Scuff vs heat cycle

[blacksheep-1]

Scuff vs heat cycle.​

I had a recent discussion with the Michelin rep concerining this. Being from the southeast I have always used the term " scuffing" for any tire that was not a
" sticker" tire. That is not a proper description. A tires first 5 laps will always be its fastest, however there are times when a tire needs to run for a longer period of time. So the tire is slowly brought up to operating temperature, without abusing the tread area of the tire. This gradual increase in temperature chemically changes the makeup of the tire, giving up its grip for an increase in long term performance.
A " scuff" tire is basically any tire that has been used prior, and , generally speaking, has had any mold release wax scuffed off and the tire allowed to take a set on the wheel. It is not intended to increase the overall life span of the tire, and may not even see operating temperature. A
" heat cycled" tire is designed to do exactly that.
So.. a scuff tire is any used tire, a heat cycled tire is one that has been introduced to operating temperature and is intended to increase the usefulness of the tire long term, as opposed to a qualifying ( short term) application.
Why does this matter, well as Bruce Foss used to say..
" Old track, new tires, new track old tires" . Application is everything.

 

[Droop347]

Got into a conversation with a tire rep from Continental trying to decide on what tire to run when I start doing HPDE's. He asked if I was going to order from tire rack which I told him I was going to. He then started talking about the benefits of having them heat cycle the tire. As I was turning to walk away he said " just remember, heat cycled doesnt mean scuffed". Which sparked a whole new conversation, and many eye rolls from my wife. He put it almost exactly the same as you just did. I still havent decided if I should go with a high performance summer tire or a 200tw tire, but I learned a ton from my discussion with him.

 

[blacksheep-1]

Got into a conversation with a tire rep from Continental trying to decide on what tire to run when I start doing HPDE's. He asked if I was going to order from tire rack which I told him I was going to. He then started talking about the benefits of having them heat cycle the tire. As I was turning to walk away he said " just remember, heat cycled doesnt mean scuffed". Which sparked a whole new conversation, and many eye rolls from my wife. He put it almost exactly the same as you just did. I still havent decided if I should go with a high performance summer tire or a 200tw tire, but I learned a ton from my discussion with him.

Here's the other point, unless you are actually forcing the tread to "squirm" you are not heat cycling the tire, according to the Michelin rep, that is part of the equation, not just putting heat into the tire, but doing so while the tread is being moved around as well, which leads me to question if some of these heat cycling schemes are actually working.

 

[Droop347]

Looking at it through the eyes of a machinist and heating treating as far as metals are concerned, it made sense. But to be honest, most of the conversation was a bit over my rudimentary understanding of tires and their construction. He seemed to think it does, or at least thats what I came away understanding. Only way I can think of to really know would to be to test two sets of tires, one heat cycled one not, and have the same driver run them till they were used up on the same course under the same conditions. There are so many variables to control that there is almost no way to truly get a 100% identical set of tires under the same exact conditions.

Relating back to heat treating metals, do different compounds react differently to heat cycling. S7 steel is heated up to a different temp than say H13. H13 can only really be air quenched where S7 can be air or oil quenched depending on the use. So does compound make a difference when considering unloaded heat cycling? Maybe for the continental tire it is good, and for other tires it is a waste?

 

[blacksheep-1]

Looking at it through the eyes of a machinist and heating treating as far as metals are concerned, it made sense. But to be honest, most of the conversation was a bit over my rudimentary understanding of tires and their construction. He seemed to think it does, or at least thats what I came away understanding. Only way I can think of to really know would to be to test two sets of tires, one heat cycled one not, and have the same driver run them till they were used up on the same course under the same conditions. There are so many variables to control that there is almost no way to truly get a 100% identical set of tires under the same exact conditions.

Relating back to heat treating metals, do different compounds react differently to heat cycling. S7 steel is heated up to a different temp than say H13. H13 can only really be air quenched where S7 can be air or oil quenched depending on the use. So does compound make a difference when considering unloaded heat cycling? Maybe for the continental tire it is good, and for other tires it is a waste?

It's been my experience that heat cycling a tire is pretty much of a crap shoot, for Daytona 24 we must have cycled at least 10 sets of tires.. in the mist.. at 30 degrees... for 1 lap. How " cycled" these tires were, who knows?. It made the engineer feel all warm and fuzzy though.
I'm sure different compounds/ brands would all be affected differently as well.
We cycled a set for the SCCA runoffs at Daytona, and it basically won the race for us, but usually the idea of having a cycled set appears after the first practice session when you suddenly realize tire deg is a thing. Generally stickers are still king.

 

[TeeLew]

It's been my experience that heat cycling a tire is pretty much of a crap shoot, for Daytona 24 we must have cycled at least 10 sets of tires.. in the mist.. at 30 degrees... for 1 lap. How " cycled" these tires were, who knows?. It made the engineer feel all warm and fuzzy though.
I

When you're doing that, it's just to knock the sheen off the tire. You can't really drive any heat into the tire in these conditions, so you're not chemically changing the rubber. Daytona can be crazy slick at night and roughing the surface up so they can trust the tire grip just a little bit can account for seconds a lap on the warm-up.

I talk about 'scrub' sets and 'cure' sets. The above is a 'scrub.' A 'cure' run is generally two laps in reasonably good conditions started at high pressures, so they can lean on the tire right away. They work the rubber and actually put heat in the compound (not abusing it, but using it). Then the tire has to sit for a minimum of 24 hours to have the time to harden chemically. This is a good way to get a tire which normally lasts a stint and a half to get to two stints.

 

[blacksheep-1]

When you're doing that, it's just to knock the sheen off the tire. You can't really drive any heat into the tire in these conditions, so you're not chemically changing the rubber. Daytona can be crazy slick at night and roughing the surface up so they can trust the tire grip just a little bit can account for seconds a lap on the warm-up.

I talk about 'scrub' sets and 'cure' sets. The above is a 'scrub.' A 'cure' run is generally two laps in reasonably good conditions started at high pressures, so they can lean on the tire right away. They work the rubber and actually put heat in the compound (not abusing it, but using it). Then the tire has to sit for a minimum of 24 hours to have the time to harden chemically. This is a good way to get a tire which normally lasts a stint and a half to get to two stints.

According to my sources at Michelin, you must not only get heat into the tire, but actually have some movement of the tread surface the change the tire composition. This seems a bit weird, but if you saw the article on the Michelin wets, that have and angled tread, that acutally turns into a slick as it wears, it sort of makes sense. They were building a rain that could be run into the dry without chunking or damaging the tire, sooooo I would assume that as the tire wears, the tire composition is designed to "harden"?? maybe?
If that is true then it would also make sense to have to get heat AND tread movement into the tire for it to be a real "scuff" (or cured, depending on where you live). I have no idea what was on the minds of the Mercedes engineers at Daytona, becuase those slickes still had their stickers on, they weren't even worn off. As opposed to a set we did for Road America, 4.5 miles, 1 outlap, 1 hard lap, 1 in lap...letting the tire build up heat slowly and cool down slowly.

 

[TeeLew]

I'm sure this is a complete over-simplification, but it's my understanding that the chemical grip in the tire is related to the weight and amount of oil they used when making the tire. The more and lighter the oil, the more grip, roughly speaking. Soft compounds have a lot of light oils in them. When we get tires hot, they're constantly boiling off the more volatile components of the petroleum cooked into the rubber and it's slowly changing the chemical composition of the tire. When you hear about tires, "Falling off a cliff," it's because there's just nothing left to cook.

The 'cure' scrub for me is something which lights off the most volatile components of the rubber, but only a little bit. You'll never get the single hero lap out of the tire, but as the tire completely cools, the lighter components in the rubber recombine to become more stable. When you go out the next day, these will take more heat and abuse than a set of virgin stickers. It's pretty cool, really.

 

[blacksheep-1]

I'm sure this is a complete over-simplification, but it's my understanding that the chemical grip in the tire is related to the weight and amount of oil they used when making the tire. The more and lighter the oil, the more grip, roughly speaking. Soft compounds have a lot of light oils in them. When we get tires hot, they're constantly boiling off the more volatile components of the petroleum cooked into the rubber and it's slowly changing the chemical composition of the tire. When you hear about tires, "Falling off a cliff," it's because there's just nothing left to cook.

The 'cure' scrub for me is something which lights off the most volatile components of the rubber, but only a little bit. You'll never get the single hero lap out of the tire, but as the tire completely cools, the lighter components in the rubber recombine to become more stable. When you go out the next day, these will take more heat and abuse than a set of virgin stickers. It's pretty cool, really.

Yes, I agree, that makes complete sense to me

 

[blacksheep-1]

Now if all of this was on Tire Guy Mafia

 

[TeeLew]

I just read it on the back of my Coco Puffs this morning. It's probably completely wrong.

 

[blacksheep-1]

I just read it on the back of my Coco Puffs this morning. It's probably completely wrong.

I stayed at a Holiday Inn Express at the last race...