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In theory you can calculate what size of tyre is to be accepted in the frame.
The limiting factor is the physical distance between the rails that runs from the swingarm pivot point to start of the rear seat – the ones where the footpegs are mounted. You have aprox. 251,4mm between these frame rails.
Of course you also need space for the chain – ex. 25,2mm. If you want the wheel centred in the frame, you will therefore need 25,2mm on each side of the tyre.
The calculation goes like this; there is 251,4mm - 2 x 25,2mm = 201,0mm. Theoretically you could slam a 201,0mm tyre in between the frame rails – but that would not be practical, because now the tyre will rub on both the frame rails and the chain, and the chain will also rub on the frame rails – therefore we need to put in some space for clearance.
There will be different levels of “safe” for clearance issue due to personal taste (read: balls) - but in this example I’ll go on the “conservative” side of “safe” and put in 5,0mm for both the:
1) chain-to-frame-clearance and
2) chain-to-tyre-clearance.
Ergo you’ll “loose” an additional 10.0mm for clearance (2 x 5,0mm) – and that will be on EACH side, if you still want the wheel to sit centred in the frame.
The end result including clearance is therefore 201.0mm – 20,0mm = 181,0mm. You can "safely" put in a 181.0mm wide tyre
If you really want a wider tyre in there, you can compromise either the centring of the wheel by a couple of millimetres, or the spacing for clearance – or both.
Or you could take a radical approach and widen the frame
....... and as Duckndive statede: if your using EFE hangers and pegs you will need to modify the L/Hand one to clear the offset chain.