uneven tire wear

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BRS
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uneven tire wear

Post by BRS »

take a look at the picture. My pilot side tire is badly worn on the inside tread. I've noticed the main gear shimmy a few times so this could be why. Has anyone seen this type of wear and what was the solution?

btw - the passenger side tire is newer so I don't really know if it is running straight or not.
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Gary
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Re: uneven tire wear

Post by Gary »

There is an alignment procedure published in the DA40 AMM 32-10-00 page 206.
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Rick
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Re: uneven tire wear

Post by Rick »

BRS wrote:take a look at the picture. My pilot side tire is badly worn on the inside tread. I've noticed the main gear shimmy a few times so this could be why. Has anyone seen this type of wear and what was the solution?
We had the same problem for the entire first year, on both sides. After adjusting the shims (a few times) we finally got it so that the last set of tires is wearing evenly.

The basic procedure we used requires a long piece of string and a carpenters square. Remove the wheel pants. Tie a loop in one end of the string. Hook the loop over one outside wheel nut, then pull the string over the front edge ot the tires and tie the other end around the other outside main wheel nut. Make sure the string is taught between the two wheels. Lay the carpenters square against the outside of the main tire and check the angle it makes with the string. That angle should be as small as possible. The angle is adjusted by rotating a shim between the axle plate and the brake torque plate. I will try to attach a couple of pictures to help explain. (The picture with the string I stole from a document I downloaded from the other site a few years ago - would like to give credit, but I can't remember who posted it - sorry!)

The vertical angle (between the wheel and the ground) can also be measured by just placing the square against the ground and the tire, but you will find this changes alot by just moving the plane, since the gear legs flex quite a bit. I believe it is the horizontal angle (between the tire and the string) that causes the tire to wear, since it will tend to pull the tire to one side and flex the leg in that direction, thereby causing a vertical angle between the tire and the ground.
Main Gear Assembly.pdf
Main Gear Assembly -
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Tire Alignment setup -
Tire Alignment setup -
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Right Front main before adjustment -
Right Front main before adjustment -
Main Tire (RF).jpg (209.36 KiB) Viewed 3168 times
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Re: uneven tire wear

Post by BRS »

Thanks Gary and Rick,

This info should get me on my way. Rick I can't get the pdf to open is it a bad file or is it just my pwtr?
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Re: uneven tire wear

Post by Rick »

BRS wrote:Thanks Gary and Rick,

This info should get me on my way. Rick I can't get the pdf to open is it a bad file or is it just my pwtr?
Yeah, I can't open it, either. Here is another attempt.

OK, it won't upload, because my pdf file is 441K, and the max file allowed is 256K. But, it was just page 203 from the AMM, Figure 2, showing the Main Landing Gear Axle Assembly. Sorry guys, you'll just have to look it up. :(

Wait, here it is as a JPG file:
Main Gear Assembly.jpg
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Re: uneven tire wear

Post by rdheath1 »

Thanks for posting the great pictures. The outboard edges of both of my main gear wear just like Rick's picture. I tried to get the Diamond Service Center that was leasing it to adjust the toe in and twice they said they did. Now, I'm just going to do it myself, so my question is, have the adjustments eliminated the wear shown on your picture of the right main tire before adjustment?

Many thanks, Bob
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Re: uneven tire wear

Post by Rick »

rdheath1 wrote:Thanks for posting the great pictures. The outboard edges of both of my main gear wear just like Rick's picture. I tried to get the Diamond Service Center that was leasing it to adjust the toe in and twice they said they did. Now, I'm just going to do it myself, so my question is, have the adjustments eliminated the wear shown on your picture of the right main tire before adjustment?

Many thanks, Bob
Bob, in the case pictured below, rotating the shim clock-wise one hole seems to have eliminated the wear on the right main. I say "seems to", because the rest of the tread is now wearing evenly, and the existing edge wear has not increased any, but I have not replaced the tire yet, so it's kind of a judgement call.

WIth my previous DA40, it took several adjustments (and tires) before we finally got it right. The edges wore down to the steel cords pretty quickly until we got the shims right, but then the last set of mains went forever without any edge wear. So I believe there is a "correct" setting that will eliminate the excessive edge wear, but finding it may be part art and part science...
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Re: uneven tire wear

Post by rdheath1 »

Thanks for the good info, Rick, I'll get started on it! Bob
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