tires don't mean anything! What is your take on the quote?

[///M SPEED]

Bah, tires don't mean anything, the coefficient of friction of the roadway is the same for all tires...

This is amazing read the sentence...the drag factor of the roadway is the same for all tires...it's pretty simple.

I've been doing this job for 10 years, done hundreds of test skids either by eyeball mark of the beginning of the skid, accelerometer, or bumper gun. I've used my patrol car, I've used the car involved in the crash (I'm a crash investigator) and the drag factor of the roadway was the same for both vehicles. It's been the same with ABS and non-ABS, new car, old car, car or SUV or truck.

One summer I had 4 crashes at the same intersection, and did test skids at all of them. The numbers don't lie, and that is a physics answer. To find the coefficient of friction of the roadway , square the speed and divide your answer by 30 times the distance of the average length of all four skids.

A car that yaws off of the roadway because he/she took the curve too fast, generally, won't be drivable for me to do test skids with. Do you honestly think the courts would allow me to use a drag factor that I got from test skids with a different car, with different tires, if the drag factor of the roadway was not the same for both? And the drag factor is a necessary part of the speed from sideslip formula.

That is all I was saying, and I'm talking about regular highway driving. Racing deals with higher speeds, higher wheel temp and greater wear in a shorter period of time than what we generally deal with. One of my old partners drove formula ford in SCCA for years in the midwest, and yes, he choses his tires based on many things for the weekend, buying the tires at the track, using new tires every weekend. Racing does not mimic general roadway driving.

So, you can put your pitchforks away; If you want to go out and spend your hard earned dollar on the most expensive set of vulcanized rubber for your car, have at it. I'll save my cash for tires with a Y speed rating and look the best on my camaro. There was less passion in a post made about road rage awhile back, sheesh.

This was on a different board. My friend sent me this quote and asked me what I thought about it. This guy basically states that it doesn’t matter what type of tires you buy. They are all the same (for street use only) and anyone who buys high-end tires is wasting their money.

I thought this would be a good topic here. Does anyone have any data to prove or disprove this guys stance? I don't believe half of what he states and I told my friend that at this time I cannot disprove his response, but I would post here and see what others my say to give him some fuel to his or the others posting against his proof......

 

[Montana]

I think he's overlooking part of his own arguement.

The "traction" is a combimination of the coefficient of friction of BOTH surfaces. If you're tires are made of polished steel instead of rubber, are they going to "skid" the same amount and wear the same? Of course not. Sure the road coefficient of friction is the same for all tires ...duh. The difference is in the tire compound.

The rubber compound "bends" or "gives" as traction-breaking forces increase...but keeps traction until the breaking point. A steel polished tire would immeadiately "break" (the quivalent to hydro-planing) traction with the road.

MAYBE at highway speed ,when you are measuring distances based on 100% brakes lockup (again, hydro-planing equivalent) it could very well be pretty close for all tires. The compounds have ALL exceeded their ability to "bend" or give" so they are now "planing" on the road surface until a full stop. Again, metal tires as an example would skid further probably but the range of tire compounds are probably so similar (or rather so different from extremes of hard metal or marshmallow tires) that the measured differences are negligible. I would agree with that and argue that as the skid approaches a stop, the rubber is able to "un plane" and begin to adhere as before. I bet if they could measure the last second of each skid, they would find a difference in skid length consistent with normal tire compound "stickiness".

As far as wear factor on everday driving, a more dense, temperature resilient compound will last longer...just as steel tires would last a hell of a long time.

 

[codex57]

He doesn't understand the purpose of ABS does he?

 

[Dutch]

Pfff..

try to mount a couple of winter tires on your car during summertime... you´ll see!
Weather down here in Holland changed real quick so I still have wintertires on the car (dealer will change them on saturday). In the wintertime those tires worked like crazy, I had traction on snowy roads where others could hardly drive. But now, with 65 degrees Fahrenheit, man it sucks to have wintertires on the car.

Later

 

[frolf]

4 crashes at the same interseciton? yeah, i'm gonna trust his math...


sure most tires roll the same down a freeway at 60mph, but who does that?


good tires = #1 modfication you can do to your car

 

[///M SPEED]

I think he's overlooking part of his own arguement.

The "traction" is a combimination of the coefficient of friction of BOTH surfaces. If you're tires are made of polished steel instead of rubber, are they going to "skid" the same amount and wear the same? Of course not. Sure the road coefficient of friction is the same for all tires ...duh. The difference is in the tire compound.


As far as wear factor on everday driving, a more dense, temperature resilient compound will last longer...just as steel tires would last a hell of a long time.

My opinion he is comparing apples to oranges. This statement, "The "traction" is a combination of the coefficient of friction of BOTH surfaces" is one of the main factors he seems to be missing. The type of tire (compound, winter, summer, all season, along with the speed rating H, R, Y, ZR etc..) has not been a factor to him. You know why? He is basing his whole argument on the skid.

The skid is the point at which the tire looses its grip. A skid is a skid. The tire has already lost its purpose for being. This is why he in only focusing on the one constant; the roadway and the "drag factor". This is why he states the court allows his findings. He is not basing it off the chemical compound of the tire at all.

The point of the thread is that there are major differences in the type of tires made. The whole point of buying a high performance summer tire in the summer and vise versa in the winter is to avoid a "skid" and "traction loss", therefore rendering his point moot IMO.

What do you think of my statements. Right, wrong, partially wrong? Bid D. do you have a professional opinion on this matter given your background? Thanks to all for their insight....

 

[BMWdude]

My opinion he is comparing apples to oranges. This statement, "The "traction" is a combination of the coefficient of friction of BOTH surfaces" is one of the main factors he seems to be missing. The type of tire (compound, winter, summer, all season, along with the speed rating H, R, Y, ZR etc..) has not been a factor to him. You know why? He is basing his whole argument on the skid.

The skid is the point at which the tire looses its grip. A skid is a skid. The tire has already lost its purpose for being. This is why he in only focusing on the one constant; the roadway and the "drag factor". This is why he states the court allows his findings. He is not basing it off the chemical compound of the tire at all.

The point of the thread is that there are major differences in the type of tires made. The whole point of buying a high performance summer tire in the summer and vise versa in the winter is to avoid a "skid" and "traction loss", therefore rendering his point moot IMO.

What do you think of my statements. Right, wrong, partially wrong? Bid D. do you have a professional opinion on this matter given your background? Thanks to all for their insight....

I would have to agree with that, he is measuring the same constant over and over because all tires have lost traction at that point and therefore have skidded(sp?) What is important is under what conditions and speed a tire looses it's traction and that I believe does depend on the type of tire.

 

[aNoodle]

MSpeed, you're right about him just thowing out the drag of the rubber itself. He's using a bunch of scientific mumbo-jumbo (and claims of expertise) to defy common sense. Think of the different types of rubber...sticky to grab vs. hard for economy.

He should just say he's a proponent of economy tires because he thinks the average driver can't take full advantage of performance/sticky tires in regular city driving and they wear out too quickly to be worth his money. But that would be his opinion/cost analysis based on his driving not a scientific rule!

 

[Average Jae]

i'll sell him my bald tires for the price of a new one. "Bah, tires don't mean anything" right?

i am smart because i added 1 + 1 four times and came up with 2 every time! have a freakin cookie..

 

[Montana]

I would have to agree with that, he is measuring the same constant over and over because all tires have lost traction at that point and therefore have skidded(sp?) What is important is under what conditions and speed a tire looses it's traction and that I believe does depend on the type of tire.

Isn't that what I just said as the first response?

 

[///M SPEED]

Big Daddy what do you think?

 

[Big Daddy]

I was afraid you'd ask

What he says about the coefficient of friction being the same for all tires is correct. What confuses people is when manufacturers and magazines talk about lateral acceleration. Lateral acceleration and coefficient of friction are not the same thing. Coefficient of friction or "Drag Factor" is an expression of gravity used to describe the slipperiness between two surfaces. I have seen the studies and even been involved with the live tests and coeffcient of friction is the same for all tires. It is kind of confusing because they all do not start skidding at the same time, you see your not dealing with the coeffcient of friction until the tires start skidding or slidding, one may get there faster than the other but once there they are all the same. Rolling Friction would be the reason tire compounds make a differrence School for Champions
I am not an "expert" but do know many and have seen their demonstrations and court room testimony. Very interesting topic!

 

[///M SPEED]

That is partly what I thought without knowing all the details. All that matters after the skid has already started. My buddy states he basis this opinion on the type of tires to buy/not to buy. He thinks high-end sport compound tires (see the original thread) are not needed and all tires are good for all occasions. This is where I believe he is confused....

 

[Big Daddy]

You are correct Scott, the high end tires will make a difference before the skid/slide but once the skid/slide starts they are all the same!

 

[Nataku]

There 2 types of frictions - static and dynamic. Static friction is the amount of force require to move an object from a stationary position to overcome inertia. In this case it is the same as rolling friction

Object Weight x Coefficient of Static friction = Static Friction Force.

Once the object is in motion Dynamic Friction is in play. This the amount of force required to continue to move the object. This is also called drag. In this case, it is the same as skidding.

Object Weight x Cofficient of Dynamic friction = Dynamic Friction Force.

In most cases, the Coefficient of Static is greater than Dynamic. So this come in play with the geometry (tread, width,design) and material the tire is made of to maximize grip or Static Friction Force. Once you break the static friction you now are skidding with the Dynamic friction. Again, It should be determined by the design and material of the tire. I would say skidding friction would be different for different tires, but by how much ?

Seems the original post was inductive. meaning, he had a position and used evidence to support his position and in a not very controlled or scientific method.

 

[Nataku]

This brings up an interesting point. Theorically, because Static Coefficient is greater than Dynamic, shouldn't you get the best 0-60 time at the point were you put down enough force to the tire just before the tire looses grip. ( no slipping of the tires ). I don't know if this is true. I read that the new M5 launch sequence lets the tires burn so rubber. So, perhaps not.

 

[Big Daddy]

Sorry you are incorrect, 1st there are three types of friction, not two: Friction
Maybe this will help explain it better than I can: Howstuffworks
And maybe this one: Treads

 

[epj3]

It's a completely stupid argument. it's the ONLY thing touching the road (Unless you're some monkey who's exhaust is half hanging off becuase you're cheap). Better tires have better tread patterns. Or else formula 1 cars wouldn't be using the tires they use.

 

[Big Daddy]

It's a completely stupid argument. it's the ONLY thing touching the road (Unless you're some monkey who's exhaust is half hanging off becuase you're cheap). Better tires have better tread patterns. Or else formula 1 cars wouldn't be using the tires they use.

Not sure what your trying to say? Like I said "high end tires will make a difference before the skid/slide but once the skid/slide starts they are all the same!" I agree that high end tires make a difference, but if you lock them up and are sliding all tires are equal, it is a simple matter of physics.

 

[///M SPEED]

Not sure what your trying to say? Like I said "high end tires will make a difference before the skid/slide but once the skid/slide starts they are all the same!" I agree that high end tires make a difference, but if you lock them up and are sliding all tires are equal, it is a simple matter of physics.

This is the point I was trying to explain to my buddy however I am not sure if he relayed the info correctly.

This all started with him saying that it doesn't matter what kind of tire you have. That due to (insert his friction explanation) that it makes the tire moot. You don't need to buy high-end tires at all. That cheap tires will do no matter what car you have them on (racing not excluded), because of the coefficient of friction. I have no idea why he believes it to be different for racing?????

He is missing the point. He is basing his point on the skid and not evaluating the usefulness of the tire before the skid....