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Old 12-25-2008, 01:13 AM   #47
warewolf
Tyre critic
 
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Joined: Oct 2004
Location: Nelson, New Zealand
Oddometer: 2,496
Quote:
Originally Posted by Zerodog
When you get the new one pop a seal off one side with a small screwdriver and pack the crap out of it with your favorite waterproof grease. That is a dirtbike trick to help seal out the water and crap.
Quote:
Originally Posted by Loadedagain
no!!!!! bearings come pre packed with a sufficient amount of grease. packing in a whole whack more could cause an overheating condition and failure. you may get lucky and heat the bearing up resulting in liquid grease pouring out... but the result will be similar... no grease... you will likely have a failure.
Righto, today had a little chat with the warehouse manager for a local bearing supplier; he offered these points:
  • Anecdotally, 90%-odd of bearings fail due to contamination, bearings put in water are the worst. The seals are not designed for water protection.
  • Bearings do have a limited life, and sealed bearings are lubed for their expected life. Once the grease is gone, the rest of it is in need of replacement, too.
  • Pressure washers and water crossings (hot bearing into cold water, sucks the water in as the bearing cools rapidly while immersed) are the enemy of long bearing life.
  • The rule of thumb for packing with grease is no more than 30% of the cavity. This is more than the manufacturers put in there, they are more exact. Any excess is pushed out of the seals.
  • If the excess cannot be displaced, then it creates friction (drag) hence extra heat which stresses the bearing unecessarily. If you want to pack the crap out of the wheel bearings, remove the inboard seal so all the excess can be displaced happily into the hub. [Which to my mind makes it a waste of effort]
  • Although they should be greased and not rusty, steering head bearings will tend to notch as they never turn a full rotation... another case of poor conditions shortening their life. Nothing you can do about it.
Given my wheel bearings have lasted 30,000km or so, my plan is to pack 30% grease in them every 5-10,000km, as the bike does a lot of water crossings.
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Colin
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