Which size for your bearing spacers?

Focus on spacers

Spacers are the small parts inserted in-between the two bearings of your skate wheel axles. They take care of the coherence between the two bearings, in order to optimize the matching and synchronization of their rotation. The bearings lean on them when tightened.
The most common model is shown on the 3D diagram below (in blue): a floating collar spacer with an axle of 8 mm.

Spacer for 8 mm axle

Sometimes, no spacers needed!

Some entry level skates are not even equipped with spacers. It might be the case if the skates are supplied with AB bearings, that is to say bearings the inner race of which is prolonged with a sleeve that serves as a spacer.

No spacer with 608 AB bearings >>

Which model to choose?

Theoretically, all spacers can do the job. Some have a collar, which enables them to stay in the axis and makes the mounting of the wheels easier.
Apart from this aspect, the best thing to do remains trying several models for the same wheel, since there are no real standards that can be used with all wheels. Follow a methodical process!

Nothing can ever be taken for granted

According to the wheel brand you use, you may have to change spacers. Indeed, molded plastic hubs vary in width, it’s a matter of a few tenths of millimeters. The diameter of the wheel hub may or may not allow spacers.
If you use micro bearings, they only fit with special sleeve spacers (longer) because their width is smaller than that of classic bearings.

Check your axle diameter to choose the right spacers

If you have to change your spacers, check whether you have 6, 7 or 8 mm axles.

If you are equipped with 6 or 7 mm axles, the spacer is often to be inserted into the bearings. Sometimes the outside of the spacer may be screwed and the axles replaced by screws.

Some other times, frames don’t have bearing seats (bulges that give space to the bearings) and you’ll have to add washers, like it is the case for Hypno skates.

If you have 8 mm axles, the spacer will be a simple floating spacer, placed in-between the bearings for them to lean against when tightened.

Hypno-type spacer >>

Plastic or metal spacers?

Many entry level and mid-range models are equipped with plastic spacers. Sometimes, they break. In this case, don’t hesitate to replace them with metal spacers, more expensive but more resistant and more efficient.
As for metal spacers, there are differences according to alloys, more or less heavy, and more or less susceptible to corrosion. Make sure that the sides in contact with the bearings are in mint condition.

What are the consequences of an inadequate spacer?

Whatever the skate and the type of wheel, the axial tightening is done on the inner race of the bearings. Bearings and wheels are essentially linked by a tight adjustment between the outer race and the hub.

• If the spacer is too big, there will be play between the hub flange and the two bearings, and the wheel will be loose.
• If the spacer is too small, the inner races will be crushed and the bearings will be constraint.
• At best, the wheel won’t turn. At worst, the sides of the bearings will wear out and the bearing will be degraded.

How to find the most suitable spacer?

First of all, be careful when mounting. Ideally, bearings are mounted in pushing on their outer race to the hub flange.

Then:
• Make the wheel turn in pressing one finger on the inner race of one bearing. The race of the opposite bearing should turn too.
• If one of the bearings sticks out when you enter the other one, your spacer is too long.
• If the spacer moves when you shake your wheel, it might be too small (rough test).
• Mount the wheel on the axle and make it turn while tightening it. If the wheel slows down right away, the spacer is too short (closer test).

Spacer for 6mm axle

Hub flange
Outer race
Inner race
Spacer

Sort through your pile of spacers

There is nothing more rational than a good old measuring tool. We use a caliper. You don’t have to have a digital version like the picture below, a classic model will perfectly do.

Useful links

Axles and spacers for skates

By Alfathor and 8wd