Hello guys, i have a Fezzari road bike that ive just bought, its carbon frame and i found out that the headset bearings need a replacement.
when i disassembled the headset i noticed that unlike usual bearings with two "open" sides my bearings had one "open" side to them and a second side that is metal cast.
Here are some photos to explain

Regular bearing with two open sides.



my bearing with one metal side.




can you tell me whats the difference between those two bearings and also can i use the "two open sides" bearing to replace my unique one?

thank you.

The closed bearing is likely an angular contact bearing. Assuming you match the angles (45X45, 45X36, etc) a normal bearing would probably work - but I would guess that it would alter the stack height of the headset. There might be gaps at the top cap or fork. Ask the manufacturer of the headset.

I think if the bearings were to be dissembled both would turn out to be angular contact. If for no other reason that a headset is a REAL bad application for a radial contact bearing (as much of the loads are nearly in line with the steerer).

A simple measurement or comparison of the specs would likely answer your question as to the interchangeability between the two types. I suspect that what you see are the two differing manufacturing designs of the same bearing spec. (Assuming as Slash5 said, that the bearing seat angles and steerer diameter are the same.)

BTW it's pretty easy to pull off most seals from these types of bearings and flush then replenish the grease. We do this often at work when we don't have the correct replacement on hand and the customer wants his bike back ASAP. Andy.

IDK one goes on the Fork, the other Up Top?

Mirror image flipped on 1st picture I see Printing on the bearing..

contact the Bearing Manufacturer the bike company Buys from. they would have to Volunteer that information.

but they may have made it all them selves and so their stock number does not correspond to standard industrial Cartridge Bearing numbers .

And, You can always cut them in half and Look..

While the bearings appear different, they are more similar than you imagine. If you look closely the "open side" on the lower set is there, it's just in a different place. As Andrew S. pointed out both are likely angular contact bearings of similar load ratings, and functionally alike.

But what matters, is how bearings fit the frame and fork, and that's determined by the EXTERNAL dimensions, not the internal workings. What matters are the seating and centering cone angles, internal and external diameters, and the heights. From the photo, I would say these are not a match, but they might be, so compare carefully.

Thanks for the help, this is the bearing i have and need replacement.

There are too many out there these days for anyone to be sure from a photo, or memorize every spec.

Find the brand of headset (probably imprinted on the upper bearing cover or top cap), and look up the spec for the replacement bearing.

i would google "bicycle bearings nnnn". where "nnnn" are any markings on the bearings you want to replace. if there are no markings i would go the the LBS and show them around, they'll probably have a good idea of what you really need.

I don't memorize these things any longer, after 40 years there's too much to track. But the seal color often denotes which (45x45 or 45x36 as an example) bearing fit spec you're working with (within the one manufacture's system). Andy.