ADVrider

Go Back   ADVrider > Bikes > GSpot > GS Boxers
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-07-2013, 09:30 PM   #46
billdonna
Ex Coelis
 
billdonna's Avatar
 
Joined: May 2011
Location: Niagara, Canada
Oddometer: 954
Quote:
Originally Posted by the_menno View Post
Due to a rotating crankshaft along a longitudinal plane, is my answer.

Like member Bemiiten said: 'Heavy crankshaft spinning along the bikes axis causes a torque effect. They all do it'.

I have to agree.

My GS pig runs straight as an arrow both under acel and cruising. Isn't the counter-balace shaft design supposed to compensate for this effect? Wouldn't all Beemers torque steer if this was the root problem?

Too much brain freeze in the Peg eh?
__________________
I do not intend to tiptoe through life, only to arrive safely at death
billdonna is online now   Reply With Quote
Old 03-08-2013, 04:42 AM   #47
roger 04 rt
Beastly Adventurer
 
roger 04 rt's Avatar
 
Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,098
Quote:
Originally Posted by billdonna View Post
My GS pig runs straight as an arrow both under acel and cruising. Isn't the counter-balace shaft design supposed to compensate for this effect? Wouldn't all Beemers torque steer if this was the root problem?

Too much brain freeze in the Peg eh?
As I mentioned the only time there is a torque effect is when you change engine speed, and then only momentarily. Try it yourself. Stopped with the engine running, balanced on your toes, quickly blip the throttle, the bike leans left. Increase the rpm from 1000 to 4000 though, and once at 4000 it takes no more force that at idle to hold the bike upright.

The root problem is either rear wheel offset which should be designed to counterbalance known weight offsets or side to side weight differences caused by fuel, transmission, exhaust, FD, etc. To convince yourself just start adding 5 lbs. at a time to one side or the other.

A bent frame could also cause tracking problems but many boxer models have 10-15 lb. side to side imbalances. And they all have some amount of rear wheel offset.
roger 04 rt is offline   Reply With Quote
Old 03-08-2013, 05:16 AM   #48
billdonna
Ex Coelis
 
billdonna's Avatar
 
Joined: May 2011
Location: Niagara, Canada
Oddometer: 954
Nope, it doesn't happen on my ride.
I am familiar with torque effect on small aircraft where one has to kick on opposite rudder to keep a straight track on takeoff.
__________________
I do not intend to tiptoe through life, only to arrive safely at death
billdonna is online now   Reply With Quote
Old 03-08-2013, 05:30 AM   #49
roger 04 rt
Beastly Adventurer
 
roger 04 rt's Avatar
 
Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,098
Hi, I'm a pilot too. I think this is the effect you're referring to (courtesy of flightgear.org):

Prop wash
A propeller pushes air not just horizontally to the back, but more in a twisting helix around the fuselage (clockwise as seen from the cockpit). As the air whirls around the fuselage it pushes against the left side of the vertical tail (assuming it is located above the propeller's axis), causing the plane to yaw to the left. The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i.e., at high power and low airspeed, which is the situation when starting the takeoff run.

To my own surprise, I realized that there's a sort-of weight and balance side-to-side calculation affected by rear wheel offset. Then I just went out and rode various weights. Of course the RT has a major fuel imbalance that I believe is not so prominent on the GS.

roger 04 rt screwed with this post 03-08-2013 at 06:15 AM
roger 04 rt is offline   Reply With Quote
Old 03-08-2013, 09:41 PM   #50
TUCKERS
the famous james
 
TUCKERS's Avatar
 
Joined: Dec 2005
Location: Villa Maria Sanitarium, Claremont, CA.
Oddometer: 11,454
Wow! Not one mention of paralever bearings/bushings and he says he has play in the rear wheel.

Choose either OEM or Rubber Chicken Racing and do your paralever.

On center stand have someone hold the rear brake down. Rock the wheel now, and if it moves AT ALL you need to do the paralever bushings/bearings.

If it only rocks with the brake off you need to do your Big final drive bearing.
__________________
James and Colleen Tucker.
Aut viam inveniam aut faciam
DMV work/insurance/registration/titles/address use/room rental/motorbike&vehicle buying/travelers help/problems solved
TUCKERS is offline   Reply With Quote
Old 03-09-2013, 04:43 PM   #51
Ron from BC
Beastly Adventurer
 
Ron from BC's Avatar
 
Joined: Jun 2008
Location: Vancouver Island
Oddometer: 1,322
Ditto

Quote:
Originally Posted by TUCKERS View Post
Wow! Not one mention of paralever bearings/bushings and he says he has play in the rear wheel.

Choose either OEM or Rubber Chicken Racing and do your paralever.

On center stand have someone hold the rear brake down. Rock the wheel now, and if it moves AT ALL you need to do the paralever bushings/bearings.

If it only rocks with the brake off you need to do your Big final drive bearing.
Is that not a symptom of worn pivot bearings.....not tracking in line with front wheel?
__________________
'02 BMW R1150 GSA
'06 Kawasaki KL250H Super Sherpa
Ron from BC is offline   Reply With Quote
Old 03-10-2013, 01:03 AM   #52
tagesk
Tuscan rider
 
tagesk's Avatar
 
Joined: Jun 2007
Location: Tuscany, Italy
Oddometer: 3,199
Quote:
Originally Posted by roger 04 rt View Post
As I mentioned the only time there is a torque effect is when you change engine speed, and then only momentarily.
....and it the effect of accelerating a rotating mass.

[TaSK]
__________________
'02 R1150GS - Adds life
My Riding in Tuscany-thread is here.
Renting out motorbikes in Toscana, Italy
Proud contributor to Wisdom and GSpot FAQ and European Ride Report Index.
IBA: 33616
tagesk is offline   Reply With Quote
Old 03-10-2013, 04:44 AM   #53
bemiiten
League of Adventures
 
bemiiten's Avatar
 
Joined: Jul 2003
Location: Hamilton NJ.
Oddometer: 4,835
Quote:
Originally Posted by billdonna View Post
My GS pig runs straight as an arrow both under acel and cruising. Isn't the counter-balace shaft design supposed to compensate for this effect? Wouldn't all Beemers torque steer if this was the root problem?

Too much brain freeze in the Peg eh?
No counterbalance on a 1150.
bemiiten 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 02:37 AM.


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