ADVrider

Go Back   ADVrider > Riding > The perfect line and other riding myths
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 12-20-2012, 05:06 AM   #1
henryroten OP
Gnarly Adventurer
 
Joined: Sep 2011
Location: Back in sunny So. Cal!
Oddometer: 232
Center of Gravity

I am considering lowering the suspension on my 990R and was wondering if by doing so the COG is effectively lowered? Or is the COG a relationship between the weight distribution of the motorcycle in relation to the sitting position of the rider (does that make sense?)?

Thanks just curious.
henryroten is offline   Reply With Quote
Old 12-20-2012, 05:15 AM   #2
anotherguy
Beastly Adventurer
 
anotherguy's Avatar
 
Joined: Jun 2009
Location: the hills
Oddometer: 6,012
There4's the vehicle COG and the bike/rider COG. Generally when a bike is lowered both follow. There are variables and unusual situations but they are exceptions.
__________________
A lie has no feet......it can't stand alone.............
Jason Newsted
anotherguy is offline   Reply With Quote
Old 12-20-2012, 05:38 AM   #3
LuciferMutt
Rides slow bike slow
 
LuciferMutt's Avatar
 
Joined: Aug 2008
Location: New(er) Mexico
Oddometer: 11,053
In before the huge argument about if standing on the pegs raises or lowers the CG.
__________________
You couldn't hear a dump truck driving through a nitro glycerin plant!

Badasses might screw with another badass. Nobody screws with a nut job. -- Plaka
LuciferMutt is offline   Reply With Quote
Old 12-20-2012, 06:22 AM   #4
Yossarian™
Deputy Cultural Attaché
 
Yossarian™'s Avatar
 
Joined: Jul 2007
Location: the 'Ha
Oddometer: 9,537
Quote:
Originally Posted by LuciferMutt View Post
In before the huge argument about if standing on the pegs raises or lowers the CG.
Me too. I want to get a good seat.
__________________
Successfully surviving motorcycling since 1976.
Yossarian™ is offline   Reply With Quote
Old 12-20-2012, 06:39 AM   #5
slide
A nation in despair
 
Joined: Jul 2003
Location: NM, USA
Oddometer: 21,123
Quote:
Originally Posted by anotherguy View Post
There4's the vehicle COG and the bike/rider COG. Generally when a bike is lowered both follow. There are variables and unusual situations but they are exceptions.
What do you hope this will accomplish? Better handling? Or what?
__________________
Why be born again when you can just grow up?
slide is offline   Reply With Quote
Old 12-20-2012, 06:51 AM   #6
pretbek
Studly Adventurer
 
pretbek's Avatar
 
Joined: Oct 2008
Location: SE Pennsylvania
Oddometer: 942
Yes the COG is lowered.
But effectively? As in: with noticable effect on handling? I doubt it.

The effect of any geometry change (rear lower than front, mess with the fork to change rake/trail) will be much greater.

Oh, and lowering will very effectively reduce your ground clearance.
pretbek is offline   Reply With Quote
Old 12-20-2012, 10:18 AM   #7
SRG
SRG
 
SRG's Avatar
 
Joined: Nov 2004
Location: Charlottesville, Virginia USA
Oddometer: 1,171
Pretbeck - I think you are right, the actual distance that the CG would be lowered is not a large amount (wouldn't it be equal to amount of lowering? i.e. if you drop the rear 1" and drop the front 1" then the CG drops 1").

However, lowering the CG a seemingly small amount may have larger effects that one might suppose. I know my Husaberg is quite sensitive to changes in the amount of rear sag and position of forks in the tripleclamp.

The only bike I ever tried lowering links on was a 640 Adv. I don't think it effected the handling much, but it did allow the underside of the rear fender to contact the tire under full compression of the shock. Made a cool barking noise when it did .
__________________
Lazy Traveler
SRG is offline   Reply With Quote
Old 12-20-2012, 11:05 AM   #8
DAKEZ
Beastly Adventurer
 
DAKEZ's Avatar
 
Joined: Mar 2007
Location: OR
Oddometer: 19,612
The lower the mass the lower the COG period. Thread over.
__________________
“Watch out for everything bigger than you, they have the "right of weight"
Bib
DAKEZ is offline   Reply With Quote
Old 12-20-2012, 11:22 AM   #9
HH
Hurricane Harry
 
HH's Avatar
 
Joined: Dec 2010
Location: Seattle/Dahlonega
Oddometer: 1,410
Quote:
Originally Posted by DAKEZ View Post
The lower the mass the lower the COG period. Thread over.
wait, what?
HH is offline   Reply With Quote
Old 12-20-2012, 11:24 AM   #10
randyo
Beastly Adventurer
 
randyo's Avatar
 
Joined: Nov 2007
Location: Northern NewEngland
Oddometer: 1,533
Quote:
Originally Posted by LuciferMutt View Post
In before the huge argument about if standing on the pegs raises or lowers the CG.
it does both

lowers COG of bike but raises COG of rider

what does it do to the combination bike rider COG

depends on the bike and the rider
an average rider on a GS, it will lower the COG
a 6'4" 265lb rider on a Rebel, it will raise the COG
__________________
RandyO
IBA # 9560
07 VeeStrom
99 SV650
82 XV920R
A man with a gun is a citizen
A man without a gun is a subject
randyo is offline   Reply With Quote
Old 12-20-2012, 11:32 AM   #11
pretbek
Studly Adventurer
 
pretbek's Avatar
 
Joined: Oct 2008
Location: SE Pennsylvania
Oddometer: 942
Yay! Here we go.

Quote:
Originally Posted by randyo View Post
lowers COG of bike but raises COG of rider
How does standing on the pegs lower the COG of the bike?
In my opinion (and that of physics in this universe), it makes no change to the COG of the bike.
pretbek is offline   Reply With Quote
Old 12-20-2012, 11:45 AM   #12
Yossarian™
Deputy Cultural Attaché
 
Yossarian™'s Avatar
 
Joined: Jul 2007
Location: the 'Ha
Oddometer: 9,537
Quote:
Originally Posted by randyo View Post
lowers COG of bike but raises COG of rider
We've got a live one!
__________________
Successfully surviving motorcycling since 1976.
Yossarian™ is offline   Reply With Quote
Old 12-20-2012, 11:48 AM   #13
randyo
Beastly Adventurer
 
randyo's Avatar
 
Joined: Nov 2007
Location: Northern NewEngland
Oddometer: 1,533
Quote:
Originally Posted by pretbek View Post
Yay! Here we go.



How does standing on the pegs lower the COG of the bike?
In my opinion (and that of physics in this universe), it makes no change to the COG of the bike.
weight that was on the seat is now on the pegs, doh ! but as I said, your body COG is higher
__________________
RandyO
IBA # 9560
07 VeeStrom
99 SV650
82 XV920R
A man with a gun is a citizen
A man without a gun is a subject
randyo is offline   Reply With Quote
Old 12-20-2012, 11:53 AM   #14
slide
A nation in despair
 
Joined: Jul 2003
Location: NM, USA
Oddometer: 21,123
Quote:
Originally Posted by randyo View Post
weight that was on the seat is now on the pegs, doh ! but as I said, your body COG is higher
How about I stand on the pegs but in a sitting posture with my ass is only .0001 mm off the seat.

Now what?
__________________
Why be born again when you can just grow up?
slide is offline   Reply With Quote
Old 12-20-2012, 12:00 PM   #15
High Country Herb
Adventure Connoiseur
 
High Country Herb's Avatar
 
Joined: Apr 2011
Location: Western Sierras
Oddometer: 7,201
Quote:
Originally Posted by pretbek View Post
Yay! Here we go.

How does standing on the pegs lower the COG of the bike?
In my opinion (and that of physics in this universe), it makes no change to the COG of the bike.
The COG (actually center of mass, to be exact) of the bike is unchanged by standing on the pegs (or getting off and walking away for that matter). The COM of the bike+rider raises a bit, because some of the mass (the rider) has moved up. If you stood on a 10 foot tall (weightless) ladder attached to your bike, it would be raised significantly. It doesn't matter where/how the two bodies of mass are attached, the issue is simply the center.

Along those lines, lowering the bike lowers the seat, which also lowers the rider. COM has been lowered. This doesn't mean the bike will be less likley to fall over, though, because now the COM is closer to the point of rotation (where the tires meet the road) and will rotate faster. (more flickable?)

I think the only major benefit to lowering the bike would be making it easier to get your feet flat on the ground when stopped. That will make it less likely to fall over.
High Country Herb is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 11:08 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014