The reason I ask is I just installed a set on my 2000, and the ride is rather lumpy at 45-50 mph.  It gets better at 55-60, but especially at 45 it feels like the rear tire is filled with cement.  I even broke it down, re-seated it and re-balanced it, no change.

I noticed the tires are four ply tread and sidewalls-the rear nylon and the front polyester.  Could that explain the really harsh ride?  TIA

I'm going to follow this thread as my '86 is due for a tire change. With the limited tire choices for the older c10's, the Sport Demons were tires I was considering.

I run the Perellis. I haven't really noticed the bumpiness you describe. They DO sometimes grab a rain grooves on the freeway. Not constant just sometimes out of the blue. Enough to wake you up. They hang nice going on the On-ramps. (The only twisties I get unfortunately)

  Never noticed the lumpiness..although it was '07 when I had one as a rear rim protector, so memory may fail me for ride smoothness...
 That said, I did notice a little sidewall flexing when pushed hard in the fast sweepers transitioning from left to right & vice-versa....
 The tire was grippy enough that I almost scraped the bags hustling along WVa Rt20 on the return trip from the National at Canaan that year. IIRC, the tire lasted around 9.5k miles too!

I ran a set of them a couple years back. No drama, good tire. Just like the Avon offerings much better.

Why not find an old used  mean streak rear wheel and do the conversion. The tire choices are fantastic and the handling is greatly improved. Such a a low cost upgrade and easy to do with massive benefits.
PR4GT's are perfect for the rear on this bike and you get good tread wear and massive grip too.

I've run the Sport Demons. No lumps for me, they handled just fine. They wear out in 5K just like every other tire that has decent grip and handling.