wompus
08-30-2009, 04:33 PM
I found this on another forum talking about car tires verses bike tires.
I don't know if this has ever been posted here before but it is worth posting.....
This was posted by BlaneB on the Delphi Vulcan forum and I thought it was a pretty straight forward explanation of why Care tires and MC tires are different and why DOT approved Car Tires are acceptable on Motorcycles while Motorcycle tires are DOT approved on Motorcycles only.
Without further ado:
What exactly makes a motorcycle tire a motorcycle tire? How is it defined as a car tire?
I'm seeing all these debates about the two, but I guess I don't really understand what makes each one what it is outside of the (sometimes) obvious shape. (Even that can't always be used as a determination it seems.)
ETA: Seriously, I'm not looking for debate. I'm just genuinely curious as to what the factors are that qualify the tire to be classified as such.
Hi Fritz.
DOT defines M\C rated tires as motorcycle specific, which means they only meet the engineering requirements for motorcycle use.
Car tires, or P rated radial tires, are not restricted to any vehicle type as long as the tire fits the wheels sizes and weight limits listed by the manufacture. There are no DOT restrictions on putting a P rated radial tire on a passenger car, light truck, trailer, two wheeled motorcycle, three wheeled motorcycle, motorcycles with side cars, or any other vehicle that meets the tires size and weight limits.
As far as construction, M\C rated tires for the street generally have much lighter weight but stiff carcasses and run at higher pressure to satisfy the main difference between tires, motorcycle specific tires are rounded in cross section which allows for a consistent small contact patch either vertical or leaning. M\C tires usually have much lower load ratings than CTs. street M\C tires are made with harder rubber compounds than street CTs, usually they are much harder due to the rapid wear caused by the small contact patch.
Tire engineers only have two ways available to control tire wear, increase the size of the contact patch or use harder rubber, or both. The rounded M\C tire can only have a larger contact patch by being made wider so there are real limits. Hard rubber is the only way to make street M\C tires last as long as they do, and that isn't very long at all compared to a CT.
Motorcycles came with car tire in the beginning, and ran flat tread bias ply tires for years. With the advent of GP racing and street sport bike there was a genuine need for the rounded tires foe these bikes. Unfortunately, when the really big cruiser and tourer motorcycles came out the rounded tire was expected by most buyers. It wasn't a really good tire for the job on the really big bikes, but marketing wanted round tires to sell bikes. Look how many people hate there M\C tires on big bikes, there is a reason.
If tire engineers actually were allowed to develop a better tire for big bikes, guess what, it would look an awful lot like a CT. And most riders would look at them and say, hey, that tire isn't round, we don't want it!!
Ct are engineered for much height weight and stress loads than M\C tires. CTs were not designed to lean at a 45 degree angle like bike tires, but they still will do it safely so, so what!
Many people use and safely enjoy CTs on the back of big bikes, and some Sport Touring riders are using them now.
Both tires will do what the other one will do safely. They just do it a little differently.
..
I don't know if this has ever been posted here before but it is worth posting.....
This was posted by BlaneB on the Delphi Vulcan forum and I thought it was a pretty straight forward explanation of why Care tires and MC tires are different and why DOT approved Car Tires are acceptable on Motorcycles while Motorcycle tires are DOT approved on Motorcycles only.
Without further ado:
What exactly makes a motorcycle tire a motorcycle tire? How is it defined as a car tire?
I'm seeing all these debates about the two, but I guess I don't really understand what makes each one what it is outside of the (sometimes) obvious shape. (Even that can't always be used as a determination it seems.)
ETA: Seriously, I'm not looking for debate. I'm just genuinely curious as to what the factors are that qualify the tire to be classified as such.
Hi Fritz.
DOT defines M\C rated tires as motorcycle specific, which means they only meet the engineering requirements for motorcycle use.
Car tires, or P rated radial tires, are not restricted to any vehicle type as long as the tire fits the wheels sizes and weight limits listed by the manufacture. There are no DOT restrictions on putting a P rated radial tire on a passenger car, light truck, trailer, two wheeled motorcycle, three wheeled motorcycle, motorcycles with side cars, or any other vehicle that meets the tires size and weight limits.
As far as construction, M\C rated tires for the street generally have much lighter weight but stiff carcasses and run at higher pressure to satisfy the main difference between tires, motorcycle specific tires are rounded in cross section which allows for a consistent small contact patch either vertical or leaning. M\C tires usually have much lower load ratings than CTs. street M\C tires are made with harder rubber compounds than street CTs, usually they are much harder due to the rapid wear caused by the small contact patch.
Tire engineers only have two ways available to control tire wear, increase the size of the contact patch or use harder rubber, or both. The rounded M\C tire can only have a larger contact patch by being made wider so there are real limits. Hard rubber is the only way to make street M\C tires last as long as they do, and that isn't very long at all compared to a CT.
Motorcycles came with car tire in the beginning, and ran flat tread bias ply tires for years. With the advent of GP racing and street sport bike there was a genuine need for the rounded tires foe these bikes. Unfortunately, when the really big cruiser and tourer motorcycles came out the rounded tire was expected by most buyers. It wasn't a really good tire for the job on the really big bikes, but marketing wanted round tires to sell bikes. Look how many people hate there M\C tires on big bikes, there is a reason.
If tire engineers actually were allowed to develop a better tire for big bikes, guess what, it would look an awful lot like a CT. And most riders would look at them and say, hey, that tire isn't round, we don't want it!!
Ct are engineered for much height weight and stress loads than M\C tires. CTs were not designed to lean at a 45 degree angle like bike tires, but they still will do it safely so, so what!
Many people use and safely enjoy CTs on the back of big bikes, and some Sport Touring riders are using them now.
Both tires will do what the other one will do safely. They just do it a little differently.
..