Has anyone ever had a problem getting a Michelin Pilot Active, 4.00 x 18 tire (using a tube) to fit on a Snowflake rear alloy wheel?

I purchased two new tires for my R100/7 and the front went perfectly. Over the years, I have changed dozens of tires, so I have had experience. However, on this one I am stumped.

The rear tire will not fully seat in the rim. About 8 to 10 inches of the "seat bead" (on both sides) will not pop out as it is supposed to. I have used pretty high pressure to get it out, in fact, up over 60 lbs., along with "soap & water" lubricant. I also on my way home I had the wheel/tire in the trunk of my car, and stopped by a large motorcycle dealer that sell nearly every brand except BMW, and asked them for advice. Thinking they could help, they offered to look at it. They tried, using regular tire lube, but couldn't get the tire to seat either.

Both of us were afraid to use more pressure.

Any help or advice from experience?