Going in for camber adjustment tomorrow

[Twin Turbo]

Interesting post..

I am planning in purchasing some new summer tyres, I dont have the same issues as I have an wee 4 Pot.

But reading in other forums - there is an consensus of having upgrading the front tyres from 225 to 255?

Whats everyone thoughts on this?

Please don't do that - plus, I don't think it would even fit under the arch. My BBS are 0.5" wider front/rear, and it was "just" flush at the front, the tyre fitter was concerned it would rub. The front could take 235 (one size up), but I won't bother.

For an experiment I swapped the front & rear wheels on my car, 255/35R18 on an 8.5j rim. It did fit just, there was no scrubbing after a fairly hard 15min drive. However the wide tyres at the front resulted in needing exaggerated steering input and also introduced turn-in understeer, this was exaggerated on direction changes. However, once settled into a corner there was a lot more grip at the front end. As 245/40R18 tyres produced even more turn-in understeer than 255/35R18, I'm thinking that 245/35R18 with 10mm lower springs at the front will dial this out.

The fronts are 245/40R18 on 8j rims:

Many thanks for trying this out,

 

[Garvin]

. . . . . if you want a track car why in gods name did you buy a E89 Z4? It's setup for 4-6/10ths GT fast road driving.

I couldn't 't agree more. The old saying "you can't polish a turd" comes to mind! E89 is a great GT car but no sports car and no way on God's good earth is it a decent track weapon.

 

[techathy]

At the risk of contradicting my self. The chassis is very capable and certainly a good base for a front engined, RWD sports car. The problem is the car wrapped around the base chassis. So much of it needs to be peeled off & reworked that it’s not really a viable platform unless you plan to go racing.

 

[stuartinzg]

I've ordered some Eibach pro-kit springs.
Looking into rear camber adjustment arms and front strut brace next.
20mm/10mm drop from the springs.

 

[stuartinzg]

. . . . . if you want a track car why in gods name did you buy a E89 Z4? It's setup for 4-6/10ths GT fast road driving.

I couldn't 't agree more. The old saying "you can't polish a turd" comes to mind! E89 is a great GT car but no sports car and no way on God's good earth is it a decent track weapon.

I don't think it's that bad. Considering I took a very slight corner at 150 mph on an autobahn and am here to tell the tale, tells me that !

It's not a Lotus but then you get the comfort and toys, metal folding roof, etc. Can't have it all.

 

[techathy]

Lob £4500 at the engine in a GT86/BRZ and you'll get a car that'll keep the 35iS honest on the straights. You can spend the same money at the suspension & weight saving of the Z4 but the Toybaru will still totally outclass it in the twisties....

 

[stuartinzg]

Lob £4500 at the engine in a GT86/BRZ and you'll get a car that'll keep the 35iS honest on the straights. You can spend the same money at the suspension & weight saving of the Z4 but the Toybaru will still totally outclass it in the twisties....

Not really a fair comparison is it? Not a convertible.

A better competitor would be a supercharged S2000, plush no, but a proper convertible.

 

[techathy]

I'm talking track cars... where a tin top is yet another Toybaru win

To put this in some context I let a BRZ go after a +6 month wait a few weeks before it got to the UK to buy a Z4 35iS. I'm well aware of the differences between the two cars.

 

[Garvin]

. . . . . if you want a track car why in gods name did you buy a E89 Z4? It's setup for 4-6/10ths GT fast road driving.

I couldn't 't agree more. The old saying "you can't polish a turd" comes to mind! E89 is a great GT car but no sports car and no way on God's good earth is it a decent track weapon.

I don't think it's that bad. Considering I took a very slight corner at 150 mph on an autobahn and am here to tell the tale, tells me that !

It's not a Lotus but then you get the comfort and toys, metal folding roof, etc. Can't have it all.

I'm not saying it is bad per se, just that there are far more satisfying cars for use on a track - Elise/Exige, Boxter/Cayman etc. Even a GT86/BRZ will be more precise although the lack of power might frustrate.

Sure, you can shell an awful lot of your hard earned on an E89 to sharpen it up but it takes quite a lot of it and a lot of fettling - much better to start with a more capable canvas in the first place.

As a GT car the E89 is almost perfect - fast, comfortable, lots of toys and the folding tin top - just needs more luggage space to get rid of the 'almost'. By all means one can 'track' it occasionally but it will never be a finely honed weapon unless it is significantly modified. But then it would compromise those things that make it a great GT car.

You're quite right, you can't have it all. Unless, of course, you obtain a second alternative car with much better 'reflexes' 8)

 

[techathy]

I'm not saying it is bad per se, just that there are far more satisfying cars for use on a track - Elise/Exige, Boxter/Cayman etc. Even a GT86/BRZ will be more precise although the lack of power might frustrate.

Interesting use of "even" at the beginning of the Toybaru sentence. Power wise it's a turbo, & debatably an oil pump, short of being an STi engine so getting 250-275whp out of the engine isn't too hard at all... with 250whp putting them in 35iS PWR territory.

 

[stuartinzg]

I'm happy to report that the car is a lot more planted with the eibach pro springs, pulling cleanly with full throttle. I think it has made a huge difference. Maybe my old springs were shot? Only 25k miles - but perhaps a few very large pot holes weakened them? (I did have 2 cracked wheels). I don't know, but I'm happy

 

[ronk]

Not noticed any neg camber induced issues on the front of my Z4, nice flat & even wear across the tyre. The thing I notice is inside edge wear on the rear tyres.

And I thought it was only me!
Mine is particularly noticeable on the nearside tyre for some reason - I was starting to worry about incorrect toe of the rears.

80% of the tyre has a very healthy tread.

 

[techathy]

If it's just inside edge wear then you've got an alignment problem. I'm seeing even but not flat wear across my rear tyre. I'm looking at the inside edge wearing 30-40% faster than the outside edge & the middle of the tyre wearing about 15-20% faster than the outside edge.

 

[ronk]

Yes, the tyre is wearing but the inside edge (30mm) is wearing more than the rest - there is no plucking or sharp edges.

Ref your quote :- The thing I notice is inside edge wear on the rear tyres

 

[goldbcfc]

All this over some tyres

Isn't that a little bit patronising? :wink:

I don't see Porsche, AM, Ferrari, Bugatti, Maserati, DTM cars, GT series - running box? Or am I missing something?

Box is cheaper if you track because you can use the same tyres all round, swap front/back, etc. I can't see grip being better with 360 hp going through even narrower rear tyres.

I would not talk about it and actually try it and see for myself because I like to test and improve things, but I can't, because I'd need to spend an extra £1700 on new rear wheels and tyres, plus spacers, unless someone will lend me some?!

So many variables to consider. I went for 265 instead of 255 at the rear because in standing water up to 1/2 the tread depth the wider tyre is more resistant to aquaplaning as void to contact ratio is higher.

Certainly my 35iS completely overwhelmed the OE 225/40R18 front tyres.

do you track much?

 

[techathy]

Because going on track has loads to do with a fundamental issue with the Z4's suspension setup, especially when looking at the MPSS:

 

[stuartinzg]

Because going on track has loads to do with a fundamental issue with the Z4's suspension setup, especially when looking at the MPSS:

I have to admit, I don't really understand that graph... the axis values don't make sense to me. Could you explain it a bit more? Sorry for being thick

 

[techathy]

The lines is when the car started to 'rotate' around the front axle (aka power oversteer) under light acceleration in a constant radius turn. We're not talking opposite lock hero, rather just easing off the lock to keep the car in that constant radius turn.. The vertical axis is speed (km/h) & the horizontal is hot tyre pressure (kPa).

Basically it's a measure of grip & faster speed is better. As tyre pressure increases grip reduces, with a single compound tyre like the RS3 it's fairly constant but with the dual compound MPSS there's a fall off.