Strut brace question

[BMWZ4MC]

For that money you could get H&R antiroll bars and have money left over, I'd think seriously about ARBs over the strut brace if you're keen to keep spending money Ditching the Conti's for better tyres is certainly a worthwhile investment as you'll realise once your new wheels are fitted. At this rate you'll have a car fit for track use...are you sure you aren't tempted by a few trackdays?

It might be worth trying to get someone near you who's modified their ///M to offer you a passenger ride (assuming there is someone) so you can get a feel for each of the different options. My car is heavily modified and pretty miserable to drive on poor road surfaces (broken teeth and lots of conducted noise) but absolutely fantastic on smooth Tarmac. On the track it's phenomenal and I'm really pleased with the transformation, but I wouldn't be if predominately it was a road car or I wanted to make more progress on country lanes (for this I would need to reduce the bump and rebound significantly).

 

[Beedub]

imo the strut brace combined with the under turret strengthen plates are essential on coil over kits especially a track driven car with a track type setup.... its cheap insurance as the turret tops can deform and the firewall brace tabs can break... i wouldn't run my car without the S/B and its been on from very few miles, I'm glad it has been.

 

[mike n helen]

I'm fairly new to the Z4 forum and my experience of modifying my car which I've owned for all of two weeks has so far only extended to changing the aerial :roll: But it is my 52nd car I've owned and I do have a bit of experience of tinkering with cars. You ask the question what else can be done to improve the handling? In my experience I have to say I 100% agree with the comments of BMWZ4MC, the biggest single improvement I made on my MX5 was to change the ARB's to thicker ones. It made a huge difference to the body roll when cornering helping to keep the car flat.

The first real mod I was planning for my Z4MC was to see if an aftermarket thicker ARB was available, if so then for sure I will be buying a set. I would be doing this before I start consider changing to things like Bilstein's or other types of adjustable coilovers etc.. For general road use you may find that the cheaper ARB option may just give you what you want. As I say this is my experience on my MX5 and may be a complete load of nonsense for the Z4, but if an aftermarket ARB does exist can somebody point me in that direction.

Mike

 

[BMWZ4MC]

imo the strut brace combined with the under turret strengthen plates are essential on coil over kits especially a track driven car with a track type setup.... its cheap insurance as the turret tops can deform and the firewall brace tabs can break... i wouldn't run my car without the S/B and its been on from very miles, I'm glad it has been.

I agree in your case Beedub (and mine - thanks for the pointers re turret reinforcement ), but the OP is looking for a tangible performance increase when driving on the road not to protect his car or make a few extra tenths with hard track use (where all if the mods discussed would be of benefit). I think if he's looking to spend a few hundred and wants to really feel the difference, the bigger bang per buck will come from stiffer ARBs and RTAB limiters.

 

[David-H]

Mike,
John (exdos) - see his comments earlier - has a lot of experience with tha Z4M suspension and this is what he said about ARBs on their own:

• Although I think that the Z4MC's OEM suspension is dreadful, it's pretty good at resisting lateral bodyroll, which it achieves via a stiff front ARB and and very stiff rear springs/dampers. I think changing the ARBs on their own won't actually achieve much because lateral bodyroll isn't really the problem, so I doubt that fitting H&R ARBs would be worthwhile on its own.

 

[exdos]

I did read Strongstrut's comments that you posted earlier on, but I have to point out that the weakest link, even with the StrongStrut "trilogy" fitted, is the OEM brackets on the suspension towers to which the firewall braces are attached and there's simply no replacement parts for those; you just repair them if they break. So I think you're just wasting money that could be spent better. But if you're wanting eye candy...

Not wishing to be contradictory, but with OEM suspension, I don't think the upgraded H&R ARBs will do that much because the OEM rear springs are so damned thick at 19mm, they're thicker than the OEM rear ARB of a Z3MC and the OEM Z4MC doesn't suffer too much lateral bodyroll because those stiff rear springs take some pressing. Aftermarket adjustable suspension has thinner rear springs so in that scenario uprated ARBs will then improve things. On the Z3MC uprated ARBs with OEM suspension are the best bang for buck, but not so with the Z4MC.

Having done quite a number of suspension mods to my Z4MC, I would suggest that if you want to spend a limited amount of money to start off, I'd get the Strutbrace, fit RTAB limiters and then fit Vibra Technics engine mounts. Then see how the car performs. If you then want to take things to the next level, you'll have to bite the bullet and buy adjustable suspension, such as AC Schnitzer Racing, Bilstein PSS10 or KWV3 and then fit the H&R ARBs.

EDIT I've just seen that DLH has quoted me from an earlier post whilst I was composing this. At least I agree with myself! :wink:

 

[David-H]

...<snip>
Having done quite a number of suspension mods to my Z4MC, I would suggest that if you want to spend a limited amount of money to start off, I'd get the Strutbrace, fit RTAB limiters and then fit Vibra Technics engine mounts. Then see how the car performs.....<snip>

John, thanks for that; makes sense and that's the route that I intend to take.

 

[BMWZ4MC]

I did read Strongstrut's comments that you posted earlier on, but I have to point out that the weakest link, even with the StrongStrut "trilogy" fitted, is the OEM brackets on the suspension towers to which the firewall braces are attached and there's simply no replacement parts for those; you just repair them if they break. So I think you're just wasting money that could be spent better. But if you're wanting eye candy...

Not wishing to be contradictory, but with OEM suspension, I don't think the upgraded H&R ARBs will do that much because the OEM rear springs are so damned thick at 19mm, they're thicker than the OEM rear ARB of a Z3MC and the OEM Z4MC doesn't suffer too much lateral bodyroll because those stiff rear springs take some pressing. Aftermarket adjustable suspension has thinner rear springs so in that scenario uprated ARBs will then improve things. On the Z3MC uprated ARBs with OEM suspension are the best bang for buck, but not so with the Z4MC.

Having done quite a number of suspension mods to my Z4MC, I would suggest that if you want to spend a limited amount of money to start off, I'd get the Strutbrace, fit RTAB limiters and then fit Vibra Technics engine mounts. Then see how the car performs. If you then want to take things to the next level, you'll have to bite the bullet and buy adjustable suspension, such as AC Schnitzer Racing, Bilstein PSS10 or KWV3 and then fit the H&R ARBs.

EDIT I've just seen that DLH has quoted me from an earlier post whilst I was composing this. At least I agree with myself! :wink:

I hear what you're saying about the rear springs, but the OEM front springs aren't especially stiff (in fact they're a bit weedy at 11mm front vs 19mm rear IIRC) so won't resist body roll as effectively especially if turning and decelerating simultaneously or with rapid transition from braking to turning in. Perhaps just up rating the front ARB would be an effective alternative...
I still remain to be convinced that a set of braces is worth £600 in terms of performance increase. I do agree about the RTAB limiters, but I hesitated to mention engine mounts for fear of opening a whole new can or worms :wink:
Someone needs to sequentially fit and remove each modification and objectively test it's effects on road and track. Volunteers? OP?!


Edit: for mike n helen - I got my H&R ARBs here:

http://www.spring-loaded.co.uk/proddetail.php?prod=H%7Eand%7ER%7EFront%2FRear%7EAnti%7ERoll%7EBars%7EBMW%7E3%7ESeries%7EE46%7EM3%7EM346%7E2000%7EOn

If you fit aftermarket coilovers you'll likely need adjustable drop links or the outboard end of the front ARB may foul the brake calliper.

 

[Beedub]

imo the strut brace combined with the under turret strengthen plates are essential on coil over kits especially a track driven car with a track type setup.... its cheap insurance as the turret tops can deform and the firewall brace tabs can break... i wouldn't run my car without the S/B and its been on from very miles, I'm glad it has been.

I agree in your case Beedub (and mine - thanks for the pointers re turret reinforcement ), but the OP is looking for a tangible performance increase when driving on the road not to protect his car or make a few extra tenths with hard track use (where all if the mods discussed would be of benefit). I think if he's looking to spend a few hundred and wants to really feel the difference, the bigger bang per buck will come from stiffer ARBs and RTAB limiters.

arhhh i see i see.... yes i agree with you.... on the circuit it definitely provides a service.

 

[David-H]

Having done quite a number of suspension mods to my Z4MC, I would suggest that if you want to spend a limited amount of money to start off, I'd get the Strutbrace, fit RTAB limiters and then fit Vibra Technics engine mounts. Then see how the car performs.

I hear what you're saying about the rear springs, but the OEM front springs aren't especially stiff (in fact they're a bit weedy at 11mm front vs 19mm rear IIRC) so won't resist body roll as effectively especially if turning and decelerating simultaneously or with rapid transition from braking to turning in. Perhaps just up rating the front ARB would be an effective alternative...
I still remain to be convinced that a set of braces is worth £600 in terms of performance increase. I do agree about the RTAB limiters, but I hesitated to mention engine mounts for fear of opening a whole new can or worms :wink:
Someone needs to sequentially fit and remove each modification and objectively test it's effects on road and track. Volunteers? OP?!

My springs are not OEM - they're Eibach with Bilstein shocks

I will be doing the mods suggested by John sequentially in the order they arrive in but don't want to fit & then remove!

Looking into the engine mounts now.

PS May even try a Novice Track Day at Oulton Park come October as it's only £129 :wink:

 

[mike n helen]

As I say this is my experience on my MX5 and may be a complete load of nonsense for the Z4, but if an aftermarket ARB does exist can somebody point me in that direction.

Mike

I stand corrected and bow to the those with the knowledge who have tried these changes for themselves on the Z4. Thanks for the link, but may have to rethink my mod strategy now.... :?

 

[BMWZ4MC]

As I say this is my experience on my MX5 and may be a complete load of nonsense for the Z4, but if an aftermarket ARB does exist can somebody point me in that direction.

Mike

I stand corrected and bow to the those with the knowledge who have tried these changes for themselves on the Z4. Thanks for the link, but may have to rethink my mod strategy now.... :?

I don't know of anyone who has uprated the ARBs with OEM springs and dampers. Both John and I have aftermarket coilovers - ACS in John's case and KW Clubsports in mine. I'm pretty sure I have the same suspension set up as Beedub except I think he's still running the OEM ARBs (unless he's added further mods since we last discussed it) so perhaps we should drive each other's cars...

 

[exdos]

I hear what you're saying about the rear springs, but the OEM front springs aren't especially stiff (in fact they're a bit weedy at 11mm front vs 19mm rear IIRC) so won't resist body roll as effectively especially if turning and decelerating simultaneously or with rapid transition from braking to turning in. Perhaps just up rating the front ARB would be an effective alternative...
I still remain to be convinced that a set of braces is worth £600 in terms of performance increase. I do agree about the RTAB limiters, but I hesitated to mention engine mounts for fear of opening a whole new can or worms :wink:

If you've got very stiff springs at the rear end only, despite the front springs being very soft, the stiffness of those rear springs, considerably reduces lateral bodyroll, because to pitch the car on to the outside front wheel in a turn, it would mean that the outer rear spring would also need to be compressed somewhat with lateral bodyroll, and since the pitching of the load onto the front end, effectively lightens the loading at the rear, this isn't going to happen. Having driven my Z3MC in OEM guise for some 18k miles, with excessive lateral bodyroll with pitching and squatting, I feel very confident in saying that the Z4MC doesn't have a problem with lateral body roll. Pitching under braking, front end lifting under acceleration and a ride which is way too stiff, yes, but excessive lateral bodyroll, no.

I paid about £350 for the Strongstrut strut brace for my Z4MC, and happy to do so, but I wouldn't pay £600 for the "trilogy'. I have a Strongstrut strutbrace and butt-strut on my Z3MC and wouldn't be without either. IMO, the Strongstrut strutbrace is a proper piece of strengthening equipment, whereas the others look a bit weak to me.

Someone needs to sequentially fit and remove each modification and objectively test it's effects on road and track. Volunteers? OP?!

Do I qualify? I've installed all the suspension mods on my Z3MC and Z4MC one at a time, and me being me, if there's any adjustment available for any of the parts, I've experimented with the various settings and test driven with all the different settings to discover how the parts and the adjustments affect vehicle dynamics. I've also experimented with the geometry of both Z3MC and Z4MC. I do most of my driving on rural A&B roads (twisties) and I've also driven hundreds of laps at The Ring in both cars so I feel I've tested what's available to improve the handling.

 

[Beedub]

Bmwz4mc for me I'm very pleased with the stock rolls bars on my roadster , they are plenty thick enough I found and once I'd done the club sports I felt they abolished roll pretty much entirely, stock we have very thick arbs considerly thicker than most ...

It's not something I feel an issue in and I like alittle body movement to help with my grip issue.

But the club sports just continue to blow me away , I see why bmw choose them for the safety cars and the M gts. Incredible dampers. Transformed my car into a weapon on the track. Wait till you put a set of semi.slicks on ! Wow.

 

[BMWZ4MC]

Do I qualify?

Yep!

 

[exdos]

Beedub & BMWZ4MC,
Are the Clubsports really THAT stiff for road use, even on their softest settings, or do you both choose to keep them on your track settings and not bother to swap between 2 different set-ups? It takes me about 10mins to adjust the KWV3s with seperate bump and rebound adjustment, and I think it's worth the effort when required.

 

[BMWZ4MC]

I found (rather suddenly) that the settings recommended by KW were too firm for road use (as I told you ). I've backed them off a bit, but there remains adjustment in both directions from my current settings. I've left it set at what I feel is likely to be the optimal setup for track use so I can learn the behaviour of the car again having upgraded so many parts at once. Once I better understand how the car handles in a variety of conditions and on different surfaces I'll make incremental adjustments and test these on both road and track.
With Clubsports; rear topmounts; RTAB limiters; camber plates, strut tower reinforcement plates and a strut brace; stiffer ARBs; competition engine mounts; and 19" wheels the car is really very stiff now. There is a modest increase in conducted nvh from the engine and a huge increase in conducted road noise. Painted road markings break teeth and the car is skittish on really badly made country roads (all improved with 18" wheels). Interestingly, the ESP doesn't activate any more often than with my previous Eibachs and OEM dampers and does so less than with the full OEM setup. At present, the best way of coping with rough surfaces is to hold the wheel lightly allowing it to self-centre and trust the car to grip. I'm sure when I soften the damping it will be more comfortable, but I don't think it will be as smooth on A roads as you've made yours.
My preferred tracks are short and technical rather than having long sweeping high speed bends, so this setup really suits me. However, I wouldn't recommend it to someone who's looking to improve their daily driver or weekend road car.
We really must meet and compare notes at some point (although I'm currently writing an MSc thesis so it will have to be later in the year).

 

[David-H]

...<snip>...
I still remain to be convinced that a set of braces is worth £600 in terms of performance increase. I do agree about the RTAB limiters, but I hesitated to mention engine mounts for fear of opening a whole new can or worms :wink:
...<snip>...

With the Pound currently being strong against the Dollar, a complete Z4 Strong-Strut set, including FW braces and both accessory kits and Global Express shipping comes in at $647 or £397. There's still Customs duty to pay of course but that shouldn't be too bad (At least I hope not - I'll find out in due course!)

I was going to go for just the strut brace as John suggested but being as it's such a good deal being offered by Paul Ebeyer, I've gone for the full monty.

 

[tertius]

Assuming you install after market suspension I think it will depend a lot on the spring rates you choose and the valving in the dampers - I'm still running OEM ARBs with Intrax 1K2 suspension. I am not yet convinced I need to uprate the ARBs, indeed several people have commented how flat my car corners on track.

I run the dampers around 10-15 clicks off full hard on track (depending on conditions, surface, how much attention I paid when adjusting them, etc.) so still some way off as stiff as they could be.

 

[exdos]

Assuming you install after market suspension I think it will depend a lot on the spring rates you choose and the valving in the dampers - I'm still running OEM ARBs with Intrax 1K2 suspension. I am not yet convinced I need to uprate the ARBs, indeed several people have commented how flat my car corners on track.

I run the dampers around 10-15 clicks off full hard on track (depending on conditions, surface, how much attention I paid when adjusting them, etc.) so still some way off as stiff as they could be.

You got it. It's the springs at each corner that do the work of the suspension and all the dampers do is control the speed of compression and expansion of the springs which affects the handling and performance relative to the road surface characteristics. A high spring rate, particularly at the front end, will prevent pitching and lateral bodyroll, which renders ARBs less effective than with softer spring rates at all 4 corners. With higher spring rates there's less vertical movement relative to softer spring rates for the same loading (Hooke's Law and all that), therefore damping can be less.