you have to measure your rim size in inches from lip to lip
GR/KR-16 6.00/6.70/7.50/8-16 Inner Tube - TR13 Valve
this one is 16" rim and fits a 6-7.5" rim size TR13 is the valve size ie.
regular size car valve opening

http://www.gemplers.com/product/182091/GR-KR-16-600-670-750-8-16-Inner-Tube-TR13-Valve

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From: "craig cowan" <phishman068@GMAIL.COM>
Sent: Sunday, August 21, 2011 7:34 AM
To: <vanagon@GERRY.VANAGON.COM>
Subject:      Re: Tubes in tires.

> Okay. Now the question is....WHERE do I get the tubes?
> I can't seem to find tubes online meant for a 225/70/16 tire.
> They seem to sell tubes based on tractor measurements.
>
> -Craig
>
>
> On Sun, Aug 21, 2011 at 12:05 AM, Eric Ley <eric_ley@hotmail.com> wrote:
>
>> we do it all the time exp. as a spare you should have no problems
>> As for the tire shop if it is in U.S. then it is for legal concerns I bet
>>
>>
>> ------------------------------**--------------------
>> From: "craig cowan" <phishman068@GMAIL.COM>
>> Sent: Saturday, August 20, 2011 10:14 PM
>> To: <vanagon@GERRY.VANAGON.COM>
>> Subject:      Tubes in tires.
>>
>>
>>  I have a BFG that was damaged at the bead upon removal from the previous
>>> set
>>> of wheels. It is still a great tire with tons of tread. It just leaks
>>> air
>>> now. I'm thinking throw a tube in it, and since it will be used as a
>>> spare
>>> anyway..... it should hold air well then and serve it's purpose right?
>>>
>>> Are there any flaws in this statement? Are there problems with tubes?
>>> Is there a reason why 4 tire shops told me today that they can't legally
>>> put
>>> a tube in a tubeless tire, but all suggest that I do that?
>>>
>>> -Craig
>>>
>>>
>