ninjette.org - View Single Post - Front/Rear Weight Distribution Vs Contact Patch

csmith12 · April 18th, 2016, 09:18 PM

@akima, this is all very well and vetted out by people wearing lab coats in TOTW2 movie. lol They even get out the scales to measure weight on each tire and calipers to measure the contact patch size. You should watch it.

Some common goals for a sportbike;

Achieve a 50/50 weight distro via good solid chassis design, geometry & suspension adjustments. The bike cannot account for the rider moving around on it. Although this may change in the future with active electronics making suspension changes while in motion. Can your bike adjust on the fly if you slide all the way front and aft in the seat?

More weight on the front is beneficial when initiating a turn, raising the rear of a 250 is an example mod that is done to many race bikes to help the bike turn faster but at the cost of a less stable chassis. A taller rear of the bike changes the geometry, shortens the wheelbase and does slightly front load the weight. This in turn helps flatten the fronts contact patch for maximum traction at the turn point.

Once under INCREASED cornering load, which contact patch can handle more load? The bigger one or smaller one?

And how do you get the load distributed? When rolling on the throttle, the rear of the bike rises... why? Because the engine pulls the chain, the chain is connected to the rear tire, which is at the end of the swingarm. The swingarm pivots at its mount point near the front sprocket. The force of the engine pulls the ENTIRE swingarm down, thus raising the ENTIRE bike, good for ground clearance, but bad for traction because we want the shock to keep the tire on the ground. What is better for maximum traction? A smooth throttle roll or an aggressive one? Maybe that question is to easy... What kind of throttle roll, lets the suspension do it's best work? HINT: Do you want your engine fighting your suspension or nah?

While straight up and down (no lean) and accelerating in a straight line, it's ALL about keeping the rear from spinning up. Contact patch and friction is not enough anymore on modern high powered bikes. With the engine producing such a force on the rear, the rear shock simply can't do what it was designed to do in a nearly topped out position. Hence we have things like traction control and such to help. We don't have worry about that on 250's with such low amounts of power, but it helps to know why people say what they say.

Hope that helps you understand and if not, I will try to help you out.

April 18th, 2016, 09:18 PM	#23
csmith12 The Corner Whisperer Name: Chris (aka Reactor) Location: Northern KY Join Date: May 2011 Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track) Posts: Too much. MOTY 2015, MOTM - Nov '12, Nov '13	@akima, this is all very well and vetted out by people wearing lab coats in TOTW2 movie. lol They even get out the scales to measure weight on each tire and calipers to measure the contact patch size. You should watch it. Some common goals for a sportbike; Achieve a 50/50 weight distro via good solid chassis design, geometry & suspension adjustments. The bike cannot account for the rider moving around on it. Although this may change in the future with active electronics making suspension changes while in motion. Can your bike adjust on the fly if you slide all the way front and aft in the seat? More weight on the front is beneficial when initiating a turn, raising the rear of a 250 is an example mod that is done to many race bikes to help the bike turn faster but at the cost of a less stable chassis. A taller rear of the bike changes the geometry, shortens the wheelbase and does slightly front load the weight. This in turn helps flatten the fronts contact patch for maximum traction at the turn point. Once under INCREASED cornering load, which contact patch can handle more load? The bigger one or smaller one? And how do you get the load distributed? When rolling on the throttle, the rear of the bike rises... why? Because the engine pulls the chain, the chain is connected to the rear tire, which is at the end of the swingarm. The swingarm pivots at its mount point near the front sprocket. The force of the engine pulls the ENTIRE swingarm down, thus raising the ENTIRE bike, good for ground clearance, but bad for traction because we want the shock to keep the tire on the ground. What is better for maximum traction? A smooth throttle roll or an aggressive one? Maybe that question is to easy... What kind of throttle roll, lets the suspension do it's best work? HINT: Do you want your engine fighting your suspension or nah? While straight up and down (no lean) and accelerating in a straight line, it's ALL about keeping the rear from spinning up. Contact patch and friction is not enough anymore on modern high powered bikes. With the engine producing such a force on the rear, the rear shock simply can't do what it was designed to do in a nearly topped out position. Hence we have things like traction control and such to help. We don't have worry about that on 250's with such low amounts of power, but it helps to know why people say what they say. Hope that helps you understand and if not, I will try to help you out. __________________________________________________ Goal: Shake A Million Hands \| Look through the corners \| Track Day Prep \| Closest track? \| The Mid-Ohio School
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