Not happy with my ///M ride....solutions..??
- Thread starter plowy
- Start date
plowy said:
A considerable improvement! The car is now a joy to drive, with all the identified problems resolved. Where are you located? (send me a PM if you wish not to publicly disclose) If you're close enough I'd be happy to give you a passenger ride on a few of many rural roads that surround me so you can experience the results.
I've probably only spent a similar amount to what many others prefer to spend on CSL wheels and aero side skirts.In an earlier posting you wrote:
What changes had been done to your car and with what consequences? TBH, the static geometry should give predictable driving response in the dynamic situation, but trailing arms that are not fully restrained (as per OEM) can move laterally and produce dynamic geometry with unpredictable driving response and that's the reason for fitting RTAB limiters. Consequently, RTAB limiters give better road manners as well as improve track performance.plowy said:
kerstien said:]
Thanks for this. Will try the settings and report back once my kit arrives and all is installed
I want the least possible drop due to clearance. Do you lower it when going on a track apart from the above settings?
thanks
kerstien
I don't use mine as a DD so don't raise and lower the car between duties. The other problem with this is that changing ride hide alters the geometry so better to find a height that works for you and stick with it. One word of caution, the spring perches on the front are made of plastic so don't over tighten the grub screw as it can strip the threads!! I found out the hard way...
exdos said:
Sorry missed this, thanks for calculating this. I also spotted that Eibach do a 29mm adjustable ARB kit so it seems there are more options than I previously thought. Based on your calculations I am not sure the 27mm is worth it so I guess if I were to go this route it its 29mm or 30mm...Decisions, decisions...
DONDP said:
I've just done the calculations for a 29mm ARB for you. If the lever arms remain at OEM length, then there is effectively a 33% increase in stiffness, but if the lever length is shortened by 3/4" then the stiffness increases to 57% over the OEM ARB. In comparison, a 30mm ARB with the drop links attached at 3/4" longer lever arm would have an increased stiffness of 30.5% greater than OEM.
The effective spring rate of the OEM ARB is similar to the spring rate of the KWV3 front springs, therefore, as I see it, uprating the springs with aftermarket suspension, render the OEM ARB ineffective, and as such once you've uprated the suspension, to reduce lateral bodyroll further, you MUST increase the ARB thickness. If you think that the minimum increase in ARB stiffness should be around 30%, then it seems to me that the 30mm ARB is the better upgrade, because it would have the option of 30.5%, 52.4% and 80% increase in stiffness options.
exdos said:
I would concur, based on those calculations it would definitely seem the 30mm is the bar of choice.
You should ask h&r for some commission as I am now swayed (no pun intended) to get a set for next years track season.
You wouldn't happen to have any spare shims/strengthening plates I could purchase from you?
Again thanks for all your input and information most handy if not expensive on my part
DONDP said:exdos said:I would concur, based on those calculations it would definitely seem the 30mm is the bar of choice.
You should ask h&r for some commission as I am now swayed (no pun intended) to get a set for next years track season.
You wouldn't happen to have any spare shims/strengthening plates I could purchase from you?
Again thanks for all your input and information most handy if not expensive on my part
I can make you a pair of shims. Let me know when you're getting the ARBs.
If you're going to get uprated ARBs, I'd also suggest that you should consider fitting adjustable front drop-links too. I fitted a pair of Prosport ones on the Z4MC: http://www.ebay.co.uk/itm/Prosport-...arts_Vehicles_CarParts_SM&hash=item27d6ebcb43 I think that getting the ARB set up with no preloading when the car is standing is essential to eliminating excessive stress on the chassis as well as for improved performance. Even the OEM fixed-length drop-links seem to have some preloading because the attachment points on the dampers are not usually identically positioned on opposite sides.
exdos said:BMWZ4MC said:And thanks
Richard, I changed the gearbox oil this morning so whilst I was doing that I took a few photos for you of the undercar aero I've done, as below.
Obviously, I've no way of properly assessing this, but the idea is that of instead of letting all the air under the car find its own way out the back end, by putting four small vertical strakes on the underside, the air should flow with more directional control from a line in front of the rear wheels and behind that line.
The strakes situated closest to the wheels should prevent some air from coming under the car from the sides and help the OEM flaps in front of the wheels to work more effectively. The OEM flaps create low pressure in front of the rear tyres which helps water on the road to disperse to improve traction in the wet. The two central strakes are intended to make the air passing between them flow longitudinally, which should make the rear diffuser in the bumper work more effectively as well as cooling the differential. At the same time, the air passing on the outside of them and between the outer strakes should also flow longitudinally, and thus pass under the curved profile of the rear silencers which should create a "Coanda effect" thus pulling the silencers towards the road and reducing any tendency to lift at high speed. I had to remove the OEM pull-rods to drill a pair of 8mm holes in each so that I could bolt the strakes in the appropriate locations.
As I see it, putting vertical strakes under the rear of the car is akin to the longitudinal strakes on speed boats which give directional stability without the need for a deep keel. The car certainly feels very stable at high speed and I did over 150mph at The Ring with these strakes and the car was going arrow straight with good steering input. When I fitted my ACS suspension I deliberately increased the rake angle by dropping the front by 10mm.
Looks very interesting John, cheers. I'll have a think about aero when I'm under the car fitting suspension and brakes next year
exdos said:I can make you a pair of shims. Let me know when you're getting the ARBs.
If you're going to get uprated ARBs, I'd also suggest that you should consider fitting adjustable front drop-links too. I fitted a pair of Prosport ones on the Z4MC: http://www.ebay.co.uk/itm/Prosport-...arts_Vehicles_CarParts_SM&hash=item27d6ebcb43 I think that getting the ARB set up with no preloading when the car is standing is essential to eliminating excessive stress on the chassis as well as for improved performance. Even the OEM fixed-length drop-links seem to have some preloading because the attachment points on the dampers are not usually identically positioned on opposite sides.
Thats great thanks, Ill let you know once they are ordered imagine it will be a couple of months yet.
Nice to see a cheap-ish option for adjustable drop links. The kw v3s come with new shorter drop links, considering its easy to swap them out, Ill see how the kw ones fare with the new arbs when they arrive and swap out for the adjustable ones if they produce pre-load.
DONDP said:kerstien said:]
Thanks for this. Will try the settings and report back once my kit arrives and all is installed
I want the least possible drop due to clearance. Do you lower it when going on a track apart from the above settings?
thanks
kerstien
I don't use mine as a DD so don't raise and lower the car between duties. The other problem with this is that changing ride hide alters the geometry so better to find a height that works for you and stick with it. One word of caution, the spring perches on the front are made of plastic so don't over tighten the grub screw as it can strip the threads!! I found out the hard way...
Just read your reply. Thanks for the info and advise. I will probably set up with the least drop possible.
Thanks
Kerstien
Installed RTAB limiter shims recently and I am very pleased with it.
The strange 'rear bump steer' wobble behaviour drove me nuts.
First replaced the 'old' bushes with brand new ones (OEM) but that didn't sort the problem.
Then Exdos advised me to place the RTAB limiters, this was the solution I was looking for, thanks Exdos!
The strange 'rear bump steer' wobble behaviour drove me nuts.
First replaced the 'old' bushes with brand new ones (OEM) but that didn't sort the problem.
Then Exdos advised me to place the RTAB limiters, this was the solution I was looking for, thanks Exdos!
Rene,Rene_Z4MC said:
I'm glad you've found that these have solved the problem.
Graeme,gwatson said:
I got mine from Simpson Motorsport see: http://www.simpsonmotorsport.co.uk/bmw-tuning/product.asp?id=67&pid=67&cid=61&pcid=59&product=98 I reckon a garage should take no more than 1.5 hours to fit, especially if they are familiar with the rear suspension of the Z4.
Today my mechanic installed the kws. I had to install 10mm spacers at the front so that the wheel wouldn't rub on the spring. Has anyone had to do the same with kw v3s and oem wheels? Once we were at it i also installed 10mm spacers at the rear. It looks really flush at the rear and makes me wonder if it will rub. I took some pics but i don't know how to upload them. So far i haven't gone for a drive. Monday i should be able to do so 
i installed the top mounts as advised but he still needs to install the limiter kit.
So far it's on the kw setup but is definitely too low for maltese roads. I will be increasing it to max possible.
I'll get back with my comments afetr driving it
kerstien
i installed the top mounts as advised but he still needs to install the limiter kit.
So far it's on the kw setup but is definitely too low for maltese roads. I will be increasing it to max possible.
I'll get back with my comments afetr driving it
kerstien
gwatson said:
I stumbled upon a pair at a local tuner here in The Netherlands. I don't think they are a known brand, probably DIY stuff but they do their job very well.
Installed them myself in about 1.5hours since I already done the job before, so what Exdos mentioned is right.
O forgot to mention that I also have Eibachs fitted.
The car is now a lot better than standard but I'm still looking for a more planted setup. Front is way too soft, not yet sure how to attack that issue without getting a complete coilover solution.
BonkersBM said:
That's weird. Could it be down to tyres? I'm on the original contis. With 10mm spacers I got about 5mm clearance between tyre and spring.
The back looks way better with the spacers as the gap between fender and tyre is completely gone. Hopefully Monday ill know If I get and rubbing. It's really frustrating that I haven't got to try the new setup out yet.
Kerstien