We’re not gentle on aircraft tires, and given the cost, we don’t like replacing them, either. From Michelin comes the latest Pilot tire, sporting the latest design in bias ply GA rubber, boasting true tracking, reduced weight and extra long life. Here’s a look at the design, with tips on tire care.
Not a radial
Product development engineering manager at Michelin’s Americas Research Center, Mark Hiscott, told us that the GA and airline tire markets are separated by radial and bias technology. And there are distinct advantages to radial tires (and requirements for wheel fitment and compatibility), including a structural makeup that allows for a flatter footprint with more contact area and optimized wear. Because the tire cords extend from one side of the wheel to the other (rather than angled across) there’s less material—which means lighter—with a similar safety factor that biased tires offer.
FAA TSO-C62c prescribes the minimum performance standards that tires (excluding tailwheel types) must meet, and that includes specific balancing requirements. Hinting at in-development new tire tech for the GA market, while acknowledging the huge effort and cost of certification, Hiscott told us Michelin is ever focused on developing designs that are lighter and stronger. On the other hand, Michelin made it clear that bias tires for GA applications aren’t going away anytime soon.
As for the new STC’d and TSO-approved bias-constructed Michelin Pilot model, list priced at around $627 each for a 6.00-6 (main) and $527 for a 5.00-6 (nosewheel), the focus is on a deeper skid depth, which equates to more life. We can’t attest to that, but will check in with a long-term report.
Two-groove contact
It’s tough to counter Michelin’s point that the tire’s redesigned summit, featuring two wider tread grooves over more conventional narrowish four grooves, increases the amount of rubber on the pavement. That means the load per unit area is decreased, better distributing the load and resulting in a slower wear rate.
Michelin was quick to point out that the tire’s skid or channel depth is 21 percent deeper than Goodyear’s latest Flight Custom. Plus, the design creates a deeper water evacuation channel.
No tire is pilot-proof
We think durability is just as important as extended wear and longevity because face it, aircraft tires take a beating in the heat of battle and when parked. Again, the advantages of a bias tire compared to a radial tire enter the discussion. When considering the pneumatic stiffness and other design traits, the vertical rigidity of a bias tire, according to Hiscott, is nearly 25 percent more for the same tire dimension and inflation pressure as a radial tire.
Putting it in terms of real-world use and abuse, that means you might make a 25 percent harder touchdown without inflicting damage and a dreaded blowout. But, there’s no guarantees, even with up to the 60 percent more nylon (hence the extra weight) that’s in a bias tire, compared to a radial. Hitting the pavement too hard with any aircraft tire is no different than a vehicle or motorcycle tire smacking a big pothole with resulting pinch shock, trapping the nylon cords between the ground and the wheel. All materials have their breaking limit and nylon pinch shock is one. “Once you break the cords, the tire can no longer maintain the same tension in each of the cords around the tire and you’ve hit the break limit of the rest of the undamaged cords, which results in a blowout,” Hiscott explained. He said even during normal operation, internal temperatures can be higher than 200 degrees F.
As we’ve long learned from mileage on motorcycle tires, you can’t define the number of hours or time before replacement. There are too many variables, including the number of takeoffs and landings. But you can do your part and keep the tires properly inflated and protected from the elements. Underinflation means more fatigue in the tire’s casing. Just a few PSI difference in pressure will make a big difference in tire longevity. Landing gear camber matters, too.
If you park the plane for extended periods, Hiscott’s advice is to unload the weight from the tires to avoid flat spots (or move the plane every month), and cover them to protect from UV exposure. Ozone cracks are common on tires that live outside.
The new Michelin Pilot line is available now through approved distributors.
Visit www.michelin.com.
