Posted on August 16 2017
We often get asked about bearing migration, and the reset procedure by clients who own Cannondale's Lefty, but what does it actually mean, and what does it actually do?
Firstly, for those who are unaware, the reset procedure is carried out on ALL Cannondale Lefty systems periodically to ensure full travel is achieved. Your needle roller bearings inside your Lefty will migrate downwards over time. There are always 4 sets of needle roller bearings in your Lefty, however it may only require 1 of those to migrate to actually affect your travel, and in some cases the affect of your rebound dampening.
When the bearings migrate down, they can pull the outer steerer down with them, which reduces your travel and the distance in which the oil damper inside is allowed to extend. This is why your rebound may be super super fast before a reset, but after the reset is done, your rebound adjustment feels like it should again - which is slow if turned all the way clockwise, and fast if turned all the way counter clockwise. In some cases, we've seen Lefty's in the workshop with just 40mm travel (out of 100mm), but a quick bearing reset can bring the fork back to life before it's next service is due.
Some quick Q & A:
So, how do i reset my Lefty?
We have a list of the reset procedure's here. Most models will take no more than 5 minutes to complete, and you can do this at home with some basic, common tools including an open ended shimano bb tool. Like this one. You can use the 'closed end' style ones also.
I have a hybrid Lefty. Does it also need to be reset?
Yes it certainly does. Cannondale made a bit of a point about 'no bearing migration' in the early days of Hybrid Lefty (2013 onwards), however in reality - They require it almost as much as previous models. The good thing though - It is much quicker and easier to do, and all you need is a shock pump and measuring tape. See here. Hybrid Lefty have an awesome inbuilt feature called a 'reset spacer' which you can see just above the green and white bearings in the Lefty cutaway image above. It allows you to compress the fork with no air in it, and the bearings will reset themselves against this spacer with a little help of some bottoming out force.
How often do i have to do a reset?
In theory, your bearings inside your Lefty COULD actually migrate on every ride. That doesn't mean that they will, but it's a good habit to get into by checking it at least every month if you're riding it say twice a week for example. Alternatively, go by time with at least every 50hours use, or every 25hours if you really want the best performance from it.