Kris, my tire is a 165/80 R15 which is indeed the "standard VW" tire size, but mine is a Nexxen tire which is built to support the current Japanese sports cars, not old Volkswagens.  

The outline form of the tire came that way from the factory, nothing I have ever done to it has "rounded the corners" or even changed them one iota.  

Square profile tires really don't exist for much any more, even in the car world.

I also have done the needed mods to allow that huge of a tire to live inside my wheel well.

MM is correct, a 145 series or 155 series would fit the bike much easier and likely as good or better performance-wise, and yes MM can buy a tube to fit inside the much smaller 145 series tire that he bought, but he just hasn't gone and done that yet.

I believe the 145sr-15 is one to try and find.  (This early type tire does not have an aspect ratio listed in the sizing- but it is something like an 82 series).

You most likely will have to get one ordered, unless you go to a specialty shop that deals with vintage VW's or similar cars.

Oldfeller got his pretty cheaply....the eBay search doesn't show anything cheap!  It appears that this size which was once common and used on the "economy" cars - is now a specialized size and hard to find (and hard to pay for).

http://www.ebay.com/sch/i.html?_nkw=145r15+tires

The issue with the bead is, that the car tire bead is very wide, and it has a lot of rubber on the inside that functions as a sealing lip.  This makes the tire incredibly difficult to get on the narrow 3.25" wide rim and also have room for the tube valve stem during the mounting process. You can trim a lot of that sealing rubber away, as you will not be using the tire without a tube.

It is important to start spooning the tire on opposite the valve stem, so that the tire bead won't be doubled up where the valve stem is while you are mounting the tire.....the bead has to drop down into the groove in the middle of the rim, and it cannot do that at the valve stem location.  

It could be that you should try a Shinko 230 before going darkside......as it is easy to get, fits, and is affordable.  Bike Bandit currently shows the 130/90-15 size to be $ 77.95 (plus shipping).

http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1181496112

and

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1342402435/0#0

have all the useful information I ever generated about Darksider tires that was worthy of keeping.   I blew a LOT of stuff away in an attempt to keep unskilled newbies away from doing this as the enthusiasm was there but THEY HAD NO SKILL LEVELS enough to tell them when they were getting into danger zones.

AND PLEASE DO NOT USE THE GOODRICH RADIAL T/A TIRE -- IT HAS AN ACTUAL PROVEN TRACK HISTORY OF BEAD BREAKAGE DURING MOUNTING INFLATION.

OK, I updated the spreadsheet.   Verslagen wore out and changed out his tire so his data is done at this point in time.   Youzguys kept on changing his story (saying he mounted his own tire, etc when he paid to have it done) but we recorded his very best story and ran the calculations on it as a base-line.   Since he can't remember his installation costs, taxes, etc he can't win the beer, but he can act as a come on for the other players.

When I started trailering my bike up to the mountains multiple times a year, I actually began feeding my rear tire a steady diet of "worst case tire abuse" that counted coup on my Darksider's tread depth, which then began predicting results that were about as bad as Verslagen actually got with his Metzler V series tire.

To my surprise, over the years my tire has actually held in there better than the first predictions ever said it would do with it eating Dragon after Dragon after Dragon.   My cost of ownership is still the lowest at a half cent a mile, even with me including all the bits and pieces that the other players wanted me burdened with (but that they thought they shouldn't be burdened with).

Since my REAL tire is the only one really still going in reality, I guess you could say that I won on "long life durability" too.  

But not mileage, I can never win on mileage when trailering back & forth to the Dragon (where I go tear up on the tread life something terrible).

I have honestly won on cost per mile though ......

  take a copy of the spreadsheet over to your desktop so you can scroll over all the players and check out the formulae used to get the reported predictions.

Spreadsheet is updated, remember to save a new copy of the changed sheet to the public drive before you exit it if you choose to update your stuff.