C63s W205 Understeeer

[Rameez-Q]

Recently changed my tyres on the rear of the car from Conti Winters which i have all round to Pilot Sport 4s.

There a little greasy and yet to bed in i believe and can cause the car to snap on damp/cold roads.

I've recently noticed with some moderate speed cornering nothing crazy but just turning in quick the car has started to understeer, nearly crashed twice! As soon as i tap the brake straigthen and reapply throttle it seems to correct itself.



I'm beginning to think that the pilot sport 4s are providing a lot more grip than the conti winters and thus with more improved traction in the rear the front's can't cope as well throwing the front off and causing understeer?

For information, the front's are about 4/5mm across and i never had this problem prior to replacing the rears?

[cduk]

You've still got the Conti winters on the front, with summer MPS4 on the rear - have I understood that right? If so, no wonder the handling has been upset. Mixing summer & winter compounds is a very bad idea.

[Rameez-Q]

cduk said:

You've still got the Conti winters on the front, with summer MPS4 on the rear - have I understood that right? If so, no wonder the handling has been upset. Mixing summer & winter compounds is a very bad idea.

Yeah i was thinking this was the cause just waiting to confirm! Anyone had prior experience? Sometime's its ok but when it's greasy its a strange understeer feeling!

[Scrump]

cduk said:

You've still got the Conti winters on the front, with summer MPS4 on the rear - have I understood that right? If so, no wonder the handling has been upset. Mixing summer & winter compounds is a very bad idea.

Definitely this.
Get some matching MPS4 on the other end.

[cduk]

Rameez-Q said:

Yeah i was thinking this was the cause just waiting to confirm! Anyone had prior experience? Sometime's its ok but when it's greasy its a strange understeer feeling!

The problem you have is that you have two very different compounds of tyre. As you've found out, in warm(ish) conditions your summers at the rear will grip better; in colder conditions or on ice/snow the fronts will grip better. As you've got such different characteristics of tyre you'll encounter real unpredictability, and you'll probably end up crashing it, such is the amount of upset. Tyre manufacturers don't recommend it either:
https://www.continentaltire.com/news/mix-tires-or-...

There's a great CarThrottle article and video on this also, explaining how lethal this is:
https://www.carthrottle.com/post/heres-why-putting...

Do yourself a massive favour and change the other pair to matching ones.

Edited by cduk on Monday 27th January 19:50

[Olas]

You answered your own question in your opening statement

[Rameez-Q]

There goes another £3/400

Will get on the lookout for a set!

[jahill]

I'm going to repeat what has already been said: please change them before you get into an accident.

I'd argue that you don't want a mix of different tyres front/year, but a mix of completely different types is asking for trouble, especially as the handling won't be consistent.