heat cycles

[hauss]

I have Nitto nt 05s on my car and just replaced the rears with the same.The rubber on the fronts is harder than the rears I was wondering is this because they were warmed and cooled to many times?

[CSX 4133]

Check for the year of manufacture on this tires using the link below. They could be just old, it's unlikely they are hard due to heat cycling, especially on a street tire.

https://www.tirebuyer.com/education/...-of-your-tires

[Michael C Henry]

If you watch NASCAR , a lot of little things you never considered, come into light. The teams are given 10 sets of tires (40) for a race. That's everything, practice ,qualifying, etc. They have a crew member that it is his job to takes the new mounted tires with the new tire sticker still in place (sticker) and wheels and make sets of 4 ( left right front and rear) out of all the tires that are compatible with the other mounted tires in the set. The crew will install a set of new sticker tires on the car and the driver will then put some hard laps on the tires and get some heat built up in the tires . The used tires are now called scuffs. The crew will take a number of tires out for practice runs for so many laps and bring the car in and change the tires. The used tires are now called scuffs. The new tires are called stickers. I found out that the tires get harder after each heat cycle. A set of used scuff tires will last longer than a set of new sticker tires., but may not stick ( cling) as well but that is the trade off. Every time they have the tires heated up during the race and they have a caution the tires cool off some and change again.

[bobcowan]

Originally Posted by hauss

I have Nitto nt 05s on my car and just replaced the rears with the same.The rubber on the fronts is harder than the rears I was wondering is this because they were warmed and cooled to many times?

Yes, it is. The NT-05 uses a fairly soft race type rubber compound. That's why they don't last long. Through heat cycles, that rubber does get harder. I use a durometer to monitor the rubber on my race tires. Just for fun, I also use the durometer on the Nittos.

[MKS427]

They will get harder with each heat cycle. That's why the sidewall says, "Not Recommended for Street Use." I run the NT-01s daily, I need the grip.