My car tire impressions- for real

[schoeney]

CT vs. MC which perfroms better in a stop?


This is a good debate...but very tiring to this old fart. I suggest that this get explored and maybe solved at each Rally this year.

I would assume most rally's will have at least one darksider and one MC tire in attendance...the bikes should be similar enough. I am sure their is someway to come to a reasonable answer...especially with all these geniuses on board!

[Kawhead]

I didn't pay attention to your pavement surface Dan. Mine was typical parking lot. Your pic looks like polished granite. :) My guess is as good as your about how a MT on my bike would have done.

I can recall two incidences when I had to brake hard enough to skid. One I me and a couple friends were riding. I had a bike tire then. We came up on stopped traffic. The other time a young-un pulled out in front of me from a convenience store. At the time of both these incidences I didn't have my rule and a camera in my saddle bag. But I will say positivly the car tire did much better.

I'm gonna go back a look, but did you do all of your hard leaning turns and test on that smooth asphalt with a brand new car tire that was yet to have sufficient miles to burn off the mold coating Dan ??? Is you crazy ???

[blaneb]

Originally Posted by upside22

I'm sorry, poisoning the well type arguments such as this don't carry much weight with me.

Force = Pressure times Area.

If the pressure on any different element of area goes down then the normal force exerted on that element of area goes down as well.

You are trying to argue that *ONLY* the total normal force needs to be considered. That makes no sense at all.

If it did then putting a 10 speed racing bike tire on a Nomad 1600 *would* provide as much traction as a stock motorcycle tire.

That is obviously incorrect based on real-world empirical evidence. That makes your argument incorrect.

I will submit again that the friction supplied by a tire contact patch is a statistical function based on the pressure per unit area, the deformation of the tire at each unit area of the contact patch, and the change of the coefficient of friction on each unit area of contact during the interval torque is applied to the surface of the tire.

The bigger the surface contact area the smaller the normal force being applied to each unit area of the patch will be (the F=PA formula) and thus the less deformation of the material of the tire on each unit area.

Look at it this way, you are trying to assume that the coefficient of friction is always a constant based on a simple comparison of interfacing materials. This is an incorrect assumption based on the real world. In the world of rubber and the road, a larger contact patch provides a higher coefficient of friction than a smaller patch. Since the only variable is the pressure per unit area between a small and a large contact area then that has to be the controlling factor.

The theoretical physics you are trying to throw out here has so many hidden assumptions that it has almost no relation to the real world we are discussing here. It might work well in the physics lab using blocks of wood and inclined planes of wood where deformation is so small it can be ignored. Lab experiments like this are certainly valuable for teaching basic physics but you simply cannot extrapolate experiments like this to cover any and all real world situations.

I'll repeat, simple empirical data proves your claim to be incorrect. If your claim was correct NASCAR racers would be using 10speed bike tires on their cars in order to reduce rolling friction and gain speed in the straightaways.

I can't poison the well with facts. Only gibberish is poisoning any well.

Again, your basic premis is completely wrong and also irrelevent.

"Force = Pressure times Area" is wrong.

No, pressure is equal to force (Newtons) divided by area (metres squared) and it relates to fluid dynamics, not to friction so it is irrelevent to the topic.

I think if you keep trying, you might actually get something right. Even a broken clock is right twice a day.

I again invite you to prove the Amontons\Coulomb laws of friction give any relevence to the apparent area of contact. Your not arguing against me, your arguing against basic physics.

If a ten lb. brick of rubber with one side twice as large as the other, along the surface it is on, result in a coefficient of friction of 1.0, it will take 10 lbs. of frictional force to overcome static friction.

The apparent area of contact is irelevent, it will take 10 lbs. to move the brick whether it is placed on its largest side, or its smaller side. The coefficient of friction is independent of the apparent area of contact. Do you disagree??

If you want to continue arguing against this simple fact then have at it. Just because you don't understand something doesn't mean it's wrong.

Here is a link to a site that does a nice job of explaining this:

http://www.stevemunden.com/friction.html

If you want to argue the point more, maybe you will write to him and disagree, but take a look at his references first.

[Kawhead]

I gonna go out of my mind if y'all keep this physics stuff up!

[glwilson]

Do we have any "Tribologists" here?

Interesting read on the subject... in the link just previous to this post. I think it answers a lot of questions people are having. ;)

[sharps45100]

Ok my brain is full and time to empty it with good Kentucky Bourbon!

[oldbikers]

Thanks Kaw-Head because If I couldn't stop my bike in less than 15 ft at 15 MPH with any tire I was going to sell it before I got hurt

[Kawhead]

Originally Posted by oldbikers

Thanks Kaw-Head because If I couldn't stop my bike in less than 15 ft at 15 MPH with any tire I was going to sell it before I got hurt

Your right. That really had me concerned, because sometimes when I'm in a parking lot I think I ride around at that speed wiff juss my foot over the brake. :-/

[flavor]

All right I said I wasn't going to read any more about this post. I couldn't resist in checking it out again. Three pages going on since my last post so my curiosity GOT THE BETTER OF ME.

Blaneb great post and an easy read.

You know twice I started a post about temp of tires, pavement properties, weight of rider, how the rider uses his weight in a turn, slippage such as gravel on part of the traction patch etc. But when I went to post, all I had written was lost for some reason. I don't know if it was the internet or the Kawanow site itself.

[bigsid1]

LMFAO Mike.Thats some funny S**t right there.

[dantama]

Blaneb's link was good
http://www.stevemunden.com/whyfriction.html

Here's a part lifted from that link

*If you switch to tires with a better coefficient of friction, you'll immediately notice that stickier rubber is also softer; it wears out much more quickly. Motorcyclists accept the need to replace high-performance tires more often than touring-oriented rubber, but the auto types have another option: They can use wider tires to spread the wear over more rubber. And there, finally, is the reason high-performance auto tires are wider. It isn't to get better traction. Better traction comes from stickier rubber. The tires are wider to get acceptable wear from the stickier, softer rubber. (As well as for other things like heat management, rigidity under the stresses of cornering and braking and acceleration, etc.)*

As stated a few times, my bike tire vs car tire tests were done in the exact same spot so that one tire didn't have an advantage over the other.

The bike tire stopped faster, but showed much more wear where the contact patch slid.

The car tire took more distance, but perhaps due to a less drippy rubber compound didn't show as much wear. Being perhaps less grippy, and having the same amount of weight pressing on it made it take longer, but show less wear.

That would be consistent with everyone's findings with car tires. Get more miles out of one= less wear. A bike tire consumes more tire going about it's duties.

I remember buying a 5.0 Mustang with grippy tires. It was way fun to go way to fast around curves. Freeway onramps that circle were great fun etc. When those tires wore out, I replaced them with some 40-50,000? mile warranty tires. I was so disappointed in how they went around those same curves. They took the fun right out of the car. I sacrificed grippy tires and fun, for no fun but longer wear.

The bike tire vs car tire on my bike isn't as big of a contrast as it was in my Mustang. I was just using it as an example. It doesn't matter if you have less grip, unless you run out and need more. From what the car tire guys report, they've never run out in corners.

I wish I had tested the bike tire on more surfaces, and seen if the car tire took longer on all surfaces. I suspect that it would have, both tires would have stopped shorter on a better surface, but the bike tire a little better.

Because in an emergency stop the front tire does most of the stopping, having a grippy front tire is most important for stopping. I know some have run a car tire on the front. Unless it was a grippier tire than what I'm running, I wouldn't do it. I wouldn't give up stopping distance for more miles.

[Kawhead]

Dan, I'm impressed with you giving a CT the good ol' academic try. You're coming into this deal with an open unbiased mind, and so far you haven't knocked the idea.

Stevie's article is full of scientific facts as far as my memory from basic engineering classes from vocational school goes. Where I get the rub from is is if he and thousands of others are right, then how cam me and thousands of others be right to? They have to be leaving an equation out. An event that's common place in science. Articles like this border on sophistry, in that they don't try to determine why a CT work on a motorcycle. Maybe it's the tread pattern. It's us common folk on discussion boards and threads like this who'll come closer to the truth.

I've mentioned other reasons for riding a CT, but the first reason is remnants of youthful rebellion. I get a thrill when I'm doing something, (fun most of the time) and some intellectual turd gets his nose bent out of shape. It makes me grin like this>

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Bigsid, my dear Mama use to go off on me and my brother like that every morning at breakfast before school. Oh the memories!

[coacha]

Kaw-Head, sometimes book learned and life learned don't quite match up and usually the later is more useful.

[Kawhead]

One other thing. I godda address the 400# gorilla on the board. If you obey the speed limit most of the time and occasionally push it by 20 mph, you wont have a problem on a ct. I've seen Goose, Dkdixon, and a few others push the envelope with the ct. So far they haven't reported any problems, and they're still on 'em.

I bring this up to enter more facts into the discussion.

[Kawhead]

Originally Posted by CoachA

Kaw-Head, sometimes book learned and life learned don't quite match up and usually the later is more useful.

Some of thease folks have neither. I'm doing research to find out if the motorcycles had ct's or mt's.