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rv4bill

Well Known Member
I need to shim the wheels on Harmon Rocket that has the larger, 380/150 tires.
The outside wore pretty bad and rotated them at 50 hours. I ran two 1" angle irons on the inside of the tires towards the front of the aircraft. I put both wheels on two greased plates and filled wings full of fuel and added 200 lbs of lead shot to front seat. Here are my measurements:

Inside measurement between brake linings was 74.25" wide.
Measured forward from center of tire and put a mark at 68"
I did this to both tires and the measurement between the two points out in front and it was 69" wide. A difference of 5.25" at the 68" mark. Assuming both wheels are equally toed in, I came up with the tires each about 2.5 degrees of toe in.

Do my measurements add up?
Should I mark the centerline of the plane and do each wheel on its own?
Vans and grove both sell shims. If the wheels are 2.5" out of toe would I put the two 1" shims plus a Half inch shim on each wheel?

Y'all please go easy on me if I did this all wrong

Thanks
 
Titanium gear legs

Hi Bill. I set up my tires at 0 degree toe in, toe out in the 3 point position as recommended by J.H. . I have many hours in T.G.'s so I am reasonably smooth. I am getting similar tire wear to you. My RV4 was pretty easy on tires compared to my rocket. I believe the tire wear is associated with forward and back movement of the very springy and long titanium gear. This is my best guess.

Steve
 
Bill,
I pretty well followed John Harmons instructions. I set mine up for zero toe in or out with no weight other than the fueselage and tail less engine. I snaped a straight line from the center of the tailwheel to the center of the firewall and extended the line a few feet. I then clamped a piece of angle about 2 feet long to each brake disk. I shot for an equal measurement from each end of the angle to the centerline on each gear. The camber was a bit off but John sells shims that bolt right up (very nice) and 1 shim on each side corrected my camber. The airplane tracks straight as an arrow and it only has about 65 hours on cheap tires but they appear to be wearing evenly. I would suggest using a center line and check each wheel seperatly. John will be able to provide you with the shims you need.
Ryan
 
rv4bill said:
Should I mark the centerline of the plane and do each wheel on its own?
Click to expand...

Short answer, YES. In addition to having the tires wear evenly this is the best way to insure the airplane tracks straight especially when you land.

:cool:
 
Whoever came up with the idea to set the gear up with zero toe with no weight on was flat out not thinking. My friend Jim Winings set up his F1 for zero toe zero camber at a typical flying weight (used bags of salt on the wings to simulate) and gets 6-700 hours out of a set of tires. My rocket is set up the same.
 
So is my Cessna 180, and except for a recent set of soft Goodyear Custom III tires, gets lots of life. Won't buy those again.

Dave
 
Tires that wore in 100 hours were the aero classic
However, I think any tire would be worn pretty bad considering the noticeable amount of toe in. I like the desser retreads but they won't fit in my wheel pants which just barely fit the larger 380's
 
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