Tire Losing Air; Vibration

[andyb]

A few weeks ago, after a month without flying, I had a flat tire.  A local A&P, who I have known for years and is very good, replaced the tube.  I examined the old tube and there was a slice about 1/8" under the valve stem.  I assumed this caused the flat.

Since the tube was replaced, I have noticed both a vibration at speeds above about 40kts when taking off and landing, as well as a gradual loss of tire pressure.  It loses 5-10 pounds over a 2-5 day period, and seems to stabilize around 24 psi. I'm now wondering whether whatever is causing the gradual leak has continued, and perhaps whether the cut under the valve stem was symptomatic of the original loss of tire pressure, rather than the cause.

Before I go back to the A&P, I wanted go see if anyone has any ideas about how to address this.  He doesn't routinely work on CT's, so there may be some plane-specific things he's not aware of.

Thanks much!

Andy

[Tom Baker]

Check the valve core first.

I have pinched tubes with the Matco wheels before. I found out when I changed tires the next time and there was a couple elliptical shaped pieces of rubber cut out of the tubes. Make sure you use the heavy Leak Guard tube. Amazingly the held air like that.

The tires are nor very well balanced, and it could have been install with the wrong orientation.

Also I have seen failures of the Aero Classic 4.00x6 6 ply tires that cause vibration.

The mechanic may have not set the bearing tension correctly.

The last and least likely is a warp in the brake disk.

[Roger Lee]

Usually a tear around the stem comes from too little pressure in the tire and it wants to turn on the wheel when you land. Always make sure tire pressures at are least 30 - 35 psi.

Most likely the mechanic has pinched the new tube and it will get worse.

Balance ALL aircraft tires.None are in balance. Average weight is 4 to 8 x 1/4 oz. weights. If you have large 6.00 x 6 tires and it takes a huge amount of weights like 20 weights send it back. Vibration is usually unbalanced tires if it happens at lift off.