I don't know about legislation in your area but over here in Europe, our bikes need a certificate of conformity (COC) in order to be allowed on public roads. Amongst various other technical items, the tire sizes are included in the certificate. That means changing tire sizes is prohibited.
In case of an accident/incident there could arise an insurance problem.
I am not an engineer. I guess the engineers that built the bike know best and determine what tyre size to use.
Imho changing sizes is changing motorcycle geometry, handling, load capacity, overall "feel of the bike", etc.
That could make a difference in case of an emercency where one has to rely on one's reflexes, skill and training in a split second,
without forgetting to mention that the bike and its behaviour has changed and might not react in the way one expects.
Also, the contact area tire/road has increased by using a wider tire.
That means lesser load per square inch which results in lesser grip by equal weight and power of the bike.
Perhaps that is a good thing riding in a straight line but e.g. in the rain it's a whole other ball game.
Experimenting with different brands and models could present the solution you are looking for.
Or is slowing down *the* solution for tire life and grip in the rain?
Best of luck and Stay Safe,
Ed.
Holy Cow Ed, no, you are not an engineer. Much of what you have written is only partially correct. And you've not worked with many engineers, it would seem, or you'd understand they limit their focus very narrowly to the project for average conditions, at best.
If you consider it a bit more, you may realize that any change you make to the bike will mean your awareness of how it behaves will also change. You will adapt to those changes.
Tires, round and black. Tread is nice too. You don't need to slow down in the rain until it becomes biblical proportions. It helps if you ride smoothly. If you're riding 10/10ths in the dry, yes, you should slow down, rain or no rain, for street riding.
The friction between two surfaces is proportional to the force pressing them together, so more force = more friction! A larger contact patch, doesn't automatically mean less friction in real world terms of traction for a given bike, rider, load and conditions. The degree of change for street riding has minimal impact.
Please
do share your personal, first hand experience. Please refrain from posting your thoughts on things you have no direct experience with.
@thommo - Thanks for adding some actual content on the subject. Part of the change you mention is tire profile and I suspect a slight diameter difference that helps turn in as well.