Wheel Alignment

Bill Riggs · #1 08-14-2008, 05:32 AM

I am showing quite a bit of tire wear on one side of the tires. Is there a procedure for checking the alignment of the wheels? (toe in and out camber)
If so are there shims available to correct the alignment and does anyone have a copy of the procedure ??? The airplane tracks perfect on TO and Land. just tire wear is the problem.

Thanks
Bill

Lycosaurus · #2 08-14-2008, 06:48 AM

Quote:

Originally Posted by Bill Riggs

I am showing quite a bit of tire wear on one side of the tires. Is there a procedure for checking the alignment of the wheels? (toe in and out camber)
If so are there shims available to correct the alignment and does anyone have a copy of the procedure ??? The airplane tracks perfect on TO and Land. just tire wear is the problem.

Thanks
Bill

Bill,

Only procedure I have heard of for our RVs is to flip the tires. That involves removing the rubber from the wheels, and remounting so the wear will even out. Unfortunately, you can't just rotate the whole wheel assembly, since the disk brake is attached to one side of the wheel.

Bob Martin · #3 08-14-2008, 07:45 AM

http://www.aircraftspruce.com/catalo.../tapershim.php

Aircraft Spruce lists shims for aligning wheel, but I haven't used them?
Anybody else tried them??

From ACS page:
For wheel alignment. Ideal setting is zero toe-in and zero camber at normal operating weight. shims may be rotated to any one of four positions to obtain desired result.
Axle Size Shim Part No. Approximate correction value
Price Buy CAMBER TOE-IN
500x5
0441157-1 1/2? 0.06" $45.80
0441157-3 1? 0.12" $79.90
0441157-2 2? 0.006" $388.95

Seems pretty pricey but if you only needed 1/2 degree and doubled the life
of a set of tires it could be worth it.
I'm wondering if a little toe in....or camber is required for stability????
Any body have thoughts to share?

mannanj · #4 08-14-2008, 08:00 AM

You didn't state which aircraft, but if you're talking RV-8, Van's has shims for about 8 bucks apiece. They have 1 degree and 1/2 degree shims IIRC.

I aligned mine as best I could according to the builders manual but still had to remove a 1 degree shim after about 100 hrs.

sandifer · #5 08-14-2008, 09:45 AM

You can't shim rod landing gear (RV-3,4,6,7,9). Once the gear leg/mount is drilled, it's very hard to adjust the angle of the axles. Jack the plane, remove the wheels and use a long piece of angle to check alignment. To precisely measure both sides, you could snap a chalkline perpendicular to the fuse, clamp a piece of angle to the axle, transfer that line to the ground and measure the difference with a protractor. Setting wheel alignment is in the builder's manual if you have it.

Bob Martin · #6 08-14-2008, 03:15 PM

Eric,
My manual is at the hangar and I didn't build my -6 but are you saying the axle
is part of the gear leg and not a separate piece?
Thanks

Bill Riggs · #7 08-15-2008, 08:30 AM

Quote:

Originally Posted by sandifer

You can't shim rod landing gear (RV-3,4,6,7,9). Once the gear leg/mount is drilled, it's very hard to adjust the angle of the axles. Jack the plane, remove the wheels and use a long piece of angle to check alignment. To precisely measure both sides, you could snap a chalkline perpendicular to the fuse, clamp a piece of angle to the axle, transfer that line to the ground and measure the difference with a protractor. Setting wheel alignment is in the builder's manual if you have it.

I don't think the shims would be for the gear leg I belive they fit on the axel to slightly change the angle of the wheel in relation to the ground. ??????

n5lp · #8 08-15-2008, 08:40 AM

Quote:

Originally Posted by Bill Riggs

I don't think the shims would be for the gear leg I belive they fit on the axel to slightly change the angle of the wheel in relation to the ground. ??????

Bill I don't believe you ever did state what model you are talking about. If you are talking about an RV-6, which is stated as your interest in your profile, the gear leg and axle are all one piece. The gear leg can be rotated but it is a difficult job after it has been drilled. Shims can be used on the RV-8 because it has a separate axle.

A lot of us steel rod gear folks just put up with tire wear and do the tire rotations as necessary.

noelf · #9 08-15-2008, 08:56 AM

The first post in this thread is of a -6, and I have a 6A that is 99% complete. The alignment of the gear legs for the -6A was called for in the initial fitting of the wings, as the gear leg sockets are matched drilled to the wing spars and cabin side frame structures.
The -6 gear legs are inserted into leg sockets that are welded / attached to the engine mount. The wheel alignment is controlled by the rotational position of the gear leg in the leg socket (as it is for the -6A).

The "normal" , on-the-ground position of the main wheels for the RV-6 series a/c has the top portion of the wheel tilted outboard from the a/c. In flight,with the weight off of the gear, it is more so. On the ground, this will allow more wear on the outside portion of the tire tread, and I believe you find this to be normal and expected. Grass field operations tend to minimize this wear characteristic. There is no real fix for this "normal" condition, but periodic flipping of the tire on the rim will put the "worn" section on the inside of the rim and the "less-worn" on the outside of the rim.

If the tire wear is only on the outside edge of each tire, and both the left and right tires show equal wear, well then, it sounds like the alignment is consistent, and the same, for each wheel. That's good. And it sounds like that is your impression as the a/c does not "pull" to either side with ground taxi conditions.

A question on landing techniques: do you routenly grease the landings by skimming along the runway? Or, is is a firm and deliberate plant?? It seems that skimming would allow the wheels to just kiss the surface and allow tire outside edge rubber to be worn away. A plant may minimize this. Also, with the kiss technique, the geometry angle of tire alignment-to-flight path direction may be changing as more weight is slowly transferred to the wheels as air speed decreases.

So how can you determine if each wheel is tracking "straight", or if both are pulling to one side, but in equal but opposite amounts? A technique that can be used to see what the tire alignment is actually doing is to try the following:
1. use two appropriately sized sheets of tin, aluminum, whatever.
2. place one sheet under each tire, with full a/c weight on the gear
3. secure the a/c by whatever means to prevent the a/c from moving
4. simultaneously, pull each sheet rearward with the same force and speed.
5. the wheel should be free to rotate as the sheet is pulled
If the sheets can be pulled straight back, the alignment is parallel to the a/c center line. If the sheets rotate, or move to one side or the other, then the alignment is such that it is forcing the sheet to one side.

Hope this helps.

n5lp · #10 08-15-2008, 09:13 AM

Quote:

Originally Posted by noelf

...A question on landing techniques: do you routenly grease the landings by skimming along the runway? Or, is is a firm and deliberate plant?? It seems that skimming would allow the wheels to just kiss the surface and allow tire outside edge rubber to be worn away. A plant may minimize this....

Uh yeah, that is exactly why I use the "firm and deliberate plant" technique! Never did like that method where you "kiss" the pavement. It's for tire wire reasons. Yep, that's the ticket!