Lets start off with sizes. The standard size for a skate bearing is '608'. If you ever need bearings and can only find a hardware store, asking for a '608 bearing' is your best bet. The standard dimensions are-
-8mm Internal Diameter (The hole that your axle slides through)
-22mm Outer Diameter (Diameter of the bearing as a whole)
-7mm wide
Bearings are rated on the Abec scale, the Abec scale does NOT determine how fast the bearings are, it is actually a scale of precision and accuracy.
Some things you should know about the abec scale:
- The abec scale stops at Abec 9. Any item rated higher than Abec 9 is falsely advertised
- Higher is not always better. Higher rated bearings are more precise, but are easier to knock out of whack and bust because of it.
- The speed of a bearing is not so much determined by the Abec scale, more the lubricants and cage options that have been chosen by the manufacturers.
Next comes the big difference between bearings, the material and type of ball cage. There are two common type of ball cages used in smaller bearings, 2 piece cages and one piece cages (A no cage alternative also exists, but good luck finding a commercial skate bearing without one).
2 piece cages are ALWAYS metal, you will never find a synthetic two piece cage, because it's impractical and near impossible to create one strong enough (If anyone finds one, I'll paypal you 1 dollar).
Most once piece cages in skate bearings will be synthetic, or man made nylon. Nylon plastic cages are much faster rolling and create much less friction than steel counterparts. If you get a chance always check to see if the bearings you are buying have plastic ball cages.
Next comes the type of balls in the bearings. Standard bearings use stainless steel or polished steel balls. Both of these materials are quite hard and roll adequately fast for skateboarding. Other types of bearings utilise different types of balls, for example titanium bearings. Titanium bearings use titanium balls instead of stainless steel or polished steel, because of the more beneficial properties titanium presents. See the list compiled below for more information on titanium and ceramic bearings.
- Titanium bearings
Titanium balls are lighter than steel and are also harder. As a result, titanium bearings are lighter, faster rolling and create less friction. Titanium balls do cause more wear to races than steel because of their hardness. Titanium bearings do require lubrication for prolonged life and better performance
Ceramic bearings
Ceramic bearings use balls made of Silicone Nitride (N4Si3). These balls are much lighter than steel and are also much harder. Ceramic bearings create FAR less friction that steel balls and therefore run a lot cooler. Ceramic balls are also hard enough to prevent damage from debris inside the bearing, meaning that ceramic bearings do not have to be regularly cleaned and lubricated. That doesn't mean it's a useless process though, all bearings gain from the occasional clean.
So, next up is seals/shields. Seals are really just the way that you access the inside of your bearings, for cleaning or oiling or whatever. The type of seal doesn't really matter as long as it is a non-contact seal. This means that the seal does not actually touch the moving parts of the bearings, it just shields them.
Listing every single type of seal/shield combination is a waste of time, so I will just list the basic ones. If you don't understand what a shield is, refer to the next image.
Metal shields -
In my opinion metal shields are the worst. Near impossible to remove without damaging and they add more heat potential to the rolling bearing. Can be removed by prying off with the tip of a knife or something similar, but will be damaged.
Rubber shields -
Usually rubber shields can be removed and replaced without damaging the shield itself, proving care has been taken. Rubber shields protect the bearings well whilst not adding unnecessary weight or heat potential.
No shields (Rear of ball cage acts as shield, see bearing to far left) -
Remember earlier when I mentioned one piece nylon cages? Well that in itself can act as a removable shield, taking the balls of the bearing out with it. Most skate bearings will have one side without a shield, leaving you the rear of the bearing cage to see and play with. It can be removed with a knife or some sort of small prying tool. If you do have bearings like this, I recommend you point the un-shielded side of the bearing towards the inside of your wheel, protecting it somewhat.
Some shields will have retaining rings holding in the shields, this is usually because the shields themselves can't lock into position. You can remove retaining rings by pushing one side out towards the inner race of the bearing and then popping it outwards, running around the ring with a knife also helps. This video is good, but most rings on bearings will be much tighter. If using a knife, be careful not to cut the seals if they are rubber. Pictured below is a retaining ring.
Shields are really up to you. Use them though.
- Remove the bearing shields, place the exposed bearings and shields in Kerosene. Petrol, Degreaser, rubbing alcohol and WD40 also work for this step. (I know about WD40, I'll tell you why after these steps)
- Leave them soaking overnight, or for at least 6-7 hours
- Remove the bearings and shields from the cleaner, dry them off with a clean rag
- Leave them sitting for at least 2-3 hours, the longer you leave them the better
- Grab some oil (not grease, grease is to thick for 608 bearings, leave it for your headset) and put it in the bearing, spinning the bearing as you do it making sure that you cover most of the bearing. What works? 3in1 oil, bike chain lubricant, even your mums sewing machine oil will work if you're desperate.
- Replace the shield and go ride. Your bearings will take a while to 'break in' or reach optimal performance.
Now, WD40. It's a sin right? Your uncle told you to use it but your friends told you not to? Both of them are right. WD40 is a water dispersant, I assume that's what WD stands for. Putting it on your bearings will destroy all of the lubricant, leaving them what people call a 'Dry bearing'. Dry bearings are bearings that are running without oil or lubricant, and yes they will be quick. Dry bearings always run quicker than oiled bearings, but they will seize quicker, they will overheat quicker and they will wear quicker. Using WD40 to clean your bearings is fine so long as you make sure they are completely dry and free of WD40 before you put lubricant/oil in. If they aren't, it will just eat all of the new oil as well.
You can help prevent your bearings from rusting by putting a light coat of oil around the outside of the bearing, somewhat making a little resistant to water. This will attract dust and debris so I wouldn't recommend doing it by default every time you clean your bearings, only do it if you HAVE to go riding in the rain or something, and wipe it off when you've finished riding in the wet.
You'll need the following
- Rear axle
- 2 good bearings
- 2 Allen keys
- Shitty old bearings
Procedure
- Get your rear axle handy and slide on a shitty old bearing
- After the old bearing you'll want your new good bearing WITH THE OUTSIDE FACING THE SHITTY BEARING
- Then place your wheel on, it won't go right on (well it shouldn't) but just keep it reasonably straight
- Then you've got the optional bearing spacer that I would recommend using. If you don't have on it's not a biggy.
- Then slide on your other good bearing WITH THE INSIDE FACING THE INSIDE OF THE WHEEL
- Then simply fill the rest of the axle up with shitty old bearings until there's overhang at the end
- When there's overhang you can put the tightening bolt inside the axle and tighten
- Make sure that the good bearings are reasonably parallel to the wheel, stop every 1/2 turn or so to check AND CHECK ALL AROUND
- Keep tightening
If you stop turning you've run out of overhang, undo the tightening bolt and add another shit bearing to the others then go again.
