Vague steering at speed

JoeZed said:
What Tyres have you got on the car ? How old are they ? A few hears ago, I put on new tyres - Run Flats - can't remember the brand but anything over 60mph on them the car felt like I was towing a a caravan in a cross wind. It felt like the rear of the car was constantly snaking. Also tram lined like hell. It took about 3k miles for the tyres to come right. Now I'm back on Conti's non run flat the car is very stable.
Click to expand...

They are Uniroyal RainSport 5's (Uniroyal is a Continental brand). Guess I've done about 2000 miles or so on them since they were fitted in April. Can't rule out the problem is tyres (or pressures) but I have had the 'vague steering' problem since before I changed the tyres.

Interesting that you say your car felt like it was in a cross wind. That's EXACTLY how mine feels at high speed, and was the reason I initially got the car looked at (and ended up finding I had cracked wheels and damaged tyres). I was driving up the M6 and when I got to the office told everyone how windy the motorway had been! But then it happened every time since, wind or no wind...
 
MMMM..... The Z4 Steering is vague anyway. To expand on how my car felt with the new run flats....The tyres were fitted a couple of days before I did a road trip to Scotland. On A and B roads, when steering into any corner when going down hill (at speeds I was used to prior to fitting the tyres) , the traction control light would come on, the rear end felt like it was about to swing out and I could feel the car braking on its own. I knew it was the tyres because I just had them fitted.
 
Blurredman said:
There does seem as much art as science when it comes to deciding on tyre pressures! I'd assumed that BMW recommended pressures for my front (standard) wheels with RFTs should hold true for non-RFTs, but am now tempted to run them with a little more air in them and see how that changes the handling.

For my non-standard rear wheels (19" 8J) I have 235/35 non-RFT tyres running 37 psi - and that is just guesswork, 'cos few people have this configuration. On reflection I might have been better off with 235/30 tyres, but I can't believe it makes much difference and surely the steering 'feel' is way more influenced by the front wheels/tyres than the rear? But I think I will eek the rears up +1/+2 psi too and see what happens.

:driving:
Click to expand...

The RFTs fitted to the E89 were an early aka primitive design..the high tyre pressure was mandated to allow 155 mpg autobahn cruising on very smooth roads..

All the E85s and G29s that bracketed the E89 ran pressures in the area of 28-30 through 34-36..unless set for sustained 100mph + speeds..

So why do cars that share common design architectures, and common suspension designs and even components run much lower pressures?

Because over inflated tyres bounce around as if they were in a cross wind..

I’ve had 2 sets of BMW runflats in 18 and 19 sizes and at least 10 sets of non run flat tyres on 5 different sets of alloys..running 34/36 or 32/34 I’ve never, ever had a tyre related handling issue..but putting the rears upto 42/44 did result in an unstable uneasy feeling at high speed on bumpy roads ..

So best thing is for you to do some structured testing ..try 36/42 then go straight to 32/34 and compare and take it from there..if nothing else if the change has no significant effect then your issue is not tyre pressures..
 
B21 said:
So best thing is for you to do some structured testing ..try 36/42 then go straight to 32/34 and compare and take it from there..if nothing else if the change has no significant effect then your issue is not tyre pressures..
Click to expand...
That's the scientific method, right there.

I will give it a go and report back...
 
Just experiment, noting maximum tyre pressures on the sidewall of the tyre.
Try it on the roads around HG! Although a bit better now some have been resurfaced.
But the steering and suspension i never had any concern on any other car than this car.
I have on few occasions thought i will sell my car due to how it rides..
Has improved with some mods.
 
Early days, but I have tried increasing the fronts from 33 to 35, and rears from 37 to 39.

Ride / handling and low speed (up to 50mph) - better

Not yet tried at >50mph

The experiment continues...
 
Blurredman said:
Early days, but I have tried increasing the fronts from 33 to 35, and rears from 37 to 39.

Ride / handling and low speed (up to 50mph) - better

Not yet tried at >50mph

The experiment continues...
Click to expand...

What were the pressures ?
 
B21 said:
So best thing is for you to do some structured testing ..try 36/42 then go straight to 32/34 and compare and take it from there..if nothing else if the change has no significant effect then your issue is not tyre pressures..
Click to expand...
I agree. That said, the pressures element of the testing is easy, of course. The difficulty is finding a road for the tests that can be used consistently.

I have a lovely one. Countryside/bendy 'A' verging on 'B', predictable busy & very quiet times, good surfaces, 12.1 miles. Objective to complete as many miles as possible without slowing below xmph and without using the brakes. Changing down permissible, but only above x and remaining above x. In other words, x is the minimum, not the average. An excellent test of tyre pressures, among other elements.

Completing it is difficult, not least because, even when the road's empty, you have to concentrate very hard. Well, I do, anyway.

To my surprise, the 35iS can do it as well as an AWD 3.6 911 I had. Indeed, I've done it twice in the Z above x +10.

If nothing else, it's informative about tyres.
 
You must log in or register to reply here.

Similar threads

O
Twitchy/nervous/vague steering at speed
Replies
9
Views
3K
Toe-side
T
Griffo46
2007 3.0si Roadster - vague steering
Replies
8
Views
736
iksander
I
P
Vague Steering - 2004 M54b25
Replies
0
Views
190
portculisz4
P
R
Vague/light steering
Replies
16
Views
1K
Rldee007
R
R
Vague steering after replacing tyres
2
Replies
32
Views
2K
roblightbody
R
Back
Top Bottom