When do you change tires?

[4RNB]

Yesterday on a practice short field landing I locked up my brakes and wore through some rubber, more so on one side. No threads showing. How do folks think about changing tires? There is a bit of a flat spot, no vibration noted on takeoff or landing. Tires are less than a year old.

What tires do you favor for your planes? Why? I was thinking to end up with what I think was a Goodyear FC III, but I only have 80 hours in planes so far. I think yesterdays landing was an anomaly. I also feel confident enough to put my wheel skirts/pants back on.

 

[MBDiagMan]

If you can’t feel the flat spot and it is not so pronounced that there is no tread in that area, I can’t see the need to change it. I would like to talk about your brake usage though:

On any vehicle with tires and brakes, locking up the wheels does NOT give you your best braking. Applying the brakes as hard as you can WITHOUT locking up a wheel will give you the shortest stopping distance. From this description, I assume that you were in a tricycle gear aircraft. In a tailwheel aircraft, that much braking aggression can easily lead to nosing the plane over forward finding yourself upside down. Not lecturing. Just want to kindly make sure you are aware of this.

 

[Dan Thomas]

If you can’t feel the flat spot and it is not so pronounced that there is no tread in that area, I can’t see the need to change it. I would like to talk about your brake usage though:

On any vehicle with tires and brakes, locking up the wheels does NOT give you your best braking. Applying the brakes as hard as you can WITHOUT locking up a wheel will give you the shortest stopping distance. From this description, I assume that you were in a tricycle gear aircraft. In a tailwheel aircraft, that much braking aggression can easily lead to nosing the plane over forward finding yourself upside down. Not lecturing. Just want to kindly make sure you are aware of this.

Touching down at anything higher than minimum airspeed often results in flat-spotting tires. It happens real easy. Those wings are still lifting right up until the time the airflow over them stops, reducing the weight on the tires, and therefore the traction is low. The stall warning should be sounding by the time the airplane touches down. If it's set right, that it. And the elevator should be held full up in braking, which puts more weight on the mains.

 

[TonyG]

IMHO: Why use brakes at speed? A few bits of information:

• For the airplanes that most of us fly, the takeoff roll significantly exceeds the landing ground roll, even without braking until slowed. For my Cessna 170, if I land it in a place where I HAVE to use the full short field approach/landing even without early braking, then the airplane is leaving on a truck: I won't have room to take off.
• When you look at the physics, it takes the same energy (from brakes, or from aero braking) to go from 55kts to 50kts as it does from 23kts to stopped. Aerodynamic forces slow you a LOT at high speed, not so much at low speed.
• As a CFI, what I see is that most rated pilots will miss their intended touchdown spot by MORE than the ground roll. (Student pilots tend to do better)

If you put all this together, here's what I encourage my students to do:

• Get really good at hitting your intended touchdown spot on landing, at your intended airspeed.
• Let aero forces slow you down until they're ineffective. Then use brakes, but only if you really, really need them. (As a TW instructor, I'm inclined to believe that brakes were invented by the devil himself.)

That'll save brakes, save tires, and be easier on the airplane, and, if you get good at hitting your touchdown spot, use less runway. Win, win, win.

--Tony

 

[MBDiagMan]

Correct! Most of our GA planes can very easily get into places where you can’t get them out. In the OP’s defense though, he is trying to jump through all the hoops of a checkride where they want a short field landing demonstrated. I’m sure that the incident he describes was a lesson for him.

 

[Dan Thomas]

Short-field practice is mostly for that possibility of a forced landing on some small bit of ground. So minimum touchdown speed, max braking. From the 172M POH:

 

[Radar Contact]

Yesterday on a practice short field landing I locked up my brakes and wore through some rubber, more so on one side. No threads showing. How do folks think about changing tires? There is a bit of a flat spot, no vibration noted on takeoff or landing. Tires are less than a year old.

What tires do you favor for your planes? Why? I was thinking to end up with what I think was a Goodyear FC III, but I only have 80 hours in planes so far. I think yesterdays landing was an anomaly. I also feel confident enough to put my wheel skirts/pants back on.

I use Goodyear FC III’s and Michelin Airstop tubes. Why? I just researched a couple years ago and those seemed to be high quality with good reviews among people I trust.

As to when I change them. If I noticed an issue with their physical appearance, ability to hold air or during ground ops, I’d change them if needed. Otherwise, I use a shop I trust and that’s one of the things I leave up to them on when it’s time.

 

[Clip4]

What may happen is the next time you improperly use the brakes is the tire stops on flat spot and you are sitting on the runway with a flat. Change the tire and next time don’t get on the binders until the elevator control is full aft.

 

[GRG55]

Another vote for Goodyear FC IIIs.