..you may not have taken into account...
This is probably one of the best short discussions regarding tires and motorcycles I've seen, and no doubt needs to be taken into consideration, though unless you've taken physics and done vector analysis, it may "mean" very little, though the effects discussed cannot be discounted, ignored, or explained-away....
Tires
Tires have a large influence over bike handling, especially on motorcycles. Tire inflation pressures have also been found to be important variables in the behavior of a motorcycle at high speeds. Because the front and rear tires can have different slip angles due to weight distribution, tire properties, etc., bikes can experience understeer or oversteer. Of the two, understeer, in which the front wheel slides more than the rear wheel, is more dangerous since front wheel steering is critical for maintaining balance.[7] Also, because real tires have a finite contact patch with the road surface that can generate a scrub torque, and when in a turn, can experience some side slipping as they roll, they can generate torques about an axis normal to the plane of the contact patch.
![Image]()
(Bike tire contact patch during a right-hand turn)
One torque generated by tires is due to asymmetries in the side-slip along the length of the contact patch. The resultant force of this side-slip occurs behind the geometric center of the contact patch, a distance described as the pneumatic trail, and so creates a torque on the tire. Since the direction of the side-slip is towards the outside of the turn, the force on the tire is towards the center of the turn. Therefore, this torque tends to turn the front wheel in the direction of the side-slip, away from the direction of the turn, and therefore tends to increase the radius of the turn.
Another torque is produced by the finite width of the contact patch and the lean of the tire in a turn. The portion of the contact patch towards the outside of the turn is actually moving rearward, with respect to the wheel's hub, faster than the rest of the contact patch, because of its greater radius from the hub. By the same reasoning, the inner portion is moving rearward more slowly. So the outer and inner portions of the contact patch slip on the pavement in opposite directions, generating a torque that tends to turn the front wheel in the direction of the turn, and therefore tends to decrease the turn radius.
The combination of these two opposite torques creates a resulting yaw torque on the front wheel, and its direction is a function of the side-slip angle of the tire, the angle between the actual path of the tire and the direction it is pointing, and the camber angle of the tire (the angle that the tire leans from the vertical). The result of this torque is often the suppression of the inversion speed predicted by rigid wheel models described above in the section on steady-state turning.
High side:
A highsider, highside, or high side is a type of bike motion which is caused by a rear wheel gaining traction when it is not facing in the direction of travel, usually after slipping sideways in a curve. This can occur under heavy braking, acceleration, a varying road surface, or suspension activation, especially due to interaction with the drivetrain. It can take the form of a single slip-then-flip or a series of violent oscillations...." When the slipping rear tire suddenly regains traction it is not moving in the same plane as the rest of the bike. This causes the motorcycle to straighten up so quickly the rider is almost always thrown off, even at low speed.
Technical explanation:
Forces occurring between the motorcycle and the road (such as accelerating, decelerating and turning) are transmitted by friction occurring at the contact patch. There is a limited amount of force that the contact patch can transmit before the tire begins to lose traction, and therefore slide/ skid.
When going through a curve on a motorcycle, centripetal force (added to the other lateral forces such as acceleration or deceleration) is transferred from the road to the motorcycle through the contact patch, and is directed at a right angle to the path of travel. Applying too much throttle during the curve (or taking a curve too fast) would increase the centripetal force, thereby increasing the total net force through the contact patch. If the net force is greater than the static friction coefficient of the tire multiplied by the normal force of the motorcycle through the tire, the tire will skid outwards from the direction of the curve. By locking a tire during a curve using the brakes, the friction giving the tire its traction would be overcome by the previous forces discussed.
Once a tire slips in a curve, it will move outwards under the motorcycle and cause the motorcycle to lay down in the direction the rider is already leaning to counteract the moment applied by the centripetal force and lead to a lowsider.
If the tire regains traction after the rider starts to skid while the motorcycle is moving sideways, the tire will stop its sideways movement causing the motorcycle to suddenly jerk into an upright position (and beyond). This movement can easily cause the rider to be thrown off.
The name derives from the side of the motorcycle that the rider will separate from. If forcibly thrown over the bike, the rider is said to have dismounted on the high side.
The "highsider" has the additional disadvantage of the rider often being catapulted into the air by the sudden jerking motion of the motorbike and the increased possibility of the motorbike sliding behind the rider, threatening to crush them.
Because "highsider" accidents are so much more deadly than low-side accidents, the Motorcycle Safety Foundation recommends that if a rider locks the rear brake at higher speeds and the traction is good the brake should not be released.[1]
(and of course, our Burgmans could/would never experience such a situation with a car tire installed on the rear.... :wink: )
Would somebody who is inexperienced (or even 'experienced' riders), happy with their CT on the rear know this? Again, with our Burgs, it probably is not that big of an issue, however, all things considered, it MUST be considered for that possible ONE time that you could experience 'loss of traction' of that 'fat' CT on the rear....you'd better know how to react...
:cheers:
I posted this because several times this past week, while riding my bicycle along the road here, at the same time, I tend to see the same cars and motorcycles traveling down the road (both directions)...I've seen a couple of 'fat' tire choppers, you know, the ones with the real fat tires...and I wondered, if the tire is that PHAT, then why not put a car tire on the back (after all, it doesn't get leaned that FAR over for the sidewall to be an issue, like a CT on a Burgman)...well, in watching the choppers operate, I've seen them take turns and corners and that fat tire, a motorcycle tire, DOES roll quite well and when they lean, there is a very noticable 'sidewall' area up the tire that the tire rolls onto....so I started looking at the traction, slippage, "roll curves", slip angles....etc... anyways, this post probably won't be very 'popular' but whether or not you've darksided, the physics are the physics and CTs and MC tires are very different beasts. Ultimately I don't care what tire is on whose bike (I do care on MY bike, though), and this is just more food for thought.
This is probably one of the best short discussions regarding tires and motorcycles I've seen, and no doubt needs to be taken into consideration, though unless you've taken physics and done vector analysis, it may "mean" very little, though the effects discussed cannot be discounted, ignored, or explained-away....
Tires
Tires have a large influence over bike handling, especially on motorcycles. Tire inflation pressures have also been found to be important variables in the behavior of a motorcycle at high speeds. Because the front and rear tires can have different slip angles due to weight distribution, tire properties, etc., bikes can experience understeer or oversteer. Of the two, understeer, in which the front wheel slides more than the rear wheel, is more dangerous since front wheel steering is critical for maintaining balance.[7] Also, because real tires have a finite contact patch with the road surface that can generate a scrub torque, and when in a turn, can experience some side slipping as they roll, they can generate torques about an axis normal to the plane of the contact patch.
(Bike tire contact patch during a right-hand turn)
One torque generated by tires is due to asymmetries in the side-slip along the length of the contact patch. The resultant force of this side-slip occurs behind the geometric center of the contact patch, a distance described as the pneumatic trail, and so creates a torque on the tire. Since the direction of the side-slip is towards the outside of the turn, the force on the tire is towards the center of the turn. Therefore, this torque tends to turn the front wheel in the direction of the side-slip, away from the direction of the turn, and therefore tends to increase the radius of the turn.
Another torque is produced by the finite width of the contact patch and the lean of the tire in a turn. The portion of the contact patch towards the outside of the turn is actually moving rearward, with respect to the wheel's hub, faster than the rest of the contact patch, because of its greater radius from the hub. By the same reasoning, the inner portion is moving rearward more slowly. So the outer and inner portions of the contact patch slip on the pavement in opposite directions, generating a torque that tends to turn the front wheel in the direction of the turn, and therefore tends to decrease the turn radius.
The combination of these two opposite torques creates a resulting yaw torque on the front wheel, and its direction is a function of the side-slip angle of the tire, the angle between the actual path of the tire and the direction it is pointing, and the camber angle of the tire (the angle that the tire leans from the vertical). The result of this torque is often the suppression of the inversion speed predicted by rigid wheel models described above in the section on steady-state turning.
High side:
A highsider, highside, or high side is a type of bike motion which is caused by a rear wheel gaining traction when it is not facing in the direction of travel, usually after slipping sideways in a curve. This can occur under heavy braking, acceleration, a varying road surface, or suspension activation, especially due to interaction with the drivetrain. It can take the form of a single slip-then-flip or a series of violent oscillations...." When the slipping rear tire suddenly regains traction it is not moving in the same plane as the rest of the bike. This causes the motorcycle to straighten up so quickly the rider is almost always thrown off, even at low speed.
Technical explanation:
Forces occurring between the motorcycle and the road (such as accelerating, decelerating and turning) are transmitted by friction occurring at the contact patch. There is a limited amount of force that the contact patch can transmit before the tire begins to lose traction, and therefore slide/ skid.
When going through a curve on a motorcycle, centripetal force (added to the other lateral forces such as acceleration or deceleration) is transferred from the road to the motorcycle through the contact patch, and is directed at a right angle to the path of travel. Applying too much throttle during the curve (or taking a curve too fast) would increase the centripetal force, thereby increasing the total net force through the contact patch. If the net force is greater than the static friction coefficient of the tire multiplied by the normal force of the motorcycle through the tire, the tire will skid outwards from the direction of the curve. By locking a tire during a curve using the brakes, the friction giving the tire its traction would be overcome by the previous forces discussed.
Once a tire slips in a curve, it will move outwards under the motorcycle and cause the motorcycle to lay down in the direction the rider is already leaning to counteract the moment applied by the centripetal force and lead to a lowsider.
If the tire regains traction after the rider starts to skid while the motorcycle is moving sideways, the tire will stop its sideways movement causing the motorcycle to suddenly jerk into an upright position (and beyond). This movement can easily cause the rider to be thrown off.
The name derives from the side of the motorcycle that the rider will separate from. If forcibly thrown over the bike, the rider is said to have dismounted on the high side.
The "highsider" has the additional disadvantage of the rider often being catapulted into the air by the sudden jerking motion of the motorbike and the increased possibility of the motorbike sliding behind the rider, threatening to crush them.
Because "highsider" accidents are so much more deadly than low-side accidents, the Motorcycle Safety Foundation recommends that if a rider locks the rear brake at higher speeds and the traction is good the brake should not be released.[1]
(and of course, our Burgmans could/would never experience such a situation with a car tire installed on the rear.... :wink: )
Would somebody who is inexperienced (or even 'experienced' riders), happy with their CT on the rear know this? Again, with our Burgs, it probably is not that big of an issue, however, all things considered, it MUST be considered for that possible ONE time that you could experience 'loss of traction' of that 'fat' CT on the rear....you'd better know how to react...
:cheers:
I posted this because several times this past week, while riding my bicycle along the road here, at the same time, I tend to see the same cars and motorcycles traveling down the road (both directions)...I've seen a couple of 'fat' tire choppers, you know, the ones with the real fat tires...and I wondered, if the tire is that PHAT, then why not put a car tire on the back (after all, it doesn't get leaned that FAR over for the sidewall to be an issue, like a CT on a Burgman)...well, in watching the choppers operate, I've seen them take turns and corners and that fat tire, a motorcycle tire, DOES roll quite well and when they lean, there is a very noticable 'sidewall' area up the tire that the tire rolls onto....so I started looking at the traction, slippage, "roll curves", slip angles....etc... anyways, this post probably won't be very 'popular' but whether or not you've darksided, the physics are the physics and CTs and MC tires are very different beasts. Ultimately I don't care what tire is on whose bike (I do care on MY bike, though), and this is just more food for thought.
:blackeye:
