One tire had always had a slo leak since new ( 1 year old),..the other tire is fine.
Now, it goes flat evry 10 days,.......ideas to fix?
IT is not the valve......thanks for your ideas.
Bruce
St. Croix 
It's leaking around the seal of the rim and tire. You can go and have the tire taken off and try to buff the rim around the seal so that it will seat cleaner. What I did was take it to an ATV shop and have them put a tube in mine. It took about 4 years till it leaked again from saltwater corroding the valve stem on the tube. I just had them put another tube in the tire this year. My other tire never has leaked.
YMMV.
Mike Hill
H20 #907
Take to a tire shop and have them fix it. On mine the valve stems leek every couple of years. They just glue them in and I give them $5.
Put in a tire tube to both tires. You will have no more problems.
Bob 
I know you said it's not the valve, but.... On mine the valve stem developed a crack where it passed through the rim. The valve itself wasn't leaking, but the one tire kept going flat with no visible leak. It wasn't until one of the times I was pumping the tire back up that I deflected the stem a bit and heard air rushing out. The valve looked perfectly good - the crack was hidden from view. New stem, no problem - something to look for anyway,
OK!
Thanks for the help,........
1) will look at the valve stem again,.......hope that us ut.
2) No ATV's down here ( park service and police have a few),...but the Inner tube idea sounds great,.......any of you have a link to a dealer that I can buy from and they would throw it in the mail to St. Croix, US Virgin Islands?
....again,...thanks to all,...the tires are real nice when they stay full,....aren't they!!!
Bruce
St. Croix
USVI
An alternative to inner tube - "fix a flat". Supposedly temporary, but that's for cars - high speeds. Fix a flat is messy inside the tire, so once you do it, if you ever take the tire off, it's a real mess.
I think there is a variant called "slime" that's more heavy duty, but doesn't add the weight of foam.fillers.
http://www.slime.com
There is also a foam that is used by farmers on things like tractors, and industrial (forklifts) so they never have to worry about flats. Kind takes up the stress even when air pressure doesn't. Downside (for your application) is the weight.
http://www.noflat.com
http://www.fixaflat.com/
http://www.otrwheel.com/ff.htm