Aircraft Maintenance: Busting aircraft tire myths
There’s an old Trade-A-Plane lying around my office from about three years ago. I keep it handy to reminisce about the “old” days, when we all thought aviation parts were expensive but had no idea what was coming.
Browsing those pages now reads like a fairy tale of great deals. This is especially true for aircraft tires and tubes. Take this example: The price from a few years ago for a Goodyear Custom III 6.00x6 6-ply tire was $234. That same tire now sells for $360 (a 53-percent increase). Tube prices have literally doubled.
Myth No. 1: You can’t control how long your tires last. There are many factors that determine how long tires last, but how you fly tops the list. Touching down in a crosswind crab can cause flat spots as the leading tire scuffs on the runway at an angle as the upwind tire swings around. If you use your rudder—rather than the friction of your tires—to straighten out, you’ll add a lot more landings to the life of your tires. Using more runway, and less braking, also helps extend the life of your tires. While we’re on the topic of runways, avoid grooved runways when possible. The sharp cuts in grooved runways can tear chips out of your tires, dramatically shortening their life. Storage matters as well because ultraviolet light from the sun can accelerate tire degradation. High-wing aircraft are more susceptible than low-wing aircraft, so consider tire covers if your high-wing sits out in the hot sun routinely.
Myth No. 2: Tires don’t need maintenance. There’s a fair amount that you can actively do to maintain your tires. Keeping them at the proper air pressure tops the list. Under- or overinflated tires will wear unevenly between the center and edges of the tread. Many aircraft specify a tire pressure range rather than a single pressure. In these cases, you can monitor the wear pattern and vary the pressure to maintain even wear across the tread. Higher pressures increase wear at the center of the tread and lower pressures focus wear on the edges. Always use the pressures specified by the aircraft manufacturer for safety.
If you notice more wear on one side of the tread than the other, look for alignment issues with the landing gear. If nothing needs to be corrected with the gear itself, you can remove the tire from the wheel and “flip it” to balance out the wear. Be sure to deflate the tire first and follow proper procedures for tire replacement.
Myth No. 3: You don’t balance aircraft tires. Contrary to popular belief, aircraft tires can and should be balanced to reduce vibration, landing gear component wear, and overall tire wear. This starts with installing the tire with the red dot (lightest point in the tire) aligned with the valve stem (heaviest point in the tube). Unfortunately, most shops lack the equipment to dynamically balance a tire-wheel combination. If your shop doesn’t have the equipment, consider finding a shop that does, or even taking the wheel to a local tire shop that can test and balance it using adhesive weights. I’ve yet to find any legal prohibition for using adhesive balance weights on most aircraft wheels, even after contacting a major wheel manufacturer. As opinions vary on this topic, be sure to consult your local A&P for advice before proceeding.
Myth No. 4: You don’t need to replace a tire until it shows the fabric. Any tire showing the inner fabric plies is unairworthy and must be replaced before further flight. However, that’s not the only go/no-go for when you should replace a tire. Once tire wear progresses beyond the bottom of the grooves in the tread, the tire loses its ability to resist hydroplaning on a wet runway. This can lead to unpredictable behavior during critical touchdowns in bad weather. You may balk at the price of a new tire, but I assure you that the repair costs for skidding off the side of a runway are much higher. So, if your tires are worn beyond the tread depth but not yet showing fabric, the time is now for replacement.
Another factor is cracking. Any sign of cracks in the sidewall of the tire is cause for replacement, but cracks in the tread are acceptable until they progress beyond the tread into the rubber “buff line cushion” just above the fabric plies. Finally, there is the issue of contamination damage. Hydraulic fluid and oil can damage the rubber in the tires, soften it, and make it unsafe for flight. In extreme cases, you can see visible bulges where the fluid has soaked in and allowed the tire pressure to deform the tire. If you see signs of this, replace the tire before further flight.
Myth No. 5: More expensive tires last longer. At this year’s Sun ‘n Fun Aerospace Expo in Lakeland, Florida, I spent some time talking with Ken Faire, an avid pilot and vice president of sales and marketing at Desser Aerospace. Faire is one of the most knowledgeable people in the world when it comes to choosing and maintaining aircraft tires. With over 40 years of experience in aerospace, you can imagine that he has easy access to whatever tires he wants for his personal aircraft. So, what does he use on his own airplane? Retreads.
Faire explained how the best combination of quality, durability, and value in aircraft tires today lies in retreaded tires. It starts with laser shearography analysis, ensuring that only the best tire carcasses are used as the basis for the retreading process. Then Desser rebuilds the tire tread using specially formulated compounds optimized for tread use (versus sidewalls). The company offers different tread patterns, as well as “Monster” retreads with additional depth for applications that require additional tread. The result is an extremely high-quality product that lasts longer than most new tires, at about one-third the cost of new.
One last myth regarding retreads: According to Faire, standard size retreads are absolutely fine to use on retractable aircraft. It seems that this myth started decades ago with worries about retread tires getting stuck in the wheel wells. Since they are produced to the same dimensional specs as new tires, this is one more myth…busted.
If you plan to attend EAA AirVenture in Wisconsin, the folks from Desser will be there to answer your tire questions directly. I’ll also be walking the show for the entire week, so perhaps we will cross paths. Until next time, I hope you and your families remain safe and healthy, and I wish you blue skies.
