Thank you for the info but
I may have mis-spoke . I meant to ask if your bike originaly took radials can you change them to bias instead of radials on both the front and back?
So the speed ratings don't change the tire thread patterns?
I should also mention that the lower speed rated tire should be on the front to avoid any oversteer problems. Don't want that, especially on a bike!
Back to switching out your tires. From Dunlop's FAQ center:
Bias and radial tires have significantly different dynamic properties. They deflect differently, create different cornering forces, have different damping characteristics, as well as other differences. In order for radial tires to be introduced into the two-wheel market, it was necessary to change certain characteristics of the motorcycle. The introduction of the radial tire led to such things as modified frames, wider wheels, new steering geometries and suspensions. Therefore, it is recommended that a motorcycle be used with the type of tire construction that it came with originally. If a change is to be made, then it should only be done if the motorcycle or tire manufacturer has approved the change. Above all, do not mix bias ply and radial tires on the same motorcycle unless it is with the approval of the motorcycle or tire manufacturer.
Now, some of that may be corporate law mumbo-jumbo, however most of it makes sense.
When I was a kid, the Grand Prix racing motorcycles converted from bias ply tires to radials in the late '80s. They found the need for stiffer frames, better forks, and stronger swingarms to deal with the additional traction. The suspension components and frames that worked well enough with bias ply tires twisted too much with the newer radial tires making the bikes much harder to ride. They also found that the tires no longer overheated after ten laps, so the tires kept their initial traction much longer ... at least until they had worn off all of the good rubber.
Being not a professional racer nor aggressive rider such as on a sport bike, I would assume you may not even feel a difference.
As for the tread differences regarding speed ratings, I'm certain there are differences, although it's not something I've explored.
Question(s): What bike do you have, and are (as you say) switching from radials to bias???