So my FiL has a
CUBE REACTION GTC 29
And the headset is knackered.
Rocking like hell.
It looks as though it needs an FSA Cube Orbit Z Headset, but I’m not sure?
There are a million different types and I’m massively confused 
Help a brother out?
Link me up…
Ask LCB?
A complete nightmare subject - there are so many different standards. You may need to know the year of the frame to have a chance of being sure what is fitted. Top and bottom bearing are often different types, diameters and angles.
Search bikeradar for ‘the-ultimate-guide-to-headsets’, or better, see Parktool’s ‘standardized-headset-identification-system’ page. (WHY CAN’T I POST LINKS??).
You shouldn’t need a whole new headset, just the top and/or bottom cartridge bearings, assuming that they are actually worn and it is not just a case of adjusting and tightening the headset correctly.
If you are lucky there should be some engravings on the bearings telling you the type, bore sizes and maybe angle e.g. ZS44/28.6. Look for this first. The bearings should run nice and smoothly with no slop - if they are noisy or loose in your hands then they are worn out and need replacing.
Good luck figuring it out!
Cheers.
This is my FiLs bike and I can’t get round to fettle it and don’t want him ordering the wrong thing.
But he can’t take the top cap and stem off.
Bloody Covid again. 