Looking for some advice or experience opinons

[Enigmatik]

Hey folks, having had me Z4 (2006 2.5 sport) for coming up for a year, it's getting to the point where I need to start planning some work. So far work has extended to:

- replace the Oil cooler/Oil filter gaskets which were leaking
- oil change with Millers EE Performance
- fitted a factory Wind Deflector
- good clean and detail
- sanded and Restored Headlights
- replaced HID bulbs, a ballast and ignitor
- replaced headlight washer jet
- replaced broken rear bumper bracket
- replaced high level brake light with clear

Next on list are (and reasons I'm asking for advice):

- wheel refurb and tyre replacement. (It has aftermarket alloys on 225/40/R18 all round and spacers fitted) I think tyres are 18x8 but need to check, tires look at little stretched
- suspension refresh, think it's on standard sport suspension. Looks good but a little more travel might be good as it tends to bottom out on fast dips
- brake refresh and updates

So the questions and opinons I'm looking for are:

- Should I stick with 225/40 or go to 235/40?
- Suspension opinions are personal and vary and I've read a few of the threads. I think shock wise Bilstein B6 is aim, springs seem to be the hard bit, I don't find the car particularly hard or firm at present, but the bottoming out on A or B roads does take the fun out of it.
- I've read the cheap update option post suggesting e46 330i brakes 325mm front and 320mm rear, but it notes this combo was never fitted to a Z4, which maxed out at 294mm rears. Does anyone have the full 330ci set up and how is it for balance and weight, I can find a set fairly cheap and as I need to do the brakes I'd rather upgrade while I can.

If you have taken time to read all this thanks and all thoughts or opinons are welcome.

 

[enuff_zed]

Regarding the suspension, I would suggest the bottoming out is far more likely to be a symptom of knackered dampers, not the springs.
I think you would probably find you can swap the dampers and keep the springs you have unless they are obviously damaged.
I have done exactly that a fw times now and it stops all the crashing and banging.

 

[Rockhopper]

Agreed. Also your wheels should be staggered so the rears are wider than the fronts. Its not uncommon to find people fitting the same size tyres all round which is why they might look stretched.

 

[Enigmatik]

Hey enuff_zed

Regarding the suspension, I would suggest the bottoming out is far more likely to be a symptom of knackered dampers, not the springs.
I think you would probably find you can swap the dampers and keep the springs you have unless they are obviously damaged.
I have done exactly that a fw times now and it stops all the crashing and banging.

So just some new shocks, ok, that's cheaper, works for me! B6 or B8?

 

[Enigmatik]

Agreed. Also your wheels should be staggered so the rears are wider than the fronts. Its not uncommon to find people fitting the same size tyres all round which is why they might look stretched.

Might mean new wheels then as the wheels are same sizes front and back, with different spacers to fill the arches.

 

[enuff_zed]

Hey enuff_zed

Regarding the suspension, I would suggest the bottoming out is far more likely to be a symptom of knackered dampers, not the springs.
I think you would probably find you can swap the dampers and keep the springs you have unless they are obviously damaged.
I have done exactly that a fw times now and it stops all the crashing and banging.

So just some new shocks, ok, that's cheaper, works for me! B6 or B8?

No experience of either I'm afraid. I fit Sachs myself. Others will be able to advise I'm sure.
I would also budget for new top mounts, bump stops and for the front end, new knuckle bolts which clamp the bottom of the strut in. As it's all apart it would be false economy not too, unless these items have been replaced recently.
From personal experience do NOT use Meyle HD rear top mounts as they can knock badly.
My personal shopping list is usually OEM Sachs shocks, Febi Bilstein bump stops and Lemforder top mounts, purely because I've used them before and know they work.
Will you be doing the work yourself?

 

[Enigmatik]

Thanks for that enuff_zed, I'll do a list, agree with replacing other stuff while things are off. I'll probably order from Autodoc. I'll take a look at the Sachs, are these just same damping levels as the originals?

 

[enuff_zed]

Thanks for that enuff_zed, I'll do a list, agree with replacing other stuff while things are off. I'll probably order from Autodoc. I'll take a look at the Sachs, are these just same damping levels as the originals?

The Sachs are direct replacement. No upgrade as such.
I get almost everything from Autodoc, though be warned they seem to have slowed their delivery times over the last month or so.
I got the knuckle bolts from ebay.
https://www.ebay.co.uk/itm/175141185140

 

[Zedebee]

Agreed. Also your wheels should be staggered so the rears are wider than the fronts. Its not uncommon to find people fitting the same size tyres all round which is why they might look stretched.

Might mean new wheels then as the wheels are same sizes front and back, with different spacers to fill the arches.

Which wheels are you running? Plenty of owners run “square” sets, which are more practical in some respects as you can swap them front to back to manage wear. I have a square set on for winter (et34, so no need for spacers) and a staggered set for summer.

 

[Enigmatik]

The Sachs are direct replacement. No upgrade as such.
I get almost everything from Autodoc, though be warned they seem to have slowed their delivery times over the last month or so.
I got the knuckle bolts from ebay.
https://www.ebay.co.uk/itm/175141185140

Ok I'll take a look as that might work, the A and B Roads around Scotland tend not to be the best so don't need anything too stiff as it corners pretty flat as it is. Know what you mean about Autodoc, just taken delivery of some stuff for friends car I ordered nearly 3 weeks ago. I'll get some of the bolts ordered up. Thanks really appreciate the help.

 

[Enigmatik]

Which wheels are you running? Plenty of owners run “square” sets, which are more practical in some respects as you can swap them front to back to manage wear. I have a square set on for winter (et34, so no need for spacers) and a staggered set for summer.

I think after some googling these are them:

https://www.wheelbasealloys.com/alloy-wheels/drc/dmf/gun-metal-polished/18-inch/bmw/z4/e85-e86



They have the same DRC centre caps, I need to pull one off to check the et, but looks like a 10mm or 15mm spacer on the front and 20mm or 25mm on the back. They need a refurb as the spokes project a bit past the rim, definitely seem to be 18" by 8" and with 225/40 wheels.

 

[LittleZ4]

Just my 2 pence worth when it comes to the brakes. The fronts upgrade easily using the 330i set up but the rears don't. I understand you can fit them but you won't have a handbrake unless you machine an insert for the drum (I think there's a 26mm difference on the internal diameter compared to the 294mm discs) or weld two sets of handbrake shoes together.

 

[Enigmatik]

Just my 2 pence worth when it comes to the brakes. The fronts upgrade easily using the 330i set up but the rears don't. I understand you can fit them but you won't have a handbrake unless you machine an insert for the drum (I think there's a 26mm difference on the internal diameter compared to the 294mm discs) or weld two sets of handbrake shoes together.

Thanks Little, so I'm better upgrading the fronts, but looking for z4 3l rears to get to the vented 294mm then?

 

[LittleZ4]

Yeah I'd say so. Don't try to upgrade the rears with the 320mm off the 3 series. Another option is seeing if there is a 3.0si being broken. That would give you the 325mm fronts and the 294mm rears. Whilst you're at it get some braided lines. Are you refurbing the calipers?

 

[Enigmatik]

I was hoping to overhaul and tidy the replacement carriers and carriers before I ordered the discs and pads if seal kits are available. I was looking at the 3 series stuff as it seems to be a cheaper option than getting from a z4, but I'll have a look around the usual places and see what I can find. Appreciate the help, you guys are helping narrow down the shopping list.

 

[LittleZ4]

Big red do a decent refurb kit. You can order the fronts and rears separately

 

[Zedebee]

Which wheels are you running? Plenty of owners run “square” sets, which are more practical in some respects as you can swap them front to back to manage wear. I have a square set on for winter (et34, so no need for spacers) and a staggered set for summer.

I think after some googling these are them:

https://www.wheelbasealloys.com/alloy-wheels/drc/dmf/gun-metal-polished/18-inch/bmw/z4/e85-e86



They have the same DRC centre caps, I need to pull one off to check the et, but looks like a 10mm or 15mm spacer on the front and 20mm or 25mm on the back. They need a refurb as the spokes project a bit past the rim, definitely seem to be 18" by 8" and with 225/40 wheels.

That’s not a bad looking wheel on your silver car.
Moving to the slightly wider tyre will give your rims a bit more protection, but 225/40 is perfectly normal on an 18x8.

 

[Ewazix]

Check the springs carefully as the OEM rears are prone to snapping off the dual rate 'pig-tails' and can be hard to spot. Most cars of our age will have snapped at least the rears, mine first went before the first MOT, then again a few years later so mine is on it's third set. I gave up on the dual rate type and fitted single rate springs that have lasted twice as long so far, with no noticeable deterioration in ride TBH.

 

[Enigmatik]

Big red do a decent refurb kit. You can order the fronts and rears separately

Cool, I'll add to list and see if they come with pistons.

 

[Enigmatik]

Which wheels are you running? Plenty of owners run “square” sets, which are more practical in some respects as you can swap them front to back to manage wear. I have a square set on for winter (et34, so no need for spacers) and a staggered set for summer.

I think after some googling these are them:

https://www.wheelbasealloys.com/alloy-wheels/drc/dmf/gun-metal-polished/18-inch/bmw/z4/e85-e86



They have the same DRC centre caps, I need to pull one off to check the et, but looks like a 10mm or 15mm spacer on the front and 20mm or 25mm on the back. They need a refurb as the spokes project a bit past the rim, definitely seem to be 18" by 8" and with 225/40 wheels.

That’s not a bad looking wheel on your silver car.
Moving to the slightly wider tyre will give your rims a bit more protection, but 225/40 is perfectly normal on an 18x8.

Thanks I liked how it looked, having looked at a rough 3.0l with 19" or 20" on it, I figured 18" were bit more useable and different from standard. Just need to decide if they stay plain silver or go gunmetal when refurb. Kind of torn as 235 would protect the rims, but extra rubber might be bit too much performance wise.