Hi All,
So I was down my very local bearing supplier yesterday and I was after a set of C3 grade bearings as per Ian’s guidance in the tech section.
They could supply 3 out of the 4 with that being practically impossible to obtain (from a bearing manufacturer I would trust).
We were chatting and I suggested that if they could supply a crank set of the four, all C3, there would probably be some interest.
So, straw poll to try and convince them (as they would be getting the fourth commissioned especially).
Who would be interested in such a deal (please note this is very early doors conversation)?
The C3 grading for bearings does not affect the external dimensions (O.D,I.D.,width) which are the same for C3 and 'standard' fits...It relates to the internal clearances (a few microns more than a standard bearing)...Operating temperature and the 'fit' into the crankcase were the key factors that led to the adoption of that specification...
Personally I'm not entirely sure it may be necessary for many, or even most engines...Most crankcases have probably now had multiple bearing changes, sometimes done without pre heating of the crank cases.
As a consequence many engines have lost some 'fit' off the cases and the tolerances are no longer exactly as they were originally..That is certainly the case with some crank case bearing housings I have measured in the past...
I suppose if C3 bearings are fitted then you will know they aren't too tight but I have run standard bearings without any discernible problems on occasion.
I suppose the thing to do is to accurately measure the crank cases to determine the current state of play..Ian
Hi Ian,
I was taking guidance from the bearing sheet in the tech section, which has your name at the bottom.
Are you the same Ian?😃
If it is not that important then I can move on, but maybe we should amend the sheet to avoid confusion of others in the future.
Hi Scott...Yes, it was me that put that piece in the Tech Section..An additional note may indeed be helpful with regard to clarifying the possibilities but of course each case would have to be assessed individually...
For example, I recently fitted NOS crank cases to my own bike so no wear there at all!...
If C3 bearings are available and the cost isn't prohibitive then I would think fitting them may be the best option...If a very high cost is involved then measuring the cases and, if appropriate, using standard bearings may provide another solution..
I might be interested in a specially manufactured bearing...I have had some done myself in the past. However, it would have to be determined that all sources had been investigated first before getting into going down that route...It can be quite expensive...
By the way, you didn't say which bearing you couldn't source in C3, your location or whether you have searched any further than your local supplier....Ian
