Motorbike frame question

[El guapo]

Maybe this is a dumb question, but how can I tell if a motorbike frame is 26" or 28"
How should I measure
Thanks

 

[B607]

Put a 26" wheel with tire on the back of the frame and see how much of a gap there is to the fender bridge. A 26" frame will have an inch or less clearance. A 28" frame will have 2"-3" inches of clearance. Gary

 

[wheelbender6]

Test fitting wheels is the only way I know of. Take your frame to a shop and they will likely allow you to try on some different wheels.