Included on the FAA-approved Owner Maintenance List is tire replacement. With basic tools and a couple of specialty items that many of us have already, changing your tires can be a relatively quick and easy thing to do. In addition to saving the labor costs, you can save even more by replacing tires with retreads.
Retreads aren’t just for the 18-wheel trailer trucks. These days they can be a high-quality option for light aircraft that results in a sizable value if you understand the technology and buy from the right sources. Here’s an overview.
Living a Tough Life
Aircraft tires are highly engineered and are remarkably strong for their size. They often go from 0 MPH to 80 or more MPH in an instant without distorting enough to come off of the rim, plus they have to hold pressure at these high speeds. If the airplane is a little cockeyed on landing, the tires sustain tremendous side loads, far greater than ever expected of an auto tire. The tires have to be balanced to eliminate wobble, which can be quite pronounced at landing speeds and can transfer vibration to the airframe, creating shaky rollouts. There’s plenty of engineering involved. The tires are designed by computer for different loads and speeds, and the tread design is optimized for landing on the different surfaces we see in our operations.
And they must be as small and as light as possible because they induce drag on a fixed-gear airplane and occupy space and add weight to retracts. Tires are a combination of rubber, steel and cloth, all built into a design that creates a stable and strong unit.
How a tire wears depends on a multitude of factors, including the basic rubber formulation and hardness, the speed of the touchdown, temperature and the load on the tire.
If you haven’t shopped for new aircraft tires, you’ll find that compared to auto, truck and SUV tires, they may seem a bit pricey for their small size. There are sizable differences. While it’s tempting to compare aircraft tires with car or truck tires, the comparison is flawed. The applications are very different and so aircraft tire design is rather different from vehicle tire design. An important consideration in tire design is heat dissipation.
Most of the heat is generated in a tire by the flexing of the tread as it contacts the ground and again when it rolls off contact with the ground. Car tires are designed to run for hours without overheating and one way that’s done is by limiting the deflection to only about 17 percent.
Aircraft tires don’t need to run for hours. In fact, they only have to handle a taxi to takeoff followed by the takeoff roll, or a landing roll followed by a taxi back to parking. In both cases, they have sufficient time to cool before they’re called upon to perform again. Aircraft tires aren’t designed to handle a maximum-braking-effort abort. If you abort a takeoff and use maximum braking effort, most tire manufacturers recommend a tire inspection and, for heavier aircraft, a mandatory tire change.
Tubeless tires are also almost universal for cars but not widely used in airplanes. That’s because a tubeless tire requires an airtight wheel. Most light aircraft wheels consist of two halves that bolt together and few are designed to be airtight. Tubeless tires show up on a wider variety of aircraft than radials-King Airs, Conquests and Aerostars, for example.
It’s About the Savings
Tire retreading is such a big industry there’s an entire organization (TRIB, for Tire Retread and Repair Information Bureau) dedicated to the cause. The website, www.retread.org, is a good source of reference.
According to TRIB, a retreaded tire generally sells for between 30 and 50 percent less than comparable new tires. Additionally, retread folks claim that not only are retreads no worse than new tires, they may actually have a few advantages. Every retread candidate is carefully inspected and only the best carcasses are chosen.
And, some studies have found that the stretching of inflation increases the tensile strength of the nylon plies, so a used carcass is actually stronger than a new one. It’s easy to argue that retreads may be better than bottom-feeding the new tire market.
For instance, a value tire like a lower-end McCreary or the house brand at Aircraft Spruce (to name just one supplier) is easier on the checkbook in the short term, and if you do the exchange yourself it may seem like a smoking good deal, but in the long term this tire might not last nearly as many cycles (think landings) as a more expensive tire-say a Michelin or Goodyear Flight Special or Flight Custom, for example.
And don’t just go by the brand. Based on my experience swapping my own rubber, within their lines most companies have both a premium and an economy tire. We’ll look at new tires in a separate article. For now, we’ll concentrate on retreads.
There is a wide range of pricing for new tires-anywhere from $85 to $300 per tire-so changing all three could get a bit pricey. Add tubes and labor to the project and you will see this firsthand, plus how quickly the invoice will grow. Retread tires, on the other hand, are priced at roughly half the cost of a new tire.
I know that owners with high-end aircraft or perhaps a show-plane may scoff at retreads. Still, in all fairness this process-retreading or recapping as some call it-has been around nearly as long as we have had tires and it has proven to be an effective economy.
Moreover, major airlines and commercial operations often depend on retreads to reduce this consistent maintenance cost. In general for airline ops, a good core can be retreaded up to 10 times at a fraction of the cost of a whole new tire.
In fact, a couple of airlines have maintenance contracts with tire companies to provide and replace tires at regular intervals and they work with dispatchers to organize the downtime without involving regular crew. The old tires are removed, processed, retreaded and reinstalled in cycles. I was told that as many as 95 percent of all tires used by the airlines are retreads.
During my research I spoke with Jose Murillo of Desser Tire and Rubber. Desser has been in the tire business since 1920. The company has a long history selling new and used tires and a number of other rubber products. Around 20 years ago, Desser began to focus on aircraft tires-both new and retreads-in hopes of becoming a diverse market leader.
Since reliable distribution is critical in the tire replacement business, a warehouse was opened in Memphis, Tennessee, in 1989 to serve the eastern and southern parts of the country. Murillo told us that Desser sells over 100,000 tires a year to pilots in 85 countries. The company has been highly visible in Trade-A-Plane for years and has earned a good reputation among shops.
Desser gets its cores from airports, mechanics, owners and wherever else it can find them. But it can’t take just any tire. The core has to be good, with no tread or belt punctures, no sidewall punctures, no torn or ragged belts, no damaged beads, and it must be evenly worn. Desser prefers to buy its cores in numbers on pallets, but the company also has a group of owners who send their tires in for the retread process.
The Retread Process
When a core comes in it gets cleaned and visually inspected. The tire gets spread open so that a close inspection can be taken of the inside. If it’s good so far, the tire is then put through a Shearography machine, which determines if any belts have moved or slipped.
Causes for rejection include any worn core layers, weather checking and sidewall damage. Once approved, the core, or carcass, is put on a machine that shaves it to a consistent roundness.
Starting with a good, perfectly round core, and the tire put in a mold with a new rubber compound where lettering and tread grooves are formed, the tire is cooked. This bonds the new rubber to the prepared core. The length of this process depends on the size of the tire.
For the new tread, a high-performance rubber compound is used, and Murillo told us that the retread tire should actually get considerably longer life than OEM tires. The number of grooves in the tire depends on its type and part number.
Out of the mold, a tire is trimmed, visually inspected, balanced and put through the Shearography machine again to check for thorough bonding, ensuring there are no gaps or bubbles. Then it is checked for leaks and painted. The name of the retreader is generally imprinted on the side of the tire.
How Much Savings?
If a tire has enough tread remaining but is damaged, a repair might be made. Desser said it’s able to repair some tires through its sister company Aero Wheel and Brake Service. This is an FAA repair station and is able to issue an FAA Form 8130-3 for every repaired tired it sends out, going as far as snapping a photo of the tire and the paperwork before shipping it out.
I present this overview of the retread process to make the point that aircraft retreads are not cheap repairs; rather they are fully certified, well-built products with decades of experience in both commercial and GA operations. Think about it-when was the last time you ever saw a “road gator” thrown casing laying alongside a runway? It just doesn’t happen.
As for bottom-line savings, I checked the prices on Desser-supplied factory-new tires. Using the ubiquitous 6.00 by 6, 6-ply tire as a sample I found that a Michelin Air was $185, a Superhawk (Specialty Tires of America) was $232 and a Goodyear Flight Custom III was $228.43.
Comparable retreads from Desser range from $90 to $103, and the company offers their “Monster” tire, which has a thick 11/32-inch tread thickness-the thickest in the industry-priced from $92 to $104. This shows that retreads are about half the price of new tires.
Desser also sells tailwheel tires, a newly approved retread process for a new smooth Tundra tire for Piper Cub drivers who want to land on sandbars or unimproved surfaces in rough terrain. Tires of all sizes and for nearly all aircraft uses can be found on its website, www.desser.com.
Murillo told us that growing numbers of buyers are having a couple of sets of tires retreaded so that they can remove a set and send it in for retreading while they run on the second set. Four cycles with two sets offers a lot of extended life for the investment. For comparison shopping, Desser will quote a price for retreading your tires when you call.
Our special thanks to Jose Murillo at Dresser Tire for providing the photos for this article.
