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Flat Tire Woes - Defective Tubes?

R

rv7adriver12

I'm New Here
I have had 4 flat tires in the last year on my RV-7A, all 3 gear. In each case, a new tire and tube was installed. The tubes seem to be good for about 30 landings before a pin hole leak forms in the side wall of the tube. I am installing with tire talc, the wheels are new with all surfaces smooth. Wheel halves are torqued and tires inflated to about 26 psi in mains, 22 or so in nose. I know tubes are not being pinched during inflation. Is anyone else experiencing this problem? I seem to be getting defective tubes. I'm working with Desser to try and identify the problem.

Gary
 
45 in the Mains and 50 in the nose should solve your issue, you're running way to low pressures, nothing defective about the tubes IMHO. :)
 
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Pressure

I agree, tire pressure is too low!
I'd say at least 40, 45 sounds about right.
 
I agree on the pressures, just be a little wary as you increase the nose pressure, you may get shimmy.

Also, quadruple the amount of talc that you are using. I've found talc to be an important variable. The first few years I thought I was using talc, but had 2 or 3 flats on the nose, all with 40ish pressure. After that, I've been using a ton of talc, zero flats.
 
50 psi RV7, 130 hrs, no flats, tread looks new
. 90% landings are on paved run ways. 1 year this july.
 
Hmmm. All this tire pressure talk is disorienting. I kind of went by the Cessna 150 which is similar weight and the same size tire, in some versions. 30 PSI is recommended and that has always been the starting point for my RV-6. When it gets down to around 20, I air it up.

Maybe I need to open my mind a bit. I did have an unexpected flat a while back with no obvious puncture and I do seem to wear out tires pretty quickly.

Just aired my mains up to the unheard of value of 35 PSI. I'll see how that goes.
 
Flat Tire Woes

Thanks all for your quick response. I spoke with one of the Desser tech reps today who has worked with the Van's factory. He also was very quick to point out that I'm running pressures way too low. He said pressures should be 40-45 for the mains if using 6 ply tires, which is the ply rating Van's recommends, and 50-55 for the nose with the newer 2 rib higher ply tire. I was running 26 in the mains, slightly less in the nose, because when I asked Van's what pressures they recommend for a -7A, I was advised that is what they use. According to the Desser rep, he said they should have asked what ply I'm using. The pressures quoted by Van's are said to be in the ball park for a 4 ply tire - not 6. The pressure he said is very ply dependent. So I'm again installing new tubes and will hope for better luck. Thanks again for all the advice, which further confirms. :)

Gary
 
n5lp said:
Hmmm. All this tire pressure talk is disorienting. I kind of went by the Cessna 150 which is similar weight and the same size tire, in some versions. 30 PSI is recommended and that has always been the starting point for my RV-6. When it gets down to around 20, I air it up.

Maybe I need to open my mind a bit. I did have an unexpected flat a while back with no obvious puncture and I do seem to wear out tires pretty quickly.

Just aired my mains up to the unheard of value of 35 PSI. I'll see how that goes.
Click to expand...


Be aware you may get some main gear shimmy at 35 psi in the six.

George
 
rv7adriver12 said:
Thanks all for your quick response. I spoke with one of the Desser tech reps today who has worked with the Van's factory. He also was very quick to point out that I'm running pressures way too low. He said pressures should be 40-45 for the mains if using 6 ply tires, which is the ply rating Van's recommends, and 50-55 for the nose with the newer 2 rib higher ply tire. I was running 26 in the mains, slightly less in the nose, because when I asked Van's what pressures they recommend for a -7A, I was advised that is what they use. According to the Desser rep, he said they should have asked what ply I'm using. The pressures quoted by Van's are said to be in the ball park for a 4 ply tire - not 6. The pressure he said is very ply dependent. So I'm again installing new tubes and will hope for better luck. Thanks again for all the advice, which further confirms. :)

Gary
Click to expand...

Desser (i use their Monster retreads) could make this a lot easier if they weren't so coy about tire pressures on their tire pressures for RVs page. I mean, geez, if they're giving recommendations out over the phone...
 
sailvi767 said:
Be aware you may get some main gear shimmy at 35 psi in the six.

George
Click to expand...

~35psi works perfectly fine in my -6, easy to roll, plus not rock hard on landings either. Over 40 and higher, main gear shimmy does begin to show up, so I usually inflate to 38 psi and when it gets down to around 30, I'll fill them up again. I do have wooden stiffeners installed on the gear legs.
 
45psi all around on my 7A. No shimmy.

2 years and approx. 250 landings on the original Aeroclassics.

Planning to replace mains in Sept.

The nose tire is still going good. Not sure when that one will need replacement.
 
Flats

My brother and I were getting flat tires on our RV-7A. The flats are caused by the tube abrading inside the tire. We increased the tire pressure on the mains to 35 - 40 PSI and replaced the nose wheel with a Berringer tubeless wheel and tire and have not had a problem since. If I had the $$ I would get Berringer main tubeless main wheels and tires too.
 
Tire gage

Check to be sure gage is accurate. I have a gage integral to the refill valve. Something seemed wrong after a few fill ups and I tested pressure with another gage and it was 15 psi too low. The gage on the refill valve was defective, it was a Harbor Freight model, go figure.

Cheers
 
from our own experience, i can only state that there are quite a few variables...

we just replaced our first set of original main gear tyres at 240ish h with 450+ landings. even wear, and not even fully spent, just coincided with annual/250h inspection and brake pads were at the same wear level, could have gone maybe another 50 landings or so...

replaced the default tubes very early on before first flight with michelin airstop tubes after we had to constantly reinflate.
always kept >35, around 40psi. 45psi in the nose gear.
nose gear still looks like almost new.
landings only on asphalt.

now, with the new tyres (6ply, have to look up the brand), despite going to 45psi, they still sit, look and feel "low". don't know yet how they will hold up, but i fear the tubes and tires may "interact" more this way.
will likely have to inflate more.

bottom line, psi likely shouldn't be a constant to go by.
 
I run 40-45 psi in the mains and in the nose of my RV-7A. Be sure to use real tire talc, and NOT Johnson's Baby powder. Baby powder turns to small rocks over time, which will cause flats. Tire Talc is a much finer powder, but even used in excess, can cause the same issue over time. IMHO the tube and tire inside should just have a light coating, nothing more....
 
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