tuj wrote:The bike has two very small contact patches that are about the size of your palm. The car has 4 contact patches which are all bigger, especially laterally, than the bike tires.
I have driven on a track (the Nurburgring) where they mix bikes and cars. The bikes can accelerate crazy fast once they get out of the corner but they brake much sooner and longer than a car and corner slower. Also, there is of course the fact that on a bike, if you screw up, you are probably going down. In a car, maybe just a slide or a spin.
Long story short: Bike wins on the straights, car wins in the corners and braking zones.
Erunanethiel wrote:Friction is independent of surface area, so having a smaller contact patch doesnt mean anything in terms of mechanical grip. It does make a bit of difference as I have explained in OP
Tim.Wright wrote:Erunanethiel wrote:Friction is independent of surface area, so having a smaller contact patch doesnt mean anything in terms of mechanical grip. It does make a bit of difference as I have explained in OP
One of the main points I made in the other thread was that surface area does have an influence on grip. The tyre produces grip from 2 mechanisms:
1. Coulomb friction - this is independent of contact patch area
2. Adhesive forces - these are proportional to contact patch area
So if you increase the tyre size, you increase the adhesive component of the total grip.
I've seen the same tenancy on the Nordscleife too. The bikes get in everyone's way in the corners, and then disappear on the straights.
tuj wrote:you are simply wrong about the size of the contact patch area not mattering. If contact patch area didn't matter, race cars would all use skinny tires to reduce rolling resistance.
Oh and as for the Nurburgring? I was driving a rented 190 Kompressor with crap tires and I was passing liter bikes all day long in the corners and under braking. No aero needed.
Jolle wrote:It's not about grip, if you factor that out, a bike can only brake or accelerate with around 1G because of the high cog. In corners it's a bit more, depending how far you can vr bring the cog down. Marquez has a lean angle maxing out of 61 degrees, so he should get around 1,2-1,3G around a corner, road bikes do around 45degrees max.
Because of the mental weight/power ratio they can maintain maximum acceleration much longer and be fast on the straights.
With cars cog is not so much a factor with braking and accelerating (never saw a "normal" car do wheelies or stoppies).
Erunanethiel wrote: ..... By the way at 61 degree lean, from TAN(61) you are pulling around 1.8g.
Erunanethiel wrote:The bikes have a lot to lose on a track like nurburgring (their lives) so I dont think its a valid comparison since they might not be pushing the limits like you are. If you could be bothered there is a 458 italia vs panigale comparison and since a pro rider and a driver is used, I think panigale even pulled a bit more g's.
The use of wider tires is not for grip, but for better distrubition of heat.
sgth0mas wrote:Tire size and contact patch size matter because rubber does not have an infinitely high shear strength. Sure you can get the same theoretical frictional and adhesive forces from contact patches of different sizes, but as contact area goes down, so does the shear area. As this area goes down the shear stress goes up. When the frictional loads surpass the shear strength of the rubber, you lose rubber to the ground as your material cannot physically support the loads demanded of it.
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