Know your tires!!

  • What are the things to look for when you're trying to determine the general health of a drag slick?
  • What does the tread surface tell you, and are there things to look for in the sidewall?

The tire can give a pretty good account of its life and health in several ways. One of the first things we recommend is to determine the manufacturing date found in the serial code on the tire. Generally it's the last four digits and represents the week and year of manufacture.  Knowing the date is not the only key, but it establishes the lifeline of the product. A visual inspection of the bead area is strongly recommended to insure there has been no damage due to mounting, movement of the tire on the wheel, or improperly installed wheels screws.  The tread can be a strong indicator.  Inspect the entire tread looking for any cuts or potential punctures. Older tires tend to be "dryer" than those that are new.  This is not to suggest the tire's condition is unfavorable, but can be a factor if the tires were stored improperly.  Also, a close inspection of the tread and shoulder area can offer clues to determining the correct duration of your burnout.  If tires are worked hard in the water box, there will be evidence on the shoulder's edge. Finally, a thorough history of the tires circumference measurement should be documented.  The size of your tires, especially Bias Ply tires is critical to the entire combination as the roll out and growth of the tire establishes the final drive ratio.  In most cases each inch of roll-out can change finish line by about 125 RPM.  Also Bias tires tend to grow from their originally mounted dimension.  Radial race tires are not generally affected with this trait.  Because of the construction, Radial tires are almost always identical in size and do not grow during the run as do the bias constructed race tires.

  • Will a slick typically "go away" before getting all the way down to the bottom of the wear indicators?

Not in every case.  We have had many customers bring their tires to our M/T Service trailer with the cords showing.  They always brag about how well the tires worked right down to the cords! Honestly, there are so many different combinations at the drag strip that to attempt to predict the life of a Drag tire on any particular car is a real gamble.  Too many factors weigh in. Also there are other components in the tire that can affect performance.  Heavy cars with big power can reduce the resilience of the tire reducing its spring rate. Ultimately it's the measured performance that will tell the truth on your tires.  Look hard at the incremental times provided on the time slip.  Check the performance of your fellow racers.  Track conditions and ambient temperature also weight heavily in the consistent performance of your car.

  • Will a bias-ply drag slick change rollout over its lifespan, or once it's taken its initial "set", does it only change due to tread wear?

As mentioned above, yes the tires can grow.  Most often your tires will grow from 5/8" to over 1".  Different combinations will yield varying growth. Typically the tire will be "set" after 3 to 5 runs.

  • Obviously, an Outlaw 10.5 car and an 11-second bracket racer put very different loads on their tires - what are the similarities and differences in how you'd "read" tires at those extremes?

Well, the 11-second bracket car should be a dead-hook program, but that's another topic!  Really it comes down to understanding the conditions and the time slip.  What you want ideally is consistency and efficiency.  If you see your 60 ft. times going up and down then look to the track conditions and draw comparisons to your competition.  If your 60 ft. times go down consistently then your tires may have lost their ability to hold your car or create enough grip.  PS – other things in the car can cause the same problem...

  • Is there a difference in what you're looking for on an ET Street DOT-approved tire, versus an ET Drag?

I believe so.  When shopping for a DOT tire, most customers have an option to go bias or radial. Since the majority of those with street based performance cars utilize automatic transmissions, the radials become an ideal choice for most in the DOT applications.  Most "street based" clutch cars lack the high end adjustability required to benefit from a radial. If you run a clutch then stick to the bias ply ET Street tire. Most racers shopping for ET Drag tires have made their tire size choice based on what the car can fit.  Most are looking for a certain roll-out to insure they retain the combination that they have.  Others are looking for the ideal tire to achieve success.  Bracket or Index racing depends on a high degree of consistency from all components.  Some prioritize consistency over performance.  Heads-up racers are performance driven.  Smaller lighter tires will take less energy to turn so if the tires produce the proper amount of grip to hold the combination the performance/efficiency will be enhanced.

  • How do you know when it's time to rotate bias-ply tires?

Watching your 60 ft. times closely along with a visual inspection of the tread are your best indicators.  Some applications will never see a benefit from rotation, while others will.  If you notice the tread of your tires "feathering" (a unique texture that's much easier to show than describe) this could be indicating tire slippage.  Rotation can extend the effective life of a tire, as some cars can establish wear patterns that reduce the contact patch.
  • Can you tell anything about which direction to go with your tire pressure by visually examining them?

I'm sure it's possible to get close to your ideal tire pressure by visual inspection but I believe that that time slip is the ultimate guide.  Always consider the ambient conditions and try to develop an understanding as to how they affect your combination.  Good data is very important.

  • Drag radials are a whole world of their own - what do they have in common with bias-ply slicks when it comes to reading the tire, and how do they differ?

The radial tire has a different shape in the shoulder area.  Bias ply tires tend to be square at the edge and the radial is rounded.  This makes "reading" the radial a little more challenging.  There is no distinct edge.  I'll go back to the good old time slip – it tells you what the car wants! Here is a general statement regarding the inflation of Radials versus Bias ply type tires.  Radials require greater air pressure to perform optimally when compared to Bias tires and most of the benefit in performance comes from reduced rolling resistance.

Author: Carl Robinson

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