After Lefty bearing replacement, still knocking feeling...

[Christopher Robin]

Originally my problem was a knocking feeling upon the intial compressing of the fork. With the guts of the fork out, it felt like there was a 'dead space' at the start of the fork's compression so I knew it was something with the bearings. I've tried that bearing reset trick and nothing happened.

So after I got the bearings out, they looked fine. I bought a new set anyway to be on the safe side. So after EXTENSIVE struggling, and A LOT OF TIME LOST with getting the bearing races lined up (and following the how-to's for bearing placement), I still get that knocking feeling. It's like the bearings don't start rolling right away at the start of the stroke. They feel like they have play in them.

I like to consider myself mechanically inclined (I do all my own work, I've rebuilt Manitou, RockShox, Stratos, Marzocchi forks) and I've had it with this thing. Unless someone can miraculously give me an answer, look for this thing in the classifieds soon enough and I'll be going with a normal fork.

By the way, since I'm in Canada, sending it to Mendon's isn't too practical. I'd sooner put the rebuild and shipping costs towards getting my 6" Manitou Sherman installed.

[Christopher Robin]

Well whatever I did, it seem to work. Somehow now it feels fine. Weird.

I didn't wait until the end to fill the fork with oil. I still had to install the spring. I noticed there was a little bit of oil slightly bubbling out of the top of the damper. It wasn't much of a surprise when after it was all said and done, rebound didn't work. So I'll have to get new o-rings for that. At least I don't have to screw around with the bearings anymore.

[MarkHL]

On older Lefty's with Manitou internals, there's a crimped area on the damper assembly (see red arrow) that I suspect is responsible for the knocking of some Lefty's. After a period of time it gets worn and develops play. A good test for this is to compress your fork partially, and rock it up and down a small amount and listen for knocking and a feeling of play each time the fork reverses direction of travel.

BTW - I finally "had it" with the fork and my Prophet now looks like this. However, the local C'dale rep was able to get me a new damper assembly and after installing it the knocking seemed "fixed".
I gave the fork to a friend to replace his Lefty.

[MendonCycleSmith]

Stiff, or too much grease can make it feel that way. Often times, breaking in with use makes it go away, sometimes not....

[Christopher Robin]

MarkHL: The knocking is there when the damper assembly is out of the fork completely. So it can't be the damper. But thanks though.

MDS: Too much grease. You know, I thought of that. When I put the new bearings in, they were dry. The bearing races were dry too (for ease of installation). When I had the fork assembled, with new oil in it, the fork actually felt good. I still hadn't put grease on the lower tube.

So I bought new grease, put a decent amount on, secured the boot and cycled the fork a bit. Still worked fine. When I went for a ride, it felt alright and the knocking came back. Towards the end of my 30min ride, I could really feel the knocking. That made me think that maybe there was too much grease: As the fork bearings need to change rolling direction, (ie when you initially compress the fork), maybe there's too much grease causing the bearings to 'slip or slide' on the bearings races until they start rolling again.

I might just try pulling it apart when I have a few days off and trying again... this time without grease (there will be a little bit). I'll make sure to have a case of beer to keep me calm.

edit: and the rebound is fine. Not enough oil went through the valves. I just had to top it up.

[maryana]

What about the good old inner races thickness that cause the effect? Looks like they were misplaced after rebuild.

[Christopher Robin]

I'm not sure what you mean

[maryana]

Can`t remember the thread on this topic. Something from Mendon`s experience and discussions on lefty rattle. In general the thing is when Leftys are factory built, they measure the exact thickness of each inner race and put them in so as the inner leg appeared as square as possible. Here counts every digit after the comma. For example we have 4 races with thickness 1,25, 1,40, 1,35, 1,22. First we put them onto the lower leg and start measuring with a digital caliper. For example we get 5,34. Then measure the length between other two races on the leg, for example 5,48. Not square. Change the races and measure again till you have like 5,41 x 5,40- as square as possible.
That is the reason it`s advised to hold inner races in place by band when disassembling so as not to measure the square again .
Think I got the same problem after rebuild. Bought the digital caliper now and going to put the races in place.

[Christopher Robin]

Ohhhh I see what you mean. Hmmmm, I didn't think they were put together that way. The next time I pull it apart to clean out the grease, I'll juggle things around and make sure things are as square as possible. I suppose not being square would cause front to back or side to side knocking where my issue is up and down. But I'll give your idea a try for sure!

[maryana]

Just read the previous threads on Lefty rattle or Lefty problems and you may find any discussion on your problem.