Tires

[170C]

In the past when the inside of my tire ('s) wore the inside grove smooth, I have taken the tires off the rims and reversed them so I get more usage before replacement. Couple of questions: Anyone know of any reason not to turn the tires around (not switch from side to side, but switch on the same wheel/rim)? I heard someone say that by running the tire backwards from the way it had been orgnally put on was bad??? Also, are others finding the left tire wearing on the inside more than on the outside or more than on the right main inside? Don't know if this is normal or if my camber (?) is off. Sometimes it looks like the tire is canted out at the bottom.

N6888A

[GAHorn]

When U.S. tiremakers first tried their hand at making (what was popular in Europe for over a decade) radials, they were not as experienced in laying the fabric prior to the vulcanizing of the carcass. This resulted in the tires taking a "set" and if they were reversed (such as switched to the opposite side of the vehicle during tire rotation) they would fail prematurely with belt seperations. This is no longer the case, as mfr's now vulcanize the unit after the belt is applied rather than before.
This was never the case with aircraft tires (which are bias ply tires anyway.) It does not hurt to reverse the direction of travel of aircraft tires. (If it did, could you imagine the problems airlines would have with re-caps?)
(For green airplanes that travel at green tractor speeds you might first check to see if there is a direction arrow imprinted on the sidewall of the tire. Joe's airplane has an unusual chevron-traction-tread design, if you've noticed.)
RE: one tire wearing more on inside than other, and/or "stance": Frank, if you're like most pilots, you subconsciously prefer to make left hand turns. You taxi for takeoff and make a left hand turn onto the runway. You return to the ramp and make a left-hand turn into the chocks. If so, this will preload your left tire and make it appear to have excess wear on it's inside tread and, depending upon how much forward travel you allow after completing the turn, may leave the tire slightly cambered "negative" when parked.
(Note: Positive camber places the top of the tire leaning outboard, while negative camber places the top of the tire leaning inboard, allowing the tire to sit on it's inboard tread area.)
Try relieving the preload by pushing/pulling/taxying forward a few feet with the airplane in the unloaded state. (removing yourself from the plane will lighten it, and also preload the tire tread, leaving it with the appearance of negative camber. Rolling the airplane forward a few feet will allow the tire to "unload" and sit in it's natural stance. Keep in mind that the wheel alignment procedures for the 170 are designed for a weight of 2,000 lbs. If you operate heavier than that, even with exactly correct alignment, the inside of the tires will receive more wear than the outside, and vice-versa.

[N1478D]

(For green airplanes that travel at green tractor speeds you might first check to see if there is a direction arrow imprinted on the sidewall of the tire. Joe's airplane has an unusual chevron-traction-tread design, if you've noticed.)

OK - just for that you have to read a green tractor joke!

What did the plow say to the tractor? Pull me up a little closer John Dear!

How you planning on getting your old slow non-climbing B up on top of Mt Petit Jean George? If you need help pulling the wings and trailering it up there before the flyin let me know. You could land at Paris, Ozark, Booneville, Clarksville, etc - lot's of fellars around those parts with trucks and trailers.

[170C]

Thanks George. You are right, I do tend to turn left much more than to the right. Hope that is why my left main tire is wearing quite a bit more than the right main tire. I would rather not get involved in trying to adjust the camber on the mains.

You and Joe need to get together up at Peite Jean and have a fly off. You guys have got me curious which plane is the fastest now. Aren't you going to have new cylinders?

Hope you can make it to AR!

[GAHorn]

Nope, not buying new cyls. Only repairing the exhaust valve leaks and pressing on with the original cyls. (Worn valve guides from infrequent use was the verdict.)
I expect to bring my daughter and Jamie both to Petit Jean, so full fuel, camping gear and three folks to the mountain top with a cruise prop should prove my point. Looking forward to it.

[N170CT]

George, et al,

Don't mean to be argumentative, but...How will a turn to the left "pre-load" the left tire??? One would think a left turn will "unload" the left tire as the centrifugal force/weight/mass shifts slightly over to the right (outside) tire . Unless, of course, I am completely misinterpreting the discussion. Continuing this a little further, 170C states that "Sometimes it looks like the tire is canted out at the bottom". Sounds like the negative camber George described. Owned my 170B for four years without replacing the tires. No abnormal wear pattern on either tire detected to date and I am very meticulous re the tires/pressures. Suggest 170C perform an alignment/camber check which is a relatively simple procedure and I will bet my two cents he finds a camber problem on the left main. This is dangerous, cuz if-in I lose, I won't be able to put my two cents in anymore .

[GAHorn]

N170CT, if you turn left, the left tire tread will grip the pavement and pull the tread which is in contact with the pavement outboard. This will cause wear on the inboard tread. If the airplane is left in that condition without rolling forward, the tire will remail preloaded like that. Same thing if the airplane is heavily loaded (like with my brother and me) and we get out. The spring gear will attempt to "pull" the tires toward each other, leaving them in a negative camber (and impressing a viewer that they are improperly aligned) unless the aircraft is relieved by rolling forward or backward.
(And BTW, both tires will receive ample wear on their outboard tread each time the gear spreads as the airplane lands. All the above combine to explain why an airplane that makes more frequent turns to the left will appear to wear it's left tire's inboard tread more than the right side, even on a perfectly aligned gear.)

[zero.one.victor]

Pokey,to get back to your original question: I don't think anything's wrong with reversing the tires on the wheels to equalize wear-- in fact, I do it myself. You might want to check the caster (toe-in/toe-out). There's an easy way to do this shown in the SRAM Book (page 5-16),using an 8 foot straight-edge across the front of the tires & a carpenter's square on the wheels or better yet the brake discs. The article doesn't mention it,but before checking the wheel alignment this way I think you should check that the main wheels are in line fore & aft by triangulating from a point near the tail. I did it the SRAM way, as well as by plumbing down centerline marks off the airframe,snapping a centerline on the floor,,and measuring the wheel alignment off that centerline. I came up with the same results using both methods.
Caster and camber both should be zero at 2000 pound aircraft weight. I measured the camber on mine with aircraft weight at around 1500#,it was off a bit but within spec--zero plus/minus 1/16". Usual flying weight on mine is probably around 1750#. Camber should be neutral at 2000#, so empty you should probably have a little positive camber (top-out). Mine has probably too much positive camber but it handles well so I ain't gonna mess with it. That positive camber is why my tires wear faster on the outside,but then by reversing them I get twice as much mileage out of them ( over 600 hours mostly on paved airstrips) so I'm happy.
If yours handles OK I woldn't mess with it,I'd just reverse the tires & keep a-flying.

Eric

[Dave Clark]

A couple of plastic garbage sacks on the floor under your tires makes a nice grease plate. It's amazing.

[GAHorn]

Whooo-Hooooo!!! Dave!! You're the Man!! (Thanks for the great idea!)

[N1478D]

I expect to bring my daughter and Jamie both to Petit Jean, so full fuel, camping gear and three folks to the mountain top with a cruise prop should prove my point. Looking forward to it.

Hey George, Frank and I have been planning on flying up on Thursday. Now, Megan is changing her mind and wants to go. She gets out of school at about 4:30 on Friday. When are you guys headed up? Would you be interested in stopping at GPM, and going up as a flight of two, or three if Frank delays? There would be three of us in 78D - Megan, me, and the new Parrot.

[GAHorn]

Haven't planned that far ahead just yet, as Ashley's school also comes into play. I'll advise by email, but it sounds like fun. gh

[170C]

Now Joe, just admit it , you really are wanting to have a chance to see which of those two planes is REALLY the fastest AND beyond that I'll bet you are wanting George to show you how to make a flyin after dark with no runway lights!

PS: Does that parrot count as a third passenger and/or extra power?

[N1478D]

If that parrot starts biting me there isn't a plane in the sky that has a chance, that is some BEAK! Going to get where we are going in a hurry so that one of us has some relief if that happens. That would be worse than when that duck got loose in the cockpit on short final.

Landed at Ozark one time after dark with the runway lights not working. That was not fun. Kept making lower passes till the landing light finally picked up the runway. The only reason I attempted that was because I knew how the runway was oriented to Interstate 40 which the headlights outlined. It's a long runway which alllowed me to make approaches and climbouts where I thought was inside the ends, but still don't look upon it as one of my smarter judgements, and don't plan to ever repeat it. Will not be landing at Petit Jean without runway lights at night because I am not familiar with that area. Would rather get older and be known as a chicken than a short lived bold pilot.

George has commitments that is going to keep him from my invite to stay over here and then us fly up together. Maybe the return trip will provide an opportunity for us to get them side by side and open the throttles up. Need to be some witnesses up in the air for that one.

[AR Dave]

Joe, didn't you ever skip a day of school? Megan will enjoy my girls, I'm sure of it. And Randal's bringing his new 170 pulling a trailer full of kids. They've got a big swimming pool up there on Petit Jean. The kids will probably want to do that. There is also horseback riding!
We're going up for the Petit Jean Easter Egg hunt in a few weeks, I'll see if I can stash some eggs.

Those landing lights really pick up the runway don't they? That is so interesting how people are comfortable and uncomfortable depending on how they learned to fly. We're going to have some story telling around the fire at that fly-in let me tell ya! I'm sure you'll be convinced I'm a total idiot before you leave there! I've been wondering about that lately myself. Wheel skiing is out also, since opinons were voiced about that. Duck roundup is officially counceled!
George, should I set up a generator 1/2 way down the runway at Petit Jean International. Then use my Christmas lights for runway lights. Is this a bad ideal? A lantern at both ends would be more than sufficient for any B on the darkest nights!

Oh, here is something interesting! There are 7, 170's member's n Arkansas. Only 4 have 170's.. Following the links to FAA Registry, I pulled up Arkansas registered planes 3840 total. Then by county, I was able to find every registered 170 in Ark.. Would you believe there are 15? My wife put 15 letters n the mail today, encouraging them to join us.
Will be interesting to see if we get a response!
Wish it would warm up here, still minus 39 f..
Dave