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  #61  
Old 07-06-2017, 09:15 PM
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Blain Blain is offline
 
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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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  #62  
Old 07-07-2017, 08:37 AM
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Quote:
Originally Posted by Blain View Post
When 1 (groove) remains? Wouldn't that assume consistent wear pattern?
Safe enough assumption for repeated sets on the same airplane, but the wear pattern shown here many not be true for another airplane.

Quote:
At the bottom of groove there will only be 3/16" between me and running off the side of the runway
The "run 'em until you see cord" camp is down to 1/16". However, we have no direct correlation between tire carcass thickness and the chance of a flat tire. Offhand, it does not appear that carcass thickness alone is an issue given a clean running surface. When we worry about flats due to thin tires, I think we're really talking about foreign object damage...and then the size and shape of the object becomes an entirely random factor.

Same category as primer, really
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  #63  
Old 10-19-2017, 10:41 PM
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Blain Blain is offline
 
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Default 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.



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  #64  
Old 10-19-2017, 11:22 PM
BobTurner BobTurner is offline
 
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Clearly, you’re not a fan of tire rotation.
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  #65  
Old 10-20-2017, 12:57 AM
scsmith scsmith is offline
 
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Quote:
Originally Posted by Flying again! View Post
The T-38 tires have a red cord, when that shows it is time to replace them.

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
Wow, X-24B, that takes me back a ways!
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  #66  
Old 10-20-2017, 01:13 AM
scsmith scsmith is offline
 
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Default 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?
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  #67  
Old 10-20-2017, 06:51 AM
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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.
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  #68  
Old 10-20-2017, 11:53 AM
scsmith scsmith is offline
 
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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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  #69  
Old 10-20-2017, 09:41 PM
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Blain Blain is offline
 
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Quote:
Originally Posted by scsmith View Post
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.
I know the community has beat up the alignment issue but now I'm addressing my wear pattern. Maybe Steve or Dan can weigh in. I aligned per Vans instructions using laser levels out 30'. The toe was -0-. I attribute my particular wear because of a large amount of taxi time both prior to phase 1 and due to the hangar is a mile from departure end of calm air runway.

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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  #70  
Old 10-20-2017, 09:53 PM
maus92 maus92 is offline
 
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Quote:
Originally Posted by bret View Post
Forget where I saw this interesting fact, but, 90% of all flats happen within the last 10% of tread depth.
I can confirm this....
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