pans out

 

[Thrustyjust]

Could be up for the boot nets if you do

 

[Toppy]

Only got a brief bit of time on the car this weekend, which was spent trying to do my first DIY alignment/camber setting. Having changed both steering tie rods to go straight meant having the steering wheel 90 degrees to the right

I bought a cheapo camber gauge from Amazon, then got some string going front to back. Its a massively unscientific approach given my driveway isn't flat, but I was just hoping to get it somewhere close so it felt OK to drive somewhere for a proper geo.





To sort the camber meant taking both front struts off to get at the adjustable top mounts, but was then relatively simple to sort - I've managed to get both sides around 2 degrees negative camber now.

On the alignment, the passenger side wasn't too bad - just toeing out by a couple of mm. The driver's side was another story - it was toeing in by a whopping 73mm! No wonder it felt a bit pissed.



Managed to get them to a point where they are toeing out by 1 - 2mm on each side and took it around the block - hey presto it'll actually drive straight with the steering wheel centred now. It's not perfect, but at least it feels safe enough to drive somewhere to get the geo done properly.

Next up, hopefully the brakes - I've got new discs, lines and fluid, just waiting for the Pagid RS29 pads to arrive and it'll all be good to go.

 

[Toppy]

Could be up for the boot nets if you do

They've come out already...let me find where I've put them and I'll let you know!

 

[Thrustyjust]

Thanks Toppy, let me know what you want for them

 

[Z4C_er]

I may have asked you this before, but if you have subwoofers and are going to strip out the interior, could you let me know when you'd like to sell the grilles please?

Sure thing. Are there different audio system specs? There are 2 speakers with round grilles behind the seats...does that sound like what you're after? If so, I reckon I'll be doing full interior strip in 3 - 6 months depending on how the year pans out

Thanks Toppy, but no, I'm after two large rectangular grilles. Sounds like you don't have the subbies. Thanks anyway!

 

[Toppy]

Been quite a while since the last update...progress has been slow due to bad weather, work, lockdown and general laziness.

Finally, I got round to sorting out the brakes - I have swpapped lines for HEL braided ones, new OEM discs and Pagid RS29 pads, followed by a full flush of RBF660 brake fluid.




After this I wanted to do the water pump and thermostat as there was no history of them having been done previously. I managed to get some these delivered from Poland at a decent price <£300 for both, including the Pierburg OEM pump. The swap was easy, but I did struggle to get the system filled again without airlocks to allow the bleeding process to happen. A good bit of faffing later and a fair bit of coolant split on the driveway got it going.




The car has now spent the last week at Abbey Motorsport. I managed to shear one of the ARB bracket studs a while back and depsite my attempts to resolve using a rivnut, couldn't get it sorted to my liking. Abbey have now welded in a nut, and then done a full geo setup for me - ride heights, alignment, camber and droplink lengths to get the suspension pre-load done.

I've just had a set of Nankang AR1s delivered, so next up is an attempt at refurbing the front 2 spare set of MV1s I've got and getting them fitted.


Hopefully, all in time to get out on track at Donington Park in April!

 

[Liam22]

Good progress. I'd be interested to know what length your front ARB drop links ended up at.

Did you run the water pump auto-bleed cycle? I've found it to be pretty reliable. Ign pos II, WOT for 10s.

 

[Toppy]

I got the auto-bleed to run, my issue was getting the new coolant far enough around the circuit first for that to work...got there in the end.

I'll take a wheel off and have a measure of the droplinks for you next weekend.

 

[Liam22]

Thanks! FWIW, after starting out too short, I've now ended up with 200mm drop links from a Proton!

https://www.ebay.co.uk/itm/233715926533

 

[Tanel]

What are the advantages of an offset bushing?