Stock rear wheel, if you go from a 190 tire to a little larger...

[jellyrug]

They have run out of things to argue about can't you tell

Gotta love this place.

 

[BoostCreep]

This can only be settled one way.

I have a racing data logger that measures speed via GPS, g-force, and tracks your individual points that I can hook up. Who has a 180, 190, and a 200 tire, a Busa, and is at least a B level rider?

 

[m_ridgeway]

Assuming that the surfaces are comprised of the same material (tire compound and pavement) and assuming they are equal temperature and the force (weight)pressing them together is the same, the friction generated is the same regardless of surface area contact.

Regardless of the common assumptions of the motorcycling community ((Tufbusa)) and tire manufacture babble this is BASIS physic and has been proven for hundreds of years.

Laws of dry friction

The elementary properties of sliding (kinetic) friction were discovered by experiment in the 15th to 18th centuries and were expressed as three empirical laws:
Amontons' First Law: The force of friction is directly proportional to the applied load.
Amontons' Second Law: The force of friction is independent of the apparent area of contact.
Coulomb's Law of Friction: Kinetic friction is independent of the sliding velocity.

cheers
ken

Weight applied will not be the same for two diff surface areas

 

[Tufbusa]

Okay, I'll bite! So tire size and contact size has no effect on grip and a bicycle tire has the same grip as a 200/50 series MC tire.

Then explain to me why throttle is required while at maximum lean angle?

Oh, and that dumb a$$ Keith Code tells us to apply throttle as soon as the steering is complete. Why?

I'm sure there is at least one Genius in the bunch?

 

[BoostCreep]

My question was more of "on the same 6 inch wheel same tire brand and model, but 190 vs 200, what is the contact patch difference (upright, half lean, full lean) and how does it effect tire shape?"

 

[SLEEPERBUSA]

I'VE never measured, but it was stated years ago that a STOCK Busa tire actually measures 198, so you would see very little difference if you go with an aftermarket 200, but you would see a smaller tire if you went with an aftermarket 190.

 

[BoostCreep]

Huh, didn't know that. I wish tire manufacturers stuck to what is actually written on the tire more closely. I've never measured the difference between my tire and my friends but, mine is on the right... Can't tell if it's an optical thing because of the tire pattern or if it's actually skinnier, either way, it doesn't really bug me.

 

[kml]

Okay, I'll bite! So tire size and contact size has no effect on grip and a bicycle tire has the same grip as a 200/50 series MC tire

Assuming you have not overloaded the bicycle tire, and the weight both tires are supporting is the same, say 100 pounds on each tire, and assuming the coefficient of friction is the same (ie, the tires are constructed with the same tread compound) then the force required to over come the friction generated is the same for both tires regardless of surface area.

Chat with your local high school physics teacher or ask at a physics forum.

cheers
ken

 

[Tufbusa]

Assuming you have not overloaded the bicycle tire, and the weight both tires are supporting is the same, say 100 pounds on each tire, and assuming the coefficient of friction is the same (ie, the tires are constructed with the same tread compound) then the force required to over come the friction generated is the same for both tires regardless of surface area.

Chat with your local high school physics teacher or ask at a physics forum.

cheers
ken

"Assuming" you never overload your tire, one would "Assume" you will never have issues with grip? Your "Assumption" of grip takes you all the way to the scene of the crash, eh? :dunno"

Oh Please, spare me the sermon! Go back and read the OP. This googled copy & paste tidbit of physics has absolutely nothing to do with how enlarging tire size on a standard rim affects contact patch which directly affects grip.

Next time you visit the man in the black suit wearing a bowtie ask him about your ability to comprehend. ???

 

[kml]

"Assuming" you never overload your tire, one would "Assume" you will never have issues with grip? Your "Assumption" of grip takes you all the way to the scene of the crash, eh? :dunno"

Oh Please, spare me the sermon! Go back and read the OP. This googled copy & paste tidbit of physics has absolutely nothing to do with how enlarging tire size on a standard rim affects contact patch which directly affects grip.

Next time you visit the man in the black suit wearing a bowtie ask him about your ability to comprehend. ???

Tuf you win.

I will grant you surface area is proportional to grip when it comes to motorcycle tires but they are the only surfaces that I will allow this exception for. All other materials I will still consider to follow Amontons' laws. OK?

cheers
ken

 

[jellyrug]

Okay, I'll bite! So tire size and contact size has no effect on grip and a bicycle tire has the same grip as a 200/50 series MC tire.

Then explain to me why throttle is required while at maximum lean angle?

Oh, and that dumb a$$ Keith Code tells us to apply throttle as soon as the steering is complete. Why?

I'm sure there is at least one Genius in the bunch?

I was joking with you and here is some practical and theoretical information.

First the theory in a laboratory:

If you take a square flat block made of exactly the same rubber as your rear tire and you center a 200lb weight on it you can start the experiment.
Attach a spring scale to the block and pull until traction breaks, taking the lbs. reading just before you loose traction. The value would be 200lbs plus the weight of the rubber x the coefficient of friction of the rubber.
Now turn the block on its narrow edge, with a very small contact area and repeat the experiment. Over an average of 10 readings for each experiment you will get the same lbs value to break traction.
Expedia and mathematicians do not explain this very well, but I can try: Pressure = lbs/square inch. So, if you reduce the contact area, or contact patch, the pressure increases proportionally, making the force needed to break traction in each case exactly the same. For instance, if if you reduce the area 2 times, meaning half the area, you have less square inches and less square inches as the denominator divided into the numerator which in lbs remain the same in this instance will give you twice the pressure.

So, in short, as you reduce the contact patch, the pressure between the rubber and the pavement increases proportionally, leaving traction exactly the same.

Consider practical application on the track:

Because a bicycle tire is so narrow, the pressure between rubber and pavement will be so high, that first you would need to inflate to around 1,000psi (guess) and the heat generated would be so great that you would have failure before you even reach the first corner. Because of the high pressure between pavement and rubber, the rubber would overheat way beyond its capability to function. ( I am a cyclist and put 150psi in my tires, because the bike only weighs 18 lbs, and I only put out around 1/2 horsepower, this works just fine)

With motorcycle tires the front brake at high speed is able to apply more torque to the front wheel in braking, than the motor could put on the rear wheel in power. So, traction on the front for short periods before corner entry is just as important as the rear under power. The smaller contact patch in the front does not give us less traction, but because the front tire does a lot less work than the rear in total time, we can afford to use a thinner tire to our advantage.

Finally, the coefficient of friction with rubber is not a constant, it changes with temperature, which makes the application of pure physics practically impossible. But there is a lot of science and knowledge that goes into the perfect MotGp tire, which can clearly make a win or loose on the track. The fundamentals remain the same though and the tire Engineers attempt with compounds and profile to provide best traction for only the duration of the race.

I worked for Mercedes in South Africa up to 1983, as an Automotive Engineer, as 75% of Mercedes manufactured in the country had to be local content. I did a lot of work with Dunlop and Firestone back then to try and equal performance for local manufacture, which we got close with. It can get really complicated though. Don't know how this happens, but right now I am back in Germany, three months gone teaching hard headed Germans and can't wait to come home.

We can discuss the need for throttle at maximum lean angle more, but it is not related to tire contact patch. That has to do with what makes a bike turn and this time the contact patch on your puck can actually help a little.

 

[Popie]

Never had the urge to go wider then 190. Will a 200 fit? I'm only seeing about a quarter of an inch between the tire and the chain. I'm running a Shinko.

 

[DVFEIT]

Interesting comments... If a Formula 1 car weighing under 2500 lbs why use wide tires? I understand & believe in the "Laws of Dry Friction" . However those test were compared in an controlled environment/surface. Unfortunately,the tracks surface has multiple variances in construction, dips, lose gravel or minature thrash items.. A small diameter tire will have a lower advantage over the wider tire I these inconsistent track surfaces are the norm...

 

[ZRXMAX]

Reducing tire pressure makes a bigger contact patch. It also creates a lower profile and lowers the effective gear ratio. Watch slo mo wrinkle wall drag slicks on the launch. The axel center actually drops increasing the torque applied to the tire.