Your experiences of aftermarket suspension on the Z4 MC

[Beedub]

the difference between a wardrobe weight and the ARB is the arb is being pulled against not a simple weight rested on.... still fair enough if your happy soemtimes though john just sometimes you have to concede and get things done 110% over engineered, and a car like this is imo worth that little extra outlay and time......john excise me for saying but that bit about developing a horse treadmill made me laugh out load!! awesome stuff!!! i believe in your ability 100% and trust your word.....

anyway, did you need to make the wholes bigger for the e46 Front ARB??? or was this a complete bolt on unit??? also what about the rear??

 

[Beedub]

also john, why does the drop link get so close to the caliper is that because this is an adjustable part?? i.e the HR has 3 levels of stiffness??? obviously you cant adjust this position on the stock bar as its placed in one fixed whole if you get me.

 

[exdos]

the difference between a wardrobe weight and the ARB is the arb is being pulled against not a simple weight rested on....

I've touched on that point when I wrote: "If there are no shims, then the chassis is in contact with the flexible bushing which will permit flexion, but a 2mm shim tightly fastened between the chassis and the bush will hardly permit any flexion". This is a bit like giving Rolf Harris a thicker wobble-board - he wouldn't be able to make any records (would've been a blessing "Altogether now!"...)

still fair enough if your happy soemtimes though john just sometimes you have to concede and get things done 110% over engineered, and a car like this is imo worth that little extra outlay and time.....

I agree, but I still reckon all those failure we've read about are with people using 600+ lb/ins springs and 30mm GC ARBs on stiffer settings than a 30mm bar (which is 52% stiffer). I had a good look at the chassis where the brackets are attached, and it's formed metal into a box-like shape for strength, which should be pretty rigid. My ACS suspension doesn't have 600lbs/in springs and I'm not going above the 52% stiffer. If I get any hints of cracks, then I'll go to town on the job.

john excise me for saying but that bit about developing a horse treadmill made me laugh out load!! awesome stuff!!!

Excellent! It is an awesome piece of kit too.

]anyway, did you need to make the wholes bigger for the e46 Front ARB??? or was this a complete bolt on unit??? also what about the rear??

If I hadn't put shims under the brackets, then the ARB would've probably rubbed against the chassis at the point indicated by the green arrow in the 4th photo in the posting above, but with the shims, it was just a straightforward swap. I don't intend to fit an uprated rear ARB, and from my test drive I didn't notice any great imbalance or change to under/oversteer characteristics by just uprating the front ARB, only. The steering just felt more precise and what I'm used to with my Z3MC.

 

[exdos]

also john, why does the drop link get so close to the caliper is that because this is an adjustable part?? i.e the HR has 3 levels of stiffness??? obviously you cant adjust this position on the stock bar as its placed in one fixed whole if you get me.

The ends of the OEM ARB are turned inwards at a slight angle to the arms, whereas on the H&R ARB the ends are a continuation of the lever arm. If I were to use the holes at the end (softest setting) I think an adjustable drop link would be necessary to give more clearance, because the ends of the OEM drop links are a bit bulky. I think the lever arms are also a cm or 2 longer than the OEM, to accommodate the softer setting.

 

[Beedub]

ridiculously cool info!!! well done!!!

how about some pics of how the car is sitting, whats the ride height, im being a complete nancy and wanting to run my coilovers at the highest setting possible which is about 5-10mm lower than stock..... i have a pet hate for decked cars. whats your feeling on ride heights ect???

 

[exdos]

ridiculously cool info!!! well done!!!

how about some pics of how the car is sitting, whats the ride height, im being a complete nancy and wanting to run my coilovers at the highest setting possible which is about 5-10mm lower than stock..... i have a pet hate for decked cars. whats your feeling on ride heights ect???

I'm 100% with you about ride heights. I think that they can look great when they're slammed (i.e Dubsed's) and that's fine for photos and posing, but I'm not into "filling the wheel arches" just for the sake of appearances. I'm all about improving performance and handling. From floor to top of wheel arch, fronts are 665mm and rears are 680mm. I've settled at those heights to increase rake angle to increase high speed stability. I wouldn't want to go any lower because I want be able to drive without worrying about damaging the car. The Z4MC is plenty low enough OEM and lowering buggers up all the geometry and unless it can be corrected, which I've managed to do, then you've also buggered up the handling. I want a car that handles so much better than OEM and nothing else and if it looks cool too, then that's just a bonus. For me, improving a car is all about getting it to go around corners quicker because that's where the greatest improvements in performance are to be had.

As for photos of my car: there are a quite a few that forum members took of the car at Silverstone last Saturday here: http://www.z4-forum.com/forum/viewtopic.php?f=14&t=32876&start=855 Someone did a video from behind my car here: http://www.youtube.com/watch?v=iqNKgOwjaXQ&sns=em

 

[Beedub]

John why do a lot of these suspension setups have a slightly higher rear???

The ke clubsport minimum lowering is 5mm rear , 10 mm front. Also the stock ride is slightly higher at the rear.

 

[exdos]

Byron,

It's imperative to preserve a "rake angle" for aerodynamics, so the rear needs to be higher than the front so that the gap under the car at the front is smaller than anywhere along the length of the car underneath, with the greatest depth being at the rear. Since a fixed amount of air passes under the car, because the gap is least at the front, the speed of the air at this point is faster than when the air can start to expand as it passes along the length of the car. The pressure of of air is lower when it's moving fastest whereas the pressure on the bonnet will be relatively higher, which gives some downforce at the front.

Likewise, the rear springs have to fit within a given space between the chassis and the suspension arm, and for a given spring rate, there have to be sufficient coils with wire of a specific diameter, which will not bind under full compression, so space limitation dictates the amount of drop that can be obtained at the rear. At the front, there is more scope for greater adjustment.

 

[Beedub]

ok john, so like i say the minimum i can lower the car is 10mm front 5 mm rear.... would this be acceptable in terms of aero dynamics and rake angel??
like i say if i could have ran the car atr stock ride height i would have... in order for the uprated shocks to do their business they NEED travel, sure i can wind them down to 60mm lowered but i just dont get that on a car like this..... im glad you echo my feeling with this.

in terms of mm how much lower is your car from stock?? about 15mm fr 10mm rear??? that seems about fair..... ?? woulod you raise the car IF you could??

 

[daz05]

Just to say, I took some advice from what John has said in this thread regarding alignment on my own car, and I'm very pleased I listened.

Going into turns I can feel the rear helping to push me round now, and the steering response and bite has also improved.

Steering is also less busy and the car more relaxed but that was because before alignment my toe was running 'in' on one side and 'out' on the other!

 

[exdos]

ok john, so like i say the minimum i can lower the car is 10mm front 5 mm rear.... would this be acceptable in terms of aero dynamics and rake angel??

That's fine. Provided that the front drops as much, or more than, the rear, you will maintain a rake angle.

like i say if i could have ran the car atr stock ride height i would have... in order for the uprated shocks to do their business they NEED travel, sure i can wind them down to 60mm lowered but i just dont get that on a car like this..... im glad you echo my feeling with this.

in terms of mm how much lower is your car from stock?? about 15mm fr 10mm rear??? that seems about fair..... ?? woulod you raise the car IF you could??

That's the drop I've got. I wouldn't want to raise the car back to OEM because lowering the Centre of Gravity (CoG), within reason, helps performance, provided that the geometry is adjusted to compensate for the changes to camber and toe that occur from simply lowering the car. The problem that I have with lowering is that it just isn't practical for normal road use if you overdo it.

 

[exdos]

Just to say, I took some advice from what John has said in this thread regarding alignment on my own car, and I'm very pleased I listened.

Going into turns I can feel the rear helping to push me round now, and the steering response and bite has also improved.

Steering is also less busy and the car more relaxed but that was because before alignment my toe was running 'in' on one side and 'out' on the other!

Daz,

I'm glad you find my suggestions an improvement.

 

[exdos]

UPDATE

I've now installed Turner Motorsport Rear Trailing Arm Bush Limiter Kit, as shown in the photos below.

The rear trailing arms are held captive in brackets just inside the cills in front of the rear wheels. The position of the brackets can be adjusted laterally, which affects rear toe angles, and there is considerable scope for lateral movement of the OEM rubber bushes within these brackets. This permits the rear toe geometry to change in dynamic situations, particularly during hard cornering, which in turn will adversely affect the handling of the car. The TMS RTAB Limiter Kit is a simple way of narrowing the space within the RTA brackets so that there is little scope for lateral movement of the bushes, thus preserving rear toe geometry.

Two TMS discs are fixed to the inside of each RTA bracket.

Two holes are drilled through both sides of the bracket (using a template supplied with the kit) and the discs are screwed in position.

The discs reduce the lateral space within the brackets by 14mm.

The OEM RTABs protrude from the trailing arms and the sides of the bushes will now make contact with the limiter discs when installed.

This photo shows the trailing arm housed inside the bracket with the limiter discs in situ.

This shows the RTA bracket installed.

It's a simple enough job to do, but before you start you need to mark the position of the bolts on the brackets so that when you refit, the brackets are returned to the same positions to preserve the original geometry.

I chose to fit the limiter kit rather than fit polyurethane RTA bushes because form my previous experience of polyurethane bushes which need to move, they can squeak which I find very irritating. Also by keeping the OEM rubber bushes, the bushes still retain their compliance, and only their lateral movement is restricted.

I think that I've now done all that I want to do to the suspension apart from possibly fine tune the geometry.

 

[Beedub]

lol john ive got this exact piece to fit!!!

walk me throught it please... once i unbolt the sill side does this just drop down??? looks pretty easy anyhow...

edit just read instructions, seems very easy..... i will tackle this, this weekend and finally get a new alignment done

At some point john i hope you dont mind but id like to drop you a phone call in the coming weeks to discuss some fine tuning i need to do but could do with some solid advice hope you dont mind, will pm before i call

byron

 

[exdos]

Byron,

I got mine from Simpsons - cheaper than buying directly from TMS and paying freight and import taxes etc.

Why BMW had to make a bracket which allows so much play in the bush beats me :roll:

Here you go... Once the wheel's off, remove the front panel of the wheel arch liner. Now the hardest bit of all: carefully undo the lower plastic part with the flap in front of the wheel and then let it hang on the wiring. Place a jack under the wheel hub and undo the bolt on the bottom of the damper so the trailing arm is less restrained.

Mark the positions of the 3 bolts holding the RTA bracket with paint/tippex and whilst drying, remove the bracket that attaches the brake pipes and undo the other wires attached to the TA. then undo the 3 bolts that hold the bracket to let it descend, then undo the bolt through the bracket to release the TA and then remove the bracket.

Once the TA bracket is removed, fit the Limiter kit and then reassemble. It's simple enough to do but would be a harder task if you were replacing the bushes at the same time, but when I inspected mine, they didn't need replacing although I'd got some new ones just in case. If you keep a jack under the wheel hub, you can lower and raise it as required. Also don't fully tighten the bolt through the bush when the TA is refitted into the bracket without a trial test-fit of the bracket against the car so that you don't preload the bush. I've given you a few tips there that you don't read in the instructions. 8)

Enjoy

Yes, sure give me a shout if you want a bit of input. we must meet up soon too.

 

[Beedub]

Byron,

I got mine from Simpsons - cheaper than buying directly from TMS and paying freight and import taxes etc.

Why BMW had to make a bracket which allows so much play in the bush beats me :roll:

Here you go... Once the wheel's off, remove the front panel of the wheel arch liner. Now the hardest bit of all: carefully undo the lower plastic part with the flap in front of the wheel and then let it hang on the wiring. Place a jack under the wheel hub and undo the bolt on the bottom of the damper so the trailing arm is less restrained.

Mark the positions of the 3 bolts holding the RTA bracket with paint/tippex and whilst drying, remove the bracket that attaches the brake pipes and undo the other wires attached to the TA. then undo the 3 bolts that hold the bracket to let it descend, then undo the bolt through the bracket to release the TA and then remove the bracket.

Once the TA bracket is removed, fit the Limiter kit and then reassemble. It's simple enough to do but would be a harder task if you were replacing the bushes at the same time, but when I inspected mine, they didn't need replacing although I'd got some new ones just in case. If you keep a jack under the wheel hub, you can lower and raise it as required. Also don't fully tighten the bolt through the bush when the TA is refitted into the bracket without a trial test-fit of the bracket against the car so that you don't preload the bush. I've given you a few tips there that you don't read in the instructions. 8)

Enjoy

Yes, sure give me a shout if you want a bit of input. we must meet up soon too.

awesome..... sounds easy.... will have a crack asap

definitely need to hook up soon, got ALOT to mull over, ideally when your over next id like to invite you over, i really need to bounce some ideas off someone!!

 

[Woots]

can you guys like write a massive blog on on the stuff inside your head so others can learn?
i know thats sort of what you do anyway...but easier to learn it all if its on one easy page/post etc
i will make it worth your while with sexual favours :lol:

 

[exdos]

can you guys like write a massive blog on on the stuff inside your head so others can learn?
i know thats sort of what you do anyway...but easier to learn it all if its on one easy page/post etc

With regards to my views on suspension, just read this thread from the start which is essentially my blog on all the suspension mods I've done. Alternatively, save this thread as a PDF and delete all the irrelevant chit-chat and you'll have an illustrated guide

i will make it worth your while with sexual favours :lol:

I hope you're intending to provide gorgeous nubile women for me 8) and not offering the services yourself! :wkr:

 

[Woots]

do you have lots of knowledge on other stuff like engine, brakes etcc
i dont have the funds to mod/tune my car but ive just got an engineering thrist for knowledge lol

just interested in all the stuff you know lol

 

[exdos]

do you have lots of knowledge on other stuff like engine, brakes etcc
i dont have the funds to mod/tune my car but ive just got an engineering thrist for knowledge lol

just interested in all the stuff you know lol

I wrote a "how to" on brake ducting here: http://www.z4-forum.com/forum/viewtopic.php?f=34&t=38775

I don't claim to be an expert on any of this stuff, I've just got a lifetime of experience of lots of diverse things and learn about everything that interests me at any moment in time and I like rolling my sleeves up and having a go. If you're interested, I suggest that you read as much as you can and you'll soon soak it all up.