We know, there’s no such thing as a stupid question. But there are some questions you might not want to ask your local shop or riding buddies. AASQ is our weekly series where we get to the bottom of your questions – serious or otherwise. Hit the link at the bottom of the post to submit your own question!
Without things that spin, your bike would never go anywhere. That makes the humble bearing a fairly important part of the bicycle equation – which is probably why they remain a hot topic.
That was clear given the number of bearing related questions we received for this week’s AASQ. Kogel is an interesting company in that they offer only ceramic bearings for all of their products. This seems to have led to a number of questions about their function, durability, maintenance, and how they compare to other bearing types.
To get to all of the different questions, we’re splitting this AASQ into two – with today’s installment focused on functionality and durability. Part Two focuses on maintenance and different bearing types!
Functionality
Hi Kogel! First: I love your bearings! I work as a bike mechanic in Austria, and I often get asked about the price/performance ratio. As you may know, Austrians tend to be loyal but price sensitive customers. Could you provide me with an ultimate & logical (for Austrians) answer to why the hell would an average Austrian mountain biker need to pay $175 for a GXB BSA BB instead of $25 for a regular one that would last maybe few kilometres less but won’t cost that much? Nothing personal, but it would help me to deal with my customers in a better way! 🙂 Love,M
If I have a good set of wheels with steel bearings, what advantage would it be to replace the bearings with your ceramic bearings? – Michael
Kogel: There is no single answer to this, rather there are several answers that lead to the justification of buying high quality bearings:
- Durability: all our bearing products have a two year replacement warranty with very few questions asked.
- Better performance: Since every part of the bearings is optimized, the result is a better working bearing
- Cost of ownership: Kogel only requires a single annual maintenance to keep the bearings under warranty (but recommends sooner if the bearings feel gritty). Sounds better than buying and paying for installation every two months, doesn’t it?
- Time: Everybody is pressed for time nowadays, switching to a bottom bracket that lasts longer will save you some trips to the bike shop or your workspace
Your BB performance is partially depending on the frame manufacturer BB geometries. Recently Cervelo has increased their “official” tolerances for their BB up to 0.1 (45.88-45.96mm versus previous 45.96-45.98). Do you foresee such a wide tolerance as something acceptable for any bearing to properly work? – Jordi
Kogel: While the tolerances are tight, the executions in mass production are hard to follow for frame manufacturers. In carbon fiber more so than aluminum. Even though the manufacturing tolerance is roughly 0.05mm on a PF30, we have seen frame shells with much broader results. For our bottom brackets we consider frames of +/-0.2mm (four times the tolerance!) to be workable. Any smaller and you have a chance of breaking the frame, any larger and the cups will sit loose in the frame.
We have designed our bottom brackets to be tight where possible and relieve pressure on the bearings if they are pressed in slightly undersized frames.
Another (small) BB manufacturer ran some Bike-BB stiffness tests on a frame equipped with different BB-kits and found significant differences (the lowest one being with nylon bushings holding the bearings and the highest one with single piece BB-shell). Did you run similar measurements, any results you can share with us? Seems a key point so far no other BB manufacturers communicate around! – Jordy
Kogel: We did not run a similar lab test to quantify bottom bracket stiffness, but I am very eager to study this more. In order to increase bottom bracket stiffness, we believe in using metal cups, maximizing the contact area between the frame and cups, but mostly in moving the bearings out as close to the crank arms as possible. A wider platform puts less stress on the bearings, resulting in better stiffness and longer bearing life due to the reduced loads.
Is there actually an advantage to ceramic bearings? What about solid oil technology? – Troy
Kogel: The benefits of using a high quality bearing were covered in the first response. We consider hybrid ceramic bearings the most optimized version for bicycle applications (also check out Kogel’s posts on ‘Problems with Ceramic Bearings’ Pt. 1 and Pt. 2)