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6/12/18, 10:40 PM   #1
Rubber Down
flagboy55
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2 things get my goat when they occur in my world of sprint car racing. (There's probably more, but for this post we'll say 2). Fuel stops, and locked down, rubber down race tracks. While enjoying my dirtvision fast pass watching the Outlaws this past month, I saw at least 3 races that became a single lane, rubber down track, so bad that if you're leading and reach the back markers, you almost have to follow them instead of putting them a lap down, miss the rubber and the train goes by. While I watched the 40k to win, Jackson Nationals wind down and turn into one groove in about 25 of 40 laps (granted, they had 3 shows in 2 days) It got me wondering about the 100 lap late model race going on at the same time at Eldora and wondering if it turned into one lane? After watching the highlights the next day, turns out that the full body cars were racing from the inside wall to the outside wall, no single groove and the race distance was more than twice as many laps. So why do the sprints rubber down a racetrack in 30 laps or less, and the late models can go a hundred. I know there are plenty of factors, but in my mind it has to be tire compound more than anything. Curious if anyone else feels that way and if anyone has a real answer.
 
6/13/18, 12:48 AM   #2
KingRandomUser
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Not a total expert on the subject but there are numerous factors that can come into play.

First, let's start with the most obvious: Track Prep. No secret to know tracks that have been extensively worked won't rubber up as fast as tracks that get a bit more neglected. Sometimes this is intentional, depending on the classes of cars running. It can also be on how was the track prepped and what equipment worked and packed it in too. Was it a tiller? Disks? Sheep's foot? What packed it? Big heavy roller? Push Trucks? Water Truck? Sprint Cars? Stock Cars? Anything can make a difference.

2 - Weather. Sunshine and wind, even humidity play a role in moisture content. And thus how fast it dries out and sickens up.

3 - Dirt Composition. Not all dirt is equal. Different types of dirt hold different amounts of moisture and react differently to weather, water, and even pressure from being packed down. This also includes whatever additives, such as small wood chips, are also mixed in with the soil.

Then we can compare the cars themselves.

1 - Tires. Sprint Car rear tires are obviously much larger in both width and circumference. Thus more surface area to hit the dirt with. Compound also plays a role as softer compounds stick more to the dirt.

2 - Transmission. Sprints have a lack there of, so all that horsepower is pretty much at the rear wheels. Unlike in a Late Model in which power is lost through the tranny. More wheel spin causes the dirt to pack in tighter and take on rubber faster as well. Compound this with bigger tires and you can see the results.

3 - Downforce - This applies more to the wing cars, but any added Downforce will push those tires into the dirt more. Factor in the previous 2 points with more pressure and moisture goes away quickly.

4 - Car Count. More cars = more rubber

5 - Other classes of cars. Kinda goes into tires and tire compositions too, but other classes tires, while laying down rubber as well, can affect the track surface. Modified tires for example are narrow and kinda act like a slight disk cut to some extent. Any other narrow tire class can have this effect as well.

Just a few tidbits. Someone else might have a bit more insight or technical reason, but these do play factors on a track rubbering down or not.
 
4 members like this post: chrismattlin, fishnman, Simon_says17, tirespinner
6/13/18, 11:01 AM   #3
Re: Rubber Down
chathamracefan
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I was at both the Fairbury WoO show & the Dream late model race at Eldora this past weekend. Been to Fairbury for several late model shows & a few sprint shows in the past. My uneducated guess there is that they prepped the track with so much grip in the middle/top side that it became the dominant line early in the night & stayed that way. Took on rubber about 1/2 way thru feature. Races were good up to then tho. I've not seen Fairbury take rubber ever before. Track prep is top notch there. They don't have much experience with prepping for sprints. My guess is future events will have better results.

As to Eldora, they had lots of rain over the 3 days so there was moisture in the track. They also know how to prep a track for the long races so it slicks off but doesn't take rubber. Lots of prep equipment & lots of experience really help their cause there. They just know what they are doing. The track crew there busted ass all weekend to get all 3 nights in (one run during the day Friday) when most every other track would have packed it in.
 
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6/13/18, 11:04 AM   #4
Re: Rubber Down
Charles Nungester
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It rained all weekend at eldora with the racing taking place between showers. The first nights track sucked.
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