Tesla Model S Makes Use Of SKF Ceramic Motor Bearings – Video




Did you know that Tesla relies on SKF ceramic bearings for the Model S motor? Should you care?

Well, in this video both SKF and Tesla discuss the importance of something so seemingly minor as motor bearings. Of particular interest is that SKF claims that one of its goal is to assist the automotive world in making the most energy efficient vehicles possible.

But what actually grabs our attention is where the video is shot and who hosts the video segment. Race car driver Jeff Burton of NASCAR is the host and the video is shot within Tesla’s Fremont factory, providing us with one of those rare glimpses inside Fremont.

Categories: Tesla, Videos


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21 Comments on "Tesla Model S Makes Use Of SKF Ceramic Motor Bearings – Video"

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Motor bearings are not minor at all; if you reduce the friction you reduce the energy loss. Theoretically a magnetic bearing would be ideal because it would be frictionless. That is why a maglev train (or a Hyperloop) is more interesting than a standard train. However since Tesla hasn’t applied magnetic bearing to their motor they applied the next best thing, ceramic bearings. Although they still could find better in graphene lubrication less systems but they have to start somewhere and ceramics is a quiet good.

Beside, tires are not ideal neither because they impose friction losses all the time instead of only when you need it during acceleration and breaking. Actually, you should have kind of electro adaptive material tires that would bring rolling resistance only if and when you need it. The rest of the time, straight line constant speed your tire material should ideally exhibit no friction at all. An electric current would change the tire material when necessary. By doing so you could reduce rolling losses even further. Kind of hover crafting between accelerations, if you like.

“Motor bearings are not minor”. Remember, what motor bearings for a gas engine look like (google image search)-


The two thin half moons, a pair for each “rod”, connected to each cylinder. Very different application of a “bearing”, than what Tesla/SKF are talking about. They probably couldn’t consider ceramics bearing sleeves in “regular” cars. The conversion of longitudinal, to rotational, energy would beat the crap out of them, as they get pounded from the side with every ignition.

“straight line constant speed your tire material should ideally exhibit no friction at all”

That would only work if the vehicle was moving in vacuum (i.e. there was no wind resistance at all).
Since that’s clearly not the case on Earth, you need friction from between the tires and the road to keep the vehicle at constant speed – else wind resistance would slow it down.

Yes you need some indeed for that, that’s correct. So, we should do our best at reducing it but not go all the way to 100%. Or the software should constantly calculate what’s needed to balance the wind resistance according to the speed of the car.

I wonder if they are causing the “milling” sound?

Maybe these bearing are what is failing in the S power unit.

Probably. Due to high speed spin rates and tight tolerances that are required.
I had wheel bearing go or going out on my company van. It produced a high pitched squealing sound, not really loud but noticeable, and it would vary depending on speed. It got worse as you went faster.

Electric Car Guest Drive

Did anyone notice that both front and rear wheels of the Model S were spinning on that dyno test at 2:15? Most interestingly, the front wheels spin up later than the rear wheels. No transfer cases needed here!

most intresting. 🙂
4wheel drive test Unit?

Good observation, but that could well be the dyno turning the front wheels.

It’s probably a a factory Q&A test rather than an R&D dyno, and they’ll want to spin the front wheels as well to check for a misaligned wheel and to test the brakes.

Reliable bearings have been around as long as the 120 year old 4 pole ac induction motor, various versions of which all Teslas currently use. (Unless they’ve changed their minds and use something different mid run). The fact remains as others have said “A 13% drive replacement rate is unacceptable”. Seeing as this is 19th century propulsion technology, you would think they could come up with a system that would be reliable, even if they have to use 19th century babbit bearings. The George Westinghouse 1903 Rankine Plant in Niagara Falls, having 13 – 9000 horsepower 250 rpm machines lasted around 103 years prior to being shut down with no bearing changes, for 2 reasons – one the water the plant used was earmarked for a newer Canadian Hydro Plant and two, canada stopped using 25 hz power in general around 1957 (I have seen an old 25 hz Color TV set, though). For a while, the majority of the plant’s output was shipped to the states for the few remaining 25hz customers in the buffalo ny area, with the majority of power being converted in West Seneca to 60 HZ through 2 old frequency changers. The water lubricated wood… Read more »

Well, Bill, 250 RPM is lot easier to handle than the 16,000 RPM that can happen in a Tesla motor . . . especially since it is in an automotive environment which subjects it to NVH threats.

Yeah, well, sorry, I don’t want a car with a 13 % drive replacement rate. I’m sorry, I don’t. There’s no necessity for this motor to spin at 16,000 rpm. A little more weight for a somewhat slower, much more reliable motor and drive wouldn’t hurt. Tesla has been good enough about extending service for me, but the last time, they let a hammer-mechanic loose on my Roadster, and he only managed to 1). deform the trunk latch 2). Break the Heater and Air conditioner Blower (you can’t make this stuff up).(This was supposedly done to get the PEM cooling fan running, when the easiest way to do that is to simply charge it). 3). Rip or tear a floor panel while he was breaking the heater. And by the way, it only took them 3 weeks of having my car to accomplish the above, and they didn’t even fix my initial complaint, that of the DMC MOTOR PROBLEM alarm coming in. I didn’t see any real trouble since everything seemed to be working fine. Of course, now there are plenty of things to really fix. Now i’m waiting for them to send someone to my house, since I told… Read more »

I’m sure someone will comment that the car needs a new Flux Capacitor seeing as it is a DMC alarm.

Just watched the video. I don’t think they intended to be this funny….

The video showing the rotating shaft (the snap shot of which is above in the article), shows the knob on the shaft only wobbles around an 1/8 inch every revolution!!!

Sounds like something Hanna and Barbarra could have used for a ‘Flintstone’ cartoon.

Are you telling us that we will see Tesla at NASCAR? This would be a revolution in the sport…

Ceramic is a bad choice for that application. One chip in one ball and it takes out the whole bearing. I imagine this is the source of Tesla’s milling noise.

A lot of lighter duty applications have had bad luck with ceramic bearings(bikes, skateboards, etc.) Works fine in lighter duty applications but shock loads and impact are too much for them.

I saw that wobble too, and I do agree with Bill about reducing speed to enhance reliability.
In an earlier article on this topic I mentioned people beating on their Tesla’s like a a re-headed step child, and as with anything mechanical, the better you treat it the longer it lasts. One reason I still have an 89 Camry and had a 1970 SaaB, (last year of free-wheeling), which incidentally went down after I threw a bearing after hitting a foot deep pothole.
If it is the bearings my guess is there is a cracking of the bearing due to intense heat and a lubrication system that breaks down being a contributory cause of that failure.

I am not sure about how much ceramic bearings expand and contract due to heating and subsequent cooling, perhaps that is why they chose ceramic bearings instead of metal ones.

Well from this article it seems ceramic was the only choice. But of note is a statement paraphrased: “Under heavy load ceramic bearings may not even match the duration of steel bearings.”

Actually are there heavy loads on the motor bearings? It seems to me all what they are wearing is the weight of the motor rotor and the forces acting upon that part due to the cars accelerations, but that not really a heavy load is it? It certainly is less then what is on the wheel bearings which carry one fourth the cars weight plus accelerations.

At 9.73:1 gearing ratio, those bearings better be able to stand up to all the NVH stress on them…

Reducing RPM is the easiest way to reduce NVH impact.

Maybe GM’s approach to Spark EV is better. Higher torque but lower rpm (taller gearing ratio).