eklimek
New Member
Mounting directional tread tires.
In brief, upon discovering a tire mounted in reverse to prescribed rotation what should one do? This raises the salient question what does directional tread actually do? Note, this is not a thread about off road, agriculatrual or asymmetric tire construction. There is a lack of objectivity and scarcity of motorcycle data.
Common sources say the following.
http://trid.trb.org/view.aspx?id=980968
"Increased tread depth of the circumferential grooves in tires is an important contributor to wet skid resistance. Directional tires are now becoming a common design because the groove pattern gives the impression of more aggressive traction capabilities. However, the directional requirement makes tire rotation for maintenance purposes more difficult by requiring a dismount and remount to maintain the correct direction of rotation. This paper reports on a study that was designed to test reversed rotation with regard to braking and lane changing on wet pavements. The study was designed to address a specific issue involving the right front reversed application of a directional tire, as well as developing data from motion measuring and global positioning system instrumentation. Nineteen combinations of tire sets were tested at three test locations. Findings show that mounting one or more directional tires opposite the intended direction of rotation did not appear to adversely affect braking or maneuvering on wet pavements."
http://www.tirerack.com/tires/tiretech/ ... echid=188&
"So what is our conclusion? On dry roads and in moderate rain at city speeds, even though they always look cool, directional tires do not provide much of a wet traction advantage. However for drivers who spend a lot of their driving time on the highways, interstates or at higher speeds (during race track drivers schools and lapping days), directional tires will better resist hydroplaning.
Some question the underlying construction of the tire playing a role.. such as ..
"The other big reason for noting wheel direction has to do with the manufacturing process. The tread rubber is initially a flat strip that's cut to length, at an angle, and then spliced together with the two ends overlapping, creating a hoop. Under acceleration, a tire mounted backwards will try to peel back this splice. The opposite is true for the front wheel, where directional forces are reversed under hard braking."
In my opinion, this is backwards reasoning. All tires are built in the same manner. Why are not all tires directional? Simply because they do not delaminate if run in "contrary" directions.
We can see tread patterns of lugs and voids that appear directional, but so far I found no evidence that reverse rotation makes a measurable difference. Also there is no mention of tire construction implying any directional significance. Asymmetry of tire curb side vs inside is a separate issue.
In fact, this was explored in a law suit in which it was alleged that directional tires mounted in reverse contributed to a (automobile) motor vehicle accident.
There was no evidence before the courts of a measurable effect on tire traction resulting from such a mounting error in an automobile.
No similar trial for a motorcycle was found in my search. (I welcome any evidence relevent to this.)
The measurable differences in hydroplaning seem to relate to coefficient of adhesion, pavement fluid depth, fluid viscosity, fluod density, tire inflation pressure, tire load (normal to the track), tire tread pattern (Size of lugs and voids) and tire tread depth.
As far as I can find, the rotational appearance of tread pattern seems to have more to do with effective marketing suggesting "higher designed performance" is thereby attained.
http://books.google.ca/books?id=Pvsv78x ... ty&f=false
As it turns out the literature on hydroplaning is extensive and much of it begins with engineering study of landing on wet runways. It has a more specific title of elastohydrodynamic tyre-road interaction. (Tyre is tire)
The 1960 video documents tests of aircraft tires to examine hydroplaning
http://m.youtube.com/watch?v=TFOoFkYGqL8
Dynamic hydroplaning occurs when the amount of water encountered on the roadway by a rotating tire exceeds the combined drainage capacity of the tread pattern of the tire and the texture of the pavement. The mass and viscosity of the water cause it to resist being displaced from between the tire and the pavement, thus generating lift forces on the tire which reduce tire contact with the pavement. When the lift forces are sufficient to completely support the load on the tire, contact with the road is no longer made and full dynamic hydroplaning is said to occur.
Prior to the onset of full tire hydroplaning, a transitional condition occurs in which the surface contact area of the tire footprint is decreased as the vehicle speed is increased. This condition is sometimes referred to as “partial hydroplaning” and it is associated with a reduction in the effective friction coefficient.
The capacity of the tire tread grooves for water flow is a factor in limiting the development of partial hydroplaning. Thus, at a given operating condition on wet pavement, the effective friction coefficient is reduced by worn tires.
The following physical factors are involved in the occurrence of hydroplaning of automobile tires:
• Tire construction type, size and aspect ratio
• Tire loading
• Tread depth
• Tread pattern
• Inflation pressure
• Pavement surface texture
• Water depth
• Length of path in standing water
• Vehicle speed
http://www.mchenrysoftware.com/board/vi ... ?f=9&t=282
Interesting that tire pressure increases the rigidity of the tread in contact with the surface and gives greater resistance to the inward buckling of the tread by fluid attempting to lift the leading edge. Increased air pressure also tends to reduce tread groove closure. The grooves are necessary to allow water to be redistributed from the contact patch.
Equations for predicting hydroplaning from speed are empirically derived best curve fit equations. The fundamental mechanism is not understood and predicting tire deformation by the thin film of fluid during hydroplaning is far from complete.
Page 83
Surface texture versus skidding: measurements frictional aspects, and safety ...
By J. G. Rose, American society for testing and materials. Committee E-17 on skid resistance, ASTM.
http://books.google.ca/books?id=CRDEneS ... ne&f=false
Only one reference from a truck tire manufacturer said,
"Once directional tires are worn greater than 50%, there is generally no negative effect of running them in a direction opposite to the indicated direction of rotation.
Operating directional tires from new to 50% worn in the opposite direction of that indicated on the tire will result in the premature onset of irregular wear, excessive noise levels, and significantly reduced tread life."
http://www.aircrafttyres.com/manuals/Mi ... a_book.pdf
Overall one sees that marketing literature mentions the benefits of "directional" tread.
The current market for airplane tires does not mention tread patterns of a directional nature.
At least one other writer seems skeptical in noting inconsistent tread directionality among manufacturers of motorcycle tires.
http://www.msgroup.org/Tip.aspx?Num=035
In brief, upon discovering a tire mounted in reverse to prescribed rotation what should one do? This raises the salient question what does directional tread actually do? Note, this is not a thread about off road, agriculatrual or asymmetric tire construction. There is a lack of objectivity and scarcity of motorcycle data.
Common sources say the following.
http://trid.trb.org/view.aspx?id=980968
"Increased tread depth of the circumferential grooves in tires is an important contributor to wet skid resistance. Directional tires are now becoming a common design because the groove pattern gives the impression of more aggressive traction capabilities. However, the directional requirement makes tire rotation for maintenance purposes more difficult by requiring a dismount and remount to maintain the correct direction of rotation. This paper reports on a study that was designed to test reversed rotation with regard to braking and lane changing on wet pavements. The study was designed to address a specific issue involving the right front reversed application of a directional tire, as well as developing data from motion measuring and global positioning system instrumentation. Nineteen combinations of tire sets were tested at three test locations. Findings show that mounting one or more directional tires opposite the intended direction of rotation did not appear to adversely affect braking or maneuvering on wet pavements."
http://www.tirerack.com/tires/tiretech/ ... echid=188&
"So what is our conclusion? On dry roads and in moderate rain at city speeds, even though they always look cool, directional tires do not provide much of a wet traction advantage. However for drivers who spend a lot of their driving time on the highways, interstates or at higher speeds (during race track drivers schools and lapping days), directional tires will better resist hydroplaning.
Some question the underlying construction of the tire playing a role.. such as ..
"The other big reason for noting wheel direction has to do with the manufacturing process. The tread rubber is initially a flat strip that's cut to length, at an angle, and then spliced together with the two ends overlapping, creating a hoop. Under acceleration, a tire mounted backwards will try to peel back this splice. The opposite is true for the front wheel, where directional forces are reversed under hard braking."
In my opinion, this is backwards reasoning. All tires are built in the same manner. Why are not all tires directional? Simply because they do not delaminate if run in "contrary" directions.
We can see tread patterns of lugs and voids that appear directional, but so far I found no evidence that reverse rotation makes a measurable difference. Also there is no mention of tire construction implying any directional significance. Asymmetry of tire curb side vs inside is a separate issue.
In fact, this was explored in a law suit in which it was alleged that directional tires mounted in reverse contributed to a (automobile) motor vehicle accident.
There was no evidence before the courts of a measurable effect on tire traction resulting from such a mounting error in an automobile.
No similar trial for a motorcycle was found in my search. (I welcome any evidence relevent to this.)
The measurable differences in hydroplaning seem to relate to coefficient of adhesion, pavement fluid depth, fluid viscosity, fluod density, tire inflation pressure, tire load (normal to the track), tire tread pattern (Size of lugs and voids) and tire tread depth.
As far as I can find, the rotational appearance of tread pattern seems to have more to do with effective marketing suggesting "higher designed performance" is thereby attained.
http://books.google.ca/books?id=Pvsv78x ... ty&f=false
As it turns out the literature on hydroplaning is extensive and much of it begins with engineering study of landing on wet runways. It has a more specific title of elastohydrodynamic tyre-road interaction. (Tyre is tire)
The 1960 video documents tests of aircraft tires to examine hydroplaning
http://m.youtube.com/watch?v=TFOoFkYGqL8
Dynamic hydroplaning occurs when the amount of water encountered on the roadway by a rotating tire exceeds the combined drainage capacity of the tread pattern of the tire and the texture of the pavement. The mass and viscosity of the water cause it to resist being displaced from between the tire and the pavement, thus generating lift forces on the tire which reduce tire contact with the pavement. When the lift forces are sufficient to completely support the load on the tire, contact with the road is no longer made and full dynamic hydroplaning is said to occur.
Prior to the onset of full tire hydroplaning, a transitional condition occurs in which the surface contact area of the tire footprint is decreased as the vehicle speed is increased. This condition is sometimes referred to as “partial hydroplaning” and it is associated with a reduction in the effective friction coefficient.
The capacity of the tire tread grooves for water flow is a factor in limiting the development of partial hydroplaning. Thus, at a given operating condition on wet pavement, the effective friction coefficient is reduced by worn tires.
The following physical factors are involved in the occurrence of hydroplaning of automobile tires:
• Tire construction type, size and aspect ratio
• Tire loading
• Tread depth
• Tread pattern
• Inflation pressure
• Pavement surface texture
• Water depth
• Length of path in standing water
• Vehicle speed
http://www.mchenrysoftware.com/board/vi ... ?f=9&t=282
Interesting that tire pressure increases the rigidity of the tread in contact with the surface and gives greater resistance to the inward buckling of the tread by fluid attempting to lift the leading edge. Increased air pressure also tends to reduce tread groove closure. The grooves are necessary to allow water to be redistributed from the contact patch.
Equations for predicting hydroplaning from speed are empirically derived best curve fit equations. The fundamental mechanism is not understood and predicting tire deformation by the thin film of fluid during hydroplaning is far from complete.
Page 83
Surface texture versus skidding: measurements frictional aspects, and safety ...
By J. G. Rose, American society for testing and materials. Committee E-17 on skid resistance, ASTM.
http://books.google.ca/books?id=CRDEneS ... ne&f=false
Only one reference from a truck tire manufacturer said,
"Once directional tires are worn greater than 50%, there is generally no negative effect of running them in a direction opposite to the indicated direction of rotation.
Operating directional tires from new to 50% worn in the opposite direction of that indicated on the tire will result in the premature onset of irregular wear, excessive noise levels, and significantly reduced tread life."
http://www.aircrafttyres.com/manuals/Mi ... a_book.pdf
Overall one sees that marketing literature mentions the benefits of "directional" tread.
The current market for airplane tires does not mention tread patterns of a directional nature.
At least one other writer seems skeptical in noting inconsistent tread directionality among manufacturers of motorcycle tires.
http://www.msgroup.org/Tip.aspx?Num=035
