Front/Rear Weight Distribution Vs Contact Patch

[allanoue]

Originally Posted by Motofool

When I am not sure of the available traction (rainy day on unfamiliar road, for example), I use that learned feeling as a reference to test it.
I wait for a safe opportunity and progressively apply the front brake until the front tire skids, immediately releasing the lever before steering is lost.

[csmith12]

Originally Posted by choneofakind

from looking at sporty motorcycles, I assume they carry the majority of their weight on the front wheel as during static conditions.

While your not totally incorrect, don't assume such things my good man. The general accepted rule for weight distro for pedal bikes would be that 30:70, but those figures do not transfer to road bikes 100%. From my research, a good starting point for a sport bike might be something more like 45/55, it mostly holds true to what most of us are riding these days. To finally reach the 50:50 goal... we must take the rider's weight into account.

From Ducati:

The 959 Panigale features a weight distribution equivalent to 52% at the front and 48% at the rear without the rider or fuel. Fully fueled and with the rider, this becomes a perfect 50:50 balance to guarantee absolute stability and handling. To achieve this distribution, placement of the engine, exhaust, and rider were carefully evaluated and determined.

[choneofakind]

Originally Posted by csmith12

While your not totally incorrect, don't assume such things my good man. The general accepted rule for weight distro for pedal bikes would be that 30:70, but those figures do not transfer to road bikes 100%. From my research, a good starting point for a sport bike might be something more like 45/55, it mostly holds true to what most of us are riding these days. To finally reach the 50:50 goal... we must take the rider's weight into account.

From Ducati:

huh. Good find!

The engine throws me off from visually estimating a CG position, leaning forward and hugging the front wheel.

[Misti]

From Twist of the Wrist II:

"Considering that most machines in a static or constant speed situation have a 50/50 weight distribution (+or -5.0 percent) front-to-rear, we begin to calculate the guidelines of correct acceleration through a turn. By the numbers we want to transfer 10 to 20 percent of the weight rearwards, using the throttle. Technically, this is 0.1 to 0.2 G of acceleration. Simply put, it's the force generated by a smooth fifth-gear roll-on in the 4000-6000rpm range on pretty much anything over 600cc. That's not much acceleration, but it does the job."

Traction Specifics:

"When we talk about cornering we are talking about traction as the rider's main concern. To determine an ideal scene for traction, machine-wise, we start by simply measuring the contact patches of the tires to discover what the basic distribution of loads should be while cornering. Roughly speaking, those measurements show that 40 percent of the total load should be up front, 60 percent at the rear. Bikes set up for racing and real GP machines carry more rear rubber, changing the useable load bias (possibly to as much as 70 percent on the rear) to favour hard acceleration coming out of turns. Each bike's exact ideal weight distribution may vary a bit from the basic 40/60 percent rule. The rider's task is to match the exact load specs of his machine with expert use of the throttle."

[HighsideUK]

This is a very old post, but an interesting question.

I think the reason rear tyres are wider on race bikes is because you need a larger contact patch to exert more force (put down more power).
Despite the fact that brakes can easily be made more powerful than engines, the way back wheels on motorcycles lose traction is much easier to control than the way front ones do.
So we are much happier drifting the rear coming out of corners than scrubbing the front going in to them.
Or, more to the point, the racers are.
So we want our rear wheels to handle more power.
On cruisers, it is just convenient to have more weight, and so a bigger tyre, on the back.
Either way rear tyres are wider.

But, if you only consider the physics/mechanics/material science, then for getting into and around corners as quick as you can, the optimal weight distribution and contact patch is 50/50.