[Paul Copioli]

Kevin B.,

We actually have never been asked to put up the specifications on our web site. My team is working on getting the specifications for all of the bearings since most of them are standard ABEC 1 (or ISO 492 Normal Class for the Metric Bearings) bearings.

The total ratings (mostly the load ratings) have zero applicability in FRC for many reasons (I will make another more detailed post about this later), however the speed rating is important.

So, the Thunderhex bearing limiting speed is 31,000 RPM

The standard 3/8 and 1/2 hex bearing theoretical limiting speed is also 31,000 RPM.

However, the nature of hex bores make them oversized a bit in order to practically install the shaft. So there will be clearance between your shaft and the hex bearing (this is true with ALL hex bearings no matter who makes them or what they tell you). This clearance causes extra load at high speeds.

The reason you can only find AM and VEX (and at one point WCP) who make the 1/2" hex is because it is extremely custom for our application. Most bearing volume usage is for industrial, high precision applications and the Hex tolerance is unacceptable for that use case. For most FRC applications that don't involve high speed shooting, the hex has served us well.

Now, I absolutely despise hex bearings for many reasons. I almost despise them as much as mecanum wheels but that is a story for another day.


We wanted something more from a hex compatible bearing that could give us the flexibility of the hex bearing and the precision of a regular ball bearing.

For this reason, we decided to create the Thunderhex bearing. Bearing manufacturers are really good at making round things round with very little total indicated runout. As a matter of fact, no one does that better than bearing companies. However, they are not very good at making hex holes in bearings. We inspect 100% of our hex bearings to make sure they meet our drawings. The factory scraps about 20% of the hex bearings they manufacture for us before anything gets shipped because they do not meet our specs. The Thunderhex bearing scrap rate is below 0.1%. The reason is simple: Thunderhex bearings are just round bearings with a special inside diameter of 13.75mm.

So my recommendation is use Thunderhex shaft with Thunderhex bearings and you will never have an issue. By the way, for high speed applications we recommend a slight press fit between the bearing and the shaft in order to keep the system balanced at high speed.

The basic issue for high speed applications with Hex bearings is that the clearance to make the hex shaft install properly causes eccentric loads on the bearing which causes premature wear and higher loads on motors, which is the most probable reason you saw a speed difference.

So let me be clear, the VEXpro bearings all use standard industrial balls and bearing raceways and can attain the speeds of their industrial counterparts.

One last thing: my team does not use hex bearings anywhere. We use Thunderhex exclusively and Thunderhex shaft in most places. It has made life so much easier.

I hope this helps.

Paul