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  #1  
Old 07-27-2012, 06:18 AM
Bob Axsom Bob Axsom is offline
 
Join Date: Mar 2005
Posts: 5,685
Default Tire Problems

I like the shape of the Air Trac 500-5 tires for my application. The tread is rounded (a sectional cutaway would have the profile of an inflated inner tube) and I can closely fit my subfairings to them without any pressure points during operation. However, I have recently had two right main landing gear flat tires. The first was on 4-21-12 on the way home from the Hill Country Air Race and the second was on 7-23-12 on the way home from the AirVenture Cup Race. In both cases the middle of the tread was worn through completely in a spot an inch or more in diameter. After the first flat I went to an Air Hawk tire which has a square profile. I installed it and it didn't touch the subfairing. I was a little concerned but after safe operation with the subfairings since I made them and a successful landing I though it would be OK. I was wrong. On a subsequent landing with a little more stress the square sharp cornered flat tread caught the edge of the subfairing and caused significant damage to the subfairing. It required packing modeling clay around the tire and building it up again with new fiberglass. In some unrelated testing I found that the MLG subfairings were good for around 1 kt so I am not going to abandon them. I bought a replacement Air Trac and all seemed well again until the hot landing on 7-23-12 which instantly destroyed it and damage the sub fairing again (ground the bottom off on the concrete).

This obviously will not work for me. I looked in Aircraft Spruce's catalog to see what other tires had a rounded profile. I bought another Specialty Tires & Tubes Air Trac ($62), a Goodyear Flight Special II ($97.85) and a Goodyear Flight Custom III ($164.75) with Air Stop tubes for each (Total $531.60). All three are 6 ply rated.

I intend to come up with a good solution for myself but I thought I would share my findings. The Air Trac tires are very thin from the surface of the tread to the inside of the tire. I think that is an important parameter but I do not have an accurate way to measure it at this time.

I weighed the tires and came up with these numbers:

Air Trac = 4.5 lbs
Flight Special II = 5.4 lbs
Flight Custom III = 6.6 lbs

I photographed them and when they are grouped together the Air Trac is the one on the left and the Flight Custom III is on the right.




Note the 120 mph marking

Note the 160 mph marking

There is no speed marking on the Air Trac tire that I could see.



That is all the information I have at this time.

Bob Axsom

Last edited by Bob Axsom : 07-27-2012 at 11:58 AM. Reason: Typo
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  #2  
Old 07-27-2012, 07:40 AM
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hydroguy2 hydroguy2 is offline
 
Join Date: Sep 2006
Location: Townsend, Montana
Posts: 3,179
Default

When I was just learning to drive...actually before I was driving, My Dad (who was a long haul trucker at the time) said "buy the best tires you can afford. Flat tires sux!"

So I'm running the oversized Wilkerson Retreads. They are stiff and wear like iron. They are heavier and I installed the pants higher for dirt/strip, so probably costing me some speed. BUT no flats. I would guess, the stiffness would allow a person to fair them much tighter and add subfairings.

remember: flats sux
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  #3  
Old 07-27-2012, 07:43 AM
sailvi767 sailvi767 is offline
 
Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,388
Default

Bob, You have a lot more experience with this kind of stuff then I do but a single round worn spot in the middle of the tire sounds a lot like a possible dragging brake on touchdown. The fact both were on the same side also supports the possibility. Any chance the brake calipers are not retracting or another malfunction in the parking break valve ect..? I would at least double check everything.
It also sounds a lot like the result you see with a catapult shot and the parking brake set. I think we can rule that one out in this case!

George

Last edited by sailvi767 : 07-27-2012 at 07:46 AM.
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  #4  
Old 07-27-2012, 08:02 AM
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SmilingJack SmilingJack is offline
 
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Location: Hilton Head Island
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Bob, what are you using to Jack the aircraft when this happens away from home base?

I keep worrying about that kind of thing and not sure what I would do with my 8.
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  #5  
Old 07-27-2012, 08:43 AM
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Noah Noah is offline
 
Join Date: Jun 2007
Location: Rhode Island
Posts: 952
Default

Quote:
Originally Posted by Bob Axsom View Post
I think that is an important parameter but I do not have an accurate way to measure it at this time.
I think your C-Frame or DRDT-2 could be used to get a pretty good measurement on this Bob! Just measure the depth the plunger goes before contacting the tread...
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  #6  
Old 07-27-2012, 11:54 AM
Bob Axsom Bob Axsom is offline
 
Join Date: Mar 2005
Posts: 5,685
Default This is in strictest confidence

Quote:
Originally Posted by SmilingJack View Post
Bob, what are you using to Jack the aircraft when this happens away from home base?

I keep worrying about that kind of thing and not sure what I would do with my 8.
I do not carry anything to handle that situation. Airports with an FBO will be able to take care of your needs typically. One thing I found is helpful seriously, is a telephone of any kind to call for help. Who do you call? Well, in April I called 911.

This is just the kind of improvisation I do when faced with the problem in the worst case. Everyone else should get professional help. This is not a recommended procedure, it is the kind of irresponsible behavior you should avoid to prolong your fragile existence.

The tire is a different problem but if I have ground transportation, money or credit card and I can use available materials to build a stable platform under the wing tie down (my lift point) to a level that will allow a car jack to lift it. It is dangerous and with a tail dragger I suspect I would need to stabilize the plane with a tail tie down of some sort but what I typically do is put down a 3/4" thick piece of plywood as a base then lay two pieces of 2x4s not less than a foot long in parallel on the platform several inches apart, followed by two more such 2x4s parallel to each other on top of and perpendicular to the first two, then two more in log cabin fashion until the stack is high enough for the jack to work its magic. At that point I cap the stack with another piece of 3/4" plywood and if I have done it right I have a very stable base to put the jack on. Then I saw a notch in a short piece of 2x4 to accommodate (fit) the tiedown ring as the jack to airplane interface. I put the the jack and the interface block on the platform with careful alignment and slowly jack up the plane monitoring the alignment and the situation for any indication of instability knowing that the higher the jack is extended the greater the risk of it tipping over, puncturing the wing and injuring me.

If I am on dirt or grass like off the side of a runway I can build a support platform to my lift point then dig the ground out from under the wheel.

Bob Axsom
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  #7  
Old 07-27-2012, 12:02 PM
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SmilingJack SmilingJack is offline
 
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Location: Hilton Head Island
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Understood Bob! I won't tell anyone

I'm sure this is one area you wish not to be a "Pro" at!

Thanks for the advice and I'll hope not to have to use it.

Best Regards,
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  #8  
Old 07-27-2012, 12:07 PM
Bob Axsom Bob Axsom is offline
 
Join Date: Mar 2005
Posts: 5,685
Default I believe you have the right idea

Quote:
Originally Posted by hydroguy2 View Post
When I was just learning to drive...actually before I was driving, My Dad (who was a long haul trucker at the time) said "buy the best tires you can afford. Flat tires sux!"

So I'm running the oversized Wilkerson Retreads. They are stiff and wear like iron. They are heavier and I installed the pants higher for dirt/strip, so probably costing me some speed. BUT no flats. I would guess, the stiffness would allow a person to fair them much tighter and add subfairings.

remember: flats sux
I plan to go with the Flight Custom III on the right MLG first and I intend to verify that it can accommodate my flying style. I do not intend to pussy foot around an incompatible situation - I am what I am. I do have to retain the drag reduction of the subfairings so there is more to it than just upgrading the tire as I learned with the Air Hawk earlier.

Bob Axsom
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  #9  
Old 07-27-2012, 01:23 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,065
Default Flight Custom III

I'd been using retreads from Wilkerson Tires for a couple decades with pretty good results. I decided to treat my Cessna 180 to brand new Flight Custom III tires last year.

It looks like these are good for about 150 landings on my plane, then the tread's all worn off. I was very disappointed. I've never had that much tread wear so rapidly.

Dave
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  #10  
Old 07-27-2012, 01:40 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,968
Default JAcking an RV-8

Quote:
Originally Posted by SmilingJack View Post
Bob, what are you using to Jack the aircraft when this happens away from home base?

I keep worrying about that kind of thing and not sure what I would do with my 8.
Sorry for the thread drift, but.....

Search the threads, there are many suggestions.
One great way is to drill the wheel pant attachment bracket for the same diameter hole that is in the middle of your stock landing gear. Then, make a short steel rod that fits in that hole and sticks out several inches, and you can jack it with a scissor jack.

I've found that I can lift a wheel off the ground by putting my back under the wing just outboard of the tie-down and lifting. Then, an assistant can slide a block of wood under the steel rod.
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