There seems to be a difference of opinion on reusing collets if they are ok or installing new with regards to bedding in and valve clearance. I have only just come across this after buying new. Also after watching "Brad the Bike Boy" he says if reusing to put the shims back in the same way. Question is how do you tell. I have a jewelers loop magnifying glass and can see some marks but I don't know which marks indicate up or down. Does anyone have any close-up picture or can describe the marks, or draw me a quick picture. Stay uninfected Cheers Gaz
If you can imagine a circular cross-section of a collet, the top will show wear on the inner radius and the bottom will show wear on the outer radius. Sorry I can't describe them any better. There used to be some drawings on Chris Kelly of CCW's tech website but that was years ago. I've no idea if they can still be found.
Thanks both for that, that has given me a bit more of an idea. I think Ive seen it mentioned before that the indentation is more pronounced on the ends of the collets. Ive done some reverse lens (poor mans macro) photography so if I get the chance will take some close-ups. Also I can see some dark oil discolouration to the upper outer quadrant of the collet which is the bit thats exposed, so looking on top of the collet the inner half is shiny and outer half is darker oil stained. Cheers Gaz edit: Both pictures of same end, based on that I would say: 1st pic - is looking on top of collet (shiny inner / oily dull outer) 2nd pic - top of collet upper most in photo with witness mark. Any thoughts Cheers Gaz
I've just done this, I found it very difficult to tell which side had any wear. I used binoculars backwards as a magnifier and could just about see a shiny side on some, but only just. 16500 miles.
Yes it is difficult. I think unless there was a definate difference in colour which is the oil staining on the exposed outer top part I would have difficulty, but the more I look the better I am getting. What I am concentrating on is identifying the top of the ring and if you refer to the diagram from aero I look for the flattening out to the inside and I seem to be seeing it more on the ends where the collet is deformed from cutting it to length. I found the jewelers loop very useful and I have used it on planty of other occasions, I would recommend getting one they are not that much, a few £. Cheers Gaz
While waiting for a closing shim and closing shim measuring tool to arrive - I had a theory. I thought "you have the valve, you have the shim, you have the collets" - why can't you measure the shim thickness. So, this is what I came up with. Happy to be shot down in flames, but it comes out pretty close. At the minute I am putting the difference down to the tool measuring to the corner, while my set up measures the shim as it is seated on the collet (as in operation) and I think there is a small depression in the shim seat as over time the shim has become compressed in that area. I bought a closing shim from ebay advertised as 6.82mm. I measured 6.76mm. It would be good if someone could check with a known "NEW" shim without any wear. The trouble I had was keeping the Vernier square. I had to rock it from side to side and front to back to make sure it sat square on the end of the valve. I have a depth micrometre on order in the hope this will make the measurement more accurate. I think at the end of this we will be still no wiser and you will get a shim roughly the right thickness but may have to change it by a size anyway. Also as other have stated I don't think the "loaded" "unloaded" method is that accurate to measure closing clearance. All feed back welcome Cheers Gaz
I think your reasoning is correct. Ok if you have a spare valve but not the sort of thing you could do with the head Insitu.
