Standing on the pegs?

Im thinking the best explanation might be that standing on the pegs allows the weight of the rider to adjust the centre of gravity(by adjusting their body mass) quicker to take into account changing conditions.

Originally Posted by Spank86

Im thinking the best explanation might be that standing on the pegs allows the weight of the rider to adjust the centre of gravity(by adjusting their body mass) quicker to take into account changing conditions.

That's better

SK and I were just being typically facetious and yanking your chain.

To be honest I'm struggling to model the physics of it in my head because the rider must operate as a semi independent mass. I'm thinking that although the centre of gravity is slightly higher it can be moved further over the wheels when the bike leans/turns by the riders shift in position (and weighting the outside peg)making it seem like the COG is lower?

[SoulKiss]

Originally Posted by -Ralph-

That's better

I was just being typically facetious and yanking your chain. SK was just being himself

Fixed for ya

And there was me going to get all into complicated arguments involving pendulums and other cobbled together because it sounded vaguely plausible even if unplausible theories until you poiled it Ralph

[Balky001]

When upright, transferring weight from the seat to the pegs lowers the CoG. If leant over this alters as forces are not straight up and down. If you were upside down the CoF would be on nearer your head.

Back to the original post, yes, often stand on the pegs, especially trackdays or off roading. Can save a highside purely as you aren't wiggling your backside from side to side if you have the pegs weighted and slightly off the seat.

Originally Posted by Spank86

To be honest I'm struggling to model the physics of it in my head because the rider must operate as a semi independent mass. I'm thinking that although the centre of gravity is slightly higher it can be moved further over the wheels when the bike leans/turns by the riders shift in position (and weighting the outside peg)making it seem like the COG is lower?

When sitting on the seat your COG is what it is and it's not very mobile, you can shift in the saddle a bit, ie: hanging a butt cheek off in the corners, which is sufficient for the road, but you and the bike as an assembly still pretty much act as a single mass and a mass can only have one COG.

When standing up off road you can put your weight over the bars for hill climbs, or over the tail for descents, and as you rightly said it centralises your weight between front forks and rear shock, giving the rear shock an easier time and allowing the front forks to do more of the work. You can also weight your pegs to help with slow speed turns and technical stuff.

Standing up you are still on the pegs, so the bike and rider still have a single (higher) COG as an assembly, but what you are effectively doing is making that COG the sum of two separate bits of mass (weight is a combination of mass and gravity) within the one assembly, one lower down and pretty much fixed (the bike) and one higher up and adjustable (you), so you can move your overall COG around as you need to.

The reason you feel like it has a lower COG, is that you can move the weight of the bike independently of your own weight, but a mass can only have one COG and so long as your and the bike are still attached to each other, that COG is for the whole assembly, and it's higher than it would be if you were sitting down.

Imagine drilling a hole in the handles of two hammers, and fixing a pivot between those two hammer handles. You have one assembly, with two bits of mass, and one adjustable COG.

Simples,
Bike with rider in saddle makes 1 homogeneous mass.
Bike with ride off of saddle makes 1 homogeneous mass and 1 human counter balance.

The thing which makes NO SENSE is when you see enduro events and riders have thier feet off the pegs but their bums on the seats Robbbeerrrrtt will no doubt remember my bambozled shouting of "feet on the pegs feet on the pegs" when we went to the nationals event at Tong last year.

Originally Posted by Owenski

The thing which makes NO SENSE is when you see enduro events and riders have thier feet off the pegs but their bums on the seats (((WWWWWTTTTFFFFF)))))?

Just so they can dab a foot down or kick the bike back upright if they loose it.

On a speedway style corner it makes loads of sense.

Originally Posted by Balky001

When upright, transferring weight from the seat to the pegs lowers the CoG.

That depends upon how heavy you are in comparison to the bike. If your 18 stone in your riding gear, on an 18 stone enduro bike, then dropping where the weight rests, isn't going to compensate for raising your fat rrssss higher in the air.