Currently, the Cobra is made for speedway kart racing. The Cobra tire has been tested against other tires on the market and proven to be highly competitive even after hundreds of laps on them.
Cobras have a shoulder that is slightly more rounded and a stiffer sidewall that gives racers what they need - explosive corner speed. And that leads to better straightaway speed and ticks off the stopwatch.
Cobras are made with a natural rubber blend that does not require hours and hours of prepping. We highly recommend ZERO prep inside the tire. The tire generates enough bite without having to prep from the inside.
Manufactured for use on six inch wheels, the right side tires are 12x8.50-6, the left rear tire is 11x6.00-6, and the left front is 10.5x4.50-6. The 8.50" tire measures approximately 33-7/8" (on a 10" wheel) in circumference. The left rear 6.00" tire measures approximately 32-3/4" (on an 8-1/2" wheel) in circumference.
Cobras are unique and can't be prepared in the same manner as other tires. Just like you can't prep a Maxxis the same way you prep a Burris tire and you can't prep a Vega tire the same way you prep a Hoosier tire. Cobras can't be treated the same way as other tires. The rubber compound is unique and so is it's construction. This will help you better understand how to successfully prepare your Cobra Racing Tires for a successful night at the track.
You can easily feel the weight difference between Cobra tires and other race tires. It is lighter because of the way it is constructed. With 0.070" of tread, the Cobra still has plenty of rubber to get the job done. The lighter weight provides faster acceleration and roll speed but doesn't compromise corner speed.
Mounting the Cobra requires no special tools or methods outside of normal means. You'll find the Cobra mounts easily and quickly.
The first rule to prepping a Cobra tire is DO NOT inside prep them. Cobra tires are fresh from the factory when you get them and does not need additional chemicals inside to make the tire "work." If you choose to inside roll Cobra tires, you'll find that the tire is very fast for about three laps and then lap times begin to fall off. That makes for a great qualifying tire but if you want it to last throughout a race, we recommend not to inside prep the Cobra.
An advantage to not inside prepping (besides saving time and money) is that the tire's rubber is consistent throughout from inside to outside. That means during a race that has multiple caution flags, the Cobra will refire each time the green flag drops again. On long green flag runs, laptime falloff of a properly prepared Cobra is almost non-existent.
As we've pointed out, Cobras are fresh tires and fresh tires already make their own grip. You may enhance that to meet the needs of the track surface you race on by adding chemicals to increase grip or condition the tire.
It may take some experimentation to determine exactly what the Cobra needs at your home track but as a rule of thumb, we recommend using half of what you normally use. For example, if you prep with two wipes of Prep "A" for one week prior to an event, prep Cobras with one wipe instead. Go easy with the prep, it doesn't take much. Like every other tire out there, if you over prep the Cobra, it will either be fast for a few laps and then slow down or it may simply be slow throughout the duration of the race. If the tire feathers, you've used to much prep. On hard tracks, do not prep the Cobra - mount it and go.
Chassis and Air Pressure
The chassis setup and air pressure is fairly consistent with other tire manufacturers but may need some slight tweaking to find that "sweet spot" your Cobras need. For reference, if you normally use Maxxis tires, increase crossweight by one percent and air pressure by one half of a pound when using Cobra tires.
Need the perfect circumference? Cobra tires size extremely easy and they stay there. When sizing tires, gone are hours spent in tire warmers with a crazy amount of air in the tire. If sizing is new to you, read through the steps and the more you do it, the easier it gets!
Growing a Cobra
To grow the circumference of a Cobra, determine what size the tire needs to be. Inflate the tire until it is one quarter inch larger than the ideal size you need (if you need a 34" tire, simply inflate the tire until it is 34.25" in size). Next place the tire in an already-heated tire warmer or hot box. Some racers use a propane torch to heat tires but they're dangerous and we don't recommend using one. Leave the tire in the warmer or box for 30 minutes MAXIMUM. Cobras can stretch easily and quickly and have the ability to grow as large as 35" or more so be careful with the length of time the tire is in the heat source. Remove the tire from the heat source and allow it to cool to room temperature, usually about thirty minutes. Once cool, reduce the air pressure to the race pressure you intend to race on. Measure the tire. Usually, it's dead on. If not, repeat the procedure.
Shrinking a Cobra
Yes, Cobras shrink easily, too! If you have a tire that is too large in circumference, again you're going to need a heat source (warmer or hot box) and a five gallon bucket of ice water. First step, remove the valve core from the valve stem in the wheel. Second, put the tire in the heat source and heat the tire until the tire and wheel assembly is hot. Third, (you have to move fast!) while the tire is hot (use a towel to hold the tire and wheel to keep from burning yourself) quickly squeeze all of the air out of the tire and (IMPORTANT!) replace the valve core in the valve stem. The tire should be squished down pretty tight and then immediately... Fourth, dunk the tire and wheel assembly in the bucket of ice water. Keep moving the tire in the ice water to evenly shock and cool the hot tire causing it to shrink. Once the tire and wheel are ice cold, remove it from the ice water and allow it to warm back to room temperature. Once it's back to room temp, slowly inflate the tire to race pressure. Wait two minutes, recheck the pressure, and then measure it. Repeat if necessary.
Once you've reached the perfect size, whether shrinking or growing, we recommend storing right side tires at eight psi, the left front at racing pressure you normally use, and the left rear tire uninflated. This usually keeps the stagger consistent. You may need to tweak this formula, but do what works best for you.
You can surface Cobra Tires using an angle grinder or tire surfacer, whatever works best for you. We recommend 120 grit (or finer) to just knock the smooth surface off of the tire to give it a surface to accept prep (if you choose) and removes the glazed surface.
A balanced tire is faster than an unbalanced tire. There's no doubt about that. We recommend balancing your tires for optimal performance.
We hope this has provided some insight that will help you get going with your Cobra Tires. If you have questions, contact us! We love talking racing!