Another Tyre Thread - Swapping MPSS to PS4S

[stuart-b]

Hi guys,

Another tyre thread.

I've never been happy with the MPSS on my Z4 - they almost seem to have less grip than the RFT that they replaced. After a lot of reading and talking to people in the know, it appears that they do not work well with high negative camber. I've tried to lower the rear camber to the minimum I can, within the adjustability of the OEM suspension setup, but it's still not good.

Even with throttle regulation the tyres spin up into 3rd gear, they create nervousness in the rear and do not inspire confidence at all.

They are also hard as nails. I mean, brutally hard. This set has done 20k miles and still has 3.5-4mm left !

This weekend I'll replace them with PS4S and will report back the difference after they run for a few hundred miles.

Anyone else fitted PS4S - opinions?

[stuart-b]

Very good to hear. I'm a mixture of UK and Europe. It sees all temps.

What is frustrating is that other BMWs are getting traction where I am not, on the same bit of road - so it must be down to tyres/suspension setup.

I will report back how it goes and probably do a small gopro video before and after (but I will run them in a bit first)

[stuart-b]

jon- said:

Are you just talking about wet grip? There's no way a MPSS should be spinning in the dry in any gear.

Hi Jon, I thought I was quite detailed in my initial post.
The person overseeing my camber adjustment and 4 wheel laser alignment is rallying and was regularly winning country level drift competitions. He has driven a lot of cars and has a lot of knowledge about suspension and wheel setups. The car is setup as good as it can be - you take only take my word for that. I've changed the wheels (less unsprung weight), changed the springs, changed the tyre width (increased to 265 which is what the current MPSS are).

His feedback is, the tyre is too stiff and provides more cornering grip than straight line in my case.

Whether that's Z4 specific or not, I don't know - perhaps it's the weight on the rear, but I'm not a prat who gives it WOT a few times and jumps to irrational conclusions either. I've driven the car for 20,000 miles in various conditions, in more than 10 different countries, across a mixture of tarmac types.

I've tried different camber, different tyre pressures, different maps - the result is the same, the car cannot put down the power and is severely limited up to 60 mph. Even after 60 mph it will wiggle and move around at full boost FROM 60 mph up to 85-90 mph.

Other owners are seeing 4.1/4.2 seconds 0-60 with a basic map - I would be lucky to see 5.5-6 seconds since these tyres are on. Only with traction control and stability completely off will I get anywhere near that, but it's rather lively for public road use in that case. I'd rather have a more predictable acceleration.

I have noticed some surfaces in the UK where the tarmac is so rough and grippy, it performs a lot better on this surface - but within Europe, many tarmac surfaces are almost smooth. However, you would expect everyone to suffer, but I'm not seeing that when driving alongside other BMWs.

My question is, would you expect UHP tyres to still have almost 4mm of tread left after 20k miles? I'm not driving like a daisy, I've already gone through one set of rear pads because of the ediff.

[stuart-b]

Smuler said:

Yes.
So far very impressed, on my E46 M3. more grip more feedback than what was on it when I bought it: Continental 5Ps
I had the Michelin Pilot Super Sport in 2015 on my 335i, found them a massive improvement over the RFTs.
Six months later tho, I'd put 17s rims on for winter tyres and the following Spring I kept the 17s on and tried the Michelin Pilot Sport 4.

That combo was even better, tho it's not exactly a like for like comparison.

But gave me confidence the PS4Ss would be the best yet, I'd say they are

Interesting, thanks. The 335 guys do seem to have an easier time putting the power down than the similarly engined Z4. I priced up a mechanical LSD so that I have a similar power chain to that of the M cars (it's the same engine as the 1M, and the basic Getrag unit is used within the M3 among others), but it's using a crap ediff (if you can even call it that, rear brakes providing a simulated diff) and cheap suspension components, which as we know, make all the difference.

There is one owner on the Z forums who has put parts of the E92 M3 front suspension in place and E46 M3 rear (where he could, bushing if I recall), along with swaybars and special trailing arms and it made a significant improvement - but that's a bigger project than I can stomach at the moment as there is some customisation required.

Edited by stuart-b on Friday 21st July 11:36

[stuart-b]

Update on the tyres.

Turns out that the MPSS i was running, I thought it was 265 already, it was actually 255. Looking back at the emails, the provider of the tyres was trying to tell me that I was ordering the wrong size, but I was insistent since I'm running 9.5 inch rear now, not 9 inch. I guess it doesn't matter how often you look at something, as I've checked those tyres probably more than 50 times whenever I clean the car!

The new tyres are 265, meaning no stretch. The old tyres were completely knackered on the very inside edge, being a very stiff tyre, and stretched, this was not a good combination. 5mm left in the middle and bald completely on the very inside (difficult to see when looking under the car, only became apparent when the tyres were off). It should be noted that traction wasn't very good even when the tyre was new.

These are the new tyres are night and day. I can manage full throttle second gear pulls without losing traction - finally after 2 years !

I've taken the plunge and will be replacing the fronts too, with 235 size, even though the old tyres have 7mm left - will throw them in the garage.

Anyone else considering PS4S - do it !