Hi, Does anyone happen to know what size bearings are used in a 2021 Sonder Cortex? I've got the bearings out no problem but I can't read the writting on them, all I know is it's IS42/28.6 | IS52/40.
Those are the dimensions for the outer and inner diameter of the bearings, in mm and they’re integrated. You’ll also need the depth (thickness) and the angle of the inner and outer chamfer, in degrees. Some have an inner lip so check for that carefully. Kinetic Bike Bearings should be able to help or any shop that deals with Madison, their Elite bearings are very good.
Hope this helps!
What Wheelsonfire said, although I'm fairly certain that all IS bearings are now 45deg on the outside these days? So the only one to check is the inner taper will be either 36 or 45.
If it's worn out and rusty then it might be better to just cut your losses and buy a better headset with external seals. It just means replacing the crown race as well.
I'm just building up a Sonder Frontier which is also a fully integrated headset, something I've no experience of. I asked Alpkit/Sonder for the headset specs and was told 'we use FSA Orbit C-40 ACB headsets.' Oh right... anyway, ordered one, and replacement bearings seem readily available: lower spec 52/40, 45deg external, 36deg internal. I'm not impressed by the lack of a seal on the bottom race, though, so will probably go for a Hope J at some point.
My questions - presumably all these integrated headtubes are machined to the same spec? 52/40, 45 degrees. They're the only dimensions Hope make theirs to, with no depth mentioned (but 8mm top and bottom seems standard). So the only variable between bearings is the contact with the crown race, which will come with the bearing anyway?
Be careful re. lower bearings. The FSA Orbit C-40 ACB headset uses a 51.8 lower bearing. a LOT of replacement bearings are 52mm and either don't fit or fit tightly depending on tolerance of the headtube.
Original FS bearings aren't cheap.
Cheap source of alternative which works perfectly, the same thing on ebay is about 8 quid a piece.
Thanks for that, I did some searching last night and found out which headset is used (as mentioned by Montgomery).
I contacted FSA and the got back to me quickly and confirmed the following bearings are used:
MR127 (073E-RS)
MR121 (870E-RS)
They are a bit pricey (for bearings) so I'll have another search tonight for any cheaper alternatives.
FSA are usually excellent quality but as above these bearings can be purchased from Madison dealers or online via Freewheel. They do M-Part Elite and Shimano Pro both excellent quality. You can get cheap but why compromise on something so vital? Fill around both bearings with waterproof grease, I find automotive CV grease is excellent if a bit grubby looking!
