Scooterotica

Any ideas on what the "clearance" is on these 2 bearings, the cheaper one says "clearance standard" the other one says "clearance C3"



NU2205 ECP SKF Roller Bearing

NU2205 ECPC3 SKF Roller Bearing

Martin, think this refers to how tight the bearing play is (look at second chart)

http://www.smallparts.com.au/technical/ ... clearance/

This explains it a bit better.
In ball bearings, as the radial clearance increases, the axial clearance increases as well. The more room between the balls and the rings (radial clearance), the more the elements can shift in relation to each other. Generally, internal clearances are designated from C1 (the tightest) through to C5 (the loosest or largest). The 'normal' clearance is CN, a range sitting between C2 and C3. It is worth noting that if the bearing clearance is not stated in the bearing reference it can be assumed to be normal clearance. With a higher clearance there is more tolerance of thermal expansion effects on the rings and rolling elements. When noise and vibration must be restricted, lower clearances are necessary. Ultimately the specific application and operating conditions determine the appropriate internal clearance. For example, paper-drying machines that operate under hot conditions usually need C3 and C4 clearances. The severe vibration in vibrating screens normally means that C3 and C4 clearances are required. Selection of the correct radial internal clearance group is by calculation and you should refer to your bearing manufacturers handbook. If you weren't such a lazy Fecker, you would have googled it like me

I know from past checks that the Lambretta was originally listed as running on a C3 clearance for both Drive and Mag bearings in the FAG bearing books of old, thats from when Lambrettas were a big enough customer to be listed.

dapper wrote: This explains it a bit better.
In ball bearings, as the radial clearance increases, the axial clearance increases as well. The more room between the balls and the rings (radial clearance), the more the elements can shift in relation to each other. Generally, internal clearances are designated from C1 (the tightest) through to C5 (the loosest or largest). The 'normal' clearance is CN, a range sitting between C2 and C3. It is worth noting that if the bearing clearance is not stated in the bearing reference it can be assumed to be normal clearance. With a higher clearance there is more tolerance of thermal expansion effects on the rings and rolling elements. When noise and vibration must be restricted, lower clearances are necessary. Ultimately the specific application and operating conditions determine the appropriate internal clearance. For example, paper-drying machines that operate under hot conditions usually need C3 and C4 clearances. The severe vibration in vibrating screens normally means that C3 and C4 clearances are required. Selection of the correct radial internal clearance group is by calculation and you should refer to your bearing manufacturers handbook.

Kinell my brain hurts now.

I'm an electrician and we rebuild the occasional motor at work.
We use C3 bearings in vacuum pump motors because of their high rpm (high rpm for motors that is) and the high internal temps they reach.

I'd suggest that if you had a choice and the C3 bearings aren't too much more than standard, go with the C3.

doesn't the guy with the 100mph lambretta use c4 bearings to reduce friction? im almost certain this was mentioned in the write up about his scooter that was in scootering a while ago

C1, C2, C3, etc
C1=Standard tollerance on the rolllers or balls Etc Pluss 1 micron additional clearance

C2=Pluss 2 microns

C3=Pluss 3 microns

Etc. Etc

That`s what the bloke from Fag bearings told me

Use C1 in normal room temperatures and C3 when the bearing is going to run in a hot environment