Just replaced my Michelin PR tires (radial) with the Michelin Activs (bias ply) and now have about 1,500 miles on them.
Verdict: The Activs cannot match the Pilot Road tires for handling. The difference is quite noticeable. I have now become a 10-15 mph slower rider. I will be going back to the PR (4) tires when these wear out...or before.
If you have not ridden your brick with radials, you have NO idea what you are missing.
curious your definition of "cannot match..for handling". 10-15mph slower? really? were tire pressures the same? same size tire? lean angle? type of use?
i think that comparison has more to do with modern multi compound tire design than a bias vs radial ply design. the PR4 is a multi compound tire that may have a different radius profile.
as i mentioned before, the modern compound on the Activ and the tire design is pretty amazing. having spent several hundred miles on the Activ on a race track...the tire is not the limiting handling factor, the bike is (well, and the rider a bit). Activ had easy tip in and more grip at the edge of the tread than the bike has lean angle available. it only took a few laps to get total confidence in the tires....at the limit, not tooling around on the street.
I have PR3's on my K1300s. less impressed with those. have not put them on a track, but on street the tip in is slow and the stabilty of the front tire in a decent turn is not inspiring. but that is just my limited impression of some half used tires.
the tires capabilities are different, but it is not a bias vs radial ply issue, there are so many other factors involved. heck, modern RACE car tires are....bias ply..in many cases.
everyone has their own "feel" for a tire, but let's not dis bias tires just because of their ply direction. ALL tires have different capabilities....and there are some junk radial tires...