How to remove understeer

[Twin Turbo]

I planning in making some changes to my car handling, as currently it has understeer on high speed corners.

Currently plan is to remove the run-flats, and go for NON-runflats.

I have read an lot of things can be done - but unsure what would be best one thing to fit?

 

[GazHyde]

I guess the tyre change (assuming they are better softer tyres) should have a positive effect. Would be worth seeing what difference the tyre change makes on the front end before progressing too far with other changes, or else you won't know which bit resolved the issue!

Am I right that the car in general is completely standard at the moment suspension wise?

 

[5harp3y]

Moving to standard tyres will help top start with.

BMW convertibles are set up to be a little understeery as standard to make them feel safer.

 

[EnthuZiaZT]

I have a small issue with my E89, that is, when I come off a roundabout at speed, it feels like the front N/S wheel is in the air. BMW have checked the rear suspension especially the rear offside but cannot find a fault. I wondered TT if you have experienced a similar effect on your car as they are very similar. With regard to tyre changes I quickly got rid of the run-flats on my E85, the car was a lot quieter on the road and I felt handled more predictably.
Sorry for going off topic.

Mike

 

[hard top]

If I were you, I would hire/borrow a set of wheels with winter tires as they are a softer compound and have a softer side wall and see if it makes a difference, I ran them all year round on my Z3 and never had problems, tramlining, etc.

 

[Twin Turbo]

If I were you, I would hire/borrow a set of wheels with winter tires as they are a softer compound and have a softer side wall and see if it makes a difference, I ran them all year round on my Z3 and never had problems, tramlining, etc.

I have an set the shed, but only 225's - waiting to get below 7 degrees before i swop them over

 

[hard top]

I have an set the shed

Have you run them before on this car?

 

[Twin Turbo]

My current thinking is completing the following work:-

- H&R lowering springs
- Front M3 tension struts
- H&R 27mm sway bar
- EBC Red Stuff

 

[Twin Turbo]

Have you run them before on this car?

Yes last year, but not cold enough to swop over and want to run my RF long as possible - so in the spring put some NRF

 

[Dino D]

I would also look at how much adjustment can be made with the wheel alignment settings on that model and especially how much camber you can dial in the front (there probably are camber adjustable top mounts available for it by now).
Although you not going for coil overs it still can be corner weighted using spring pads (well at least the Z3 can).

A proper alignment session and some camber on the front has made mine feel nice and pointy enough.
Not got ARB's yet but wouldn't mind giving them a try if I ever get round to tracking mine.

 

[hard top]

Yes last year

OK, just out of interest, did you notice any difference?

 

[t-tony]

Well I'm looking to put some decent winter tyres on my Z4 Mike, 225/45x17 .. I seriously don't like the run flats that it came on, noisy, harsh ride etc. I will sell the run flats on, loads of tread still on them, good tyres, if you like that kind of thing.

Tony.

 

[hard top]

Well I'm looking to put some decent winter tyres on my Z4

Don't be put off about running winter tyres all year round, I got "Oh, you will be buying a new set every six months"...total BS.
You only get that if you run Pirelli, and I have.

 

[t-tony]

I don't know how many sets of winter tyres we have in storage at our place Mike, last winter consisted of about 4 days of White weather. Many people never even came in to have them fitted (for free). Only one I've seen up to now is a Lady had her's fitted on a Porsche Cayenne last Saturday.

Tony.

ps. My old boss put some on his wife's Fabia 2 years ago and they're still going strong

 

[Twin Turbo]

My experience of winter tyres is not an fair comparison - as I don't rag it lol - also my rears are 225 same as the fount - so I can swap them around - had the same set for 4 winters now.

However winters I understand you lose about 10% in breaking performance - and I dont have the best WT - as Summer Tyres as I understand loose there effectiveness temperature below 7 degrees.

Regarding camber on the Z4 as I understand is

OEM alignment tolerances for the E89:

Front Camber -0.1 to -1.1
Front Caster 6.5 (fixed)
Front Toe 0.02 to 0.22
Front SAI 14.2 (fixed)
Front Inc. Angle 13.6 (fixed)
Rear Camber -1.9 to -2.8
Rear Toe 0.05 to 0.25

I been recommended if the above work is completed to change the camber to the following settings:-

Front Camber -0.5
Front Toe 0.06
Rear Camber -2.5
Rear Toe 0

Regarding coilovers - did look at this as an option - but you can get some China Coilovers for £500 or go upto £1500 for an well made set.

 

[5harp3y]

Don't buy cheap coilovers ... . ever.

Front camber will help turn in.

 

[Chazzy]

Basically you want to increase the weight transfer and hence tyre load to the front outside wheel.

If you are running standard springs/dampers/ARBs etc, then I'd go for an H&R anti roll bar kit, run the front soft and the rear stiff.

Also, increase the negative camber on the front wheels to around -1.5°. This loads the tyre better and hence results in more grip.