What Are the Differences of Rollerblade Bearings?

Inline skates can use many bearing sizes and specs

Young girl putting on skates

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Most inline and roller skate wheel bearings are the standard 608 size, with an 8mm bore, a 22mm diameter, and 7mm wide (open, sealed or non-serviceable and shielded) used for inline skates, scooters, skateboards and some quad speed skates. Other sizes Include:

  • 627 size, with a 7mm bore, a 22mm diameter, and 7mm wide (open, sealed or shielded) used on artistic and recreational quad skates and some quad speed skates.
  • 688 size, with an 8mm bore, a 16mm diameter, and 4mm wide (unsealed) or 5mm wide (two shields). This extra light micro bearing is used with some of the new speed skate wheels. 
  • 698 size, with an 8mm bore, a 19mm diameter, and 6mm wide (open, sealed or shielded). This extra light micro bearing is used with some of the new speed skate wheels. 

Many inline and roller skate bearings are graded according to the ABEC scale, but some companies use their own rating systems. Each bearing usually contains seven steel or ceramic balls, but some bearings systems use more. Here are some bearing types you may find when skate shopping or upgrading your equipment:

ABEC and other Rated Bearings

ABEC stands for Annular Bearing Engineering Committee, the committee that rates bearings all over the world. In this system, the scale uses odd-numbered levels 1, 3, 5, 7 and 9, with 9. The higher this number is the tighter the tolerance of the bearing and the better the degree of precision of the bearing. A higher ABEC rating does not necessarily mean a faster standard 608 size bearing, the rating just indicates that it is more efficient.

  • ABEC 1 bearings are the least expensive and the least precise but may be more durable.
  • ABEC 3 bearings are found in some children's and entry level budget skates and are not good for speed.
  • ABEC 5 bearings can be found in many recreational and fitness inline skates.
  • ABEC 7 bearings can be very fast and smooth, but they are expensive.
  • ABEC 9 and higher bearings are not necessary for most inline skating activities.

The ABEC rating of a bearing is determined by asking these four questions:

  1. How close is the bore to 8mm in microns (a micron is one millionth of a meter)?
  2. How close is the outer diameter to 22 in microns?
  3. How close is the width to 7mm in microns?
  4. What's the rotating accuracy in microns?

ABEC is not the only rating system used for inline and roller skate bearings. There is also the International Standards Organization (ISO) system and the German National Standards Organization (DIN) system. Here is a list to help you compare the three systems:

  • ABEC 1 = ISO 0 (or "normal") = DIN P0
  • ABEC 3 = ISO Class 6 = DIN P6
  • ABEC 5 = ISO Class 5 = DIN P5
  • ABEC 7 = ISO Class 4 = DIN P4
  • ABEC 9 = ISO Class 2 = DIN P2

Precision Bearings

There are also standard 608 size precision bearings in the market that do not follow the ABEC rating. They are identified as titanium, Swiss or ceramic bearings, and since they are not part of a formal rating system, it is very hard to compare them. Most bearings in these classes are good performers – with ceramic bearings as the top in performance.

Manufacturer's Bearings

Today many skating equipment companies are naming the ratings of bearings they produce in other ways, too.

  • Rollerblade uses “SG” rated bearings.
  • Bones Bearings are Skate Rated™.
  • K2 uses “ILQ” rated bearings.

Micro Skate Bearings

Micro bearings can be ABEC, precision or manufacturer rated and they come in a 688 size - much smaller and half the weight of standard 608 skate bearings. These bearings are often not rated at all but they are known as great performers. Micro bearings have more ball bearings in each bearing housing to distribute a skater’s weight more evenly and permit the bearing to work with more efficiency.

All of these bearing types also can be found in a variety of sizes to suit various skate needs.