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Big end bearings, are they oversize
Posted: Tue Sep 04, 2007 5:59 pm
by youngun
Im going to be ordering new big end shells soon, how can i tell if they are oversize or not? I can see on the underside of mine they have 020 written in very small lettering above what looks like a serial number or something, does this mean they are 20 thou oversize?
Thanks
YG
Posted: Tue Sep 04, 2007 7:18 pm
by rayofleamington
in official terms they would be 'undersize' as a crank would be ground to a smaller diameter. Thought I'd mention that in case you got a sarky parts supplier!
if they say 020 on them I'd bet they are undersize - however the correct way to tell is to measure the crank - this is also required to determine crank wear. If your crank is very worn then best to have it reground anyway and then get bearings to suit the new size.
Posted: Tue Sep 04, 2007 7:36 pm
by bmcecosse
No - you are right - the bearings are oversize - to match the undersize crank! And yes - that 020 will indicate 20 thou oversize. Make sure though that the carnk pins are in good condition and not 'oval' - ideally you should check the size with a micrometer.
Posted: Wed Sep 05, 2007 12:33 pm
by youngun
Righto, thanks guys!