E86 z4 3.0si - road and track build - upgrades advice

[Jt23]

Hey all, recently picked up a 2008 e86 z4 3.0si as a fun weekend car and occasional track use. Been wanting to get into track for a long time and after a day at palmersport in August I finally bit the bullet and bought a car to build out for next season.

Looking for some advice for upgrades I plan to make. Some will go on over winter before getting out on track in spring, some after I get started - I don't want to entirely pre-prep the car because I want to experience the shortfalls I'm trying to remedy so I better understand what benefit they have for the car when they do go on. I feel this will make me a better driver and give me a stronger understanding of how cars perform on track.

Been digging through historic threads and have gotten some ideas already, but would be great to get some feedback, comparison, or suggestions I've not come across.

Suspension
So far it looks like popular options for mixed use on the e86 are:

Kw v3 - £2-2.3k

Bilstein b16 pss10 - £1.5-1.7k

Bc racing br series - approx 1k

Ohlins are likely to be out of budget unless heavily discounted for black friday.

Bc are most budget friendly but I don't want to end out swapping later to upgrade again, leaning toward kw or bilstein - any thoughts?

Brakes
I know less here, how are the si brakes on track? I know they got a bigger set than the 3.0i, and that cooling and pads are key.

Upgrade wise, to begin with I'm hoping to focus on cheaper upgrades, thinking:

Braided lines

EBC bluestuff track pads

Brake cooling ducts to replace the fog lights (already had these made).

Further down the line, I'd like to upgrade to floating calipers, 4 or 6 pot. I've heard 130i/135i bmw performance brakes with e46 m3 discs can fit, and there are some dedicated bbks out there, some using renault calipers, but really not sure what's best for my application, and most cost effective. I've also heard the 130/135 calipers have ceramic pistons which can crack under track temps.

Any tried and tested approaches, kits, or swaps from other models for brake upgrades? And when upgrading discs and calipers, is it best off doing all 4 corners? Seems like it's easier and cheaper to just upgrade the fronts, but concerned this might mess with brake bias?

Limited slip diff

Fairly certain i'll go with a Quaife helical ATB fitted at birds. Seems to have solid in the field feedback and birds are well regarded.

I know the wavetrack won't spin a wheel if it lifts, but from what I've heard more is made of this than is really an issue, and it's a bit of a gimmick. For the extra money, I suspect I'll notice little difference.

Aero

Lowest priority on my list, definitely wrll into next year, but I do currently have a fairly large gt wing on the car (came with it) seems like a cheap ebay special, looks ok, but is aluminium and the mounts look weak. Considering replacing this

Almost purely on looks, I'm also considering a fancywide rear diffuser.

I'd like a front splitter, again largely for looks but any performance gains are welcome. Have had trouble finding one I like.

For areo in general i don't like the maxton design stuff, AP and varis are nice but very expensive. Any suggestions are welcome.

--
Thanks for any advice you can give, or if I've missed anything. I know I don't need everything here to get out on track, but would love to slowly build it up into a street/track weapon - comfortable with the compromise dual use brings

[danb79]

Jt23 said:

Hey all, recently picked up a 2008 e86 z4 3.0si as a fun weekend car and occasional track use. Been wanting to get into track for a long time and after a day at palmersport in August I finally bit the bullet and bought a car to build out for next season.

Looking for some advice for upgrades I plan to make. Some will go on over winter before getting out on track in spring, some after I get started - I don't want to entirely pre-prep the car because I want to experience the shortfalls I'm trying to remedy so I better understand what benefit they have for the car when they do go on. I feel this will make me a better driver and give me a stronger understanding of how cars perform on track.

Been digging through historic threads and have gotten some ideas already, but would be great to get some feedback, comparison, or suggestions I've not come across.

Suspension
So far it looks like popular options for mixed use on the e86 are:

Kw v3 - £2-2.3k

Bilstein b16 pss10 - £1.5-1.7k

Bc racing br series - approx 1k

Ohlins are likely to be out of budget unless heavily discounted for black friday.

Bc are most budget friendly but I don't want to end out swapping later to upgrade again, leaning toward kw or bilstein - any thoughts?

Brakes
I know less here, how are the si brakes on track? I know they got a bigger set than the 3.0i, and that cooling and pads are key.

Upgrade wise, to begin with I'm hoping to focus on cheaper upgrades, thinking:

Braided lines

EBC bluestuff track pads

Brake cooling ducts to replace the fog lights (already had these made).

Further down the line, I'd like to upgrade to floating calipers, 4 or 6 pot. I've heard 130i/135i bmw performance brakes with e46 m3 discs can fit, and there are some dedicated bbks out there, some using renault calipers, but really not sure what's best for my application, and most cost effective. I've also heard the 130/135 calipers have ceramic pistons which can crack under track temps.

Any tried and tested approaches, kits, or swaps from other models for brake upgrades? And when upgrading discs and calipers, is it best off doing all 4 corners? Seems like it's easier and cheaper to just upgrade the fronts, but concerned this might mess with brake bias?

Limited slip diff

Fairly certain i'll go with a Quaife helical ATB fitted at birds. Seems to have solid in the field feedback and birds are well regarded.

I know the wavetrack won't spin a wheel if it lifts, but from what I've heard more is made of this than is really an issue, and it's a bit of a gimmick. For the extra money, I suspect I'll notice little difference.

Aero

Lowest priority on my list, definitely wrll into next year, but I do currently have a fairly large gt wing on the car (came with it) seems like a cheap ebay special, looks ok, but is aluminium and the mounts look weak. Considering replacing this

Almost purely on looks, I'm also considering a fancywide rear diffuser.

I'd like a front splitter, again largely for looks but any performance gains are welcome. Have had trouble finding one I like.

For areo in general i don't like the maxton design stuff, AP and varis are nice but very expensive. Any suggestions are welcome.

--
Thanks for any advice you can give, or if I've missed anything. I know I don't need everything here to get out on track, but would love to slowly build it up into a street/track weapon - comfortable with the compromise dual use brings

Do the BMW Brembo 340mm front calipers fit this series of Z4 like they do with the 1 series (thinking of them for my 2007 130i and they're plug n play with 340mm discs); those, HEL lines and Motul fluid etc

Also considering coilovers myself as part of the Spring 2025 suspension overhaul; I'll more than likely be going for the KW V2s or the ST equivalents; not interested in BCs or Bilsteins. But the Meister R coilovers are very good too, worth having a look at them if they fit your Z4. What about GAZ coilovers?

Edited by danb79 on Saturday 9th November 20:23

[helix403]

The 340mm Brembos fit as long as they clear the wheels.

[paulwirral]

They’re a great car on track out as std , I’ve had a couple and wasn’t convinced on the road but around the ring they were great as standard .
Don’t take this the wrong way but the best way to get more out of the car is driving instruction on a track by someone who knows what they’re talking about .
Try it first before spending money on anything else , it’s genuinely the best investment you will make in a car .

[Jt23]

danb79 said:

Do the BMW Brembo 340mm front calipers fit this series of Z4 like they do with the 1 series (thinking of them for my 2007 130i and they're plug n play with 340mm discs); those, HEL lines and Motul fluid etc

Also considering coilovers myself as part of the Spring 2025 suspension overhaul; I'll more than likely be going for the KW V2s or the ST equivalents; not interested in BCs or Bilsteins. But the Meister R coilovers are very good too, worth having a look at them if they fit your Z4. What about GAZ coilovers?

Edited by danb79 on Saturday 9th November 20:23

Any particular reason you're not keen on bc or bilstein? Gaz came up at the lower end of the budget but similar range to bc and I was more familiar with the brand. I'm also leaning towards future proofing with two way adjustability, buy right buy once kind of mentality. Kw seem to be the choice there but painful if doable price tag, hoping to luck out black friday.

paulwirral said:

They’re a great car on track out as std , I’ve had a couple and wasn’t convinced on the road but around the ring they were great as standard .
Don’t take this the wrong way but the best way to get more out of the car is driving instruction on a track by someone who knows what they’re talking about .
Try it first before spending money on anything else , it’s genuinely the best investment you will make in a car .

For sure, I'm more compiling a purchase list so I can buy when convenient or on sale then install later. Will be taking it out on track before swapping anything so I get to know the car and experience the changes modifications bring. Even then one by one so I can tell which part has done what. I'm in it for the build as well as the driving, like a bit of spannering .

I did get out at Bedford with instructors previously but just an exp day, planning on going back there and taking some 121 tuition in my own car on a track day. Thruxton is close to me too so will be taking a go on the skid pan, and got myself a budget sim rig with assetto corsa to lay down some hours over winter, I've rinsed gt7 for all it's worth at this point lol.

[danb79]

Jt23 said:

danb79 said:

Do the BMW Brembo 340mm front calipers fit this series of Z4 like they do with the 1 series (thinking of them for my 2007 130i and they're plug n play with 340mm discs); those, HEL lines and Motul fluid etc

Also considering coilovers myself as part of the Spring 2025 suspension overhaul; I'll more than likely be going for the KW V2s or the ST equivalents; not interested in BCs or Bilsteins. But the Meister R coilovers are very good too, worth having a look at them if they fit your Z4. What about GAZ coilovers?

Edited by danb79 on Saturday 9th November 20:23

Any particular reason you're not keen on bc or bilstein? Gaz came up at the lower end of the budget but similar range to bc and I was more familiar with the brand. I'm also leaning towards future proofing with two way adjustability, buy right buy once kind of mentality. Kw seem to be the choice there but painful if doable price tag, hoping to luck out black friday.

Re GAZ; they have varying levels of coilovers; see what they do for your car on their website. UK made, very serviceable too

Re Bilstein; superb coilovers, the B16s are very stiff. Not good for road on the F3X platform (I test drove a 330d with them fitted, belting on the back roads/country lanes etc), but heading back on normal town roads at 30mph; we were bouncing everywhere...

BCs are fine; but they are budget unless you go up in the range. Been around a long time and are good; but they can have issues and they do like to corrode

STs are made by KW, they're just not galvenised like KWs are; worth looking at as they're generally cheaper than KWs

But as you said; buy 1st time right and no need to revisit etc

You could always go hardcore and go Nitrons

[(steven)]

I run a Z4MC as a track car and I also own a 3.0si Coupe so hopefully I can offer some advice here.

Brakes: It is the one thing you need to do for trackdays. BMW’s from this era have rubbish brakes.

I have a set of AP’s bought from Reyland motorsport with Pagid RS29 pads and they are great, but not cheap. I was chatting to a guy at Anglesey who had some second hand (Renault ???) callipers on his Z4 that he had managed to get a fitting kit for and he was having a great time.

Suspension: I would go cheaper on the suspension (BC’s or HSD Monopros) if it allows you to spend on brakes.

2/3-way suspension is great if you’re a race team and have a couple of test days and timing gear to dial a car in, but if you are just going to pitch up to a track day, set the suspension by eye and send it, I can’t see the point. Spend the money on decent alignment and brakes. Plus expensive race suspension isn’t designed for road use, so won’t take kindly to salt in the winter.

I had a mad moment and bought Intrax suspension at great expense and while its very good, I can’t help thinking I should have just stuck with the mono-pros I used to run on an old M3 track car. It’s a track day, not Le mans.

If you are going to use it on the road a lot, then suspension with decent weather protection is worth the extra spend (The HSD's hardly ever went out in the wet and were corroding after a couple of years).

Just remember a lot of track day suspension is really about spring rates. (I'm sure a suspension Guru will join the thread and properly explain how suspension works but this will do). Hard spring rates are great for the track, but are rubbish for the road. You have to prioritise one.

EBC pads: They're ‘okay’, but they are budget pads – You get what you pay for! They throw off a lot of material which sticks to your wheels & callipers when used on a track day and the wear rate isn’t great. Something like a Pagid RS29 is in a different league, but then so is the price and I wouldn’t recommend them for the road as they are grumpy when cold.

Other stuff: It’s a rabbit hole really. You could put bucket seats in, but the SI seats are so good, I’ve not fitted mine. Refreshing the bushes with poly bushes isn’t a bad shout. You can swap the rack to hydraulic as the electric steering can occasionally get confused. You could drop the diff ratio for a bit more grunt, not going to need 155 MPH top end on a track day or in the UK.

[Jt23]

steven said:

I run a Z4MC as a track car and I also own a 3.0si Coupe so hopefully I can offer some advice here.

Brakes: It is the one thing you need to do for trackdays. BMW’s from this era have rubbish brakes.

I have a set of AP’s bought from Reyland motorsport with Pagid RS29 pads and they are great, but not cheap. I was chatting to a guy at Anglesey who had some second hand (Renault ???) callipers on his Z4 that he had managed to get a fitting kit for and he was having a great time.

Suspension: I would go cheaper on the suspension (BC’s or HSD Monopros) if it allows you to spend on brakes.

2/3-way suspension is great if you’re a race team and have a couple of test days and timing gear to dial a car in, but if you are just going to pitch up to a track day, set the suspension by eye and send it, I can’t see the point. Spend the money on decent alignment and brakes. Plus expensive race suspension isn’t designed for road use, so won’t take kindly to salt in the winter.

I had a mad moment and bought Intrax suspension at great expense and while its very good, I can’t help thinking I should have just stuck with the mono-pros I used to run on an old M3 track car. It’s a track day, not Le mans.

If you are going to use it on the road a lot, then suspension with decent weather protection is worth the extra spend (The HSD's hardly ever went out in the wet and were corroding after a couple of years).

Just remember a lot of track day suspension is really about spring rates. (I'm sure a suspension Guru will join the thread and properly explain how suspension works but this will do). Hard spring rates are great for the track, but are rubbish for the road. You have to prioritise one.

EBC pads: They're ‘okay’, but they are budget pads – You get what you pay for! They throw off a lot of material which sticks to your wheels & callipers when used on a track day and the wear rate isn’t great. Something like a Pagid RS29 is in a different league, but then so is the price and I wouldn’t recommend them for the road as they are grumpy when cold.

Other stuff: It’s a rabbit hole really. You could put bucket seats in, but the SI seats are so good, I’ve not fitted mine. Refreshing the bushes with poly bushes isn’t a bad shout. You can swap the rack to hydraulic as the electric steering can occasionally get confused. You could drop the diff ratio for a bit more grunt, not going to need 155 MPH top end on a track day or in the UK.

Thanks this is all really helpful, I have heard of renault compatibility, could it be this set?

https://k-system.pro/en/product/bmw-e36-e46-z3-z4-...

Funds wise, not so much of an issue, saving on uneeded spend is definitely worthwhile, but equally happy to pay out to avoid revisting a mod later.

Bc's I've heard can knock a bit, hadn't looked at hsd, what's the quality like?

Suspension wise, Kw v3s are stainless steel which attracted me from a corrosion pov as it will see some road use like you say, but I was also thinking about over complicating set up / how often I'd be adjusting. The V3s are their top end street / sometimes track suspension, but they can be upgraded to clubsport further down the line using most of the v3 components though which would be a bonus if I pushed further down the track focused route with time.

This is a third car for me, purely for weekend blasting and track, so it's possible it might go that way. I don't need to daily it, but that said I'd still like to be able to enjoy it on the road still even if it is stiffer than I'd go for a pure street build.

I'm also keeping the seats in, you're right they are too nice. Look great in the car too.

Good shout on the pads, any other brands I should consider? Also how long does a set last you on track?

[paddy1970]

To do in this order:

1. Geometry

2. Brake (braided, duct, track pads)

3. Semi slick tyres

4. Sway bars

5. Seats

6. Steering wheel

7. Suspension

8. Wing

Try to do a track days between each step...and don't forget about the roll bar... preferably before step 3...

[(steven)]

Jt23 said:

Thanks this is all really helpful, I have heard of renault compatibility, could it be this set?

Could well be.

Jt23 said:

Bc's I've heard can knock a bit, hadn't looked at hsd, what's the quality like?

They are about £800 a set, which means they cost £200 a corner, which must mean they are made for about £50 each, so they aren’t going to be the highest quality, but probably no worse than anything else at that price point. However, other than the corrosion resistance being fairly poor I never had any issues with mine!

The main issue I had was they were a bit difficult to adjust on the car, so I was forever jacking it up and sticking it on axel stands on track days which was fine, but a bit of a faff. I suspect if you tried to do 10K miles on them a year they would be dead pretty quickly. I had mine on a track car for 5 of so years and they were fine.

From what I remember when I looked, there was no perfect coilover for the Z4. Some are cheap, some are easier to set up, some are better at corrosion resistance and some are better at being suspension.

There wasn’t an easy to setup, corrosion resistant (to OEM levels), top quality coilover available at any price. If I remember correctly from when was looking, the KW were well liked but I believe the rear coilovers are hard to adjust when on the car, but I might be mistaken.

I also thought the V3’s came with relatively soft spring rates (could be wrong), but if you’re using it on the road, that isn’t a bad thing. The spring rates on my Intrax are way too hard for the road.

Jt23 said:

Good shout on the pads, any other brands I should consider? Also how long does a set last you on track?

IIRC blue stuff was probably 2 maybe 3 days. The RS29’s last for ages. There is a couple of threads on here which are worth going through. Track pads the trade off is price, heat resistance and on-road performance.

paddy1970 said:

To do in this order:
3. Semi slick tyres
7. Suspension

I would have suspension higher up the list if doing track work if for no other reason than it will allow you to run more extreme geo, which will make your tyres last longer.

Plus sticky tyres will make you go faster, but sticky tyres if you haven’t sorted your suspension out will make your car feel very wobbly on track.

[Jt23]

One thing I've been meaning to find out, when upgrading front brakes, what about the rears? Upgrade too or leave stock, and maybe just upgrade pad and disc?

See a lot of kits just offering the front

[danb79]

Jt23 said:

One thing I've been meaning to find out, when upgrading front brakes, what about the rears? Upgrade too or leave stock, and maybe just upgrade pad and disc?

See a lot of kits just offering the front

Upgrade pads / discs / lines for now. The fronts do all the work really