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Getting Traction At The Track By Bret Kepner


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#1 missouri_guy1973

missouri_guy1973

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Posted 30 September 2004 - 04:06 PM

Originally posted on STLSR.com by Bret Kepner:

Track temp is usually good down to 60 degrees at night for cars with slicks! For 90% of all street tires, things get pretty stupid below 70 degrees. That's why some people were spinning past 330 feet, where track prep very seldom matters except for cars which are already close to overpowering their tires in the first place.

I'd venture to say not many folks on this board run at any other track which hosts a "street tire only" program. One reason traction at other tracks' "test 'n tune" programs is much better in almost all conditions is because those tracks are simultaneously running high-powered cars with slicks which stay in the groove, keep the surface temp up, and keep it sticky.

VHT is a very tricky proposition on a street tire night and Ace & Chuck, (the starters), agreed it would only make things worse. The rosin is used to keep street tires from peeling the rubber off the starting line (called "bald spots") and is not really used to help traction.

I hate to say it, but the only "big tire" car which I saw have any problems off the starting line last night was Rob Nolan's turbo Regal and he was really spoolin' the blower trying to run quicker than 11.26...hence, overpowering the tires on a 69-degree surface.

When a car has a giant footprint, it'll hook. Case in point: the S-10 ran nonstop 9.70s and 9.80s including on the very last run down the track. The really funny example is NHRA Pro Stock racer Jason Line, who ran 6.72 at 204 mph (on a 6.68/207 National Record) only minutes before they opened the gates...and they hadn't prepped the track all day!

A few important points:

1. As I pointed out in the Results thread, the most common reason most folks blow the tires off at Gateway is they're nowhere NEAR the "groove". At almost ANY track, if you stage six inches out of the groove, you're gonna spin. Period. This might sound silly, but if you don't know where the groove is, walk up to the starting line and ask the starters. If you've got an armband, you can go up there and they'll tell you because they know (It's their job!). I'll help anybody who asks, as well.

2. In drag racing, traction comes in a relatively narrow temperature band. For cars with slicks, it's usually between a surface temp of 60 degrees (extreme lower limit) and 105 degrees. For street tires, it's between 75 degrees and 95 degrees (extreme upper limit). Above 95 degrees, street tires will spin on any track...unless changes are made.

3. An honest 75% of all multiple-purpose/application street tires work much, much worse when they're heated in a burnout. First of all, they're designed to rapidly dissipate heat rather than retain it, so the tires are usually almost air temp by the time the car is staged. (Don't believe it? Buy a $30 temp gun and you'll be amazed!) Likewise, the rubber compounds in most multi-purpose tires are A) a fairly hard compound which gets slimy rather than sticky when heated and B ) use extremely stiff sidewalls. Low-profile tires work about as good as shopping cart wheels on a hard launch because they're designed to work in every scenario BUT that. Don't believe it? watch the start of a Formula 1 race; they're using the highest-tech multiple application tires in the world and they smoke 'em like a Top Fuel burnout when leaving the grid. When a tire is built for multiple compromises, it's just not gonna do some things perfectly.

4. Most tires can be made to work (well, sort of) with just one simple change: tire pressure. If the tire spins, drop the pressure until it doesn't...50% if you have to. If it keeps spinning, then there's obviously a problem. Most likely, it's a simple one...you're overpowering the tires.

Bottom line: If everybody's spinning, the track is junk. If even one car ISN'T spinning, there's a reason that car is hooking up.

Jim

2015 Oxford White F-150 Lariat SuperCrew Sport 4x4 2.7L EcoBoost


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