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Discussion Starter #1 (Edited)
So, in the process of replacing all the seals from the main back including that pesky O-ring, when mounting my rear wheel, I noticed that I had some play in the FD. This concerned me as I had replaced the crown bearing last season and had put something around 1k on it since then. I made an educated guess and pre-ordered a couple more shims, knowing what I had in already so I could make a good number of combinations as needed.

I went into it this weekend first looking at the drain plug for any signs of degradation. There was almost nothing on the drain plug magnet as I would expect for the mileage ridden. The bearing was smooth as glass and the wear pattern on the gears was good and did not look to have changed any. Nothing looked to have changed so I went ahead and did the measurement, bolting the FD housing to a piece of steel and them mounting my dial gauge to that piece of steel so I would have a point of reference that would not change as i moved the crown wheel up and down.

Once I got the cover heated and bolted down, the crown wheel moved very easily up and down and the measurement I got with just using my hands to move the crown up and down was 16 thousandths or .406 mm Doing the math, I would need a shim set between .45 and .5mm

Taking into account that I was not prying up on the crown wheel, I decided to go with a .55 shim pack which would put me just over the high end of the preload. I am counting on that 16 thousandths being slightly higher if i had used pry bars ( as I did previously) is why I went to the high side.

My previous pack was a .2 and a .15mm shim for .35 and I didn't have any noticeable play after the first go round yet after some riding, it was obviously not correct. I may have not gotten the bearing totally down flat and that may have corrected itself after some riding as my girl and I run it up close to max load and the additional side thrust of the twisties at SMFR might have been enough to make it seat. Just a thought to account for the difference then and now.

My hope is that now I have a preload somewhere in or very close to the specified range and if I am a tiny bit over, that it is nothing as severe as the .2 most of the FD that have failed were to discovered to have that is believed to be the major cause of early failure.

I think it was katnappin who also did a crown bearing D-man method like me ( couldn't find the thread to confirm, just from memory) and when he got it back on the bike, found he had no preload so he put the original shim back in and that at least took up the play he was feeling. Both of us did as good a job of measuring as we could and somehow still got it wrong.

My original shim was a .7 so now at .55, I am still shimmed less than the one I removed. Still going to look for a spare to rebuild this summer as I noticed the signs of pinion bearing race creep this go round as I now know what to look for so this is not the last time I will be into this FD.

Next time around, I will build a more proper clamp in apparatus to totally immobilize the FD housing in relation to the measuring device so I will have very little doubt on any measurement. Either that or just buy the BMW measuring ring tool and do measurements by the book.
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