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  #31  
Old 11-22-2016, 09:31 PM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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John,

I don't know if a flat would ruin a wheel pant, but I suspect it might. I helped a guy with a tire that went flat in his hangar. We had to jack up the wing just to get to the wheel pant bottom screws to get it off.

The wheel pants look great, but from a practical stand point they don't seem to be worth the expense and maintenance complications. --- And yet mine are still in place. I guess it's like my bad comb over --- looks good to me!😜

Rich
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  #32  
Old 11-23-2016, 05:47 AM
todehnal todehnal is offline
 
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Thanks John. Desser has both, and the 6 ply is only $5 more, but the 6 ply tires are on a short 7 day waiting period. I guess I will just wait for the 6 ply. My thoughts were that I could run just a bit more pressure, and still retain the cushion with the 4 ply tires. My guess is that the 4 ply would be a tad lighter as well. Appreciate your thoughts.........Tom
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  #33  
Old 11-23-2016, 06:41 AM
Dave12 Dave12 is offline
 
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Quote:
Originally Posted by RFSchaller View Post
I guess it's like my bad comb over --- looks good to me!😜

Rich
I hear these are becoming fashionable?
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  #34  
Old 11-23-2016, 08:32 AM
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Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by Dave12 View Post
I hear these are becoming fashionable?
I didn't know Alec Baldwin flew a 12...
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  #35  
Old 11-24-2016, 08:51 AM
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n82rb n82rb is offline
 
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Just a little thinking here, pressure sensor, Bluetooth module, now to get it to talk to the dynon and garmin units..... fun project to work on on overnights......

Bob burns
Rv-4 n82rb
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  #36  
Old 11-24-2016, 08:59 AM
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JPalese JPalese is offline
 
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Default RV-12 Maintenance Manual on Tires

[quote=Jetguy;946169]I recently put on my third set of main tires at 632 hrs. I thought I would
try something new and changed from the Desser Aero Classic All Weather tire to the Desser Elite retreads.

FWIW:

Page 5-8 of the maintenance manual (Rev 4) specifies "All three tires are 5.00 x 5 size, either 4-ply or 6-ply tube type aircraft tires are acceptable."
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  #37  
Old 11-24-2016, 11:58 AM
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DanH DanH is offline
 
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My go-to reference for aircraft tires is the Michelin Aircraft Tire Databook. Most of what is found there will apply to other brands in the same sizes. I winnowed the little chart below for 5.00-5 main tires.

Note that inflation pressures may be adjusted downward in proportion to load. For example, a 5.00-5 4-ply has a 31 psi max pressure when unloaded. Max static load is 800 lbs per tire. If we assume 90% of the load is on the mains, an RV-12 at 1320 lbs would load each tire...

(1320 x 0.9) / 2 = 594 lbs

So:

(594 x 31) / 800 = 23 psi minimum pressure to achieve design spec, which is mostly a matter of how much the tire can compress before the rim and bead mash into the carcass. See the "bottoming load" values.

For an RV-12 at 1320 lbs, a 4 ply rating is more than enough. An 1800 lb airplane could maybe use the 4 ply rated tire, but it would be right at the maximum allowable load...

(1800 x 0.9) / 2 = 810 lbs

and thus would need a slight boost in tire pressure:

(810 x 31) / 800 = 31.3 psi

A 6 ply tire on an 1800 lb airplane can run an unloaded tire pressure as low as....

(810 x 50) / 1285 = 31.5 psi minimum pressure to achieve design spec

Note that minimum pressures for both 4 and 6 ply are (as a practical matter) the same, given the same load. That's not a coincidence; they're dimensionally the same. The difference is burst pressure (maximum strength, if you will), not operating pressure.

Remember two details. First, these are unloaded pressures. Add 4% for rated load.

Second, these are tire manufacturer's numbers. An airframe designer or wheel engineer may specify something different for reasons of their own, and as an EAB operator, you also have a say. For example, as Scott noted recently, a higher than specified tire pressure may increase airframe component load, given a maximum smash into the runway. A landing gear analysis says running tire pressure at max (for example, a 6-ply at 50 psi) does in fact increase component load, but the actual difference is not large. Me? I'll take the higher pressure and try not to crash into the runway with maximum gusto.

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Last edited by DanH : 11-24-2016 at 07:17 PM.
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