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RV-7A front tire problem

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chuckh1197

Member
I am having a problem with the front tire on my RV7A. I have had 3 tire failures in the past 3weeks. 1st was in Reno . I repaired tube which had a large break on side of tube. Had similar failure in same place as repair. Then had failure today in Dominican Republic on landing. I am very conscious of no nose wheel contack and all failures have been on roll out.

Tire pressure is 30psi.

Tire rotates by hand pressure but does not rotate freely when spun. Any ideas.

Cant keep changing tires!
 
I have two recommendations, and I am assuming that the leaks are on the sidewall, the widest portion of the tube. They seem to come from a spallation of the inner tube as it moves around against the tire.

First, use LOTS of baby powder. I mean, perhaps a tablespoon. Make sure the entire surface of the inner tube is white. Second, keep the air pressure towards the high end (which it appears you are). I can never remember exactly what I use (it is written on the wheel), but I think it is 35. This is minimize flexing of the sidewall, and it has the added advantage of lowering risk of flipping. When initially inflating to seat the beads, be sure to completely deflate again, so that the inner tube can relax where it stretched across the moving beads.

I had about three flats in the first 250 hours, and none since doing these two things. I think the baby powder will fix your problem.

See another thread that I started about one method for installing the tire without risk of mashing the innertube. On that picture, you will see how much baby powder is being used.
 
Are they tube or tire failures? If it is a tube fail, it is not good to repair and is best to have an extra tube with you. They are hard to find. But most airports have 5X5 tubes for the mains.
If it is the tire that is failing, then check the clearance on the wheel pant. A finger down the side and 1 1/2 fingers at each end. Check the inside of the tire with a rag, wipe around in there to see if there is anything that can cut the tube. GOOD LUCK
 
Nose flats

I can't reinforce what Alex P says enough. I had the exact same problem you are having. Lots of nose flats early on, if fact 3 in the first 130 hours. The solution seems to be using so much baby powder it's almost scary and increasing the tire pressure. The problem is that too much tire pressure can lead to nose wheel shimy.


A buddy of mine has a vari-eze and the mains are the same size as our nose wheel. I talked to him last year about the exact same problem, cuts on the side of the tube. He said that early on all of those vari-platic guys were having the same problem. Now I guess they all run like 40 or 45 psi, but I think this is just too high for the RV nose wheel. It's way over Van's specs, but I suspect Van is trying to run pressures too low to try to prevent nosewheel shimy. So personally I run 35psi and have not had a problem since (but I do have an extra tube in the back).
 
That many failures in such a short time. I wonder if some how when you are installing the tube that it might be getting pinched during assembly. It doesn't take much to pinch it and cause a weak spot or a tear.
 
like everyone ...
1. LOTS of baby powder
2. Up the air pressure to 40psi
3. check the inside of the tire for a rough spot that can stick the tube
 
Thanks

I will try the baby powder and a little higher inflation. The cut is on the side wall of the tube about the same spot in the tube from the valve stem. I just put on a new tube and tire which we brought with us just in case. I would suggest if you are going anywhere outside US to take a tube and maybe a tire with you. No chance of getting one of these anywhere. Just before I left Reno I spent several hours and contacted every tire repair, tire shop , RV, ATV store and no one has this size tube.
 
Chuck,

When you put the new tube on take the valve stem out, but don't inflate the tube at all. Leave it flat. Coat it with powder, slide it into the tire and then put the valve through the rubber grommet on the wheel. Lay the wheel half flat on the table and make sure the tube is seated over the wheel and clear of the aluminum mating surface. Have your traveling partner carefully place the second half of the wheel on until you hear the mating surface come together (metal on metal). While holding the halves together put the bolts in and tighten them, so the halves are held together. My tube had gotten pinched between the halves and I suspect that may have happened to yours. I have flown two more years on that new tube and haven't had any problem since. I do carry a new tube with me just in case, though. Good luck and call me (970-259-5988) if you need any of this clarified.

Jim
 
chuckh1197 said:
I will try the baby powder and a little higher inflation. The cut is on the side wall of the tube about the same spot in the tube from the valve stem. I just put on a new tube and tire which we brought with us just in case. I would suggest if you are going anywhere outside US to take a tube and maybe a tire with you. No chance of getting one of these anywhere. Just before I left Reno I spent several hours and contacted every tire repair, tire shop , RV, ATV store and no one has this size tube.
Click to expand...
I had the same problem. The area you indicate is the same as mine. Some of these shin fin tubes have a built in defect. That is what i found. I posted about this sometime back.
 
I have been running for 3 years, 700+ hours and never had a problem. I also replace the tire/tube every year whether it needs it or not (cost is about $50). Lots of talc, careful assembly and 40-45 psi religiously.
 
JAT said:
Chuck,

SNIP My tube had gotten pinched between the halves and I suspect that may have happened to yours. SNIP

Jim
Click to expand...

I've done this, but the originator of this thread had a different problem. I agree that there is a flaw in the tube's sidewall, and baby powder seems to be the only thing that prevents the spallating (chewing out little bits until it leaks) on the sidewall.
 
n468ac said:
like everyone ...
1. LOTS of baby powder
2. Up the air pressure to 40psi
3. check the inside of the tire for a rough spot that can stick the tube
Click to expand...

I agree with #1 and #3 but I strongly disagree with #2.
You can not indiscriminately use 40 PSI in the nose tire of any trigear RV.

A high nose tire pressure is a major cause of nose wheel shimmy.
The higher the pressure, the more round the contact area of the tire becomes and the less actual contact footprint the tire has on the ground/runway.
You need footprint/contact area to produce a friction resistance to the tire twisting...this friction helps reduce any tendency for shimmy.
The actual pressure you should use varies depending on your airplanes empty C.G. (amount of weight on your nose wheel). If you have a smaller engine and a wood prop, 40 PSI would probably be a very bad choice, especially on a 6A. If you have a heavy engine and a constant speed prop. then you can use a higher pressure.

I usually adjust the pressure so that when parked on a smooth level surface, all of the tire area that is between the two outboard most tread grooves is contacting the surface. Some people may get away with running higher pressure than that, but I believe they are pushing the limits and have a very small margin between no shimmy and a small disturbance that can set it off.
 
rvbuilder2002 said:
You can not indiscriminately use 40 PSI in the nose tire of any trigear RV.
Click to expand...

Have you tried higher air pressure? We have less nose wheel shimmy at higher air pressures.

How freely does your nose wheel turn aournd the axel and is your break out force set correctly?
 
n468ac said:
Have you tried higher air pressure? We have less nose wheel shimmy at higher air pressures.

How freely does your nose wheel turn around the Axel and is your break out force set correctly?
Click to expand...

I have worked with RV's for 20 years (probably at least a dozen A models) and this is what I have learned. Yes I have tried high pressures, low pressures, different breakout force adjustments, etc....I have found that the process I mentioned in my other post for setting the tire pressure works for all A models, giving a good resistance to shimmy but still a good margin for tire stiffness (ground clearance).
Once the ideal pressure for your airplane is determined, then you can just use that pressure value when airing the nose wheel tire. As I posted before...I think recommending a one pressure fits all airplanes airpressure is a
bad idea (there is a wide range between what weight is on the nose wheel, and the tire pressure has to be adjusted in accordance with that weight).

If you had better experience with higher pressure. I wonder if it is because your tire is slightly out of round or shape side to side, which is maybe improved by raising the pressure
 
rvbuilder2002 said:
Once the ideal pressure for your airplane is determined, then you can just use that pressure value when airing the nose wheel tire. As I posted before...I think recommending a one pressure fits all airplanes airpressure is a
bad idea (there is a wide range between what weight is on the nose wheel, and the tire pressure has to be adjusted in accordance with that weight).

If you had better experience with higher pressure. I wonder if it is because your tire is slightly out of round or shape side to side, which is maybe improved by raising the pressure
Click to expand...


I agree with you that you have to experiment with different pressures with YOUR plane, as we know there are many different configurations that make it hard to use one pressure for all RV?s. I just wanted the forum to know that higher air pressures have helped some of us.

As for our current nose wheel ? we just replaced it this fall with a new tire and tube direct from vans. Still using the higher pressure with good results ? but it could also be our take off and landing technique. We started using a higher pressure under the though that the shimmy was caused by tire dragging from being under pressure.
 
Thanks for all the good info

I have a fairly heavy plane with 200 IO360 and constant speed prop. Put a lot of baby powder in, inflated and deflated , made sure nothing pinched this time. Will let you know how it behaves. Put in about 38 psi now.
 
Still having a problem

Flew to Portillo yesterday and landed , no problem
Upon landing back in Puerto Plata, on roll out I turned off runway and bam another flat. I had put 35 lbs in. lots of baby powder. Dont know what to do. I have my last good tube. Just ordered another tire and a couple of tubes from Aircraft Spruce and having them fedexed down. Same failure on side of tube not pinched. I am just wondering if wheel is folding on turning. Breakout force is about 26 lbs. Dont know how to solve this .
 
Well, I guess you just proved me wrong...

Have you looked very carefully at the tire to see if there is a little burr or something in it?

No sign of scuffing on the outside of the tire in the location of the innertube's hole?

Hmmm. Changing the tire would seem to make sense.

With regard to your comment on turning - how fast do you taxi while making turns? Turns should be made such that you feel essentially no lateral acceleration (not like in a car). I am not sure how that could do it anyway, but good practice would suggest slow speed turns anyway.

Good luck!
 
Are the tubes that keep going flat the same brand. I had the same problem that you are having and My tubes were the shin fin or what ever tywan tubes. I still think that some of them have a manufactures defect in them. They kept going out in the same spot and you would think it was the tire, but you know what you couldn't put that tire back in the exact same spot. Think about it.
 
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