To those that have uprated ARBS, KW, H&R etc

TomK

TomK

Senior member
 West London
Did you reinforce the front mounting points? If not, why not?
I'm considering at some point to try some out, but it's not my preferred route to go down to control roll (but it is the cheapest!) and if I risk ripping the front subframe apart then I might leave it for a while. There have been quite a few failures around the world of this Z4M front subframe when used with aftermarket Arbs according to the internet, anyone on here had issues?
Also any clearance issues with the sump?
Thanks

ETA: mods please move this to the M-specific forum thanks, my bad.
 
I have H&R ARBs front and rear without any reinforcement (although I did reinforce the strut towers when I fitted my KW Clubsports). I considered the risks of using a stiffer ARB, but all the failures that I came across were cars in the US being used for autocross where very high loads would be experienced. Whilst I do use my car for tight, technical tracks, it's nothing like their use. I'll let you know if mine tears itself apart!
 
I have front and rear Ground Control Race Arb's. Both front and rear needed modification to fit, but to be fair, these were one off custom made racing sways for my car. The front did interfere with the sump. But after the required reinforcement , it fit perfectly. Both with adjustable GC end links.

It is very nice :D

not sure about the rear though?? lots of guys i know who track this car undo the rear arb.
 
I put new top mounts on when I changed my springs and arbs to H&R myself and strut brace is oem

Had bmw both do it and go over car with a fine toothed comb all good
All I get and the v bars getting loose and speaking on bulk head:)
 
Fishy Dave said:
Hi Tom,

It probably doesn't help but I fitted a rear Eibach arb and left the front standard. :)
Click to expand...

No not really dave, but thanks :poke:
Out of choice?

BMWZ4MC said:
I have H&R ARBs front and rear without any reinforcement (although I did reinforce the strut towers when I fitted my KW Clubsports). I considered the risks of using a stiffer ARB, but all the failures that I came across were cars in the US being used for autocross where very high loads would be experienced. Whilst I do use my car for tight, technical tracks, it's nothing like their use. I'll let you know if mine tears itself apart!
Click to expand...

Yes I agree it seems to be ones that get used hard, but then that goes hand in hand with someone who runs uprated arbs I'd have thought? It does look like long term metal fatigue causing the issue and like you I do track my car so for me it will be something I'm definitely considering doing should I choose to uprate the arbs. The additional reinforcement plate welded in also seems to avoid any potential sump clearance issues it would seem. It's annoying though that if I were to return to stock the mount points would not be.
How long have you had the bars on the car? Have you inspected the problem areas at all?


Vanne said:
I have front and rear Ground Control Race Arb's. Both front and rear needed modification to fit, but to be fair, these were one off custom made racing sways for my car. The front did interfere with the sump. But after the required reinforcement , it fit perfectly. Both with adjustable GC end links.
Click to expand...

Ok, so you did the reinforcement, and fixed your clearance issues, good to know :)

D4dawg said:
I put new top mounts on when I changed my springs and arbs to H&R myself and strut brace is oem
Click to expand...
erm, not sure what that has to do with the question? Nothing to do with top mounts or springs, I don't want my front subframe arb mounting points look like this, which is what can happen with uprated arbs without reinforcing the chassis there. Look it up on interweb.
IMG00080-20110704-1040.jpg

D4dawg said:
Had bmw both do it and go over car with a fine toothed comb all good
Click to expand...
Ok mate :lol:
 
They've been on the car for about three years and perhaps 60% of the miles I've covered since have been on the track, with the rest divided between motorways, London traffic and country roads. I haven't looked at the subframe recently (I'm now 10500 miles from my car :P ) but the last time I did was within a thousand miles or so and there was no evidence of fatigue (but I do accept that failing may not be obvious until the point of failure).

As for clearance, there should be no issues with the H&R ARBs with stock suspension. Mine fitted with OEM dampers and Eibach springs. However, I had to buy adjustable drop links in order to fit my Clubsports due to clearance issues at the outboard ends.
 
TomK said:
Fishy Dave said:
Hi Tom,

It probably doesn't help but I fitted a rear Eibach arb and left the front standard. :)
Click to expand...

No not really dave, but thanks :poke:
Out of choice?
Click to expand...

Yes, I was pleased to have used purely geometry changes to swing the balance into oversteer but had to add a bit more toe out than I wanted to. Stiffening the rear only with an ARB could help promote oversteer, so I fitted it, backed off the rear toe out and I am still pleased with the balance. I've not tried an uprated front ARB yet. :)
 
Ive got the H&R bars front and rear, I bonded some 5mm spacers to the subframe as per John's design.

If you disconnect bar and lie under the car and rotate the bar up and down you can see the mounting points flexing even with the spacers fitted.
 
BMWZ4MC said:
They've been on the car for about three years and perhaps 60% of the miles I've covered since have been on the track, with the rest divided between motorways, London traffic and country roads. I haven't looked at the subframe recently (I'm now 10500 miles from my car :P ) but the last time I did was within a thousand miles or so and there was no evidence of fatigue (but I do accept that failing may not be obvious until the point of failure).
As for clearance, there should be no issues with the H&R ARBs with stock suspension. Mine fitted with OEM dampers and Eibach springs. However, I had to buy adjustable drop links in order to fit my Clubsports due to clearance issues at the outboard ends.
Click to expand...
Thanks for that, perhaps it's not something to worry about then too much, though I agree to see whether it is failing could be difficult if there are no cracks.

RedUn said:
Ive got the H&R bars front and rear, I bonded some 5mm spacers to the subframe as per John's design.

If you disconnect bar and lie under the car and rotate the bar up and down you can see the mounting points flexing even with the spacers fitted.
Click to expand...
Thanks, perhaps it is something to worry about :lol:
Can you point me in the direction of info regarding the 5mm spacer mod, can't seem to find anything? Sounds like a good option, in that it is reversible, rather than welding on metal? Cheers
Fishy Dave said:
Yes, I was pleased to have used purely geometry changes to swing the balance into oversteer but had to add a bit more toe out than I wanted to. Stiffening the rear only with an ARB could help promote oversteer, so I fitted it, backed off the rear toe out and I am still pleased with the balance. I've not tried an uprated front ARB yet. :)
Click to expand...
It's 3 way adjustable right? Have you tried different settings? Do you have adjustable links also?
 
https://www.turnermotorsport.com/BMW-MZ4/c-87-bmw-reinforcement-kits
 

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d4dawg thats not a a z4 chassis in the pic... the damper is setup like that.

we dont have subframe issues, its the ARB mounting point that is being discussed.
 
TomK said:
It's 3 way adjustable right? Have you tried different settings? Do you have adjustable links also?
Click to expand...

No adjustment on mine (E46 M3 Eibach rear bar), standard (new) links. :)
 
I was probably the first person on this forum to uprate the ARBs and I made some reinforcement plates for the front. If you do a search on here you should find the details.
 
Beedub said:
d4dawg thats not a a z4 chassis in the pic... the damper is setup like that.

we dont have subframe issues, its the ARB mounting point that is being discussed.
Click to expand...
Ah well ;)
 
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