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Safe margin of tread wear

Blain

Well Known Member
Been spending most of my time shooting landings. Have tire wear to show for it.

Not sure how far to run these out before they become subseptible to puncture. Flying off good pavement but there is always the chance of sharp rocks, etc.

Do I wait until cord is showing? :eek: Haven't done that since high school.
 
Well, I would have flipped them a few hours back, to even out the wear. Now,
I'm not sure. Can't tell how thin the area is with no tread.
 
If both tires are wearing the same, which from what I can see is on the inside, I'd pull them both and remount to where the less tread side is on the outside. Still plenty of life left in that direction. Otherwise, I'd be ready to order new rubber.
 
Tires

Good Year says when the tread grooves are no longer visible . The first set I took off had minimal tread left . I cut the tire on the band saw so I could see and measure how much rubber was left . My observation was Good Years recommendation is a good rule of thumb .
A set of tires cost about the same as a tank of fuel , puts it in perspective . Don't run out of either .
 
Most RV tires wear on the outboard side. I wait until the grooves are just about gone, then flip them and basically have a new set of tread to wear on. When that side is just about through the tread, I change them. The retreads have more rubber after the grooves are gone, so I wait until hey are completely gone on the retreads.
 
Honestly, stuff like this amazes me that it would even be posted, that you would even consider risking so much for so little is beyond me.
JUST REPLACE THE FREAKIN TIRES!
 
I have to mostly agree with Walt on this. Remember that "6-ply rating" does NOT mean the tire has 6 plys. I recommend replacing the tires when the tread is gone.

Rotate the tires when the tread gets low (still visible) on one side. When the tread is low on the second side, replace them.

You REALLY don't want to deal with a blow-out on landing.
 
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+1 for Walt. Preventable down time in not an option on my -10. First sign of worn tire, replace with new. Not worth the time and hassle to rotate direction. The thin side of the tire is still touching the ground. For me, the extra tire tread is one more line of defense against flats and AOG delays.

Just had this discussion with A&P. New tires going on the -10 next month during CI.
 
Forget where I saw this interesting fact, but, 90% of all flats happen within the last 10% of tread depth.
 
I get it

Honestly, stuff like this amazes me that it would even be posted, that you would even consider risking so much for so little is beyond me.
JUST REPLACE THE FREAKIN TIRES!

I agree Walt. I'm probably not going to flip them either. The labor is hardly worth what is left. Aircraft tires are a new experience for me. My last ship had skids.

Really was interested in what to use as an indicator. I guess that indicator is when "smooth"

I should have really lit some passionate responses by asking about toe settings...:D
 
Tire Replacement

I disagree with Walt's very presumptive post. Too bad we all aren't so all-knowing with the desire to control what gets posted.

The original post asked a very rationale question - how do you manage tire wear. I do not replace the tire when one side (the outer) wears first. I monitor tread wear and when the tread gets barely visible remove, reverse and reinstall. When the "new" outer edge tread gets barely visible, I replace the tire.
 
I disagree with Walt's very presumptive post. Too bad we all aren't so all-knowing with the desire to control what gets posted.

The original post asked a very rationale question - how do you manage tire wear. I do not replace the tire when one side (the outer) wears first. I monitor tread wear and when the tread gets barely visible remove, reverse and reinstall. When the "new" outer edge tread gets barely visible, I replace the tire.

Flipping tires is the same method I and no doubt scores of RVers have been using for who knows how long. There doesn't seem to be anecdotal evidence to support this being an unsafe practice. My RV-6 tires get flipped when the outside groove is gone then replaced when the "flipped" groove is erased. This procedure has worked fine on my plane for nearly twenty years. I haven't seen any reason to modify this method.

Having said that, I enjoy performing maintenance on my RV and getting maximum use of the tires. Some RVers (or maintenance shop) may prefer to simply spend money on new tires.
 
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I do not replace the tire when one side (the outer) wears first. I monitor tread wear and when the tread gets barely visible remove, reverse and reinstall. When the "new" outer edge tread gets barely visible, I replace the tire.

I do the same with my RV-6A and the 9 other RV's that I inspect and maintain.
 
I think it's a good genuine question & good on the guy for posting it, not everyone here are rocket scientists!:)
Personally I would swap them around but that depends on the surface you mostly land on. Good condition sealed Rwys etc would mean there are still some landings left (to me). If you do some off field landings as in rough surfaces then it's time to renew.:) Like everything in aviation it's all about calculated risks & finding out what those risks are can sometimes be found by simply asking here:)
 
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Safety?

I wouldn't look at tread wear as a safety issue as much as a convenience (possibly) issue. I have landed on a completely flat tire as have many others. My experience seems to be typical in that there is no problem with directional control. My airplane happens to be an RV-6.

http://www.vansairforce.com/community/showthread.php?t=99878&highlight=Flat+Tire

I do the swap when one side gets thin deal, but was interested to see from the photo in the above thread that there was quite a bit of tread on both sides when I had the in-air flat.
 
On the subject, could be the photo, but the tire looks a bit low on pressure.
Like a radial. Blain, what pressure are you maintaining?
 
I think Walt needs a timeout or perhaps something else;). Glad you posted Blain.

Apparently it's just that I have a little different philosophy on aircraft maintenance than some of the folks here. I wonder how many "frugal" folks that flip their tires to get every last mm of rubber off them can say they have had ZERO mechanical break downs, ZERO out of service time, ZERO flat tires and 100% dispatch reliability for the last 12 years and 1500+ hours. I can assure you it has nothing to do with luck and everything to do with my maintenance practices.

If you can't afford new tires what else have you neglected I wonder?

Anyway that's just the way I see it.

Ok I'll take that time out now...
 
Apparently it's just that I have a little different philosophy on aircraft maintenance than some of the folks here. I wonder how many "frugal" folks that flip their tires to get every last mm of rubber off them can say they have had ZERO mechanical break downs, ZERO out of service time, ZERO flat tires and 100% dispatch reliability for the last 12 years and 1500+ hours. I can assure you it has nothing to do with luck and everything to do with my maintenance practices.

I can, and it has been longer than 12 years.

If you can't afford new tires what else have you neglected I wonder?

Anyway that's just the way I see it.

Ok I'll take that time out now...

Did anyone say anything about not being able to afford new tires? There is no shame in being frugal if safety is not compromised....some would even say frugality is a noble characteristic.

One of the most frugal individuals in aviation designed our beloved RVs. :)
 
One doesn't need to operate a light A/C like an Airliner, on demand maint is a normal way of life for most of us whom live in the real world. I don't plan to have a volt reg to fail but I had one recently, no way I could have seen that coming, but I fixed it. When I hear a wheel bearing become noisy I replace it, some things you can't predict so you do yr best & stay as safe as possible, has nothing to do with being fugal, just being smarter:)
There's an old saying........you don't need to be a cook to boil water!:)
 
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We flip tyres on our crop dusters without a second thought. Timing the flip is important and the tyre needs to be in good order.
 
This post came at a good time for me. The tread on my mains looks about like that picture. I have been remiss in monitoring tread wear, so I really don't know how many landings were made on bald tires, and how much life is left in them. I was going to flip them, but went ahead and bought new ones. I will keep the old ones for emergency purposes, but won't be reusing them.
 
I'm with Walt on this one.

Observation: Nothing makes an aircraft unairworthy quicker and more trivially than a flat tire. No matter what condition the rest of the airplane is in, if you let the air out of a tire you ain't goin' nowhere.

Even without considering any safety issues, the risk of being stranded somewhere far from home for a stupid preventable obvious embarrassing oversight should factor into decision making, especially on an airplane that covers as much ground as an RV.

I rotate, but I don't wait until the worn side is bald before I do it, there's always a bit of tread available. When the second side wears down to the same level: New rubber.

Remember, you're going to buy new tires anyway, we're just talking about when. Delaying it probably isn't saving as much money as you think.

- mark
 
i stopped flipping the tires at this point a few years ago. i found new tires and brake pads are needed at about this time. don't neglect those brakes. :)
 
Time out for a Belief System Alert.

Where is the data connecting tread depth and incidence of flats?

Tread grooves are for liquid escape. Sure, a pointy object (like a nail or thorn) won't reach the tube if the total tire carcass is thicker than the length, but given ordinary objects (pebbles and stones mostly), why should tread depth make a lot of difference?
 
Blain, I'm sure after all of the feedback you will make your own decision on what to do. When you decide to replace them, you should consider the Desser Retreads. This is sample of what you might consider. I have to say after owning my own plane for 20 years, both certified and experimental, these tires have been the best tires I've ever landed on. For the price and longevity, you can't go wrong. Heck change out your tires every year if you want but you won't have to because they last much longer than the ones that I see on your plane now. DISCLAIMER - I DO NOT WORK FOR DESSER OR HAVE ANY CONNECTION TO THEM. THE COMMENT IS BASED ON MY OWN EXPERIENCE.
 
Time out for a Belief System Alert.

Where is the data connecting tread depth and incidence of flats?

Tread grooves are for liquid escape. Sure, a pointy object (like a nail or thorn) won't reach the tube if the total tire carcass is thicker than the length, but given ordinary objects (pebbles and stones mostly), why should tread depth make a lot of difference?

That is why I haven't bought into the concept of tread depth being related to tire failure. The strength of the tire is in the carcass, tread just provides traction and water repulsion. As long as the carcass contains air pressure, we have a tire that will keep the rim off the ground.

I don't worry about tread depth because I rarely fly off a wet runway. When the tread wears off of the contact patch I consider that an indication that the cords can't be far below the rubber and it is time to stop depending on that portion of the tire to be the contact patch. But because my RV-6 only wears tires on the outside third of the tire I have safely used tires since 1999 that have little tread on the inside third of the tire. I just don't see the need to toss a tire that still has half of its service life remaining.

The key is to be familiar with the operational characteristics of our particular aircraft and maintain it accordingly. This is a case where one size does not necessarily fit all. :)
 
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....tread just provides traction and water repulsion.

To be perfectly accurate, tread grooves and other molded patterns in the surface of a tire reduce paved surface traction. Maximum dry traction is found with a smooth tire, aka a slick. I'm just polishing the pins here. Sam likes sports cars, so he knows that little detail. And maximum grip isn't a big deal in our application anyway.

Again, can anyone present a study of tread wear vs incidence of flats?
 
Tires

I was told that there is a Goodyear document detailing how much cord can be showing and the tire is still airworthy.
 
Tires

Disregard my previous post. I found the Goodyear document online. It allows very limited exposure of cord at bottom of a groove but does not allow flat spotting that exposes cord. Very detailed and interesting article. They call for tire replacement for any wear to bottom of groove.
 
Tires

For many years there were surplus aircraft tires available that probably dated to WWII. A lot of these were smooth tires. On homebuilt airplanes they were commonly run until cord showed. This is in accordance with the Goodyear document and there is absolutely nothing unsafe about it. 500 x 4 wheels tires and brakes were used on the Culver drones and were widely available.
awheels was late Nick D'Appuzzo, designer of the PJ260/Senior Aero Sport Biplanes. He sold surplus Culver wheels probably well into the 70's. In the 60's they were under $100 a set and I think this included tires and tubes. The brakes were Goodrich Cub style and not very good. Smooth tires.
 
Tire Wear II

One "what if" that hasn't been addressed during this interesting thread- What if the wear was uniform across the whole tread? No advantage then to flipping. At what point would you replace the tire?

I would run it down to just before the tread grooves disappear.

By flipping, I'm doing essentially the same thing.
 
Apparently it's just that I have a little different philosophy on aircraft maintenance than some of the folks here. I wonder how many "frugal" folks that flip their tires to get every last mm of rubber off them can say they have had ZERO mechanical break downs, ZERO out of service time, ZERO flat tires and 100% dispatch reliability for the last 12 years and 1500+ hours. I can assure you it has nothing to do with luck and everything to do with my maintenance practices.

If you can't afford new tires what else have you neglected I wonder?

Anyway that's just the way I see it.

Ok I'll take that time out now...

While your record is certainly a testament to your workmanship, you could put on new tires every flight and also go 15 years without a failure. You could do the same with any number of other parts. Doesn't mean it was necessary.

I thought this was a valid question. The OP was asking at what point tires become less safe, not "how long can I get away with being a cheapskate".

Replacing something more than necessary doesn't make you any safer, and in the case of maintenance-induced-failures, can actually have the opposite effect. Sure, changing tires is a simple, low-risk procedure, but it is another chance to pinch a tube, improperly torque the wheel, etc.

Chris
 
One "what if" that hasn't been addressed during this interesting thread- What if the wear was uniform across the whole tread? No advantage then to flipping. At what point would you replace the tire?

I would run it down to just before the tread grooves disappear.

By flipping, I'm doing essentially the same thing.

Agree. It is interesting how the Goodyear document says the same thing.
 
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My conclusions

On the subject, could be the photo, but the tire looks a bit low on pressure.
Like a radial. Blain, what pressure are you maintaining?

34 PSI. Part of its life was run at 24 PSI.

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...
 
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....
 
When I need to flip tires to afford to fly its time to quit.

I don't know why the "can't afford new tires" thing keeps popping up in this thread. Nobody advocating flipping tires has stated they have to flip tires to afford flying.

I didn't want to "Leave good rubber on the table"

Precisely why flipping tires has been a prevalent practice in RV-dom for a long time! :)
 
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I don't know why the "can't afford new tires" thing keeps popping up in this thread. Nobody advocating flipping tires has stated they have to flip tires to afford flying.



Precisely why flipping tires has been a prevalent practice in RV-dom for a long time! :)

Alright, In my defense, lets analyze what happens when we flip-I'm not alleging its wrong, just setting up an understanding.

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
 
Alright, In my defense, lets analyze what happens when we flip-I'm not alleging its wrong, just setting up an understanding.

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.....

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

Pilot's discretion.

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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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.

I put 7 hours of taxi time on it before lifting off. And since I've done nearly 120 landings of which were no doubt hard on the tires. They sure were on me:D

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

Ditto or +1
 
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