Z4 Feels "flighty" when going fast on straight roads

[rafcom]

Hi All

So overall I like the way the Z handles (I would, it's my first "sports" car and my last car was a Peugeot 4008 ) but I have noticed that when taking the long road and traveling at the speed limit (and slightly above) that it feels a little "flighty" (like it does not like traveling in a straight line and I have to continuously correct it).

One thing I have done which alleviates things a tad, is to hold the steering wheel like you hold on to a motorcycle's handle bars, lightly, but I suppose that's to eliminate and false inputs (so it doesn't make it better, it just doesn't make it worse).

Any idea what could be causing this?

Thanks,
R

 

[enuff_zed]

At the risk of being the first with the predictable response: is it on runflat tyres?

 

[rafcom]

Running run flats in front still, had an emergency repair on the rears and couldn't get run flats so have a set of Accelera PHI R 255/35-19

I've never had run flats on a car so not really familiar with their pros and cons.

 

[B21]

So you’ve got s**t tyres..even worse different s**t tyres front and rear…so until you get a decent set of matching rubbers it’s hardly surprising it’s shite…

Given the mileage it also could have play in a variety of bushes..but first port of call is the s**t tyres..

PS..incorrect / inappropriate respective profiles front and rear too..

 

[brillomaster]

Get some decent tyres. Don't have to be michelin/goodyear/continental etc (though they are good) a decent midrange like kumho, vredestein, Dunlop, hankook are all just fine. Once you've got a half decent set of matching, non run flat tyres, at the correct sizes and pressures, then check the alignment. Then if that still doesn't fix it, check for worn bushings and suspension components.

 

[brillomaster]

Ps it'll likely just be the front run flats sniffing out ruts and grooves, and generally tramlining.
You might just need matching non run flats on the front.

 

[flybobbie]

Don't mix tyres.
First dump rft's.
Then get a full set of normal tyres, like Goodyear asym., not expensive.
Then experiment with tyre pressures.
Then make sure the tracking is spot on.
Then finally i replaced the lower tie rod, see elsewhere on forum. That finally gave my the stability i wanted on undulating country lanes.
I can actually take hands of steering and runs straight on bumps.
But if i did say 80 on same road the stability is scary. It ain't no rally car.

 

[rafcom]

Yeah I know, as mentioned the rears were a "get me home" buy (50kms outside a little town, in the middle of nowhere, about 500kms from home, it's a miracle they had something my size) and to be fair the reason I haven't jumped on replacing them yet was that they felt ok grip wise. The fronts are Dunlop Sport Maxx RFTs, I see they don't review very well.

Been looking around and I really like the looks of the Falken FK520s (https://www.tyrereviews.com/Tyre/Falken/Azenis-FK520.htm), which surprisingly is available here (we don't have the huge variety you guys seem to have). Think I'll give those a go.

Thanks

 

[brillomaster]

I've recently put fk520s on my car to replace aging goodyears...no complaints so far, seem like a decent midrange tyre to me

 

[Busterboo]

I really like the looks of the Falken FK520s (https://www.tyrereviews.com/Tyre/Falken/Azenis-FK520.htm)

You don't drive on looks. Buy better. Not just the best you can afford, but the best there is. When all's said and done, tyres are the major contributory factor to performance (and safety) you can choose.

 

[rafcom]

I meant the graphs looked good, not the pattern (although those all season tyres with the symmetrical patterns are hypnotic )
https://www.tyrereviews.com/Tyre/Michelin/Pilot-Sport-5.htm
https://www.tyrereviews.com/Tyre/Falken/Azenis-FK520.htm

At double the price, the gain seems negligible.

Also, if I had to spend what equates to 1,400GBP (ZAR28,000) on tyres every now and again, I'd stop driving the Z all together

 

[Busterboo]

The major weakness of tyrereviews.com and similar reviews in magazines is that their statistics are nonsense: for example, their use of % to describe and differentiate 'Road Feedback' is journalists' gibberish.

Fortunately, in the highly competitive market in the UK, there is a simple inidcator - price: you get what you pay for. That said, the situation in South Africa may well not be quite so clear - I don't know.

 

[flybobbie]

Yes certainly in SA, Bernard Manning said should never mix cross ply and radials...

 

[Blurredman]

I've had exactly the same issue, and adapted my driving style (light input on the steering wheel) in the same way to compensate. The start of the problem preceded me swapping from RFTs to non-RFTs (the RFTs had all but disintegrated on the rear), and I hoped that new tyres would sort it out. In fact, for a time it was distinctly worse on the non-RFTs. I remember driving on the M6 at 40mph as I was scared sh*tless of going faster. I went back and had the tracking adjusted several times and saw small improvements, but on the motorway I would be apprehensive at speeds over 60mph as the car felt light and 'disconnected' at the front. Couldn't find any play or wear in any bushes or suspension parts.

Over time it's improved, which I put down to initially the tyres scrubbing off the mould release wax, and then gradually wearing to a profile where there is more rubber on the road across the tread. My car showed the usual pattern of inside tyre wear before I swapped them, and as that wear has repeated with the new tyres they have settled down.

Has to be said, though, the car has never felt quite as planted as it did when I had the original tyres on it and the drive is less fun than it used to be. I realise that satisfying driving relies on a certain amount of resistance to your turning inputs at the steering wheel. The light feel takes away that feedback and reduces your confidence that the car is going where you want it to. But actually, if you hold the wheel gently it still goes in a straight line, and that's how I now tend to drive - holding the wheel at the 4 and 8 o'clock position and not applying too much pressure.

 

[peter2704]

blurredman ,can i ask you something? when you went square set up on the wheels ,what profile/width did you end with? going the same way on our e89 19" but not sure on tyre sizes,any pics of the new set up ,how does it look on the car

 

[B21]

I've had exactly the same issue, and adapted my driving style (light input on the steering wheel) in the same way to compensate. The start of the problem preceded me swapping from RFTs to non-RFTs (the RFTs had all but disintegrated on the rear), and I hoped that new tyres would sort it out. In fact, for a time it was distinctly worse on the non-RFTs. I remember driving on the M6 at 40mph as I was scared sh*tless of going faster. I went back and had the tracking adjusted several times and saw small improvements, but on the motorway I would be apprehensive at speeds over 60mph as the car felt light and 'disconnected' at the front. Couldn't find any play or wear in any bushes or suspension parts.

Over time it's improved, which I put down to initially the tyres scrubbing off the mould release wax, and then gradually wearing to a profile where there is more rubber on the road across the tread. My car showed the usual pattern of inside tyre wear before I swapped them, and as that wear has repeated with the new tyres they have settled down.

Has to be said, though, the car has never felt quite as planted as it did when I had the original tyres on it and the drive is less fun than it used to be. I realise that satisfying driving relies on a certain amount of resistance to your turning inputs at the steering wheel. The light feel takes away that feedback and reduces your confidence that the car is going where you want it to. But actually, if you hold the wheel gently it still goes in a straight line, and that's how I now tend to drive - holding the wheel at the 4 and 8 o'clock position and not applying too much pressure.

That must be the first ever account I’ve read of a driver who found OE run flats better than alternatives….

What tyres did you fit ?

What tyre pressures did you use ?

 

[Blurredman]

You won't really notice any difference from a side view of the car with the narrower rear wheels, and not much difference from the rear either. I went with 19" 8J wheels on the back (standard fronts) but with 225/35ZR19 tyres front and 235/35ZR19 rear. My reasoning at the time was to go with the slightly wider tyres at the back to compensate for the 20mm loss compared with the standard 255 rears. Notwithstanding the steering issues mentioned earlier - which I do not believe relate to the square(ish) setup - the car handles just fine. In the country lanes and B roads it is solid, and doesn't feel very different to the standard setup with RFTs.

 

[Blurredman]

That must be the first ever account I’ve read of a driver who found OE run flats better than alternatives….

What tyres did you fit ?

What tyre pressures did you use ?

IKR. When I first got the car (with RFTs) it was fantastic at speed, absolutely rock solid at 70++. Then after several months I started to notice a vagueness to the steering (like the car was being buffeted by wind) at higher speeds. I went to get it tracked, and found that I had cracked rears and the tyres were hanging on by a thread. I swapped to non-RFTs expecting that to cure everything, and the result was as described.

Don't get me wrong, driving on run-flats was an absolute PIA as every bump in the road lost me a vertebrae and probably added another crack to the alloys. Swapping them out has made normal day-to-day driving a whole lot more pleasant. I think there are still other issues with the car (maybe suspension, possibly the rack) that are summing to give me a <100% solid drive now, but I have definitely seen improvement as the tyres have worn in. I guess that would happen with new RFTs too.

The non-RFTs I put on it are Uniroyal Rainsports (a Continental brand), mid-price tyres. Next time around I will probably go for the more tried and tested Michelins or Pirellis others recommend, but at the time the piggy bank wouldn't allow. I'm running 33F/40R, which seems about the best result after some experimentation.

 

[peter2704]

You won't really notice any difference from a side view of the car with the narrower rear wheels, and not much difference from the rear either. I went with 19" 8J wheels on the back (standard fronts) but with 225/35ZR19 tyres front and 235/35ZR19 rear. My reasoning at the time was to go with the slightly wider tyres at the back to compensate for the 20mm loss compared with the standard 255 rears. Notwithstanding the steering issues mentioned earlier - which I do not believe relate to the square(ish) setup - the car handles just fine. In the country lanes and B roads it is solid, and doesn't feel very different to the standard setup with RFTs.

Thec20mm loss is this overall width or to outer edge if it’s outer edge I may fit spacers to make up for it . Shame you haven’t got pics to see how 235 fills the rear arch

 

[Blurredman]

The 20mm loss is the difference in tyre width overall, but because of the difference in the wheel offset between the 8J and 9J wheels the outer edge of the wheel and tyre with the 8J fitted to the rear is pretty much the same as with the 9J. In other words, the 20mm is lost on the inside of the wheel/tyre. I spent a bit of time using https://www.willtheyfit.com/ to figure this out. If you look at the photos I've just PM'd you, you'll see that to he untrained eye you wouldn't tell they were 8Js on the back.