Main Gear Vibration

[DutchessFlier]

My 172 has wheel fairings (covers) and they vibrate ( I see this when looking to the side) and chatter on fast taxi and roll out, no braking is being applied. My A&P has flown the plane and he isn't too concerned about this, but I am not really comfortable with it. He has checked the brakes and tightness of the covers. No material is being scraped from the tires and the clearances are there between the tires and the bottom lip of the covers. Main tires are new, but this was happening before they were replaced.

First, any suggestions as to the cause? Balance the tires? Other remedies

Second, I am not a big fan of wheel covers on the mains since I cannot inspect the brake pads, rotors, or leak check without a mirror. I would like to take the covers off the mains, and keep the cover on the nose wheel. Can I do that myself, or does an A&P have to do that operation. Thanks

 

[wabower]

That configuration would be opposite to most 172's that have fairings on the mains and a bare nose-wheel. Are you using the plane to travel or mostly local? I'd advise you to perform some good speed checks with them installed, so that you know the performance penalty when flying without them.

My 172 has wheel fairings (covers) and they vibrate ( I see this when looking to the side) and chatter on fast taxi and roll out, no braking is being applied. My A&P has flown the plane and he isn't too concerned about this, but I am not really comfortable with it. He has checked the brakes and tightness of the covers. No material is being scraped from the tires and the clearances are there between the tires and the bottom lip of the covers. Main tires are new, but this was happening before they were replaced.

First, any suggestions as to the cause? Balance the tires? Other remedies

Second, I am not a big fan of wheel covers on the mains since I cannot inspect the brake pads, rotors, or leak check without a mirror. I would like to take the covers off the mains, and keep the cover on the nose wheel. Can I do that myself, or does an A&P have to do that operation. Thanks

 

[Tom-D]

Cessna does not give the option of removing 1 pant, the POH and the optional list of items on the type certificate says "wheel Pants" and gives the weight data and moment arm for the average of al three.

to be legal, remove all three, or install all three.

even when all three are removed if you have a wheel out of balance the aircraft will still shake. a bent rotor and loose bearings will also cause this

 

[Dan Thomas]

My 172 has wheel fairings (covers) and they vibrate ( I see this when looking to the side) and chatter on fast taxi and roll out, no braking is being applied. My A&P has flown the plane and he isn't too concerned about this, but I am not really comfortable with it. He has checked the brakes and tightness of the covers. No material is being scraped from the tires and the clearances are there between the tires and the bottom lip of the covers. Main tires are new, but this was happening before they were replaced.

First, any suggestions as to the cause? Balance the tires? Other remedies

Second, I am not a big fan of wheel covers on the mains since I cannot inspect the brake pads, rotors, or leak check without a mirror. I would like to take the covers off the mains, and keep the cover on the nose wheel. Can I do that myself, or does an A&P have to do that operation. Thanks

Aircraft quality tires are notorious for being out of round and out of balance. Even the cheapest automobile tire is made more accurately and costs less. If you want smooth-running wheels, get them balanced. If the nosewheel shimmies, and most 172 nosewheels are bad for this because of the flimsy mount structure and torque link design, the nosewheel needs dynamic balancing, not just static balancing. Cessna had an SB on it years ago. Just replacing nosegear parts to remove slop won't fix it. And nosewheel shimmy destroys the wheel fairing, too.

Some nosewheels wear unevenly because their bearings are set too loosely. After takeoff the wheel will stop rotating with any heavy spot on the bottom, and that part of the tire will always be the first to contact the runway on landing and will get flattened off.

There are other things a pilot can do to keep his wheels smooth. Poor piloting technique is hard on tires and gear, so getting more proficient is good for the airplane. Landing fast and flat spins the nosewheel to a high RPM and any imbalance, static or dynamic, shakes the daylights out of the gear and loosens everything, and isn't good for radios and instruments either. Landing fast and long and trying to fix the problem with the brakes just grinds off rubber and leaves flat spots that then rumble during takeoff and landing, and shortens the life of the tire. Heavy braking without holding full up elevator shifts a lot of the weight onto the nosewheel and tilts the steering axis forward, reducing the castering stability of the assembly and brings on more shimmy, and that same weight shift lightens the load on the mains, reducing traction and making a skid more likely. In our flight school it's a constant battle to prevent such habits from forming; once a student is allowed to fly like that, it's hard to relearn the techniques properly. A proper landing will let the mains touch at the lowest speed possible without whacking the tail on the runway, and holding nose off a little while. Sit by the runway someday and watch and learn.

Dan

 

[DutchessFlier]

Thanks folks: the nose wheel is not the problem, its even rolling and does not shimmy. I try to keep my touchdowns as correct and gentle on the nose gear as possible...I have seen and done enough flat landings when I was a student pilot to break that habit. I think the major issue is out of round-unbalanced tires on the mains.

Tom: Do I need an A&P to remove all three wheel pants and then redo the W&B, or is that an MX item that I can do as PP/owner?

 

[Tom-D]

Thanks folks: the nose wheel is not the problem, its even rolling and does not shimmy. I try to keep my touchdowns as correct and gentle on the nose gear as possible...I have seen and done enough flat landings when I was a student pilot to break that habit. I think the major issue is out of round-unbalanced tires on the mains.

Tom: Do I need an A&P to remove all three wheel pants and then redo the W&B, or is that an MX item that I can do as PP/owner?

You need your A&P to do the deed.