Hooked On Quack
Join Date: Aug 2009
Location: In the Shadow of the Valley of Death
Bikes: Orbea, Lemond, Trek
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Originally Posted by ErichM
I plan on replacing the crank set on my '10 Madone. I understand they have slip fit bearings and I figure I may as well re-grease those (it is a new bike) at the same time as long as I have the crank set out.
You should be aware that the bearings come in kits that are manufacturer-specific: Shimano, SRAM, or Campy. If you are changing your existing crank with another from the same manufacturer you will reutilize the present bearings. If you are changing manufacturers, Shimano to SRAM for example, you would have to have your LBS get the appropriate bearing kit from Trek.
I've changed Shimano-->Shimano without anything other than the Park BBT9 wrench, and a 5mm Allen. The bearings press fit into the BB area, and really only needed grease when first assembled. When you pull the old crank you will see where the shaft has rested on the bearings, and then can apply some grease to the new crank shaft in the same areas. Then it's just a matter on seating the crank, attaching the crank arm, putting the chain back on and going for a ride.
The Trek manual shows a plastic tool being used to install the bearings. If they are slip fit, can I just press them in with my fingers? Or is there something wrong with doing this? I suppose I could probably have the LBS order one of those plastic installation tools for me, but I wonder why this is necessary when they can be removed with your fingers...
They are "slip fit" to a point. It is a rather TIGHT "slip fit". I had to use a nylon-peen hammer to tap them into place, checking for flush fit with the edge of a steel ruler. I thought I was doing something wrong until I talked to my LBS and he said that he did it the same way. They are a tight fit!
If you have to pull the bearing races out of the frame, I don't think that you'll find that fingers will do it very easily. I saw a wrench changing out the bearings by using the crank shaft to wiggle the bearing races out; seemed to work pretty smoothly. Use the the "tap in" method to put the new, greased bearing races in, add your crank set, and chain, and go for a ride!
That took longer to explain than it did to do it in real life!
If it suits you, buy the plastic thingie, but you can do without it.