Old tires are........old

So just how bad are old tires?  Sunday I slapped a set of vintage RE-71s on my NC for a day of autocross and did ok.  But how much better would fresh rubber be?  These things had two hard seasons on them already when they belonged to a friend.  Then sat in his unheated barn for a year and a half before I bought the wheels last fall from him.  So the tread is about gone and they feel like concrete.

So for the sake of argument, with my full excuse generator operating at maximum power.  How much time might I have been able to pick up on a fairly short (~40 second) autocross course?

Depends on a few thousand things, but I ran my fastest lap, of several hundred, at Race City on a set of unused nine year old Yoko A032s, and I think it's because the asphalt was so coarse and old that anything softer just gnawed chunks out of the surface of the tire.

Weird, I thought.

Depends pretty wildly, it isnt just degraded or not, its a level of degredation.

For instance.  Ran my miata on 3 year old tires and was pretty sure it was 0.5-1 second or so off of what it would be on fresh rubber.

Ran my mustang on 10 year old azenis and it was WAYYYY off.  I couldnt apply throttle and keep the car straight, Ive had easier control in the same car at rain events on fresher tires.

Between 1.4 and 1.6 seconds. Give or take. Depending on weather. And the surface. And how tight your shoes were tied. 

In reply to KyAllroad (Jeremy) :

Wheel to wheel racing tires 4 events, one year old lost a solid 1/2 second on a 4 mile long coarse.  

When they were two years old that turned into 1.2 seconds 

Three years old it turned into 3 seconds. 

5 years old 3.2 seconds 7 years old  4.0 seconds 

After that the time didn’t get slower, and tread wear stopped at slightly less than 1/2 tread.  I did notice that in the rain tires more than 3 years old really caused a lot of sliding.  

A typical race weekend was about 200 miles of race track. 

I can tell you that 2 year old RS-3 v2's on the Forte on the same course was about 1.5-2 seconds off depending on driver on Grissom Concrete. 

12 year old Kumho 711's on the V8 Firefly made it accelerate about as fast as a 3cyl Firefly.  Much more tire smoke, though.

I think it's been pretty well covered that it's hard to tell exactly. I would guess some, but not a ton. Probably 1s or less. I've witnessed both ends of the spectrum though. At one end, winning PAX at a local event on 4 year old RE11s that were stored on the car outside for a winter. At the other end, the RS3s I had on my fiesta that, after driving on them in 30* weather for about a month the previous witnter, got so hard that they basically stopped wearing altogether and were borderline dangerous the one time I tried to autocross on them.

I probably shouldn't admit to this, but I drove my 2002 around a few hundred miles on the Pirelli P700's that were on it when I took ownership. Build date was week 32 of 2001, so these tires could have their own license at this point.

Obviously, I wasn't pushing the car by any stretch of the imagination, but they didn't do anything blatantly horrible. I wouldn't want to see what they would have done in the rain or any emergency maneuvering, but they held air and got me where I was going. They'll be first on the list for replacement this spring.

When I bought my first Miata last February, it had a set of 400 treadwear khumo summer tires on 15 x 8 storm S1 wheels. Since I was competing in es, I needed some stock width wheels.

I picked up a set of Bridgestone re71rs on stock wheels. They were dated 2016, but it been stored indoors, and had maybe 30 to 50 runs on them (I don't remember exactly). So, two years old, but way better than what I was using.

I still have them, they are still stored indoors and have never seen freezing weather. I may use them this year as rain tires in the autocross, as I suspect they still may grip in the wet better then the rivals that I have.

My tires are tires in the academic sense in that they are round and had once been made of rubber.