The "teeth" are actual hooks from which the urethane can "grab" after cured. The core is the interface between the softer urethane and the hard metal bearing. Besides providing an interface, the fact the core is harder and has an inner ring so the bearings grab to it makes it all work efficiently.

nice explaining of cores, thanks for that

Nice Video and interesting interview with famus master!

I'm getting ready to make an 8 x 90mm famus purchase. I thought they were a new brand, this vid was very informative. Just had a horrible experience with another brand of cracking plastic wheel hubs, and i;m not that aggressive. I'm excited to see if I can elevate my skate.

Thanks Ivo for another excellent video, those metal cores look super cool. Just an opinion regarding the extra weight of the metal cores. I'm a slalom skater but I did speed skating for a while and I noticed skaters being what to me seemed too obsessed by trivial weight differences in their skates and wheels. If it's a 20gram diff between metal and non-metal core for example, that's only 160grams for 8 wheels, you can lose more than that just by going to the toilet ha ha. Skaters are different heights and different weights; if you are really focussed on losing 160grams from your skating, focus more on transition to a low-fat body composition to be a lean skater, light on your feet, and your skating (and health) will improve more significantly than a small difference in wheel core weights. I was so glad to see the comment about the importance of placing the bearing correctly. It took me years to appreciate the importance of that. I now use a great professional bearing press like you have in a skate rink, and the bearings go in with the spacer perfectly, not twisted. Also using the bearing press to remove bearings, I think avoids damage you might cause if you pop bearings out with a hand tool to clean/lube them. Thanks Ivo, love your channel.

Best cores? I guess it's still the core of the good old Cozmo 72mm vert/hockey wheels, those and the ones of the Senate Eric Schrijn Toykillas or the Chimera Dominic Wagner Corpus Delicti. Still on my wanted to try list: 50/50 and famus.

for vibration and comfort which wheel is better the traditional plastic core wheels or aluminium core wheels? regards

Where to buy that bearing press?

Just wondering if there will ever be ceramic cores?..

So maybe titanium or carbon fibre would be slightly better then aluminum but the cost to difference would not be justifiable

How about wooden wheels on rollerskates ??

Reminds me of some wheels, maybe 16 years ago. Metal core aggressive wheels, and you could keep the core and just change the urethane. Don't think it was a big success. Can't remember the name... U-something.