You need 14mm inside diameter. You can go to a hardware store and get some 9/16 snap rings to use as spacers. 
I like the Macmaster Carr shims.  http://www.mcmaster.com/#98055A215

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Mike Riley
Sent: Sunday, March 18, 2012 2:04 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: brake shoe bottom spacer

---- Rob <becida@comcast.net> wrote:
> At  3/17/2012 09:14 PM,Mike Riley wrote:
> >can anyone give me a exact size for the spacer under the rear brake 
> >shoe to move it outward?
> >thanks
> >
> >mike
>
>  From the archives-
I guess I was not clear I need the diameter of the hole and the outside diameter of the spacer I seem to remember that a standard washer will not work and I don't have the luxury of going out for spacers in the middle of the job.
thanks
mike

> Date:         Sun, 12 Jul 2009 16:47:26 -0400
> Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
> Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
> From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
> Subject:      Re: Big brake conversion
> Comments: To: Don Hanson <dhanson928@GMAIL.COM>
> To:           vanagon@GERRY.VANAGON.COM
> In-Reply-To:  
> <6bc66ccf0907081011y460ec51eyc18163d2c8987424@mail.gmail.com>
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>
> I have to disagree a bit here. While some of this may be true for 
> extreme conditions or panic stops weight distribution and other 
> factors have a lot of influence. Most cars are front heavy and of 
> course weight will shift to the front while stopping but the Vanagon 
> has much more a of 50-50 weight bias particularly when loaded. The 
> rear brakes can do a lot. Most folks that complain about Vanagon 
> brakes have rear that are nor working properly, the wrong shoes, and 
> drums that are worn oversized. VW mad things a bit worse as both he 
> adjusters and cylinders are on the same end so much of the shoe is not contacting the drum.
>
> Want a low cost brake upgrade? Here's how:
>
> Rear brakes. Make sure the drums are in spec. Go to the dealer and get 
> the shoes set, 251698531LX, List price now only $60.00.
> Get the hardware kit there also 251698545, $29.10 list.  Get a pair of 
> ATE wheel cylinders. (Dealers is not a choice here).
> Remove the lower shoe mounts and shim them out 2-3mm. Put it all together.
> Make sure the cables are properly adjusted. After they seat you will 
> be surprised how much the brakes will improve.
>
> For the fronts, get the PBR metal master pads. After they seat you 
> will have brakes. Be sure the rotors are also within spec. I recently 
> pulled off a set machined under 10mm.
>
> Dennis
>