A Slightly Fettled BMW Z4 35i

A Slightly Fettled BMW Z4 35i

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SamJB

Original Poster:

83 posts

131 months

Tuesday 23rd October 2018
quotequote all
So here's the offending article;


Aesthetically it's quite similar to a standard Z4 with the exception of a retrimmed steering wheel and the recent change to an M sport front bumper after I got hold of a free one locally, following a respray the front end looks far better less the stone chips of the old one.

Mechanically is where it gets a bit more interesting however. As journalists are very keen to point out with news of the upcoming Z4 in abundance, the E89 was a bit of a lard in the handling department. In comparison to my old E85 Z4 and VX220, it's hobbled by runflat tyres and nearly 1600kg's of heft not being terribly well controlled resulting in catastrophic understeer and considerable body roll when trying to press on down an A or B road. The upshot is that I found it to be a very capable cruiser, free from the rattly interior of old Z4's and able to cover huge distances in ample comfort.

What I wanted to do then was to retain as much of the long distance capability as possible whilst making it far sharper when faced with anything other than a straight line. Some research and I found that underneath these cars are a right old mash of their own parts in the middle, E90 3 series at the front end and the outgoing E85 Z4 at the back. To improve handling then the easiest thing to do would be to rob suspension components off of the E92 M3 and Z4M. These parts are lighter, stronger and most importantly replace the squishy rubber bushings with ball joints resulting in far less deflex under load, the difference can be seen below in the E92 M3 lower wishbone;



I had tried fitting an M3 anti roll bar however found a plug on the electronic power steering unit foul's it so an aftermarket roll bar from H&R or Eibach is the only way to go. This is unfortunate as the M3 bar is a lot lighter. The plug only just fouls the bar so I did try both and franky couldn't tell the difference, I may try to modify this in the future to get the M3 bar to fit.
The end result of the front end looks like this. Apologies for all the mud, I am in Cornwall afterall!



Not so much to photograph on the rear end I'm afraid, as per the E85 Z4 it's a trailing arm with upper and lower control arms, these three parts are slightly altered for the E89 Z4's and so are unique, the rubber bushes within the hub aren't however and can be swapped for the ball joints from the old Z4M.
BMW handily fitted ball joints to the upper control arm on the E89 and changed the troublesome trailing arm bushes (presumably for the better however may look into this) so these both stay. The only change is that one bushing on the lower control arm to that from the Z4M and a stiffer rear anti roll bar.

After this (and ditching the runflats for some proper tyres) I have to say it is completely transformed. I was hoping for a bit better turn in ability, less body roll and maybe even something resembling steering feel.
Well the end result was all of the above plus what I did not expect was the huge increase in mechanical grip from the front end! It now just darts into a corner and grips, It's been this way for roughly four months now and I can honestly say I still haven't been able to get it to understeer yet, maybe I'm just not brave enough.
Turn in is genuinely sharper than that of the VX220, if less linear. It still doesn't handle quick direction changes like the VX but at nearly twice the weight and somewhat taller I don't feel it's ever going to, outright grip is definitely beyond that which the Vauxhall can manage however and in combination with the extra power, the VX wouldn't see which way this thing went down most roads (let alone the standard Z4 whose stability control light would be incessant).

Speaking of extra power, a thorough engine service involving changing the usual oil/filters as well as coolant, spark plugs, ignition coils and the rocker cover complete with a new gasket led to a visit to the kind folks at Evolve Automotive for a custom ECU calibration and roughly 360hp which really brought it alive. I'm aware the engines in these are really quite solid so may look into getting closer to 400hp if I can maintain reliability.

Apologies for waffling on, this turned out somewhat longer than I thought and I've probably missed something somewhere. Nevertheless, onto some photos (I don't have many with the new bumper on);

Up in Wales for a weekend;




In it's natural state, pasted in mud and brake dust;


Shortly after fitting the new steering wheel, well worth doing as it was the only part of the interior showing any wear


And finally, looking far too clean on the BMW stand at this years Silverstone Classic


Plenty more to come from this yet I hope! I have a feeling the brake calipers from F series M3's will fit these, just a question of whether or not they'll get under 18'' wheels as I don't want to sacrifice the better ride of them over 19'' alloys.

Number_Six

157 posts

103 months

Tuesday 23rd October 2018
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We have almost identical cars down to the year, trim, wheels and colour. Excellent choice, biased as I am!

mato

36 posts

180 months

Tuesday 23rd October 2018
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The F series calipers will fit the front of it is e90 based, you could go for the smaller disc, still retaining the 4 pot calipers.

SamJB

Original Poster:

83 posts

131 months

Wednesday 24th October 2018
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mato said:
The F series calipers will fit the front of it is e90 based, you could go for the smaller disc, still retaining the 4 pot calipers.
You're right however the problem there is that I'd be effectively taking the existing brakes and fitting smaller, less effective ones in their place. Unless I'm mistaken, I don't think it's legal to do that either.
Larger or the same size discs would be fine however smaller is a no go. It'd have to be the 370mm disc and caliper if I did do anything, for 18'' wheels it seems to be down to their design as to whether the caliper will fit or not.

shalmaneser

5,934 posts

195 months

Wednesday 24th October 2018
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A brief look at ECP seems to suggest that the 35i has 330 or 348mm front brake discs.

I'm running CSL discs @ 345mm on my e46 M3 using porsche calipers with the standard 18" wheels and there is sufficient clearance if you use a 12mm spacer on the front.

This would suggest you might be OK with four pot calipers - certainly worth looking into I'd have thought.

I was worried about the handling implications of running spacers but I can confidently say that 12mm spacers have had no discernible effect on the handling whatsoever. And they make the car look much better with the wheels filling the arches somewhat better.

Lovely looking car, and some very tasteful mods.

CarAbuser

695 posts

124 months

Wednesday 24th October 2018
quotequote all
I'm interested in the changes you made to the suspension, what hardware did you purchase?

How much of the improvement came from ditching the runflats and how much from the suspension changes?

SamJB

Original Poster:

83 posts

131 months

Thursday 25th October 2018
quotequote all
CarAbuser said:
I'm interested in the changes you made to the suspension, what hardware did you purchase?

How much of the improvement came from ditching the runflats and how much from the suspension changes?
I've put the BMW part numbers below, I hope that helps. You can get these directly from BMW if you really want the little M logo's on or TRW are the supplier for BMW so you can get the exact same part just with the M logo shaved off from any motor factor.
Front suspension:
Left Tension Strut With Rubber Mounting - 31102283575
Right Tension Strut With Rubber Mounting - 31102283576
Wishbone Left - 31102283577
Wishbone Right - 31102283578

Rear suspension:
Ball Joint (X2) - 33306852895

The order I did things went tyres > roll bars > suspension components.
In my opinion the tyres mainly improved comfort and road noise, there was a noticeable increase in traction under acceleration and braking but still a lot of understeer through corners.

The roll bars made much more of a difference by pretty much doing what they say on the tin and reducing roll, I don't think there was so much of a difference in outright grip as there was in your confidence to go that bit quicker due to the much improved control in the way the car reacts. Definitely a big improvement though as it made the car much more enjoyable. After fitting these I'd say its a little more jiggly over really bad surfaces but the rest of the time it's still just as good a cruiser as before.

The M3 parts bring the bigger differences in outright grip, I don't know how the car would react with these parts and the standard roll bars but I'm sure it can only be an improvement. The steering response is much sharper and faster to tun in along with almost eradicating understeer. Initial turn in actually feels lighter through the steering wheel before it weights up and gives little nibbles of information through the wheel of what the front tyres are doing, nowhere near the sort of feedback that comes with the VX220 but much, much improved on standard.

There are a few things to be aware of if you do want to do something similar, in order to change the rear bar you'll need to drop the entire exhaust, not too much trouble but the studs may be rusted to death making them a right pain to get apart, the levelling sensor for the xenon lights is on the other side on 3 series' so you'll need to make a small bracket to connect to the lower wishbone then check the lights are aligned correctly and after fitting the suspension components an alignment will be required too, the lower wishbones on the M3 are slightly longer than standard so you'll have a huge amount of toe in to get rid of as well, there's plenty of adjustment in the Z4's suspension but BMW track rods are extremely good at seizing up so some heat may be required.

SamJB

Original Poster:

83 posts

131 months

Thursday 25th October 2018
quotequote all
shalmaneser said:
A brief look at ECP seems to suggest that the 35i has 330 or 348mm front brake discs.

I'm running CSL discs @ 345mm on my e46 M3 using porsche calipers with the standard 18" wheels and there is sufficient clearance if you use a 12mm spacer on the front.

This would suggest you might be OK with four pot calipers - certainly worth looking into I'd have thought.

I was worried about the handling implications of running spacers but I can confidently say that 12mm spacers have had no discernible effect on the handling whatsoever. And they make the car look much better with the wheels filling the arches somewhat better.

Lovely looking car, and some very tasteful mods.
348mm discs on the European 35i, in America it's only the 35is that has 348mm discs and the 35i has 330mm for some reason.

Porsche calipers with the existing discs was another option I was looking at actually, is there a marked improvement with those fitted?

It should be said that the standard 35i brakes aren't bad at all, a little better never hurts though?

shalmaneser

5,934 posts

195 months

Thursday 25th October 2018
quotequote all
SamJB said:
shalmaneser said:
A brief look at ECP seems to suggest that the 35i has 330 or 348mm front brake discs.

I'm running CSL discs @ 345mm on my e46 M3 using porsche calipers with the standard 18" wheels and there is sufficient clearance if you use a 12mm spacer on the front.

This would suggest you might be OK with four pot calipers - certainly worth looking into I'd have thought.

I was worried about the handling implications of running spacers but I can confidently say that 12mm spacers have had no discernible effect on the handling whatsoever. And they make the car look much better with the wheels filling the arches somewhat better.

Lovely looking car, and some very tasteful mods.
348mm discs on the European 35i, in America it's only the 35is that has 348mm discs and the 35i has 330mm for some reason.

Porsche calipers with the existing discs was another option I was looking at actually, is there a marked improvement with those fitted?

It should be said that the standard 35i brakes aren't bad at all, a little better never hurts though?
The Porsche calipers are definitely an improvement for the e46 M3 which is quite badly underbraked, some fast B road driving will overheat the standard calipers pretty quickly. The CSL discs and Porsche calipers are much much better in this respect, and the aluminium calipers are lighter that the standard items, too.

While I'm sure the porsche calipers will be an improvement for the z4, I was more using my experience with similar dimensioned components to illustrate that should you want to it's fairly likely you'll be able to get four-pots on you car if you wish!

Plus it is nice to see some big old monoblock calipers poking out from behind your alloys!

scz4

2,503 posts

241 months

Thursday 25th October 2018
quotequote all
Great info above, I've taken note smile

Looks all of the above can be had for no more than £250 from here (front end) - https://www.onlinecarparts.co.uk/trw-2201926.html

What geometry settings have you gone with for "fast road"?

No lowering springs planned?

CarAbuser

695 posts

124 months

Thursday 25th October 2018
quotequote all
SamJB said:
I've put the BMW part numbers below, I hope that helps. You can get these directly from BMW if you really want the little M logo's on or TRW are the supplier for BMW so you can get the exact same part just with the M logo shaved off from any motor factor.
Front suspension:
Left Tension Strut With Rubber Mounting - 31102283575
Right Tension Strut With Rubber Mounting - 31102283576
Wishbone Left - 31102283577
Wishbone Right - 31102283578

Rear suspension:
Ball Joint (X2) - 33306852895

The order I did things went tyres > roll bars > suspension components.
In my opinion the tyres mainly improved comfort and road noise, there was a noticeable increase in traction under acceleration and braking but still a lot of understeer through corners.

The roll bars made much more of a difference by pretty much doing what they say on the tin and reducing roll, I don't think there was so much of a difference in outright grip as there was in your confidence to go that bit quicker due to the much improved control in the way the car reacts. Definitely a big improvement though as it made the car much more enjoyable. After fitting these I'd say its a little more jiggly over really bad surfaces but the rest of the time it's still just as good a cruiser as before.

The M3 parts bring the bigger differences in outright grip, I don't know how the car would react with these parts and the standard roll bars but I'm sure it can only be an improvement. The steering response is much sharper and faster to tun in along with almost eradicating understeer. Initial turn in actually feels lighter through the steering wheel before it weights up and gives little nibbles of information through the wheel of what the front tyres are doing, nowhere near the sort of feedback that comes with the VX220 but much, much improved on standard.

There are a few things to be aware of if you do want to do something similar, in order to change the rear bar you'll need to drop the entire exhaust, not too much trouble but the studs may be rusted to death making them a right pain to get apart, the levelling sensor for the xenon lights is on the other side on 3 series' so you'll need to make a small bracket to connect to the lower wishbone then check the lights are aligned correctly and after fitting the suspension components an alignment will be required too, the lower wishbones on the M3 are slightly longer than standard so you'll have a huge amount of toe in to get rid of as well, there's plenty of adjustment in the Z4's suspension but BMW track rods are extremely good at seizing up so some heat may be required.
Thanks for the info.So in addition to this you just fitted H&R anti roll bars?

Definitely adding these mods to the list as I agree that the steering feel is lacking and it does understeer. I think catless downpipes and an uprated intercooler will be first to push the power a little higher, still on the fence about a LSD.

I'm not going to touch the dampers or springs since I have the adaptive damper option and any aftermarket springs will lower the car rub on the rear because of my wider than stock wheels.

SamJB

Original Poster:

83 posts

131 months

Thursday 25th October 2018
quotequote all
Not a problem guys! If anyone else wants some help with doing similar, just drop me a message. Currently helping a friend do this with their 335d so should be familiar with the rear suspension on the E9x's soon too.

scz4 said:
Great info above, I've taken note smile

Looks all of the above can be had for no more than £250 from here (front end) - https://www.onlinecarparts.co.uk/trw-2201926.html

What geometry settings have you gone with for "fast road"?

No lowering springs planned?
Precisely, the M3 parts aren't particularly expensive. Due to the, err 'mixed' surfaces the car covers down here, lowering the suspension isn't something I want to do at the moment. I'd recommend trying this before changing out springs/dampers as it compromises the ride far less.

In regards to geometry, I just stuck moreorless to the standard settings. There could be more to have in getting a fast road setup done, I sent my old Z4 to a local Lotus specialist who did a marvellous job so may do that again in the future.

At the time I did the alignment myself with BMW's target data from Bosch.
There was nothing to adjust at the rear, that was all exactly the same having only changed one ball joint each side, the front had a whopping 3.37 degrees of toe in initially however we soon dialled that back to the target 0.14. Front camber was the only other thing that changed, before doing anything it was -0.40 degrees both sides and afterwards -0.50 degrees, these are the upper reaches of BMW's targets but within tolerance so left it as is. Hope that helps!

Mikeeb

406 posts

118 months

Thursday 25th October 2018
quotequote all
Im interested to see what you find on the 335d. Been looking at how I can improve mine and had come up with similar ideas. Was planning to start in the new year. So looks like I can use you as the test pilot!!

Mr Tidy

22,327 posts

127 months

Friday 26th October 2018
quotequote all
Really informative thread OP. thumbup

If I move on from my E86 3.0Si to an E89 then a manual 35i would be what I would want - maybe with a sneaky remap! laugh

And I love your red interior!

SamJB

Original Poster:

83 posts

131 months

Tuesday 30th October 2018
quotequote all
Mr Tidy said:
Really informative thread OP. thumbup

If I move on from my E86 3.0Si to an E89 then a manual 35i would be what I would want - maybe with a sneaky remap! laugh

And I love your red interior!
Thanks! I'd really recommend Evolve Automotive for remapping, they were one of the first to start playing with these engines so have a lot of experience, will also give you before and after dyno runs so you can see how healthy the car is beforehand and how much you've gained afterwards.

I'm really liking the read leather as well, it's a much softer shade of red than some of the more in you're face shades around (Looking at you Audi)

Julian Thompson

2,543 posts

238 months

Tuesday 30th October 2018
quotequote all
Some great info here. I was looking closely at upgrading my z4 brakes and made some notes which might be of some use if you don’t have part numbers. Some will be nonsense so just ignore.

I still can’t find a way to upgrade the rears particularly as they have the electric handbrake. Any ideas?

Z4 Brakes

20i to 30i has 300x20mm
MTEC6067 £158.60

Rear - E89 Z4 35is

34206786067 Caliper housing left
34206786068 Caliper housing right
34206786069 brake carrier x2


DISCS (324x20mm) 34216782607
PADS 34216796741

FRONT

6 piston bmw kit: 34110444738 338x26

might be these:
N/S Caliper 34116786741
 O/S Caliper 34116786742
 N/S Disc     34112282445
 O/S Disc     34112282446

BMW Performance 4 pot:
yellow: 34106855475 + ...6
red: 34106855477 + ...8
orange: 34106855479 + ...80
discs 370x30 mm (drilled): 34106797603
dust cover: 34116792237 + ...8
brake pads: 34116859066

2 pot:
N2SHA sport brake package:
235i F45
rotors 34106797602 (340x30mm, slotted/drilled)
caliper right 34116799466, 2pot blue + ///M badge
caliper left 34116799465, 2pot blue + ///M badge
pads 34116859066



Julian Thompson

2,543 posts

238 months

Tuesday 30th October 2018
quotequote all
Ps that interior looks fabulous!

SamJB

Original Poster:

83 posts

131 months

Wednesday 31st October 2018
quotequote all
Julian Thompson said:
Some great info here. I was looking closely at upgrading my z4 brakes and made some notes which might be of some use if you don’t have part numbers. Some will be nonsense so just ignore.

I still can’t find a way to upgrade the rears particularly as they have the electric handbrake. Any ideas?
Unfortunately it seems that the rear end is pretty much unique to the Z4 so upgrading the rear brakes is going to be quite an involved process! Audi brakes might be one way to go with this which would then just mean getting hold of discs of a larger size.
The rear brakes are already a fairly generous size on the six cylinder cars (I think my old Z4 only had 325mm on the front!) so shall do something with the fronts first as they do the vast majority of the work then think about the rears if necessary.

Julian Thompson said:
BMW Performance 4 pot:
yellow: 34106855475 + ...6
red: 34106855477 + ...8
orange: 34106855479 + ...80
discs 370x30 mm (drilled): 34106797603
dust cover: 34116792237 + ...8
brake pads: 34116859066
This is exactly the route I'm going, I've gotten hold of calipers from an M4 and the discs will be the 370mm ones you've mentioned (TRW's number for these is DF6600S).

The calipers I'll reseal, sand down and repaint silver. In keeping with the theme, some M4/M3 wheels are also on the way as the 18's aren't going to clear the new calipers!
Hopefully I'll have this sorted within the next few weeks so shall keep things updated here.

SamJB

Original Poster:

83 posts

131 months

Wednesday 31st October 2018
quotequote all
Julian Thompson said:
Ps that interior looks fabulous!
Thanks! I'm really impressed by how well everything in there's worn over time. Given a good tidy up and with the new steering wheel it looks very close to brand new.

spreadsheet monkey

4,545 posts

227 months

Wednesday 31st October 2018
quotequote all
SamJB said:
Speaking of extra power, a thorough engine service involving changing the usual oil/filters as well as coolant, spark plugs, ignition coils and the rocker cover complete with a new gasket led to a visit to the kind folks at Evolve Automotive for a custom ECU calibration and roughly 360hp which really brought it alive.
Yowzers. 360hp in an E89 Z4! Must really shift.

Nice car. As others have said, the red leather looks great.