I'm in process of doing a wide glide front conversion and got some oem 48 laced rims to go with it (16X3 front and back). I was looking at Shinko Classic 240 tire for front

however Im not sure about what size to get for rear can i get the Shinko 270 the size is 500X16 which makes no sense to me as i know tires sized in metric only

OEM tire size for the 48 is 130/90/16 for front and 150/80/16 for rear.

i like to have as fat as possible rear tire, so i don't want to put Shinko 240 in the rear.

 

Different manufactures have different actual widths to the stated widths. A 5X16 will be a little narrower than a stock 48 rear tire.

Not a direct rear view but this is a 5X16 Indian tire.



And a 5X16 Coker/Beck



And stock (the only pic of the rear I could find)

 

C'mon, converting metric to inches and back is dead easy! A 5" tyre is 5 x 25.4 mm = 127mm, close to a 130/90. There are converters on the internet. It may actually be slightly different to that when fitted to a rim, simply because all tyres have a nominal size, which my not be identical to the fitted width.

 

A 5.00-16 is taller than a 130/90-16 or MT90-16.
It's more like a 127/100-16.