Needle bearing migration is a situation unique to the Cannondale’s Lefty forks since it is the only fork on the market that runs on needle bearings. The needle bearings are the secret sauce to why Lefty is the world’s best suspension. They provide extreme smoothness without resistance, allowing the fork to react to small bumps far better than traditional forks.
If your Lefty is feeling a little sluggish and that you can’t use all of your travel or the front end seems to be lower than usual, the most likely problem is that your bearings are migrated. Its a relatively simple fix. This is something that every Lefty will have over the course of its life, some more often than others. Riders that ride more aggressively and catch more air, allowing the fork to fully extend quickly more often typically need to align the bearings less often. In the case of extreme bearing migration, bearings strips can get broken. I’ve seen this a few times, but it is fairly rare.
As seen in the photo, the top of the cartridge won’t descend into the upper structure as evidence that the fork has migrated bearings. After aligning the bearings, the telescope can fully extend, pulling the cartridge lower into the fork’s upper structure. (I should have taken the photo after wiping off the grease, sorry about that.) After an alignment, the telescope feels smoother and lighter in the compression and rebound. The particular fork in the picture was a Lefty DLR 110mm on a 2007 Rush 3 I worked on yesterday and literally felt as good as new. Does your Fox, RockShox, Marzocchi, etc feel like new after five years? (If you’re honest with yourself, look down at the floor and say no.)
So how do you align the bearings? If you’re uncomfortable doing it yourself, bring it to us. If you’re feeling confident, it just takes a couple of standard bicycle tools. The Lefty collar uses the same tool used to remove/install external bottom brackets, like Park’s BBT-9, although we use one with an open end which makes it ten times easier when working with XLR forks with hydraulic-powered external lockout. In the case of older DLR forks, you’ll a 1.5mm hex for the rebound knob and a deep 10mm socket to remove the lockout lever. Every Lefty looks pretty similar the one in the photo after the upper collar and adjustment knobs/buttons/levers are removed. Then remove the little split ring (two little pieces, usually anodized black with the word “TOP” written on it) that rest on the top of the upper structure to keep the cartridge in the right place. If the cartridge doesn’t descend freely into the fork after removing the split ring, you likely have migrated bearings. It seems a little barbaric, but you (gently) slam the telescope to full extension (with or without the wheel on) repeatedly it until it feels like a solid stop at the full telescope extension. You don’t need to let the air out or remove the cartridge for this routine maintenance. Then put it all back together and try it out. You might be surprised what you have been missing out on!
If you need any of the parts described in the instructions above including new knobs or levers, boots, bearings, collars, or split rings, they are available for purchase at CannondaleExperts.com. Use the coupon code “migration” and save 10% off your first order!
WARNING! In the event that you have loose rings or pieces floating in the boot, DO NOT try to align migrated bearings. Bring it to us or another Cannondale dealer for service right away. You’ll pull the lower totally out with pieces going everywhere and ruining your day. And never ride your fork if there are pieces jingling around in the boot, unless you want death. Also, if you have broken bearings or bent races, alignment isn’t going to help!