Is it normal to replace 2 sets of back tires to every set of front? I have Michelin Pilot Super Sports.

 

That's what I'm looking like on my Pirelli P Zero...maybe even three sets of rears to one set of fronts.

 

Very normal

 

Same here. Nothing unusual about that.

 

Just did my rears too. 12K miles. Fronts still good.

 

The front grip will start falling off radically before requiring replacement due to tread depth. So if you replace the rears only, just be aware of having a significant grip delta front to rear at some future point.

Although my tires wore very consistently front to rear, my front grip disappeared before the rear. Had I changed the rears only, my car would have been dangerous.

My point is consideration to grip far outweighs tread depth as the key variable to determine the replacement interval.

 

I don't understand your rationale. Grip is proportionally related to thread. If the thread is still good, then the grip will be good.

 

Tires deteriorate with time and use regardless of tread. Heat cycles, off gassing of volatile organics all decrease grip.

And for what I understand tread is really for displacing water, like when it rains. That's why they make racing tires slicks

 

As the tire is used, grip changes (falls off). It is not constant and certainly not based on whether the tire has tread. Grip has much to do with tire temperature. Perhaps the lack of blocks (or the diminished size of the block from usage) causes the slope in performance as the blocks no longer move to generate the ideal heat range. Just a theory. But the fact is grip is not constant over the life of the tire. The grip on my Michelins (PS2 and PSS on my 997.1) changed dramatically after 15,000 miles. Very noticeable under acceleration (rear) and cornering (front).

Although I think the roads here make it more pronounced as the grip here from the road surface is terrible. One reason tires last longer here.

 

Agree, well said.

People can change rears only if they want. But considering the overall short life of the tires, I don't think it's very smart. Better to have consistent grip front and rear. It's only money.

 

I wonder if this drop off in front grip is more of a characteristic of Michelin tires? I have the P Zeros and haven't noticed a drop off in front grip. Like others, my rear tread wears out in about half the time compared to the fronts.

 

There's a LOT less rubber up front to begin with and the weight is all in the rear...

 

2-1 rear wear is normal.
Spirited driving, occasional drift, rear weight bias etc.

 

2 set rears to 1 set front is a 911 thing.