Tire Scraping and Heat

[tapandrack]

OK excuse this naive question but I have a couple racing buddies that spend hours taking a heat gun and directing the heat inches from the tread to scrape the tire clean. When you touch the tread it is hot.

I mean I see how clean the tires look after spending 90 minutes with a 1500 watt deluxe Harbor Freight heat gun but my question is how does this direct heat not act like a heat cycle to the tire tread compound thereby reducing its life?

Thought I'd ask if you could tell me why this is not a problem.

Thanks!

[Dee]

F 1 guys spin the tires on a balancer and run a course file over it 5 mins ;-)

[Rick Kirchner]

I use a curry comb

[RussMcB]

I'm interested to see if some smart guys respond with an answer. I'm someone who's spent plenty of time with a heat gun and small (~1") putty knife removing a thin layer to expose fresh rubber. It always *feels* like the end product is much improved, newish tires for the start of the next session but I could be kidding myself (and adding a heat cycle/shortening the tires' effective life).

The other main reason I do it is I consider my own labor as mostly free and buying new tires is painfully expensive.

[DaveW]

OK excuse this naive question but I have a couple racing buddies that spend hours taking a heat gun and directing the heat inches from the tread to scrape the tire clean. When you touch the tread it is hot.

I mean I see how clean the tires look after spending 90 minutes with a 1500 watt deluxe Harbor Freight heat gun but my question is how does this direct heat not act like a heat cycle to the tire tread compound thereby reducing its life?

Thought I'd ask if you could tell me why this is not a problem.

Thanks!

Compound cure level is affected by time at high heat. In initial curing, within limits, pretty much the same cure level can be achieved by long cure at lower temperature, or shorter cure at higher temperature.

Since during tire scraping, any particular portion of the tread is heated for a relatively brief period to temperatures usually at or below the lower limit for curing, the effect of tire cleaning on tread life should be very small.

Obviously, excessively high temperature can damage the rubber, so some care is required.

A lot of sophisticated teams do this w/o issues, so in general the benefits of a clean tread outweigh any slight reduction in tire life.

[TimH]

Dumb question -- isn't that one reason why we do a formation lap? My tires are usually pretty clean by the time we reach the line.

[DaveW]

I'm interested to see if some smart guys respond with an answer. I'm someone who's spent plenty of time with a heat gun and small (~1") putty knife removing a thin layer to expose fresh rubber. It always *feels* like the end product is much improved, newish tires for the start of the next session but I could be kidding myself (and adding a heat cycle/shortening the tires' effective life).

The other main reason I do it is I consider my own labor as mostly free and buying new tires is painfully expensive.

A long time ago, I tried to use tire-softening fluids to see if there was any advantage to be gained.

What I found was that the main gain was in cleaning all the pickup off the tires - a necessary prep before using the softening fluid. The softening stuff, IMO, had little effect, but I did notice a difference in having the tread clean for the first lap or two, which for a race start is obviously a benefit.

[Steve Demeter]

Go Kart folks do it all the time. Heat and scrape that is.

[Jeff Read]

Like Rick I use a metal spiral curry comb. It takes about 90 seconds per tire.

[jcorsico]

F 1 guys spin the tires on a balancer and run a course file over it 5 mins ;-)

Is this true, or are you joking?

[Rick Kirchner]

comb doesn't get the out lap does

[RussMcB]

Not long after my earlier post I saw a WEC team removing tire rubber junk on TV (Nurburgring race). They were using a nice tool that combined the heat gun with the scraper. Looked really nice - much easier than my two-handed method. I Googled and found them (wasn't too hard). Pegasus has them. $800. Way too much for my "race team".

https://www.pegasusautoracing.com/gr...pID=TIRESCRAPE

[tapandrack]

Not long after my earlier post I saw a WEC team removing tire rubber junk on TV (Nurbringburg race). They were using a nice tool that combined the heat gun with the scraper. Looked really nice - much easier than my two-handed method. I Googled and found them (wasn't too hard). Pegasus has them. $800. Way too much for my "race team".
https://www.pegasusautoracing.com/gr...pID=TIRESCRAPE

Interesting tool. It says "The heart of the unit is a heavy-duty heat gun with adjustable temperature and fan output. Simply dial down the heat to prevent burning up the rubber you want to keep." which seems to suggest a heat gun or torch is a risk as it can put down too much heat on the rubber compound.

[Fred Michael]

Good heat guns put out a ton of heat, in excess of 750*F

[tapandrack]

Good heat guns put out a ton of heat, in excess of 750*F

Exactly. That's what got me thinking about this. I touched my buddy's tire he was so proudly scraping clean with his 1500 watt heat gun and the tread was freaking HOT! Had to be close to the 200 degree operating temp of a tire. At that point it seemed like the tire would be heat cycled by the scraping exercise.

I'm intrigued by the suggestion of the stainless spiral curry comb I've seen on this thread. Seems if used when tires are warm coming in from a run it would work.

[DaveW]

Good heat guns put out a ton of heat, in excess of 750*F

Heat guns usually have two settings - low and high. The low setting puts out about 600F air, while the high puts out up to 1500F air.

That does not mean the tire gets that warm. I use the high setting, since the low setting does not soften the pickup quickly enough to make tire scraping practical. And the higher setting gets the surface crud warm quickly while not having time to overheat the good tread rubber under it.

As I said previously, one has to be at least a little careful while using a heat gun not to overheat a concentrated area. However, it is pretty easy to develop a technique that effectively removes the crud while not damaging the tire.

[DaveW]

Exactly. That's what got me thinking about this. I touched my buddy's tire he was so proudly scraping clean with his 1500 watt heat gun and the tread was freaking HOT! Had to be close to the 200 degree operating temp of a tire. At that point it seemed like the tire would be heat cycled by the scraping exercise.

I'm intrigued by the suggestion of the stainless spiral curry comb I've seen on this thread. Seems if used when tires are warm coming in from a run it would work.

Remember that the crud you are trying to remove gets very sticky when hot. So it seems to me that trying to remove it with a curry brush while hot would be quite messy. You'd probably wind up with a solid gum curry brush...

Curry brushes work well removing the picked-up gravel and rubber "turds". Not so well for removing the continuous layer of pickup.

[-pru-]

The general term for tire pick up in the Solo community is OPR ("Other Peoples Rubber").

Between runs, while the tire is still warm, a curry comb works fairly well.

At the Solo Nationals, OPR can be so server that people use battery powered as well as corded (powered by a small generator) oscillating tools between runs. For ~$40, I picked up the pictured oscillating tool from Home Depot just for OPR removal:



I use the wider blade shown on the right in the picture above. You actually need to dull the blade just a bit (a couple scrapes on concrete seems to work well) so you do not cut into the tire too easily.

Attached is a photo showing how much OPR I removed after running the Test and Tune course at the Solo Nationals. It's a front tire (mounted on the rear as it makes it easy to work) with a softball size amount of OPR removed (per tire!). Tire looks good as new once complete.

[-pru-]

As follow up to my above OPR removal comments, the previous "Most Effective Technology" was a propane torch and a flat spackling blade. That took a long time and put a decent amount of heat into the tire. By contrast, the oscillating tool is quicker and puts very little heat into the tire...

[Steve Demeter]

The Go Kart guys I saw had heat guns with the scraper built into the business end of the gun.

That way you don't burn your hand.

Heat guns do get hot. Ever see someone light a cigarette with one?

[Daryl DeArman]

In my opinion, it's a mental/confidence thing. I don't believe there is any reason for a road racer to do it, autoX and karting are another story.

Karters do it because their out lap is generally very, very short and slow. AutoX don't have an outlap to build heat/clean tires.

On the cool down lap stay on line and slow down. By the time you get to the paddock the stuff you pick up will be minimal. On the out lap get heat in your tires and don't go putzing around in the clag. Your tires will be clean and reasonably hot well before T1/L1.

[DanW]

The general term for tire pick up in the Solo community is OPR ("Other Peoples Rubber").

Between runs, while the tire is still warm, a curry comb works fairly well.

At the Solo Nationals, OPR can be so server that people use battery powered as well as corded (powered by a small generator) oscillating tools between runs. For ~$40, I picked up the pictured oscillating tool from Home Depot just for OPR removal:



I use the wider blade shown on the right in the picture above. You actually need to dull the blade just a bit (a couple scrapes on concrete seems to work well) so you do not cut into the tire too easily.

Attached is a photo showing how much OPR I removed after running the Test and Tune course at the Solo Nationals. It's a front tire (mounted on the rear as it makes it easy to work) with a softball size amount of OPR removed (per tire!). Tire looks good as new once complete.

Thanks Chris, I'm going to give that a try. I already have one.

[Neil_Roberts]

On the other hand, you can drive off line during your in lap to pick up as much junk as possible if you know that your first stop is at the scales and that set of tires is done. My car consistently gained 4 to 5 lb by doing that. I forgot once, and rolled across the scales at exactly the minimum weight. Whew!

[marshall9]

Dumb question -- isn't that one reason why we do a formation lap? My tires are usually pretty clean by the time we reach the line.

"Cleaning" is not even remotely necessary or beneficial with Toyos, as far as grip. It's a street tire. What you do Tim, is necessary, as it puts heat into the tires, and brakes.

[TimH]

"Cleaning" is not even remotely necessary or beneficial with Toyos, as far as grip. It's a street tire. What you do Tim, is necessary, as it puts heat into the tires, and brakes.

Yeah, all I needed was one experience of warmish tires/cold brakes in the first turn. Never again.

[Brian.Novak]

I swear by it and have never experienced any problems with reduced tire life etc.

Just go buy a $20-$30 heat gun. Most come with an attachment that will fit on the end to scrape paint. Run it on high and wear gloves to keep your hands from turning black. It's easier to do it when they are still on the car as well. Bon apetit!

[dereklola]

Bon appétit