cfiidon

cfiidon

Well Known Member
It appears I may have to do some camber adjustment on my RV-8 with standard Vans gear and my question is about parts compatibility.

I shimmed to correct a toe-in condition and now have about 1/2 degree toe out. I noticed recently after less than 50 hours that the tires appear to be wearing excessively on the inside edge, somewhat opposite of what most experience.

I'll do measurements but want to pre-order shims. Vans sell camber shims at 1 degree. ACS sells "Grove" shims at one degree. Grove sells 2 degree camber shims. Are they all compatible with the Vans supplied gear and Cleaveland wheels and brakes?

I know I can stack shims but that gets expensive. I'm thinking I may need 2 degree shims just by eyeballing the tire wear and visualizing 2 degrees.

I just checked the landing gear bolt torques and all is good.

Don
 
If the plane handles well on the ground, why not just "flip" the tires at each condition inspection to keep the wear even?
 
1/2" degree toe out in what condition? Most of the wear comes from taxi so I would set them for zero/zero for that condition, pilot weight and 2/3rd full of fuel, which is a typical flight setup. You probably have excessive toe-out in 3pt which is why you have too much camber, it changes as the tail comes up.
 
Follow Up

The one half degree toe out is in the 3 point attitude, full fuel, no other load. As I set up to flip the tires, I'll take another look see.

I ordered and received 1 degree camber shims, I'll use them and see what the wear patterns are after that.

I needed a good excuse to change the tubes to Air Stop, and one pesky stem on the right main was not quite aligned perpendicular to the rim... so the wheels need to come apart anyway.

The reason for not just flipping them is that the wear has appeared after only about 50 hours hobbs time ... can't tell you how many miles of taxi or landings that is... just average I suppose.




Don
 
RV-8 Squirrelley on the ground - Wheel Alignment? :(

I need some advice on our RV-8, which seems to be pretty squirrelly on the ground. I talked with a few RV8ers at a recent fly in and received several comments about tire pressure, wheel alignment and tail wheel linkage. Basically, zero to a slight toe out is better than toe in? Tire pressures as low as 28 or 30PSI, and a relatively loose tail wheel linkage are all things to try. I checked our wheel alignment, and it is about 1.5 degrees toe in on both sides. I have been running around 35PSI, and am concerned about dropping this too low as a tire could rotate on the rim and sheer the valve stem. On the tail wheel chains, they allow about an inch of travel in the pedals, moving the rudder only, before acting on the tail wheel. Camber is also very positive as the outside of our tires where much faster than the center.
 
Fix your toe first. Don't worry about tire rotating on rim with lower pressure...it won't happen unless tire is almost flat. I changed from loose chains to rocket link (basically no free play) and like it much better.
 
mspenc45 said:
I need some advice on our RV-8, which seems to be pretty squirrelly on the ground. I talked with a few RV8ers at a recent fly in and received several comments about tire pressure, wheel alignment and tail wheel linkage. Basically, zero to a slight toe out is better than toe in? Tire pressures as low as 28 or 30PSI, and a relatively loose tail wheel linkage are all things to try. I checked our wheel alignment, and it is about 1.5 degrees toe in on both sides. I have been running around 35PSI, and am concerned about dropping this too low as a tire could rotate on the rim and sheer the valve stem. On the tail wheel chains, they allow about an inch of travel in the pedals, moving the rudder only, before acting on the tail wheel. Camber is also very positive as the outside of our tires where much faster than the center.
Click to expand...

I personally believe that toe-out is more stabilizing than toe-in. As for tire pressure, I have no evidence that does much at all. I have mine at 40-42 primarily for ground clearance on the wheel pants crossing the hangar door lip. They were 30 -35 before pants went on... didn't change my lousy landings one bit.

I have tried loose chains and tighter chains and think it does not make much difference, other than what you get used too. You could make the argument that looser chains would reduce this, and some might argue that it can make it worse.

You didn't mention how much tail wheel experience you have. Mine was very limited, and with experience I'm getting better. My biggest problem seemed to be after the tail comes down after a wheel landing. As I slowed, I'd start getting more and more squirrely. I called it PIRO, or pilot-induced rudder oscillations. I'd start swinging back and forth and the best way to stop it (at slow speeds) was brake application.

Much of it is technique... I read several descriptions and the best I saw explained that I was a victim of inertia. Scenario: Nose drifts right, apply left rudder, nose comes back to the left, inertia keeps the CG going to the right, nose overshoots and goes left, cycle repeats.

As I get better I am anticipating this. Scenario: Nose drifts right, apply left rudder, correction begins, rudder neutralized, repeat as necessary. Also, my perception of when the nose starts to drift is getting better so I'm anticipating the drift, applying corrections earlier, and thus the corrections are smaller.


Forgive me if your experience level is well beyond this point. I'd fix the toe-in condition and then experiment/practice. As for me, I am still learning. I am an instructor with a bunch of hours, but taming the tail dragon has been a humbling experience and I freely admit it. I understand the process of learning.

As with any low time pilot, we have not yet gained the ability to perceive small changes. As we gain experience, we see the intended point of touchdown drift, we see the ground path and ground speed change, we "sense" the .95 Gs as the aircraft begins to settle in the flare. As our kinesthesia improves, so do we.

Don
 
Thanks Don! I have a couple of hundred hours in a Super Cub, which I am much better in than the RV-8. According to most I read, the RV-8 should be more be-nine than the Cub, but it is not. I am headed to the hangar today to get a good measurement on toe in. All I did was a rough check was to determine the toe, basically place two metal sheets together with grease between them and run the wheel over it. The top sheet twists in the direction of the toe, in my case both wen toe in.
 
I used a laser magnetcally mounted on the brake disc and also tried a long piece of angle iron on the tire -- whatever works for you.

I checked your profile and you should be able to do the math;).

Please report back on results.

All my experience was in a Citabria (whopping 8 hours) and it seemed much more forgiving.
 
OK, I took two pieces of angled aluminum, 36" long, drilled holes at the center and used the wheel pant axle bolt to attach the angled aluminum to the axle nuts, which should be parallel to the rims and perpendicular to the axles. I then used a plumb bob to find and mark the center line from the tail wheel to the nose with a chalk line. I used the plumb bob to mark a line on the ground at both ends of the aluminum angle. I then measured the distance from these marks to the center line. Turns out they were off .25" on wheel, this calculating out to a .38 degree toe in. I've been told that a slight tow out is better than a slight tow in, so I ordered 1/2 degree shims from Grove. I'll report back after installing them.
 
Sounds great. Install the shims and repeat the measurement to see that it all works out as expected.

Those shims are not cheap, are they?

Don
 
NO they are not! I bought them directly from Grove at $24 each, and no shipping, since they mailed them. I actually took my measurements with the aircraft in a three point configuration, since this is where we experience the squirrel factor, but I then hacked it up to see if the toe in changed, it did not.
 
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