Standing on pegs = lower centre of gravity?

[The End]

As far as I am aware, the lower you have the mass of an object to the ground, the lower said object's centre of gravity will be?

So why in the road code does it say that in the event of riding over an object such as a pothole to


"Rise slightly on the footrests to lower your centre of gravity, allow your legs and arms to absorb the shock, and help keep you from being bounced off as the rear wheel hits."

However slight that increase in height of the mass may be, would that not RAISE your centre of gravity?

[Mental Trousers]

You're lowering the point where your weight transfers to the bike and you're also removing your body mass from impeding movement of the bike (your arse is no longer preventing the bike from moving because there's no weight there)

[Captain_Salty]

I'd say it's raising your centre of gravity too

[Ocean1]

Yeah. They're wrong, of course, standing on the pegs will raise your centre of mass.

But they're right, too, standing de-couples your mass from the bike at the seat, which lets the bike move around without upsetting your balance as much. It also lets you make use of your legs as extra suspension.

Try standing on the pegs with your knees bent some, move your weight around from peg to peg, it's a good way to get a feel for how weight change affects the way the bike behaves.

[Mental Trousers]

Ugh.

From the tyres contact patch to the top of your head is everything that contributes to the the mass of the bike when you're seated.

Lift up a fraction it's now just the bike BECAUSE your legs allow the bike to move under you. You decouple your mass from the bike's mass.

It's not the overall centre of gravity you're changing, just that of the part that needs to move around, ie the bike.

... and I got beaten to it.

[ellipsis]

...the black art of saving your arse overides all principles of moving mass, c of g and written words...

[Captain_Salty]

you would have to have no grip or weight on the bike to decouple your mass from the bike/rider mass system

[Subike]

you would have to have no grip or weight on the bike to decouple your mass from the bike/rider mass system

ever heard of unsprung weight?
yes you weight is still on the bike, but not supported by it.
its a suspension science that I understand how it works,
But would not be able to put into the right words to explain it.
I am sure that the off road riders will have heaps to say about how standing on the pegs, make you body unsprung weight. make for better handling in certain conditions.

[Fast Eddie]

ride a f*ckn dirt bike through some rough trails and mogul hills. then you'll know whats its all about.

[YellowDog]

Yip, you're raising your centre of gravity for sure

AND you are also raising your ability to keep balance whilst riding the turbulance and not fall off :yes:

[Gremlin]

ride a f*ckn dirt bike through some rough trails and mogul hills. then you'll know whats its all about.
What he said...

Your weight is transmitted through the pegs, instead of the seat... pegs are lower than the seat.

[imdying]

...the black art of saving your arse overides all principles of moving mass, c of g and written words...

Yup, completely :yes:

[bogan]

ride a f*ckn dirt bike through some rough trails and mogul hills. then you'll know whats its all about.

And its a hell of a lot more fun than looking through a physics textbook ;)

Bonus credit if you figure out how those cunts do such massive 'whips' without landing on their heads, even the TP7 is more understandable cos he just keeps spinning until landing.

[Rhys]

Ride over a speed hump sitting then try it standing, Makes a massive difference

[sootie]

This is really interesting.
If the rider were absollutely rigid and at the same height as the seat, nothing would change.
(Consider a rigid 50 foot rider - the c of g of the bike plus rider would be high alright!)
In fact, the rider acts as both vertical & torsional decoupling (via his legs) for his own mass (which rides high).
Hence FOR A LIMITED FAST MOVEMENT in each of these axes the rider mass will be decoupled from the bike to some extent.
(by allowing the rider movement to be partly independant of the bike.)
The effect on the bike by allowing this limited movement must be to lower the apparent dynamic c of g of the bike.
I still think the main benefit is to reduce the dynamic loading on the bike suspension during the hump transition, and to increase rider comfort!
Never thought about this before!

[FJRider]

This is really interesting.
If the rider were absollutely rigid and at the same height as the seat, nothing would change.
(Consider a rigid 50 foot rider - the c of g of the bike plus rider would be high alright!)
In fact, the rider acts as both vertical & torsional decoupling (via his legs) for his own mass (which rides high).
Hence FOR A LIMITED FAST MOVEMENT in each of these axes the rider mass will be decoupled from the bike to some extent.
(by allowing the rider movement to be partly independant of the bike.)
The effect on the bike by allowing this limited movement must be to lower the apparent dynamic c of g of the bike.
I still think the main benefit is to reduce the dynamic loading on the bike suspension during the hump transition, and to increase rider comfort!
Never thought about this before!

When sitting on a bike ... your weight is supported by the motorcyce seat .... almost NO weight is supported by the footrests. When you stand ... ALL your weight is on the footrests. No weight is even taken by the bars. The force on the bars is a lever action of your whole body which makes bike control easier when you stand.

[Subike]

When sitting on a bike ... your weight is supported by the motorcyce seat .... almost NO weight is supported by the footrests. When you stand ... ALL your weight is on the footrests. No weight is even taken by the bars. The force on the bars is a lever action of your whole body which makes bike control easier when you stand.

I agree with you on some of your post F J, but not all of it.

If you have ever ridden a hard tail motorcycle, then understanding this is easier,

You can control the bike when standing on the pegs, by using your weight on the pegs only.

With no need for input from the handle bars other than to keep your balance.

But this also depends upon your level of skill.

[ducatilover]

The sole purpose of raising yourself like so is to use your legs as suspension, this gives the bikes chassis/susp less problems/effort as a human body going over a bump will naturally stiffen up, and being a stiff ninny on the bars is a horribly stupid idea. So, simply, it's so you don't interfere as much as you would with the bikes "natural" movements.

Or so I'm told, I ride a GN250/300/kaboom though

[sootie]

When sitting on a bike ... your weight is supported by the motorcyce seat .... almost NO weight is supported by the footrests. When you stand ... ALL your weight is on the footrests. No weight is even taken by the bars. The force on the bars is a lever action of your whole body which makes bike control easier when you stand.
Agree with that, and the easier to control bit actually, but the original post was about changes to the c of g.
I do raise my weight on humps, and definitely prefer to do so, but I think for my sort of riding, it is mainly protecting my bum & spine!

[neels]

Just think of the force vectors, and where they are acting;

The total mass of the rider acting at the point where they meet the seat,

or the mass of the rider divided roughly in half acting lower down on the pegs.

Do the maths, you'll see why it makes a difference.

[ducatilover]

Just think of the force vectors, and where they are acting;

The total mass of the rider acting at the point where they meet the seat,

or the mass of the rider divided roughly in half acting lower down on the pegs.

Do the maths, you'll see why it makes a difference.

Yes, until you hit a bump/pothole, then your COG is shifted else where.
It's not to lower the COG, it's to stop you being a numpty with the steering