Track days - what wheels and tyres?

[brillomaster]

So I want to buy an E85 Z4 3.0 for trackdays, but before I do I thought I'd ask what other trackday goers have gone for with wheel setups...

my plan is to take the 18" MV1 alloys off my current track car and use them - which would therefore be 8" front, 8.5" rear, running a 245/35 front and 255/35 rear tyre, Federal 595 RS-Rs btw.

Does this sound a reasonable starting point? alternatively I could source some 17s, but due to a narrower wheel I'd probably have to run a 235 up front.

I ideally want to minimise the trademark BMW understeer, so normally I'd move away from a staggered wheel setup, does a Z4 work ok with a square setup?

any first hand experience much appreciated!

 

[TomK]

I can't really comment too much as mine is an M which has a different chassis set up, but I would have thought the 18s you have would do just fine. I think these days you have a bit more choice with 18 over 17 in terms of tyre selection, and the price difference isn't great? I'm not sure I would want to run on track with such a tall sidewall either as they're a relatively heavy car.
On my 18's I use a 235/40, 265/35 on an 8 1/2" front and 9 1/2 " rear, the car runs around 380hp and really doesn't understeer much unless you're an oaf. Is a 245 section not a little wide for an 8" front?
I'm not sure about a square setup on the 3.0 but I would have thought it should be possible with a lot of -ve camber at the front, which would probably require adjustable camber mounts which are quite expensive. I'm sure some more knowledgeable folk can confirm either way.
Really though I think it's best trying to dial out understeer with geo alterations rather than changing tyre size relatively which brings it's own downsides imo. At a minimum get as much -ve camber on the front as you can.
Have a look at the Nankang NS2-R (180 compound), similar price to the feds and having used both (albeit on different cars) I'd definitely say the ns2-r is the better tyre. DOn't get the softer compound(120), the z4's weight killed mine extremely quickly.
Enjoy

 

[brillomaster]

interesting that you run narrower front tyres than i do at the moment, but dont suffer from understeer - generally i'm finding that i can apex ok, but then when getting back on the power it'll have a tendency to just drift wide and i run wide on the exits. i think more negative camber would help, but i'm just working with standard struts at the moment which only give about -1.4 deg of camber, when ideally for a track car i'd run closer to -3 deg.

it may also be a rake thing, had to jack the car up at the front so the wide wheels would clear the spring perches, so i think when i get back on the power, too much weight is shifting over the rears so front end has less bite.

but i guess i'll see... but certainly i'll start with what i've got knowing it wont be a million miles away, and go from there