Adjusting wheel camber angle

yankee-flyer · #1 05-23-2013, 09:26 PM

143WM has a LOT of camber, as it seems most do. I swapped the tires around at the first CI and again at the second, I now have mains with not a lot of tread on the inside and the outside, but virtually full depth in the center. My thought is that this is due to excessive camber combined with the high drag (wheel barely spins) of the Matco bearings, scrubbing off a lot of rubber on touchdown.

It's been suggested that I put a washer between the gear leg and the axle on the lower mounting bolts. Scott, could you weigh in on this or is there a better way of reducing the camber. I sent photos to Vans after completion but just got "that's normal" in reply. Looking for thoughts from others thinking about fixing this before buying new tires.

THANKS

Wayne 120241/143WM

JBPILOT · #2 05-23-2013, 09:55 PM

just for note. I got 150 hours on the 'first' side of the original tires. Same on the 'second' side. I then installed DESSER retreads. I am over 500 hours now, and can't tell any wear, so have not reversed them.

rvbuilder2002 · #3 05-23-2013, 10:51 PM

The camber angle is designed for operations at gross weight (as it needs to be).
Trying to change it by shimming the inboard end of the leg would probably be a bad idea. It would change a lot of other things; like bending moment on the leg from the wheels being farther outboard, to higher pitch attitude on the ground, etc.

Flying light (solo) a lot does cause more outboard edge wear on the tires but a lot of people seem to still get pretty good service life.

One thing to consider is touchdown speed. It can be a big factor.

I'm not implying that for sure is your tire wear problem, just offering this...

In the past there has been many landing technique threads here on VAF. I have repeatedly seen "I always land slow... rarely faster than 50 kts"

"50 Kts?"
I make sure I am down to 50 kts on short final if using full flaps with touchdown happening probably somewhere around 35 kts.

An extra 10 - 15 kts for tire spin up on a paved runway will make a huge difference in tire wear over a period of 150 - 200 hrs.

Remember, this is an airplane that by the requirements of its certification has a Gross Weight stall speed, with no flaps used, of 45 kts.
Flying solo and using flaps, it is way below that. If when touching down at lighter weights, the stick isn't full back, you are wasting tire rubber, not to mention the safety margin you are giving up if you ever have to make a slow as possible loff field landing in rough terrain (pilots don't usually magically pull out that skill when in a tough situation, just because they need it at that moment).

This discussion would probably have been better started in its own thread, but it is (may be?) relevant to this subject so I threw it out there.

yankee-flyer · #4 05-24-2013, 09:20 AM

I probably wasn't clear on what I was talking about. I wasn't thinking of shimming the gear leg-- I agree that's bad. I was thinking of adding a shim (washer) under the lower bolts that attach the axle/brake to the gear leg, just "tilting" the wheel assembly.

Never sure what my touchdown speed is (looking OUTside the airplane) but it's a lot less than 50 knot final speed, but usually greater than 33-35 kt stall warner speed. with 5+ knot headwind I can make the 500-foot first turnouff without much braking.

Thanks

Wayne

yankee-flyer · #5 05-24-2013, 09:23 AM

Assume you can buy retreads without old carcass.

Wayne

rocketbob · #6 05-24-2013, 09:44 AM

Quote:

Originally Posted by rvbuilder2002

The camber angle is designed for operations at gross weight (as it needs to be).

I disagree. Find a typical operating weight (pilot only, 2/3rd fuel, no baggage). We have been setting up rockets this way and its common to get 600-800 hours out of a set of tires.

rvbuilder2002 · #7 05-24-2013, 10:23 AM

Quote:

Originally Posted by rocketbob

I disagree. Find a typical operating weight (pilot only, 2/3rd fuel, no baggage). We have been setting up rockets this way and its common to get 600-800 hours out of a set of tires.

An RV-12 is a certificated airplane, a Rocket is not.

JBPILOT · #8 05-24-2013, 10:54 AM

no trade-ins required. CAUTION. Talk to them when you order. Let them know what size your tires are. The retreads area available in an over-size also. Get exact same size replacements. I couldn't be happier with them so far.

rocketbob · #9 05-24-2013, 10:59 AM

Quote:

Originally Posted by rvbuilder2002

An RV-12 is a certificated airplane, a Rocket is not.

Shimming the gear is very common on certificated aircraft. But if tire wear is not important to you, shim it to whatever spec you want.

rvbuilder2002 · #10 05-24-2013, 11:51 AM

Quote:

Originally Posted by rocketbob

Shimming the gear is very common on certificated aircraft. But if tire wear is not important to you, shim it to whatever spec you want.

I guess you are missing the point.

On certificated aircraft, the camber is being adjusted to a spec. (not just what the owner wants).

On the RV-12 the camber built into the leg is the spec.
It was established based on specific tire pressures, leg deflection at gross weight. static load drop tests with measurements of gear deflection, and on and on....

Sure, an RV-12 owner (as long as it is not an S-LSA) can choose to adjust it to what they want (just like a Rocket owner can). My point was, it is wat it is for specific reasons.