What About Roller Bearings In
A Big Bike Motor?
Regarding Harley Davidson motorcycles using roller
bearings in their internal engine design, Amsoil synthetic oils
are recommended for these applications. The assumption that synthetic
motor oils are too "slippery" and cause roller bearing
surfaces to slide instead of roll properly is not true.
Harley Davidson has never been able to provide a
valid empirical explanation for their statements about synthetics.
In fact, they have been stating this fallacy for quite some time
without ever providing evidence that it really occurs.
Eaton-Fuller manufactures and designs transmissions
for large trucks and industrial equipment. Nearly all of their transmissions
contain roller bearings. If Harley Davidson's statement was true,
why does Eaton-Fuller recommend synthetics to be used in their transmissions
instead of petroleum based oils? It is because Eaton-Fuller has
found that synthetic lubricants provide enhanced wear protection,
wider operating temperatures, and other beneficial properties typical
petroleum based lubricants cannot provide.
If an oil required for this application needs to
allow friction to make these roller bearing elements operate correctly,
then there is no doubt that other components in the engine will
not be sufficiently protected. Besides, it is not entirely the frictional
characteristics of the lubricant that permits rolling elements to
operate effectively under normal conditions. Elastohydrodynamic
lubrication (EHD) is the lubrication process typically generated
in gear mechanisms and roller bearings. It is characterized by the
occurrence of two phenomena:
- The metal deforms elastically under load, and
recovers original profile exactly when the load is released. This
effectively results in the apparent contact area between the opposing
surfaces, and a reduction of the load per unit of bearing area.
- The high pressures generated in the oil film
lead to an effective increase in viscosity. Fluids in general
have positive viscosity/pressure coefficients and for synthetic
oils, the increase is nominal. The first effect increases the
surface area of the thin film of oil present between the opposed
surfaces, and thereby reduces the stress within the oil. The second
effect reduces the tendency for this oil to be squeezed out by
the pressure between surfaces and forms a wedge of oil film to
protect the rolling surfaces and maintain sufficient internal
pressures to prevent slipping or sliding. Please use the enclosed
diagram and descriptions of the three basic types of lubrication
as reference.
Amsoil's excellent lubricity and film strength will
not cause these bearings to fail; in fact, our oil helps to insure
that all engine components will be protected against even the most
severe operating conditions. Please use the following as a guide
for determining the correct AMSOIL lubricants to use in place of
the manufacturer recommended oils. For the engine crankcase, we
would recommend using our Series 2000 20W-50 motor oil. This may
also be the fluid to use in the transmission.
Harley Davidson Grade
|
Viscosity @ 210 F SUS
|
SAE Grade
|
Amsoil Product
|
|
|
|
|
#58 |
58 |
30 |
10W-40 AMO |
|
|
|
|
#75 |
75 |
40 |
10W-40 AMO |
|
|
|
|
#105 |
105 |
50 |
15W-40
AME |
|
|
|
|
Harley
Davidson Part # |
Component |
|
Amsoil
Product |
|
|
|
|
99887-84 |
Chaincase |
|
10W-40
AMO |
|
|
|
|
99892-84 |
Transmission |
|
Series
2000 75W-90 TGR |
|
|
|
75W-90
AGR |
|
|
|
80W-90
AGT |
|
|
|
80W-90
AGL |
|
|
|
80W-90
ALU |
|
|
|
|
99896-88 |
Transmission |
|
Series
2000 20W-50 TRO |
|
|
|
20W-50
ARO |
|
|
|
|
99903-96 |
Crankcase |
|
Series
2000 20W-50 TRO |
|
|
|
20W-50
ARO |
|
|
|
|
98853-96 |
Transmission (Semi-Synthetic) |
|
Series
2000 75W-90 TGR |
|
|
|
|
|
|
|
|
Elastohydrodynamic
Lubrication (EHD or EHL)
- Condition in which surfaces
of rolling elements of high speed and high load components are either
completely, or in part, separated by a very thin lubricant film.
Mating parts deform elastically, due to incompressibility of the
lubricant film under very high pressure and, therefore, trap or
create a wedge of lubricant between them. This is similar to "hydroplaning"
that cars exhibit on wet roads.
Please note the illustration below:
|