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My conclusions
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This thread drifted from the original premise. Maybe I should have phrased the question better. Probably should have asked; "How do you identify the wear life phases of New>Safe>Marginal>Dangerous?" I'm frugal to a point but I don't like changing tires. When I need to flip tires to afford to fly its time to quit. Aircraft tires are new to me. I was looking for guidance not gained in the build. That being "Do aircraft tires have some means to identify maximum wear?" I didn't want to "Leave good rubber on the table" The opinions expressed here do make me think about the various factors. Primarily safety. Not to mention entertainment value:D BTW, changed that one out last night along with the brakes. |
Just a data point. There's a thread here on vaf that discusses psi. I run 45 psi in the retreads on my RV8 as assurance against pinch flats or snake bite. I do get some wear on the sides as depicted but not nearly as severe. By the time mine are ready to flip it's time for new tires. Which reminds me...
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I'm just glad...
We aren't using the T.O. (Technical Order) that dictated not replacing the skinny little main tires we had on the T-38 (155 KIAS final approach speed!) until the FOURTH cord was showing!
By the time they got down to the 3rd cord, they were way worse than slicks and talk about fun stopping on a wet runway! (no anti-skid, either! :eek:) Good thing I was a bullet-proof 23 year old IP and didn't lose sleep over minor issues like tread depth at the 3rd cord level! Carry on... |
If looking for official guidance, even though it is an Advisory Circular and not an actual FAR, AC20-97B stipulates changing a tire when any portion of the first cord layer is showing....
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Do we agree that some wear happens across the face, with more on the outside? If so, then flipping the tire in my picture some wear will occur on the already bald side? Back to my original question-how far can it go? If flipping is going to be the plan, than the tire should be flipped before the tread depth is gone. Ideally estimating how much it will take to get "Even" with the high side. We agree so far? If so, the tire in question, in my estimation, was too far gone to justify flipping. The question of flipping demonstrates the old adage "How was copper wire invented"? Answer;2 pilots fighting over a penny. My choice as I'm sure many others would be a time vs. value decision. Jeez, I just wondered how many landings I could squeeze out of a tire..... |
Kit tires versus others
Caution: Thread drift.
Correct me if I am not remembering correctly, but aren't the tires that Van supplies in the kit known for short lives? Blain's airplane is new, I believe. |
While taking the tire off the wheel and flipping will buy more time, for the time it takes to do all that work I'd rather just put a new tire.
Carl |
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The reason I got more involved in this thread than I wanted was the very strident post early on that implied flipping tires was a stupid thing to do. As one VAFer stated, that was a presumptuous position to take which tried to squeeze every aircraft owner through the same template. To make it more interesting...the outside edge of the left tire on my RV-6 wears nearly twice as fast as the right tire. So not only do I flip tires, I rotate them to even out wear. I almost need to buy tires in threes instead of pairs. In 45 minutes I can remove the wheel pant, break down the wheel, flip the tire and put everything back together so time isn't an issue for me. I enjoy working on my planes.....my labor rate is very low. :) But that is my situation and it won't apply to many all planes (does seem to apply to a lot of older -6's, however). Do what best suits your aircraft and personal preference even thought it may not be the best protocol for someone else. I'm done. :D |
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Hours?
Brian, How many hours are on these tires?
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I think this is a matter of personal tolerance. Each of us will choose differently. If it bugs you, put new donuts on it and watch for a better time (in your own mind) to flip them. |
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It seems to me that if you flip your tires and install new tubes (as recommended), the increased savings will be at least partially offset by the cost of your parts, materials and labor.
I don't know that I'll flip my tires (Flight Custom III). I may just leave them on until they have been used up, then buy new. They aren't that expensive... ~Marc |
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My project at Test Pilot School was to modify a T-38 with a larger speed brake and use it to decrease the L/D to simulate the X-24B lifting body approach ( about a 24 degree glide slope). When I briefed the Flight Safety Board one of their requirements was to use old tires instead of new. The thought was that old tires had been heat cycled many times and new tires had too much tread for the high speeds we were touching down, increasing the chance of tread separation due to centrifical force. We crossed the threshold at 230-250 knots as I recall. After the last approach when at Bingo fuel the closed pattern and normal 3 degree approach seemed way too low:D |
If you are doing circuits go to a grass strip, stay off the seal as much as possible, rotate the tires and there will be plenty of life in them yet
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When 1 remains? Wouldn't that assume consistent wear pattern?
At the bottom of groove there will only be 3/16" between me and running off the side of the runway- if lucky. Think I'll pull them when tread disappears. I would have thought the carcass to be a bit more substantial. Thanks for the visual, Dan. |
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Same category as primer, really ;) |
Got my answer the hard way
Seconds from taking the active after run up. Ship would not roll. Figured out I had a flat and forced it off the in use area. Seemed like the right thing to do. Only about 100'.
Don't know yet what caused it but it went flat in about 5 minutes. Will autopsy tomorrow. In the meantime I have glass work to do. BTW that is a jack point product with a modification. ![]() ![]() ![]() |
Clearly, you?re not a fan of tire rotation.
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Why not fix the uneven tire wear?
On thing I find surprisingly lacking in this discussion is any suggestion of fixing the tire toe angles so as to have more even tire wear.
When I built my RV-8, I did very careful wheel alignment measurements, and shimmed the axles accordingly. It took a rather large shim on one side, a thin one on the other. But the result was that I measured essentially zero toe-in. My tires have always worn predominantly in the middle, and the wear is symmetrical on the two edges, on both tires. I removed the original 500-5 tires supplied in the kit at 100 hrs, with still 1/2 tread depth, and replaced with 380-150-5 tires. Now at 450 hrs, the inner tread grooves are getting pretty shallow, but still there. I guess its not easy to adjust toe-in on the other RV's with the round legs, but on the RV-8, why not just shim to zero toe-in and enjoy even, symmetrical tire wear, and 'normal' handling qualities? |
Steve, did you do the alignment with fuselage level or tail down? Camber and toe, or just toe?
Positive or negative camber when level would add toe in or toe out with the tail down. The gear alignment we do during construction is equivalent to a longerons level, toe only measurement. |
I ended up doing the toe adjustments with fuselage level. I made no adjustments to camber. I thought about this a long time, and there are two competing issues.
1. Wheel landing in more or less level attitude, misalignment causes a lot of scrubbing at wheel spin-up, even though there is fairly little weight on the wheels. Also this is the point where misalignment can cause more squirrelly behavior. 2. 3-pt attitude is where there is the most weight on the wheels, so presumably a lot of the tire wear occurs here. In the end, I let point #1 win, and that's where I did the alignment. There wasn't much camber sitting in the hangar with weight on the wheels, but there would be at touchdown. Ultimately, I either made the right choice, or got lucky, because the tires wear symmetrically. I wouldn't say 'evenly', since they wear more in the middle, which you have to expect with a more or less round tire profile. |
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Now I'm wondering if I could shim out some of the camber and would there be any adverse handling characteristics? |
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However, lateral friction on paved surfaces is HIGHER with tread grooves because they tend to dig in slightly. For nosewheel aircraft with the tread on the main tires, this promotes straightness down the runway, but for taildraggers, this increases, slightly, the tendency to depart from straightness in the direction of a ground loop. I worked this out some decades earlier and ordered a pair of smooth tires for my Cessna 180. They proves so successful that I continued for well over 1,000 hours. I've landed with them on dry pavement, on wet pavement, on glare ice, on dirt, on grass and on gravel. And on a beach down in Baja. In every case they proved honest, reliable, and easier to control than treaded tires had been. Smooth tires on pavement are a bit closer to what landing on grass is like, in terms of lateral control. Tire wear was superb. The tires were custom-ordered retreads from Wilkerson Tires in Crewe, VA. I discontinued doing this after they sent me two sets in a row with very poor sidewalls. Now the handling is back to normal (i.e., worse), and I've got to be a bit more careful. I suspect that treaded nosewheel tires (that is, on the nosewheel rather than the mains) might tend to be a factor in nosewheel shimmy, but have nothing concrete to base that on. On tailwheel airplanes, I do recommend that the tailwheel be treaded. Easier on the C-180, though than our RVs. Dave RV-3B, skinning the fuselage |
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