Hi everyone, I just bought a '14 C2 and the rear end seems very slippery to me. There are probably a few potential causes and I wanted to run my thoughts by the community.

I'm coming from an RS5, which would have gone cleanly around the same turns that the rear end of the Porsche seems to be sliding on.

First thought is the tires. The car is certified, and to bring it up to CPO status, the dealer had to replace the rear tires with new ones (P Zero). So they probably have about 150 or so miles on them at this point. So they could they be slippery due to having limited wear.

Second thought is tire pressure. The rears were showing 44 psi (fronts 33) at the time. I had set the tires as per the partial load, standard tire pressures for C2 and 20" rims, which was cold temp pressures of 31 front and 39 rear. Is 44 psi too high?

My strong assumption is that the Porsche would have at least as good grip as my RS5, so something has got to be up.

Thx!

 

Yes re new tires. After a few hundred miles they will get over that. And yes re tire pressures. The settings on the door (and in the head of liability crazed manufacturers and dealers) are way too high for optimal handling- they are high to compensate for 4 passengers and they loot at max autobahn speeds. The "comfort" settings in your manual (around 32 front, 35-6 rear) are far better for handling and your fillings. If you track the car you will learn to reduce the pressures as the tires get hot to return to optimal handling.

 

After about 2 years, the Michelin rears on both my 991 C2S and 981 Boxter got slippery. The tread looked fine and they had proper pressure. I replaced them and they are much better now.

 

until they are properly heat cycled they will appear greasy, I also agree that more optimal pressures will help, 32/38 cold is a good place to start. 44 at
the rear is INSANE...

I *think* you must also take into consideration the difference between the RS5 (heavier 4WD and 50/50 w/d...) and the 911 (lighter, RWD, 40/60 w/d) ... the back end of the 911 will 'move' more than the RS5

 

Thanks everyone. I went to 31 front 35 back (cold) and we'll see how it feels, and I will let the tires further break in.

As for the difference in weight distribution, etc., that could be true, but the car was sliding a bit at cornering speeds at which I would not *think* a 911 would slip. But obviously the car is very, very new to me at this point, so you could be right. I guess time will tell!

Of course, if anyone here has driven both, feel free to chime in...

Thanks!
Mike

 

you are still experiencing the behavior of the new tires: http://blog.tirerack.com/blog/tire-r...hose-new-tires

 

My vote is definitely new tire slip. They take a couple hundred to break in well.

I also find performance tires get slippery again at the end of their life, so once the back end starts to surprise you...it's "tyre" time!

I generally replace rears 2x more than fronts.

 

50:50 weight distribution on an RS5?

 

I do not think the RS5 is 50/50 weight distribution.....but they do handle darn well.

 

Road &Track puts it at 58:42. All Audis save the R8 are understeering pigs.

 

Yes, I agree. Especially on long sweepers.

In tight turns, you can feel the car fighting its weight, and it neither feels very agile nor is it much fun. As the road opens up, the car (and driver) is much happier. The car feels more in its element and you can get on the throttle very early coming out of turns with the AWD and torque vectoring providing amazing grip.

In fact, in this test, the RS5 was only 1/10th of a second behind the Boxster S on its lap time:

http://www.caranddriver.com/features...3-class-page-5

 

AWD to RWD.

Sorry you had to downgrade your grip.

I went from an RS4 to C4S and the grip is unfreaking believable.

The C4S feels glued until the tires are almost dead.

 

AWD vs. RWD has nothing to do with what I am feeling. I am not slipping due to the application of throttle.

Now, if I lost traction accelerating through, or out of a turn, then yes, I'd say that having AWD would help.

But what I am feeling is the tires slipping laterally due to cornering forces alone.

 

To me that's a good definition of loss of traction.

I just caught that the rear tires are new .... so they will come into their own after a few hundred miles.

Now one thing different than the Audi's I've had, using the sport and sport plus features allows a little more freedom from the traction control program but still keeps the car from coming around like you would achieve if you turned it completely off.

 

Yeah, I was trying to distinguish between loss of traction purely due to cornering forces versus loss of traction due to overloading the rear tires with throttle (as you would do if you got on the throttle too aggressively coming out of figure 8 on a skidpad).

Anyway, maybe I'll find an empty parking lot somewhere and play around with toggling the traction control on and off just to get a feel for what's happening.

Thanks,
Mike