Do faster bikes go round corners quicker due to fatter tyres?

weight of the bike, centre of mass, suspension set up, distribution of weight etc etc all make up the most important factors. the rs 125 and 250's are very very light, and there centre of gravity is very low so they can corner a lot faster than a heavier bike such as an r1 which has its centre of gravity heigher up. tyres do have a huge affect on cornering speeds and turn in speeds, but not as much as your general set up.

Assuming the same bike, but tested with different tyres, my knowledge of physics would seem to indicate that the tyre that has the steepest angle at it's edge would take the corner quickest.

Again this assumes all else is the same, which clearly it isn't - one big one being grip. I am also assuming the same turn in speed, which although it is part of "taking a corner", seems to be not part of the discussion here.

Grip is a weird one too, and if the laws of physics apply in the same way to motorcycle tyres as they do to car tyres, then the contact patch area thing has an interesting point people often overlook (not saying anyone has here btw!). That point is that the contact patch area is the same regardless of tyre width/size, assuming all else is equal. It's because the contact patch area is directly related to the air pressure inside the tyre. What changes about the contact patch is the shape of the contact patch, when you change tyre size/width.

This is really coming from numerous discussions with car folk on forums, that believe that a wider tyre offers more grip purely because it is wider. It may offer more grip, but that's down to something else - different pressure, different tyre compound, etc.

That all makes sense Muffles. It's got to ultimately be down to lean angle as lean angle and speed are proportionate and I guess tyre profile denotes that.

As i already said.... thiner tyres make for quicker steering in like for like tests....

same bike
same setup
same make of tyre

its the flickable ness that you lose with wider tyres.

Stop thinking of it as 1 corner and think of it as a lap, depending on how many corners of track it was you could go round faster with smaller width tyres. the benifits of smaller width really come into play with supermoto type tracks

But its all depending on the track as to whats best, some might even favour a slightly wider tyre if its a less twisty faster type track.

But theres no getting away from FATTER tyres look nicer though

Nope HTH

General rule of thumb is if you up your tyre size you slow down the turn/steering. Just about every mag, forum, armchair expert all say the same thing.

Bike(?) magazine did a pullout for all the tyres sizes, profiles, rubbers etc. There's a section about why changing to a wider tyres lessens the contact patch and slows the steering. See if I can dig it out and post it up here.

Only reason i know is cos i've got a 180/55 rear on mine.