Motorcycle weight distibution

[djsb 493]

I wonder if we could take some measurements of our bike and try to work apply this solution found on Yahoo answers

 

Question:

 

The axles of a 1956 BSA Roadmaster motorcycle are 1.37 m apart. It has a mass of 291 kg. If the center of gravity is 61 cm behind the front axle, how much force is the front wheel exerting on the display floor as the bike sits in the Museum of Modern Art?

....and how much force (in N) is the back wheel exerting on the display floor as the bike sits in the Museum of Modern Art?

 

Answer:

 

Total weight force is W = m*g = 291kg*9.8m/s^2 = 2852 N

Let F = force from Front axle (wheel)
Let B = force from Back axle (wheel)
Equating moments about the centre of gravity:

0.61m*F = (1.37-0.61)*B = 0.76*B

F + B = W = 2852 N

so B = 2852 - F

So 0.61*F = 0.76*(2852 - F)
so F = 2175 / (0.61+0.76) = 1588 N <= ANS

So B = 2852 - 1588 N = 1264 N <= ANS

 

Any physics teachers out there?

 

And how of the riders weight is on the front wheel and on the back wheel when the bike is static?

 

 

[fred_jb 10,265]

I guess that depends on where between the axles the centre of gravity of the rider's body is positioned (in normal riding) though of course this can vary a bit if the rider moves around. I would suggest that in most cases the rider's weight is somewhat rear biased, so affects the rear sag more than the front.  If you look on www.cycle-ergo.com it is apparent that on most bikes the rider sits in the rear half of the wheelbase, and the rearward weight bias will be even more pronounced if loaded up with a pillion and luggage.

 

I guess the position that all the added loads on the bike can be considered to act through will also vary with the stance of the bike - if it is nose up, then due to the slope the weight will act further back than if it is nose down, so I think it is important than the suspension is adjusted to keep the bike level so that the C of G is as far forward as possible, especially with a pillion and luggage, otherwise the steering can get light.

 

 

Edited December 20, 2016 by fred_jb

[Tex 36,817]

I accept it's not relevant - but I don't recall BSA making a 'Roadmaster'.

[Rocker66 34,466]

6 minutes ago, Tex said:

I accept it's not relevant - but I don't recall BSA making a 'Roadmaster'.

Nor do I. I remember them doing a Road Rocket though.

Just discovered that they did a pushbike under that name 

https://www.google.co.uk/search?q=BSA+Roadmaster&espv=2&biw=1920&bih=950&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwigv-GctYPRAhWJLsAKHXFuC2QQsAQIGw&dpr=1

[Andy m 23,593]

Wouldn't the wheelbase have been 4 foot five and 15/16's?

 

Andy

[Tex 36,817]

And at 640lb it would have earned itself the name "Jumbo!"..

 

Sorry, this isn't helping the OP, but..

[Guest Hati]

According to promotional material, the 2014 Integra upgrade (ally swing arm in particular) made the weight distribution without rider to be the perfect 50-50. I remember reading that from Honda when I was researching the bike.

[Tonyj 6,907]

2 hours ago, Andy m said:

Wouldn't the wheelbase have been 4 foot five and 15/16's?

 

Andy

 

Depends on where they sold it . Is that ours or the American sizes. That might make more sense on the weights though  . 650 pounds is I think the average size of young male stateside 

[Tonyj 6,907]

7 minutes ago, Hati said:

According to promotional material, the 2014 Integra upgrade (ally swing arm in particular) made the weight distribution without rider to be the perfect 50-50. I remember reading that from Honda when I was researching the bike.

 

Yer I also remember vw telling me  I was actually helping the planet. Mmmm. Perfect weight distribution how lucky is that:0)