Tire question

Most simply, primarily due to the rubber compounding. Race tires stick like glue due to extremely soft rubber compound, but have little or no life and are horrible in the wet (no tread to assist in the removal of water that causes hydroplaning).

I'm sure Mitch will chime in here with the "real" answer.

 

Thanks for the vote of confidence.....

I run my tires down to slicks. I have my suspension setup so that this happens within a 100 miles front and back. Contrary to popular belief, the tires do have more traction than treaded tires. Once I arrived at the track with near slicks, and left the track with slicks. The rears went slick first and I had massive understeer, then the fronts went slick and it was back to normal.

The particular tires were Bridgestone S03s that have a softer compound towards the belts, so the example may not be representative of all sorts of tires.

Now when it comes to tires that are not max-performance or extreme-performance rted, or have several years of (continuing) vulcanization, you probably don't loos traction from the slick-ness as much as you have already lost traction due to the hardness of the rubber compound.

Last year I started out a 2000 mile journey with 1/16-3/32 of tread, only to run into 2 days of 2 inches per hour rain. The car was (as we should say) busy on its wheels and a little on the frightening side to drive. But, overall, acceptable if you have that touchy feely understanding of how to keep the nose pointing forward at all times. Other than when aquaplaning, the traction was good to excellent.

Now when it comes to REAL race cars running slicks in the rain, remember that these things have large amounts of downforce. Downforce works just as well in the wet as it down in the dry. So you are seeing that tires with an inherent 1.6-1.8 Gs of traction, being pushed to the road surface with 1000 pounds of force (each) but carrying only 300 pounds of latteral weight can grip the road surface quite well.

Over at NASCAR, you will notice that the least little water on the track creates big disaters. This is because NASCRAP has no useful downforce. The splitter and wing represent a couple hundred pounds of DF F and R. A far cry from the couple of thousand pound F&R the real race cars generate.

The only real reason for tread is to avoid aquaplaing (and may be gravel and/or muddy roads). For smooth hard surfaces and drivers who are paying attention and understand the physics, driving with slicks in the rain is not-so-bad.

 

Slicks do NOT get good traction on wet (or oil soaked) roads, ..........LOL!

There are some DOT legal Goodyear Vintage Racing tires that have a 'shadow' of tread when new (like 5/32" or something) and are intended to burn down to "slick" after a few laps, but the matching "rain tire" is a full depth tread.....

HTH

Goodyear is #1 in Racing

 

Mitch is right, ....

I won "in the rain" on slicks once, but you are on the very edge of car control......and my crew chief had the idea to OVER inflate the kart tires, making for a dry contact patch "right in the middle" about the size of a quarter!!

Brilliant idea, in retrospect....

Everyone else had a crash fest and I luckily already had the Pole, so it was "back there"....witnesses said the other 20 karts looked like pool balls on a table in Turn #2!!!

Goodyear offered to hand cut some rain tires, but I was 'done' for the day!!!!

 

When a street tire goes near bald it "might" be faster relative to it's harness from new if pushed on dry roads but not always. The reason for groves on street tires is because of varying conditions. You really can't draw a racing parallelism because racer's choose tires specifically for the conditions unless they make a mistake or are caught out. The idea of overinflating works not because you have more grip but you change the contact patch similar to why a thinner taller tire tends to work better in the snow vs. a low profile wide tire with the same load. I'm sure the crew chief would have rather had the right tire. Those racers flying around corners are not flying in the rain on slicks really. They are well under the performance envelop of the car downforce or not but to guys that drive streets at 60mph they seem to go really fast. An example of choosing the right tire is the chance jenson button took early this season to go on rain tires while the pack was on slicks. He killed everyone. Contrary to what people think slicks work fine on damp to wet tracks without standing water and are faster than intermediate tires under the same conditions. Once rain is steady the intermediates work best even better than full rains. Full rains work best with standing water and real downpours. I love racing in the rain. The trouble at the amateur level is most are unwilling to stock all the tires. I only club race SCCA and I have 4 sets of wheels and maybe 8 sets of tires in my garage right now. That does not include all the other race cr@p.

 

rubber sticks to asphalt better than air. slick tires have a bigger contact patch and more grip. drag racers restricted to street tires use to shave the tread off for more traction.
the grooves are for the water when the road is wet thus preventing hydroplaneing.
slick tires have more grip than groved on dry pavement.

 

It's not a question of tread vs slick. Treads are to channel debris and water away from the contact surface.

But "slick vs bald" is a question of rubber in 3D -- there's the question of thickness.

Get a pencil with the eraser worn down to nothing, and a rubber block eraser. Wiggle both against your thumb. Which one slides easier?

Slicks have enough thickness of rubber to have some "give" to the contact patch.
Bald tires are just a thin rubber coating on nylon cords. Since there's no "give" to the contact, they break loose easier.

This would also be the reason that "old" tires lose traction -- the compound no longer has the ability to flex as readily.

That'd be my take on it.

 

Most street tires have two or more compounds of rubber in them. The tread compound is different than the compound in and around the plies, which can also be different than the sidewall rubber. The compound of rubber in the belt area is designed not to build up as much heat since you don't want the tire to overheat as it runs a high speed and cause tire to come apart, but that rubber isn't designed to grip the road, so when you get down to it the tire loses its grip.

On some tires the undertread (the harder compound) is actually forced up into tread blocks during the molding process. This gives the tread blocks more stability since the undertread is stiffer and it makes the tread blocks squirm less under cornering giving the tire a more crisp feel.

You can actually see the undertread get exposed on some performance tires as it wears and gets close to being bald. I have seen it on some Bridgestone RE-71's, the tire was worn enough that you could see a slightly darker tread coming thru at the tops of th tread blocks. Obviously the tire got really slippery at that point.

Racing tires (even DOT approved ones) have a sticky compound right down to the first layer of belts, since the tread isn't thick and won't build up heat like a street tire would.