Going in for camber adjustment tomorrow

I used Dunlop Sports Maxx RT on my 1 series & using the Dunlops on the front of the Z4 with Rainsport 3 on the rear. But neither of those are really VHP tyres. On my Sei' I was locked into Conti Sports Contacts or MPSS depending on what control tyre was being used in what ever race series it was my retired tyre size came from & the CSC aren't a direct relative of normal production run sizes so that doesn't help
 
Some comparisons here http://www.tyrereviews.co.uk/Tyres_For/BMW/Z4.htm

Good reviews here: http://www.caranddriver.com/comparisons/monsters-of-grip-nine-summer-performance-tires-tested-comparison-test

The test car was an E92, but only a 325i by the looks of it. They put the PSS first, although for the Z4 it may be a different story (but try finding a test like this with our cars :( )
 
E92 per side
Front toe: 0.08’ to 0.18’ (0.13’)
Front camber: -0.15’ to -0.95’ (-0.55’)
Rear toe: 0.12’ to 0.18’ (0.15’)
Rear camber: —1.75’ to -1.90’ (-1.85’)
Track F/R: 1500/1513mm
Wheel base: 2760mm

E89 per side
Front toe: 0.02’ to 0.22’’ (0.12’)
Front camber: -0.1’ to -1.1’ (-0.6’)
Rear toe: 0.05’ to 0.25’ (0.15’)
Rear camber: -1.90’ to -2.80’ (-2.35’)
Track F/R: 1511/1537mm
Wheel base: 2496mm

Okay it looks like the Z4 is a little more rear biased in it's weight distribution with a full tank of fuel then take track & wheelbase into consideration & you can start to see what BMW are doing. With a wider track and short wheelbase the car will tend to snap to lift-off oversteer, especially with a bit more weight towards the back of the car (think about the Porsche 911 for an extreme example). I think what BMW are trying to do here is prevent that as when it starts to oversteer the high neg camber will tend to catch the rear of the car bringing it back under control. This feeds in to what I was saying about moderate speed cornering traction. What I don't get is why the factory specs for the E89 are so wide compared to the E92.

So what this means with the MPSS is that you should be experiencing more rear-end instability in a straight line but when exiting corners you should be accelerating more cleanly than in a E92.
 
Yep all of that makes sense - question is how would the dynamics change with an LSD and what set up should you then consider in terms of camber etc?
 
LSD either viscous or locking will improve things but at best can simply mask the issue. If you're going to continue to run MPSS I'd be looking to get the rear camber into the E92 range.
 
why not try run a box set with all same width alloys. Im running 8.5 all round fine very even tyre wear no oversteer problems as box set counters that used alot on track m3 cars
 
goldbcfc said:
why not try run a box set with all same width alloys. Im running 8.5 all round fine very even tyre wear no oversteer problems as box set counters that used alot on track m3 cars
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Understand the benefits of box, but that's not my issue so I'll end up with even less traction, plus I can't justify 1k on two more front wheels...spacers and all that.

Main problem is I thought I was getting the 'best' tyre but I didn't consider how they work under negative camber, which is badly.

The LSD will help, plus I'll get camber arm adjusters and dial it back to -1.5 and see what happens...just a bit concerned for snap oversteer as is pointed out above. I'll have to try it on the track just to see how it behaves at the limit (not a proper track session, just somewhere safe to throw it into a corner fully committed in a controlled area).
 
Had a play with a few bits of metal and some load sensitive footprint plates. Given the dual compound nature of the MPSS I reckon for cornering you want about -1.9 to -2.05 deg camber for maximum cornering grip & for maximum straight line traction you want about -1.2 to -1.3 deg. With the MPSS there's no to go for a higher neg camber than maximum lateral grip because the sticky outside edge won't dig in anymore. IF you're looking at a single compound tyre the going over that 2.05 barrier will make the car slide a little more easily but also be easier to recover.
 
stuartinzg said:
. . . . . . Main problem is I thought I was getting the 'best' tyre but I didn't consider how they work under negative camber, which is badly. . . . . .
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Believe me, you have one of the best, if not the best, tyres on the market! Before re-jigging the suspension have you tried different pressures? When I fitted my MPSS tyres I used some old tyre pressure settings that Ferrari quoted for their original Pilot Sports - I thought I had made a terrible blunder as the grip/handling were all over the place. A bit of Internet research coupled with some trial and error and the tyres 'came on song' brilliantly.
 
The tyre patch shape and position is all wrong on the Z4. When the MPSS is square to the road the outside 50-55mm of the tyre provides about 70% of the grip. If you look at the contact patch profile on the rear tyre you'll see that the contact patch with meaningful pressure ends about 15-20mm shy of the shoulder & is shaped as a rounded triangle. At a rough estimate you're seeing about 1/3 the contact patch in the grip area compared to running the car with less than 1.3 degrees of negative camber. If you lower tyre pressures enough to get meaningful gains in that outer area you'll be looking at a very under inflated tyre.
 
What are the 'meaningful' pressures you talk about? What do you consider an under inflated pressure?
 
I think techathy hit the nail on the head - the Z4 suspension setup coupled with the tyre pressures needed meaning im wearing out 50% of the tyre and basically I feel like my rear tyres are 185 profile. It's quite frustrating now.
 
Garvin said:
What are the 'meaningful' pressures you talk about? What do you consider an under inflated pressure?
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Enough pressure to deform the tread into or around minor surface imperfections.
You'll be looking at pressures significantly less than 30psi
 
I remain to be convinced that it's just down to camber. My F355 runs -2deg camber at the rear and there is no problem with grip whatsoever - straight line or turning (well, only if I don't completely over cook it). No problem with uneven wear either. If you are wearing out only half the tread then it sounds to me like your pressures are way too high. The only other thing that can be causing such a problem is if your ride heights are out of kilter (assuming springs and dampers are OK).
 
Ah, the usual eyes rolling response, the last resort from someone who can't deal with a challenge. No debate left in this thread then so amm oot.
 
Garvin said:
I remain to be convinced that it's just down to camber. My F355 runs -2deg camber at the rear and there is no problem with grip whatsoever - straight line or turning (well, only if I don't completely over cook it). No problem with uneven wear either. If you are wearing out only half the tread then it sounds to me like your pressures are way too high. The only other thing that can be causing such a problem is if your ride heights are out of kilter (assuming springs and dampers are OK).
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Thanks for your input Garvin it is appreciated, so don't leave :thumbsup:

One other point might be that the torque delivery of the F355 might work in the tyres favor, whereas the N54 tends to come on quickly, so I may need more throttle control. Worth noting that the Z4 can go from -1.9 to -2.9, which is obviously a big difference. The guy doing my adjustments couldnt wind it back anymore on stock components, -2.0 was the max he could go. I don't have any "official" stats to prove it's better or worse, but at least it tracks properly now.

Also bear in mind that the GT86/Subaru crowd also running these tyres noted the same issues with high levels of camber.

You may also drive your car more thoughtfully :thumbsup:

I think the wear at the moment is about 25% more on the inside than outside.
 
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