Over the last 2 weeks I have been caught out with turn-in over steer on two occasions

This applies to non-constant radius turns i.e where you have to vary the amount of steering lock as you drive through the corner

I go into the corner with all my braking done and in the correct gear and on a constant throttle - When I turn into the corner I continue to apply lock and the back end just steps out

I have checked the tyre pressures and they are spot on at 32psi all round. They have around 1500miles on them so plenty of life in them but they are S03's, sizes correspond to the ones detailed in the handbook

The only way to avoid this is to enter the corner at a speed dictated by the tightest part of the corner even when the entry dictates you could carry in more speed. This is ok providing you 'know' the road, it's not so good on unfamiliar territory, yes I know that on unfamiliar roads you should keep the speed down but this is occuring as low as 25mph and in 3rd gear. There's no way I could be described a pushing it. In many ways this has what has caught me out, at 25mph and in 3rd gear losing the rear end can't be expected, not in the dry any way.

The problem is not that the car has 'gone away from me' but it's making every drive an adventure and this is not how the car felt for the first 4500 miles. The only way to drive round the problem is to be very very circumspect and when this does happen is to 'power' throught it on a light throttle.

I am worried I am appearing to look like a hooligan in front over other road users and this is most definately not the case and I especially don't want my collar felt by the law

Is it possible that the alignment could go out suddenly producing this handling or that the S03's have changed somehow in their characteristics. I don't rember this when they were first fitted. It just seems that suddenly a switch has been thrown and the car has become rather wayward. I compared the S02's I have in the garage and yes they do appear to be wider than the 225 S03's but I can't believe a 1cm reduction in contact patch could produce this problem especially since the tyres I have on meet the requirements in the handbook

Any suggestions, I don't really want to bin the S03's 'cause they cost me

 

If it's not a problem with the tyres or geometry, are you applying power too aggressively to exit the turn? This would produce power-on over-steer.

Alternatively, if your throttle is not correctly balanced, or if you're lifting off the throttle at the tightest point, this might produce lift-off over-steer.

The only solution is to enter the turn at the speed dictated by the tightest part of the turn, make sure the throttle is completely balanced (i.e. not accelerating and not slowing down), then apply the throttle progressively once you're past the apex of the tightest part of the turn.

Other than that........

 

If its any help...I run S03's on 17" wheels and have had none of what you describe.

I also have a front strut brace which seems to put the car where you want it (within extremes and subject to dry weather)


I'd be surprised if the alignment would suddenly change.

Are the wheels on tight / Shocks OK / no recent kerbing ?

(Can't think of anything else)

 

Shipley

Are the S03's 245 or 225?

I am not aware of 'powering' out of the corner to produce the oversteer. This morning it did it on a trailing throttle, it's weird

 

When you say the problem corners tighten up how sharp a bend are you talking about? If you can follow other traffic round the corner and still have trouble when they don't (not sure if you've tried this?) I'd get the car looked at if I were you!

25mph in 3rd gear should be pretty difficult to induce power oversteer as you'll be well down the rev range..... lift off oversteer is far more likely (as Mark W suggested).

 

Well I was following an SL500 the other day but I was 'trying' if you know what I mean and no such problems - it all seem to transpire at the least likely time i.e when I am taking things gently. Maybe I am coming off the throttle as I tighen the line and am in fact getting lift off o/s rather than turn in o/s

Whatever it's only just started to manifest itself. I am booking the car into make sure nothings come lose or the alignment is out

As far as the tyres are concerned they are at the correct pressures and young. Only thing is that they are 225's

 

Pretty sure the tyres should be 245 not 225. I had 225 S03's on the rear and the handling was terrible. So much so that I gave up driving it until I could get some F1's put on.

I think the tyre choices i.e. S02, S03 and F1's have there own merits and downsides but you should always run all four tyres the same, and run 245's on the rear unless they are specific S02's for the S2000.

HTH
Marc

 

Ditch the so3s get so2s have the alignment checked, get revised settings put on if out stay in for a month to pay for it all and enjoy the car.
Seriously though the undersized so3s moke the rear alot looser mainly due to the soft tyre walls so my first point of call would be get the right sized tyres on then take it from there. My own experience tells me that you wont be happy untill you have the correct size and type of tyre + the correct alignment. BTW the alignment can easilly go out, a cpouple pf drains here a few small pot holes there thats all it takes. Also if you have the aligment done make sure its on pretty fresh rubber, its a waste of money if they are getting on.

 

I was expecting the S03's to have started to wear but they haven't so maybe they are a hard compound

Whatever the cause is I need to get this sorted and soon

 

If you go over to the American side of the board you will find that everyone, and I mean EVERYONE, agrees that if you change to S03's you need to go to 245s not 225s since there is a difference in the size of the contact patch such that 245 S03s are the closest match to the 225 OEM S02s.