I have an '80 FLT that needs new tires. A friend of mine gave me an almost new set off of a newer bike. The front is the right size, MT90B16. The rear is a MU85B16. Question is, can I use the bigger 140mm tire on the rear? I know the MT is 130mm so the MU will be 10mm wider. Will I have clearance issues with the enclosed chain, fender etc? As you may know, it's way too much work to pull the rear tire on & off to guess and check!

 

Probably not issues with the fender but I would think the enclosed chain would be a problem.
Just looked at my FXRT setup, same enclosed chain and the rubber booths are very close to my tire. I run a Shinko 130-90 16 that is on the wider side...

 

how much clearance is there with the tire you have mounted now?

 

I just measured my tire and it is 141mm mounted on the alloy rim
Clearance is about 4-5mm
I guess it all depends on the profile of your 140, if it mounts narrow or wide.
I think the Harley Dunlops usually are kind of skinny