Another Tyre Thread!!

[MikeMcG]

I started a thread a few days ago where I thought my RTABs needed changing as I find my Z4MR twitchy on a motorway and it feels like I constantly need to correct the steering to keep the car straight. Someone mentioned they had a similar thing on their car and it turned out to be needing new rear tyres, which got me looking at mine. Fronts are ok, rears are definitely in need of changing and as good as on the tyre wear markers.
I have Bridgestone Potenza RE 050A fitted all round to standard Z4M 18's
255/40/18 99Y Rear
225/45/18 91W Front

Those tyres have been on the car since I bought it, but I'm wondering if rears with a load index of 99 are going to have sidewalls far too stiff for a car of this weight? From looking online, 99 index is for 775kg per tyre, the the fronts have 91 index of 615kg per tyre. Logic makes me think that if I've got tyres on the back with much stiffer sidewalls than the front, this could make the car feel a bit unstable? Surely the front of the car is heavier than the rear too?

Can anyone advise what load index they are running on their tyres and whether the front load index is the same as the rear or at least close?

Thanks
Mike

 

[Fishy Dave]

Hi Mike,

Just servicing my car now, it has standard wheels, same size tyres as yours but are Conti Sport Contact 3's. Fronts are marked extra load 95W and the rears are extra load 99Y. The gentleman I bought it from said he fitted identical tyres to what were previously fitted.

Not sure if that helps?

Cheers, Dave

 

[Scooba_Steve]

Think the stock load index is 91 front 95 rear - should be in your manual though.
As for the RTABs I can recommend poly - no squeaks and much better feel under acceleration have not found them noticeably harsher either. £40 from CP4L.

 

[mr wilks]

Why would you have runflat tyres on a ZM & especially on style 224s as they aren't set up for runflat tyres to function correctly ?
Ditch the lot , fit a set of F1s , Vorti's or Michelin & enjoy what should feel like a new car by comparison

 

[mmm-five]

Standard tyres were Continental SportContact M3. These are not the same as SportContact 3 - more like SportContact 2 with BMW 'approval' for the M3 (and then the Z4M). Never found them to be particularly brilliant in any condition so swapped them to Michelin PS2 as soon as the wore out. Then to the Michelin PSS when they became available. Each change has brought both a cost saving (SCM3 were £185 for rears, PS2 were £175 for rears, and PSS are £160 for rears) and a performance/average mileage increase (e.g. rears lasted: SCM3 10,000 miles, PS2 14,000 miles, PSS 20,000 miles).

I've had XL101 Pilot SuperSport tyres on my Z4MC for about 5 years and haven't noticed any pulling/tramlining.

If it's definitely not geometry/suspension problem then check the spec of the tyre, as tyre construction (and manufacturer specific modesl) can make a difference to how tyres perform on different cars. Can you see if they tyre is a manufacturer specific spec (i.e. M0 for Mercedes, or K1 for Ferrari).

My other concern is that someone has accidentally put a runflat version on! If so, then it shouldn't be on your car, or on the wheel at all - as the wheel isn't made for a runflat tyre.

 

[mmm-five]

Why would you have runflat tyres on a ZM & especially on style 224s as they aren't set up for runflat tyres to function correctly ?

They're now available in non-runflats too - so I've asked the OP to check just in case

 

[MikeMcG]

Hi guys, thanks for the responses so far, just to be clear, they're definitely not run flats. I had RF's on my mini and know the RF sign to look out for on the sidewall, these tyres dont have that symbol on them.
The Rears just state 'Extra Load'

I was more interested to know if the 'Extra Load' rears with an index of 99 were necessary.

Thanks

Mike

 

[Anonymous]

Michelin super sports
Trust me awesome tyres
Run flats as said
Nasty things and not for Ms as sidewalls will be rigid as plus Bridgestone are a horrid tyre for pulling

 

[robbie_t123]

I had lots of tram lining and steering wheel vibes between 70/80 mph. Changed the Falkens at the front to PSS and its like a new car. Eradicated both of these symptoms and far superior grip. To be fair the Falkens were pretty well worn in inner edges and the wobble may have been a balancing issue. Get the PSS you won't regret it

 

[MikeMcG]

The car is booked in at Walkers Autotech soon to get the RTABs looked at/changed. Didnt want to stick new tyres on and find they wear unevenly.
I think I'll bite the bullet and put two PSS's on the rear. I have a little life left on the front Bridgestones, so will change them in the not too distant future.

 

[MikeMcG]

So just to update, Walkers Autotech looked over the RTABs etc and came back saying they were good and there was no play on any other bushes, but, the tyres were badly worn and it wasn't just the rears. The fronts were worn on the inside edge. I'm not totally surprised as I had a hunter alignment done and the before and after print out's were completely different. Initially it was as good as red everywhere, then brought back into tolerance, which in itself helped a huge amount.
Walkers Autotech suggested a new set of boots all round. So I bit the bullet and went for a set of PSS's from Tyreleader and had them delivered locally to a tyre fitter. Initially I thought the car felt much better with the new tyres, but still felt it wasn't 100% comfortable at motorway speeds on a dual carriageway. A quick stop at a petrol station showed that the garage who fitted the tyres had put 2.3bar all round. 2.2 on the rear and 2.1 on the fronts has now made quite a bit of difference and the car feels so much more planted. A difference of 0.1 & 0.2 bar really does make a huge difference in my opinion.