What rear top mounts do I need?

O

oalloyd1

Member
Hi all,

I'm going to be uprating to coilovers on my track car and want to ensure this area is well supported as it can be a weak spot.

I've ordered a new set of genuine mounts but not sure if this will be sufficient?

Any steers appreciated.

O
 
Doubt very much there is anything wrong with the standard bushes as they are the same design BMW use on most if not all of their cars so you're probably fine with them, might just wear out a bit quicker with hard use on the track... However the only other option I know of would be powerflex top mounts at £85 a set which is probably what I'd go for when I eventually get around to doing a coil over install on mine.

Alternatively you can get a full kit (sort of...) from eBay for around £270 if you're going all out?
http://www.ebay.co.uk/itm/BMW-Z4-E85-E86-66mm-Front-Wishbone-Rear-Bush-Powerflex-Complete-Bush-Kit-/380963694676?fits=Car+Make%3ABMW%7CModel%3AZ4%7CPlat_Gen%3AE86&hash=item58b334a854:g:LnYAAOSwq7JT2RYl

You will need to check the diameter of the shocks in your rear coilover kit as I believe powerflex come in 2 sizes 10mm or 12mm, 12mm being for aftemarket suspension kits.

Out of interest what kit have you gone for? I've seen a few options ranging from £100's to £1000's and I'm not sure which brand and type are good, I've got my eye on a set of KW STX that Euro sell for just under £700.

Cheers
C
 
Thanks Chris, looks like we are the same age as well as the same thoughts ref suspension as was in Euro's last night looking at the exact same kit!!

Thanks for the steer, I'll look at that full kit but having poked around under my car the other night on the ramp all looked very healthy indeed even after 124k miles!

What other coilovers have you been looking at? The Spax RSX kit isn't too much but I've heard bad things about the AP racing kit?

Cheers,

o
 
I first looked into lowering springs but have been advised that standard dampers wouldn't do the job with uprated springs and looked at the Bilstein B12 kit... at around £800 it's more than entry level coilovers and found the STX which seemed very reasonable. I'd read up on the AP kit too but found mixed reviews so thought best to avoid, i think the main difference between budget and kits at well over a grand are materials used and damping adjustment so would hopefully withstand more abuse than the entry level ones! Interestingly though the AP kit is also made by KW but they do describe as their 'budget' kit!

The Spax kit you mentioned looks good, includes adjustable damping where the STX doesn't so may be a better choice? I've just spent my entire lunch break on Larkspeed website confusing myself further on what kit to go for, I'd recommend having a look if you want to deliberate over many more options and confuse yourself further! :wink:

http://www.larkspeed.com/category/view/SUSPENSION

Keep me posted on which kit you go for would love to hear a real world reviews rather than what the company selling the kit thinks!
 
You probably won't be buying true coilovers as most kits still have separate dampers and springs as per the standard setup. Therefore, you shouldn't need any welding but I would recommend you buy some reinforcement plates available on eBay for a tenner that go on the internal side of the car above the top mount & car shell. They help stop the mounts mushrooming and you can get similar for the front but I use a strut brace that has a similar effect instead.
 
Cheers guys great stuff!

Looks like I'll being going for Gaz GHA for the coilovers as you can specify ratings / usage etc yourself - 4 week wait, mind!

Also getting Larkspeed to supply poly rtabs and finding out about those off-set bushes to change the caster - has anyone had any experience with these? They sound like a good idea to help with turn-in

o :)
 
If your buying coilovers surely they will come with top mounts already?

Also Poly is a bit shyte for the RTAB, if your building a track car you need something like this - http://www.bimmerworld.com/Suspension-Steering/E46-E36-3-Series-and-Z4-Rear-Trailing-Arm-Bearing-Kit.html
 
Ah thats £££'s pal and not looking for it to be full-race.

Cheers though - next up is front brake cooling and establishing once and for all if an all-round E46 330 set-up will just bolt on.

Cheers,

o :)
 
oalloyd1 said:
Also getting Larkspeed to supply poly rtabs and finding out about those off-set bushes to change the caster - has anyone had any experience with these? They sound like a good idea to help with turn-in
Click to expand...

Actually adding caster doesnt help with turn-in, but increases turn-out.

Caster adds straightline stability, and adds camber when the suspension is loaded up (dynamic camber).
Straightline stability automatically means the car has less urge to change direction, thus less turn in.
You could say that off throttle steering becomes less and on throttle steering becomes more, so (very roughtly) pre apex steering is less, post apex steering is more.
Due to dynamic camber the inner wheel will have less grip and it will upset the balance a bit. Like having more droop on the inner suspension.

Its an easy fix for having mid corner understeer but it has its donwsides (solving it without those downsides is much more difficult)

As for the rear top mounts, I'd go for the powerflex ones.
I think powerflex is still the best poly manufacturer for the z4. Not the cheapest, but the best.
And currently they have virtually every bushing available for the z4 (that took them long though, compared to other brands)
I use a set from bimmertune (powerflex didnt have them back then).... cheaper though ;)
Dont forget to fit a pair of reinforcement plates from the z3.
 
Depends on what shocks you're going to run. (and how stiff you want them to be)
Some schocks have a 12mm top shaft, some have a 10mm top shaft.
I think all the powerflex top mounts already have the z3reinforcement plates included in the kit (normally £10/pair, part# 51718413359)

Powerflex top mounts 10mm shore95A PFR5-5630-10BLK:
http://www.ebay.co.uk/itm/BMW-Z3-94-02-POWERFLEX-BLACK-Rear-Top-Mount-Bracket-Bush-10mm-PFR5-5630-10BLK-/161561229195

Powerflex top mounts 10mm shore80A PFR5-5630-10:
http://www.ebay.co.uk/itm/BMW-E46-3-Series-POWERFLEX-Rear-Shock-Top-Mount-Bracket-Bush-10mm-PFR5-5630-10-/191483386826

Powerflex top mounts 12mm shore95A PFR5-5630-12BLK:
http://www.ebay.co.uk/itm/E46-Compact-POWERFLEX-BLACK-Rear-Top-Mount-Bracket-Bush-12mm-PFR5-5630-12BLK-/161561229162

Powerflex top mounts 12mm shore80A PFR5-5630-12:
http://www.ebay.co.uk/itm/BMW-E46-3-Series-M3-POWERFLEX-Rear-Top-Mount-Bracket-Bush-12mm-PFR5-5630-12-/191483414699

Reinforcement plates z3:
http://www.ebay.co.uk/itm/BMW-Z3-rear-shock-top-mount-reinforcement-plates-E30-E36-E46-Z4-BIMMERTUNE-/122509847334

Bimmertune mounts (specify 10-12mm):
http://www.ebay.co.uk/itm/BMW-uprated-rear-shock-top-mounts-RSM-E30-E36-E46-Z3-M3-track-Poly-HD-BIMMERTUNE-/112420001198

Thats all I can tell you about rear top mounts :roll:
 
Don't worry about all that downside stuff to the offset bushes, I put them on my car and the only thing I noticed is a lot less mid corner understeer which is what I wanted. Well worth doing imo.

I got some cheap second hand ones on here by Whiteline already fitted into the aluminium housing which is the hard part. Otherwise I was going to buy the Powerflex ones but Z4M OEM is much cheaper.
 
^you could parry the negative aspects with either linear springs and a stiff shock (which is the obvious choice for a track car), stiffer arb's front/rear or different tyres.
The only way extra caster bushings add grip in the corners is because of the dynamic camber. And extra camber is only needed because of bodyroll or tyre deformation. If you have no bodyroll and no tyre deformation, in theory you need 0deg camber
The biggest cause of bodyroll is progressive springs imo, especially on the front.

Look at a lotus. I think those cars run very low caster angle. 3deg or so?
 
Please tell that to Eibach, I don't disagree.

There's an initial pitch in then it's flat which as you say is the progressive springs.
 
Eibach's pro kit is aimed at street applications. I've had the pro kit but found it too low/soft, frequently scraping the bumper.
Progressive springs give more comfort for all the small bumps, but are not suitable for track. The progressiveness makes diving of the car unpredictable and difficult to set up the car
Now I have a KW V3 kit with linear springs, and although its set at about the same rideheight, there is much less scraping of the front bumper, even less than with stock springs. It's obviously a stiffer ride on the smaller bumps, (but perfectly do-able on the street; it has 5kg/mm front).
Cornering is a joy, the car feels more stable, and has a little bit more oversteer (or less understeer, just how you put it).
But as the TS is building his car specificly for track, I'd first see how a stiff linear spring setup (say 7-8kg/mm and matching rear) handles and then see if extra caster is needed. Cars with more caster feel less 'nippy' imho.
 
oalloyd1 said:
Hi all,

I'm going to be uprating to coilovers on my track car and want to ensure this area is well supported as it can be a weak spot.

I've ordered a new set of genuine mounts but not sure if this will be sufficient?

Any steers appreciated.

O
Click to expand...

I have a pair of Powerflex rears which were opened but never used. PM me if you would be interested in them.
 
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