Going in for camber adjustment tomorrow

Wow, 25% difference across the tyre is somewhat large and I find it hard to believe that is just down to camber or the fault of the tyre! I would just warn about spending a lot of your hard earned in search of Utopia and find it turns out to be a wild goose chase, before making sure all the basics are checked and rechecked first!

MPSS are notorious for being sensitive to tyre pressure which is why I suggested playing with these first.

Rule No 1 in setting up/adjusting suspension is to make sure the ride heights are all to spec before changing anything else. Anecdote - I borrowed a friend's Z3 many moons ago and to say it was 'nervous' is an understatement - it was just horrible and I was shocked BMW could produce something so wayward! Turns out (due to some incompetent previous modding) that the ride height was incorrect on both sides at the front and that it was about half inch difference from side to side. Once this was corrected and the rest of the suspension checked/adjusted it behaved just fine. My friend always refers to its transformation as nothing short of 'witchcraft'.

The F355 runs beautifully with 36psi rear and 34psi front. Others claim 35/35 is optimum. The Z4 is likely to be lighter at the back so pressures somewhere in the region 32 to 34 might be a good starting point but recognising the tyres are different width and aspect it may take time to find an optimum setting. The fronts may need to be a bit higher, say 34 to 36 as a starting point. I haven't checked the weight differences so these are a complete guess and I do know it takes time and dedication to achieve a good result. Yes, it's a different car etc but I have not come across a good 'sports' tyre being 'rubbish' on a different car. Suspension changes can be adapted for different tyres to get the best out of them but that is usually looking for the final 5% or so performance as the BRZ racing mob will be doing.

Finally I might drive my cars more thoughtfully but I doubt it would be any slower :driving: One of my claims to fame is wearing out the rear tyres on the three Audi TTs I owned as fast as the fronts! 8)

I wish you luck in sorting out the problem and if it does come down to some suspension mods after all it will be interesting to see the 'optimum' spec for the MPSS on a Z4.
 
Garvin said:
Wow, 25% difference across the tyre is somewhat large and I find it hard to believe that is just down to camber or the fault of the tyre! I would just warn about spending a lot of your hard earned in search of Utopia and find it turns out to be a wild goose chase, before making sure all the basics are checked and rechecked first!

MPSS are notorious for being sensitive to tyre pressure which is why I suggested playing with these first.

Rule No 1 in setting up/adjusting suspension is to make sure the ride heights are all to spec before changing anything else. Anecdote - I borrowed a friend's Z3 many moons ago and to say it was 'nervous' is an understatement - it was just horrible and I was shocked BMW could produce something so wayward! Turns out (due to some incompetent previous modding) that the ride height was incorrect on both sides at the front and that it was about half inch difference from side to side. Once this was corrected and the rest of the suspension checked/adjusted it behaved just fine. My friend always refers to its transformation as nothing short of 'witchcraft'.

The F355 runs beautifully with 36psi rear and 34psi front. Others claim 35/35 is optimum. The Z4 is likely to be lighter at the back so pressures somewhere in the region 32 to 34 might be a good starting point but recognising the tyres are different width and aspect it may take time to find an optimum setting. The fronts may need to be a bit higher, say 34 to 36 as a starting point. I haven't checked the weight differences so these are a complete guess and I do know it takes time and dedication to achieve a good result. Yes, it's a different car etc but I have not come across a good 'sports' tyre being 'rubbish' on a different car. Suspension changes can be adapted for different tyres to get the best out of them but that is usually looking for the final 5% or so performance as the BRZ racing mob will be doing.

Finally I might drive my cars more thoughtfully but I doubt it would be any slower :driving: One of my claims to fame is wearing out the rear tyres on the three Audi TTs I owned as fast as the fronts! 8)

I wish you luck in sorting out the problem and if it does come down to some suspension mods after all it will be interesting to see the 'optimum' spec for the MPSS on a Z4.
Click to expand...

Hmm you know what, I have a feeling that the people setting up the car have no idea about non-RTF's, and call me stupid, but I think I may have forgotten to check the pressures (I even have a 12v pump because of the previous cracked alloy).

I will go check what they are and report back. Why do I have a feeling they are 38-42 PSI at the rear?
 
Oh well, worth a try - seems optimum? I thought they put RFT pressures in there (I think they did at the tyre shop, but since changed)

PS. Ride hide is fine, already checked, also running adaptive suspension, was checked over by BMW when I noticed a gas leaking noise, but that was normal apparently (and often mentioned to them) - only happens on normal, sport, and sport+ it's not noticeable, due to the way the BMW suspension works compared to other types of adaptive (such as Audi, which is mag ride-apparently superior?!)

tyre2.jpg

tyre1.jpg


Offtopic: Please post a pic of this F355, thanks :)
 
Play about with the pressures - as I said the MPSS is sensitive to pressures so a little change can make a big difference. Regarding the F355 here ya go:

http://www.z4-forum.com/forum/viewtopic.php?f=16&t=40453&p=567703&hilit=F355#p567703

In these early photos she is still on the Pirellis which were replaced by the MPSS and you can see the -ve rear camber quite clearly.
 
Garvin, sorry about earlier.. I believe I need a note to self about not posting on forums after meetings with Estates.

Anyway back to business - MPSS are fairly pressure insensitive tyres once an appropriate suspension geometry dialled in. When you’re trying to force them onto an inappropriate geometry then they do get very sensitive as you need to get that shoulder properly contacting the road but you can’t go too low or the carcass starts objecting to being in an odd shape.

With MPSS The lower pressure limit is when you start running on the sidewall rubber rather than the tread rubber. Until that point lower pressure increases tyre grip at the expense of direction precision/control & tyre life. Higher pressures reduce lateral grip & increase directional precision until you go too far and start to lift that all important outside shoulder off the road, which limits over-pressure induced centre tread wear.

Examples of useable pressure ranges with dialled in suspension - my Sei’ has 12psi range at the rear and 7psi at the front on MPSS, a friends Evo XII runs well in a 8psi range & BRZ/GT86 once dialled in are about 7-10psi pressure range.

Non-RFT tyres should be running a few psi lower pressures than RFT tyres, no super stiff side wall to compensate for, and MPSS are particularly sensitive to over pressure. But even so the OE Z4 geometry is not conducive to good MPSS performance. High static neg camber and fairly good dynamic camber increase is not going to help them at all. Compared to the BRZ/GT86 will make for worse straight line grip levels.

The BRZ guys are complaining about MPSS performance in street driving more than track driving. Hardly last 5%., more like the first 50%. On track the cars are pushed hard enough to get over the high static neg camber compensating for a lack of dynamic camber increase. Also they’ll get heat into the hard compound making the straight line traction problem mostly disappear. It’s tweaking small amounts of camber to bias lateral grip v’s straight line.

It’d also mention that I found BMW actually have a different rear camber for cars with MPSS & runflat tyre options. The rear gets around 0.2 deg less negative camber when running the MPSS depending on which car you look at None of the other cars are running more than 2deg negative camber when centred.

Dynamically using geometry information gleamed from a rearward engined car on the Z4 is almost as irrelevant as using geometry info from a FWD car.

As for if it works well on one cat it’ll work well on all of them. Try putting tyres which perform very well MX5 tyres on an Elise. Another interesting one is putting good performing Porsche Cayman/Boxster tyres on 5 series & vice versa

EDIT: correct the auto correct :headbang:
 
Tech, apology accepted.

Back to MPSS and e89 Z4. The MPSS is designed to be light on the outer most reaches of its tread in straight ahead motoring i.e. only using the innermost, less grippy, rubber for straight line motoring (I have assumed this to be because the outermost reaches are softer/grippier compound and would wear away far too quickly if always in full contact with the road). Therefore the tyre should work well in this mode but Stuart is reporting a distinct lack of grip in this scenario which appears to be worse than running OEM RFTs as I do not experience this problem (well, not with my second 35is which is far better than the first). I am finding it hard to believe that the MPSS has less grip than the RFT tyre in this scenario even if it does have less rubber on the road (unless the MPSS is overheating in this short time which is also hard to believe - but see high tyre pressure later)..

Now the inner compound of the MPSS may be less grippy than the outer compound but it is hardly Teflon so I am having problems understanding why it generates so little grip unless there is some particular quirk of the Z4 suspension set up with this particular tyre that I am not seeing.

I spent quite a few minutes searching the web for comments of drivers with e89 Z4s running MPSS tyres and they are universally positive. In fact I couldn't find any negative reviews/comments at all save for this thread! They can't all be wrong can they?

There are two telling differences with Stuart's problem. Firstly the lack of straight line grip. Secondly the increased wear on the inner most reaches of the tyre. To me this is probably caused by one of two problems:

1. Stuart is driving the bollocks off the car in a straight line but is pussying it round the bends!

2. The tyre pressures are too high meaning too little of the tread fully contacting the road on a straight line (possibly overheating resulting in loss of grip and increased wear) and not allowing the outermost reaches of the tyre to contact the surface when ragging it round the bends.

I'm pretty sure Stuart will disagree with the first hypothesis!

Therefore I think that adjusting the pressures to get the majority, but not all, of the tread on the road in a static scenario is the way to go.

If the tyre pressures are set low enough to get the outer most reaches of the MPSS tyre to contact the road surface in the static scenario then a) the tyre will, overall, be too soft with too much sidewall movement with attendant detriment to handling/feel; and b) the outer edges of the tyre (soft compound) will wear out quickly and a lot quicker than the innermost compound.

It may be that the optimum setting is a combination of reducing camber and an optimum tyre pressure but I would explore the cheaper option of just the tyre pressure first before the more expensive option of camber adjustment.
 
I think option 1 is probably more likely! (my data logging from MHD and plotting in VirtualDyno estimates (312 whp / 360 hp @crank at the moment -im probably too heavy footed!)

Also the tyre pressures were higher before, the garage who adjusted my camber must have adjusted them too. I will check.

It does feel better than before, admittedly, but there is one important point to highlight again- the tarmac over here where I am driving the car at the moment in southern Europe is very,very slippery. Compared to English noisy tarmac the difference is night and day. You can get out of the car and almost slide around with your shoes.

The tarmac seems very hard almost like concrete, without the granularity of the UK roads - my guess is either a) cost,it isn't wearing out as fast, b) to deal with 40+c temps during summer, or c) it's worn out already.

I also notice the traction is poor under bumpy surfaces, most of the surfaces here are bumpy.

So I think the conclusion is that "it's as good as it gets with the current chassis" which is no where near as composed as your F355

My dad is of the opinion (and being around a long time, having driven many many cars over the years, from e-types, dino's, RS200, you name it ) he thinks the chassis is "hair dresser" and not as sorted as it could be, over engined in the 35iS and thinks the 30i would be a better drive - he may be right !

Now I can't decide if I should even bother to spend money on the LSD , but instead put that toward the Caterham!
 
Interested in your thoughts guys what tyre pressure your running ! Ordered mpss last nite for my summer wheels. I'am running 34/36 on my winters Dunlop non rfts & car feels fine. All be it I'am not driving it as hard as I would in better weather & summer tyres.
 
The F355 has the advantage of being mid engined. When one's foot is planted the weight transfer to the rear is probably a lot better than the Z4 which will help with the traction!
 
KERMIT1970 said:
Interested in your thoughts guys what tyre pressure your running ! Ordered mpss last nite for my summer wheels. I'am running 34/36 on my winters Dunlop non rfts & car feels fine. All be it I'am not driving it as hard as I would in better weather & summer tyres.
Click to expand...

I still have RFTs on the Z4 but from my experience with MPSS on the F355 and considering their respective weights I would say the pressures you're running the Dunlop's at is as good a starting point as any.
 
Stuart, reading through your last post again I would make some further comments:

Heavy footed : No matter what the tyres/road surface, a car of this weight and torque will spin the rear wheels if you just put pedal to the metal from the off in first gear!

Road surface: With surfaces as you describe (slippery under foot) then the above comment is accentuated and will easily extend to gears two and three.

LSD : This can make a difference in straight line acceleration but it can't redefine the laws of physics and create more grip where none exists - it will though stabilise the car more if one wheel gives up before the other and maximise the grip available. It can, and should, make a significant difference in cornering ability where it will stabilise the car when the lighter loaded inner wheel gives up traction. It should prevent the inner wheel spinning all the drive away resulting in a drop of drive to the loaded outer wheel, deceleration, weight transfer back to front and the resulting reduction in grip of the outer wheel and the usual lift off oversteer scenario (even if you haven't lifted off the throttle) which the stability control then has to intervene in order to prevent an unscheduled visit to the scenery. However, if the stability electrickery is too intrusive it can 'trigger' early even with the LSD fitted. I would contend though that with the ESP switched off things should be much better. It is always best to take advice first from someone like Birds who will have tested and, hopefully, matched their LSD dynamics to the car.

35is over-engined for chassis : I have some sympathy with your dad's view as I think it is marginal which is why I always advise against mapping a 35is for more power before first making mechanical (LSD, suspension etc.) changes. In stock trim I just can't see the extra power being remotely useable.

Finally, if the road surfaces are as dire as you state then perhaps some road legal track oriented rubber is the way to go - expensive and they can wear out very, very quickly!
 
Garvin said:
KERMIT1970 said:
Interested in your thoughts guys what tyre pressure your running ! Ordered mpss last nite for my summer wheels. I'am running 34/36 on my winters Dunlop non rfts & car feels fine. All be it I'am not driving it as hard as I would in better weather & summer tyres.
Click to expand...

I still have RFTs on the Z4 but from my experience with MPSS on the F355 and considering their respective weights I would say the pressures you're running the Dunlop's at is as good a starting point as any.
Click to expand...
Cheers Garvin :thumbsup:
 
A little grip experiment.
Surface temp: 1.5C +/- 0.4C
Code: 
Z4 35iS 0-100km/h using launch control
Rainsport 3 265/35R18  5.22s  5.19s
MPSS 245/35R18         5.36s  5.33s
RE050A 255/35R18       5.69s  5.60s

M235i 0-100km/h using launch control
Rainsport 3 265/35R18  5.35s  5.31s
MPSS 245/35R18         5.28s  5.20s
RE050A 255/35R18       5.81s  5.74s
Point of interest - the M235i got off the line faster but as soon as it changed into 2nd it couldn't live with the Z4. It felt like my 35iS engine produces 30-40hp more power and held on to it better once past 6000 rpm.

EDIT: typo
 
I'm impressed with the second run of the 35is on MPSS but even in my most optimistic moments I can't quite believe a 3.33s run to 100km/h - surely a typo and should be 5.33s?
 
:rofl: err... yes :oops:

So going from -235 deg camber to -1.6 reverses the MPSS/RS3 result, but both of then absolutely destroy the OE tyre in cold conditions at least. I assume we'd get faster & faster results the more runs we did as the tyres warmed up.
 
I'm not surprised by the OEM RFTs at low temperature - completely matches my experience with them. MPSS does well considering it is the narrowest tyre being tested. Like for like at a reasonable temperature and I think the MPSS will shine against these particular tyres.

I would love to see such a back to back test of the MPSS against the best non RFTs from Continental, Bridgestone and Goodyear even though this is just one particular aspect.

BTW you may wish to check the -235deg camber!!!
 
ARRGG! Today the typo force is strong :rofl:

Thing to mention is that the RS3 is a HP not a VHP tyre. I went for it because it has reasonable grip levels a, is one quietest tyres in the cabin & has massive water clearing capacity/great aquaplaning resistance. I wasn't looking for a tyre to stretch the Z4 to its limits, I wanted a quality sports/touring tyre.
 
Interesting results but seems a bit slow? Is that due to the temps? Lots of forum threads where the 35iS will average 4.3-4.5, with an LSD 4.1 and 4.0 have been recorded. Even BMW claims 4.8. Using racelogic gear in most cases i saw too. 3.x is possible with maps/piggyback

335iS - LSD+tune
attachment.jpg
 
With air temps at just above freezing, surface temp in the 1-2c range & cold tyres times were never going to good.
 
The RS3 is another tyre that gets almost universal good reviews and seems to be great value for money. TBH I was put off Uniroyals way back in the 80's when my Mk1 Astra GTE came shod with them! Rubbish tyre back then - squealed like mad at 5pmh whilst circumnavigating multi-storey car parks with that rubberised surface some use. The rear wheels used to lock up and skid with a bit of heavy braking so much so I had the balance valve checked out. When terminal understeer broke out I changed them for a set of Goodyear NCTs which were new on the market. They were a great tyre and I discovered that there was nothing at all wrong with the car - just those OEM tyres!

I have driven a lot of cars in recent years on Michelins, Continentals, Bridgestones and Pirellis. My tyre of choice prior to the MPSS was the MPS2 - grip as good as the opposition in the dry, better in the wet but the combination of good turn in yet low noise and good compliance/comfort made them a clear winner in my eyes. The MPSS is, to me, just a much better MPS2 in every way - indeed early reports state that the have more longevity as well - time will tell.

Mrs Garvin's Fiesta ST3 is running on RE050s (non RFT). I'm not overly impressed with them. Perhaps I should reacquaint myself with Uniroyal or Goodyear when they wear out . . . . . . . but I suspect I will go for the MPSS again.
 
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