A vid on the KWs and tweaking for UK roads, should start to get through the vids now that the project has moved along, and better still get to driving it more! 
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Matt’s Road & Track Coupe - Dec-25 update: Cobra Nogaro chairs
- Thread starter Matt Scarbro
- Start date
Got my corner scales back from a mate who borrowed them to set up his racer, have been looking forward to seeing what the Z4 weighs, so it was straight on them this evening.
Expectation was 1370kg, I feared 14xxkg, so this was very welcome indeed!…
Excuse crap absolutely everywhere, I have racking to go up and am making a bench (eventually.
I wasn’t in it so cross weight to be taken with a pinch of salt, but that’s a nicely balanced car right there!
Expectation was 1370kg, I feared 14xxkg, so this was very welcome indeed!…
Excuse crap absolutely everywhere, I have racking to go up and am making a bench (eventually.
I wasn’t in it so cross weight to be taken with a pinch of salt, but that’s a nicely balanced car right there!
A brief update; swapped to the Z4C for a few sessions at the end of trackdays one weekend so it was good to finally get a chance to try it on track. Some footage and impressions:
The short version is that I hadn't swapped the rear road springs out for the KW springs and it was quite disappointing on track, it felt soft and rolly, perhaps more so than I had expected. Granted the other cars I had been driving are more track focused, so not easy for a road car to feel quite as sharp, but the difference was marked.
It will be interesting to get it back to the track with the KW rear springs and the now fitted E46 M3 front ARB, up to 27mm from the 24mm 3.0 SE item. I do have a 30mm Hotchkis bar ordered, but God only knows when that will arrive...
It's a long term project and I didn't expect it to sparkle, what it did do very well at the track is air condition me, which was very welcome indeed, and was a lovely thing to drive to and from the track... attributes than cannot be under-valued, especially when the ultimate goal is trackdays with 10 hours of driving either side!
The short version is that I hadn't swapped the rear road springs out for the KW springs and it was quite disappointing on track, it felt soft and rolly, perhaps more so than I had expected. Granted the other cars I had been driving are more track focused, so not easy for a road car to feel quite as sharp, but the difference was marked.
It will be interesting to get it back to the track with the KW rear springs and the now fitted E46 M3 front ARB, up to 27mm from the 24mm 3.0 SE item. I do have a 30mm Hotchkis bar ordered, but God only knows when that will arrive...
It's a long term project and I didn't expect it to sparkle, what it did do very well at the track is air condition me, which was very welcome indeed, and was a lovely thing to drive to and from the track... attributes than cannot be under-valued, especially when the ultimate goal is trackdays with 10 hours of driving either side!
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1536Z4 said:Really enjoyed the footage and your thoughts on your current set up and improvements to be made
Of course, always enjoy comparing notes will fellow enthusiasts, I expect we will be at Oulton before the end of the year, although not sure which car is the most likely steed!
damocell said:
Thanks Damo, tyres were driven only by economy, a set of 225/45/17 DMacks with an older than ideal date stamp... but then they were £150 for the set and I'm not chasing lap records. I will fit AD09s when they bring a 225/45/17 to the UK, the current 50 profile won't fit in the arch.
17s is for cost and with a thought for wheel integrity when being greedy with kerbs! :lol:
Another little update, we've been getting to the track lots, in the MR2, MX5 (now with posh metal instead of rust for sills and a clutch that clutches) and of course the Z4...
I was able to pick up a last minute track evening at Cadwell and found time to swap in the KW rear springs that I was so hopeful would make all the difference on track. For the previous track outings I was on the standard spec rear springs that I use on the road and I had found it understandably roly-poly and quite understeery, particularly on corner exit.
Happily the KW rear springs, along with the M3 front ARB helped the Z4 to feel much more at home on track, with it rolling much less and feeling much more communicative and responsive.
However (and I must qualify this by saying the car needs an alignment and I'm idiot for going to track without having done a proper one), this immediately highlighted another shortcoming, there is a disconcerting passive steering from the back, it feels like the toe/camber angles are changing mid corner and it really does steer from the rear at times.
This was to the point of wondering if there was something wrong with it during and after the first session, but I persevered and learned to drive with it, eventually gelling with the car much better than I have before on track. It still feels to me like a road car on track and I guess that's what it is, but I will really enjoy continuing to improve it over the coming months and years.
Pace was fairly good, with a number of spectators coming to ask about the car and one referring to it as the silent assassin... with a standard airbox and exhaust it was carving its way very quietly past the other cars!
As well as the need for alignment, I'm of the mind that the rear trailing arm bushes are the culprits for the exciting handling, so I think I'll fit some black series Powerflex bushes to limit this as much as possible. It does have RTA limiters already, but I think it's asking a lot of them and standard bushes when pushing on with semi-slicks!
I do have a set of very sexy RTAs in the garage with all Millway solid bearings, but as the car is used plenty on the road at the moment, I will save them for it's retirement to mostly track work.
I've also been toying with the idea of a thicker rear bar, coming to the conclusion that should the Hotchkis front bar ever arrive I'll be needing something to maintain the balance.
Finally a bit of raw footage from the TD, I've not made a vid about this day, but thought some might appreciate even just the raw lap or two.
I was able to pick up a last minute track evening at Cadwell and found time to swap in the KW rear springs that I was so hopeful would make all the difference on track. For the previous track outings I was on the standard spec rear springs that I use on the road and I had found it understandably roly-poly and quite understeery, particularly on corner exit.
Happily the KW rear springs, along with the M3 front ARB helped the Z4 to feel much more at home on track, with it rolling much less and feeling much more communicative and responsive.
However (and I must qualify this by saying the car needs an alignment and I'm idiot for going to track without having done a proper one), this immediately highlighted another shortcoming, there is a disconcerting passive steering from the back, it feels like the toe/camber angles are changing mid corner and it really does steer from the rear at times.
This was to the point of wondering if there was something wrong with it during and after the first session, but I persevered and learned to drive with it, eventually gelling with the car much better than I have before on track. It still feels to me like a road car on track and I guess that's what it is, but I will really enjoy continuing to improve it over the coming months and years.
Pace was fairly good, with a number of spectators coming to ask about the car and one referring to it as the silent assassin... with a standard airbox and exhaust it was carving its way very quietly past the other cars!
As well as the need for alignment, I'm of the mind that the rear trailing arm bushes are the culprits for the exciting handling, so I think I'll fit some black series Powerflex bushes to limit this as much as possible. It does have RTA limiters already, but I think it's asking a lot of them and standard bushes when pushing on with semi-slicks!
I do have a set of very sexy RTAs in the garage with all Millway solid bearings, but as the car is used plenty on the road at the moment, I will save them for it's retirement to mostly track work.
I've also been toying with the idea of a thicker rear bar, coming to the conclusion that should the Hotchkis front bar ever arrive I'll be needing something to maintain the balance.
Finally a bit of raw footage from the TD, I've not made a vid about this day, but thought some might appreciate even just the raw lap or two.
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1536Z4 said:
Oh how I wish it was Sepang Bronze!!... the golden hours doing wonders! 8)
I don't expect to need, nor not sure if possible to use limiters with the Powerflex bushes, will seek guidance from them.
Matt Scarbro said:
Enjoyable read and enjoyed the video too!
Man, I miss that howling straight six induction sound in the cabin. Dare I say, I prefer it to the Z4M even with the GruppeM airbox I had on. It's such a screamer that N52 once you take the foam out. Loved it
1536Z4 said:I would be interested to here what they say
Will let you know what they say, expectation from visual inspection is that they essentially leave no room for limiters filling the space they would occupy. And therefore deeming them unnecessary.
1536Z4 said:Matt Scarbro said:
I would be interested to here what they say
Some info from Powerflex on the poly RTA bushes:
“Yes, that’s correct. Using limiters with our bushes would completely block up the angular motion of the trailing arm which isn’t a good idea.
A limiter will stop the rubber bush and arm from moving around laterally, but because of the softness of the rubber it will still allow fore and aft compression in the bush.
Our bush prevents the fore and aft movement, while allowing a required range of motion which is most important.”
Look forward to getting them in, along with an alignment.
Vanne said:I enjoyed that video immensely, nice driving, the car looks to be very loose in the front end? Really nice controlled driving.
Thanks for the kind words Vanne!
With the caveat that there was no setup much beyond it being ‘by eye’ and acknowledging that is never going to produce the best results…
At the front, it felt like it needed a chunk more camber, I’d love to be able to share figures, but I don’t have any.
I have fixed camber plates on, though suspected the camber wasn’t where it should have been. I’ve taken it apart again, slotted the camber adjustment in the strut top further and also slotted the strut brace. It looks like there was one hole in the strut brace that was restricting camber and a large washer that fouled another part of the strut brace. I’m hopeful that after some thought and changes, I should be at about -2* each side.
Not optimal for track still, but should be an improvement and a nice road and track compromise.
I also think the car will benefit greatly from some further stiffness, by way of ARBs or springs, it feels quite slow to react compared to other cars I’m used to driving.
But this one is nice to drive to and from the track and I don’t want to compromise it too greatly, so it will be ARBs that I explore before stiffer springs.
1066 Country
1536Z4 said:Abbas said:Matt Scarbro said:
I have the Polybush black fitted so am still interested to see if you think they are better than limiters as there seems to be a divide on which is better .
I've been running both RTAB poly bushes & limiters since about 2020 on my MC.
Was told it was a very tight squeeze to get them in, but rid it of its pendulum @rse swing.
Also suggest consider getting the 3 diff bushes done, again something that just tightens everything up