Trying to mount Shinko 712's on the cast rims of a 1983 GS650L. The front went on OK, but the shop cannot get the tire to seat on the rear wheel, even with 100 psi and straps, and multiple attempts and different tire positions. Apparently the tires won't go over the small inner lip meant to keep the bead in pace. The mechanic is suggesting that I grind down the lip in roughly 1/3 of the rim (120 degrees, or 2pi/3 radians if you prefer). This would provide a little give and the tire *should* then mount.
I did search via Google, but no threads became apparent.
Should I ...
- Grind down the lip as suggested?
- Get a different tire (not trying to start tire discussion)?
- Go to a different shop to see if they have any luck?
- Something else?
Pic for reference

I did search via Google, but no threads became apparent.
Should I ...
- Grind down the lip as suggested?
- Get a different tire (not trying to start tire discussion)?
- Go to a different shop to see if they have any luck?
- Something else?
Pic for reference


