Originally Posted by
Teach
Bob, sure I can, but it would be much better if I just quote a fella I know who knows more about DS conversions than anyone else.
"If the centerline of the wheel stays in the same place, then static loading on the final drive bearings remains the same, regardless of how you get there.
All that the bearings 'see' is how far away from me is the load applied (centerline) and how much (total mass being supported at that wheel).
If you offset the wheel farther away from the final drive, then the output shaft will see a larger moment load which will result in addition loading on the bearings.
Imagine a bar held horizontally in your hand, as a weight gets moved farther out away from your hand it has a greater torque load that your hand/wrist much resist in order to keep the bar from sagging.
-----
Now, imagine adding extra weight at the same spot on the bar you are holding, and you will agree that it also takes more work to hold the bar level, right?
That is analogous to what would happen if you go with a heavier wheel/tire.
OR..... if you add extra mass.
Except, our wheel assembly is not hanging out in space, it is resting on the ground and holding up the final drive (and rest of the bike/rig).
So when stopped the extra weight of the heavier wheel has no effect on the load seen by the final drive bearings.
BUT....
You didn't buy the bike/rig just to have it parked and looking pretty, so you drive down the road. And while driving down the road you will hit bumps, causing the suspension to move.
NOW that added wheel/tire mass does have some effect. The wheel/tire/final drive/swingarm is all mounted "below" the spring/shock unit and is refered to as the 'Unsprung Mass'.
Greater unsprung mass affects how quickly/well the suspension can react to being bumped. Basically, it takes more energy to both get it moving, and stop that movement when you have more mass.
Which means that with a heavier wheel/tire your suspension is going to feel harsher, and in some cases may not stay in contact with the road/trail as well.
And, there is then an inertial force that is transmitted to the bearings of the final drive as the wheel bounces around on the end of the output shaft. The larger the mass that the final drive bearings are trying to control, the more load the bearings see.
The heavier the wheel/adapter, the more force transmitted. And, the rougher the road/trail, the more inertial force transmitted through the output bearings due to larger/faster/more frequent movements of the unsprung mass.
Yes, inertial loading is probably a smaller component to the final drive bearing loads than static loading, but NOT insignificant."
Hope this helps.......
Your time at the podium was well spent
Reply With Quote