Asymmetric tread-wear on main gear tires

Not surprising given the camber of the main gear wheels and that I mostly fly solo. After 115 hours and many landings the outboard threads are getting close to being wiped out on both tires while the inboard threads are like new. Which brings the question: could I turn over the tires bringing the inboard threads outboard? Inspecting the tires shows a symmetrical thread design and no indication of direction of rotation.

yes people do it all the time on other airplanes.

Rotating is common practice... as long as you just have asymmetric Tread wear.
If you have thread showing on the tire, it should be replaced.....

rvbuilder2002 said:

Rotating is common practice... as long as you just have asymmetric Tread wear.
If you have thread showing on the tire, it should be replaced.....

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To me rotating tires like on a car is a different operation. It means swapping the wheels from front to back and left to right. This is needed because the roads are not flat, they have a crown which is not the case for runways (or is not as pronounced). Here what I mean is dismounting the tire from the wheel and remounting it on the same wheel with the outboard wall now inboard. If the wear is not symmetric between right and left wheel, due to a misalignment, a rotation may also be required but for most RV-12s correctly built I believe that the camber of the MLG wheels will be the main source of asymmetric wear of the tires. In such case I don't see the value of exchanging right and left wheel.

WingedFrog said:

To me rotating tires like on a car is a different operation. It means swapping the wheels from front to back and left to right. This is needed because the roads are not flat, they have a crown which is not the case for runways (or is not as pronounced). Here what I mean is dismounting the tire from the wheel and remounting it on the same wheel with the outboard wall now inboard. If the wear is not symmetric between right and left wheel, due to a misalignment, a rotation may also be required but for most RV-12s correctly built I believe that the camber of the MLG wheels will be the main source of asymmetric wear of the tires. In such case I don't see the value of exchanging right and left wheel.

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Jean-Pierre,
It all depends on what your definition of rotate is in this context.
In the context of aircraft (what we are talking about) we pretty much never move wheels from one location to another. So on an aircraft, when aircraft mechanics say rotate a tire, generally it means in the yaw axis on the wheel. I.E., rotate the inboard surface of the tire so that it is now the outboard surface, vs rotating them in position around the vehicle (as in a car).

My other comment was just poking a little fun in that it is not the thread of the tire that wears out.... it is the tread.

Modern automobile tires also take on a rotation bias. They are rotated front to back and back to front, but not cross rotated to the opposite side of the vehicle. Is this true of aircraft tires also? If so, then tje aircraft tire should be turned on the wheel and rotated to the opposite side of the aircraft to maintain rotational bias.

WingedFrog said:

Not surprising given the camber of the main gear wheels and that I mostly fly solo. After 115 hours and many landings the outboard threads are getting close to being wiped out on both tires while the inboard threads are like new. Which brings the question: could I turn over the tires bringing the inboard threads outboard? Inspecting the tires shows a symmetrical thread design and no indication of direction of rotation.

Click to expand...

Have been doing this for several years now to get max use out of tires. Really need to align mine better as I believe most my wear is due to toe and it would help to be more vertical.....
It's more work than I like but also good time to look over the brakes and lines etc.

Always best to go to the manufacturers before the forums.....

Per Goodyear:
ASYMMETRICAL WEAR
Some aircraft tires exhibit faster shoulder wear on one shoulder versus the other
due to non-tire influences (camber-type wear, etc.). If this condition exists, the
tire’s life can be extended by demounting and reversing (“flipping”) the tire on the
wheel as long as tire wear limit and the physical condition criteria are satisfied.
NOTE: “FLIPPING” MUST NOT BE DONE ON SINGLE CHINE TIRES.

Just remember you won't get another 115 hours, maybe about half that. Keep an eye out for anything showing through. Per Michelin:

...be removed from service for wear
using the following criteria:
Based on the fastest wearing
location, remove tires:
When the wear level reaches the
bottom of any groove along more
than 1/8 of the circumference on
any part of the tread,
or
If either the protector ply (radial)
or the reinforcing ply (bias) is
exposed for more than 1/8 of the
circumference at a given location.

brad walton said:

Modern automobile tires also take on a rotation bias. They are rotated front to back and back to front, but not cross rotated to the opposite side of the vehicle. Is this true of aircraft tires also? If so, then tje aircraft tire should be turned on the wheel and rotated to the opposite side of the aircraft to maintain rotational bias.

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Very good point, Brad. I wonder if rotational bias is important for a tire that has no rotation direction marked on it as the tires on my RV-12?

rvbuilder2002 said:

Jean-Pierre,

My other comment was just poking a little fun in that it is not the thread of the tire that wears out.... it is the tread.

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My confusion between thread and tread may result in a threat, thank you for pointing it out with humor, Scott.

brad walton said:

Modern automobile tires also take on a rotation bias. They are rotated front to back and back to front, but not cross rotated to the opposite side of the vehicle. Is this true of aircraft tires also?

Click to expand...

Not that I am aware of.
The cording material in aircraft tires at the lower end of the performance spectrum like we use is generally fabric in nature and I have never heard of there being a rotation sensitivity.

In fact, not all modern auto tires require swapping only front to back on the same side. Many cars now adays do recommend swapping side to side.

brad walton said:

Modern automobile tires also take on a rotation bias. They are rotated front to back and back to front, but not cross rotated to the opposite side of the vehicle. Is this true of aircraft tires also? If so, then tje aircraft tire should be turned on the wheel and rotated to the opposite side of the aircraft to maintain rotational bias.

Click to expand...

That rule is a carry over from when radial tires first came out.
A few modern day auto tires are marked for "direction of rotation", but that is usually because of tread design.
Today's radial tires don't typically "take a set" like the early ones did.

At 138 hours I decided to replace my original tubes with Michelin Airstop tubes because of the grass-gravel runway. The outboard tread was worn slightly more than the inboard on both wheels. So when I swapped the tubes I also swapped the tire orientation.

The right brake wear indicator was also getting close so I decided to replace brake pads as well. I added the Matco HUBCAPS since, with grass still coming in on my strip, I have had the wheel pants off. Matco will send you new brake pads, then you send them back your old ones and they refurbish them and send back so you always have spares on hand without fooling with the rivets.

This was as a "might as well" because if you take off the wheels you might as well go to the trouble of repacking the bearings, etc. etc.

Gotta remember on the first flight to fly off the grass strip to a local airport and glaze the brake pads per the manual.

rvbuilder2002 said:

Rotating is common practice... as long as you just have asymmetric Tread wear.
If you have thread showing on the tire, it should be replaced.....

Click to expand...

Enjoyed this one. You probably saw my first set of stock tires Scott. Squoze 1K+ landings outta dem.

Vlad said:

Enjoyed this one. You probably saw my first set of stock tires Scott. Squoze 1K+ landings outta dem.

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That photo must be of one of the other (FAST) airplanes you used to fly Vlad, cause it doesn't look like an RV wheel/tire.

Actually, if I am remembering correctly, I think a tire is still technically airworthy if it has worn through the first layer of cord material. If you hit the second layer, it must be replaced (The one in your photo looks way past that.....).

I once landed a rental Seneca, taxied in and as I shut down I heard what we Navy guys called the Phillipine love call "pssssst". I felt the plane take on a list. That taught me to pull the aircraft forward during preflight to inspect all the tread!

Mine wore out

at about the second annual. Flipped the tires at the first annual, and they were pretty near shot at the second one. I used a set of 0.5 deg. shims to reduce the toe-in and replaced the originals with "heavy-duty retreads. not much visible wear 1.5 years later. If it recurs, I plan to use shims to reduce the really excessive camber angle.

Wayne 120241 143WM

rvbuilder2002 said:

That photo must be of one of the other (FAST) airplanes you used to fly Vlad, cause it doesn't look like an RV wheel/tire.

Actually, if I am remembering correctly, I think a tire is still technically airworthy if it has worn through the first layer of cord material. If you hit the second layer, it must be replaced (The one in your photo looks way past that.....).

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Ran one of mine that far, by accident..... And it blew on take off. Bad idea.

yankee-flyer said:

at about the second annual. Flipped the tires at the first annual, and they were pretty near shot at the second one. I used a set of 0.5 deg. shims to reduce the toe-in and replaced the originals with "heavy-duty retreads. not much visible wear 1.5 years later. If it recurs, I plan to use shims to reduce the really excessive camber angle.

Wayne 120241 143WM

Click to expand...

This brings several questions, Wayne:

- Is there a range for the camber angle?
- Where do you get the shims for correcting camber and where do you place them?
- Where can you get "heavy duty" retreads?