I am really surprised, on my first e-bike, where I was off road probably 90+% of the time, other than a very occasional re-lube and clean (x3 maybe), and not overly heavy torqued up, I had that one headset that came with the bike for over 6 years. I sold the bike with the same headset.....I get through two sets a year on average.
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My latest bike was delivered with the wrong top bearing, but once I had the correct one and installed it, over a year ago, no problems.
Heavy usage must be down to something, for instance (but I do not consider this list in any way complete):-
1) Poor quality parts
2) Forks with maybe a slight "bend" between the bearings, that really "works the bearings very hard
3) Very hard, high speed, rough riding.
4a) Heavy frame, battery, person, and a bearing that is in some manner "not strong enough" for the total weight.
4b) No front suspension, all the shocks hit the bearings combined with 4a)
5) Wrong lubricant
6) Dirty environment is somehow entering the headset bearings, possibly up the middle of the tube (guessing only, never actually ever seen it).
7) Over tight torquing. I make "contact" slowly using the middle bolt, and then maybe up to a 1/8 turn or less more, just going by "feel".
Both my e-bikes have front suspension, and I know from my hands, that this makes a big difference on a ride. They also both have sprung rear suspension. I need that as I have suffered from back problems all my life, operations on my spine, and suspension has helped dramatically.
As far as I remember, on my first bike I covered a total of around 18,000 Kms.. With no real problems except for a single controller failure.
Have you yourself found out why you need new headsets so often?
It has certainly piqued my curiosity!
Maybe others here also need them as often as you!! Hopefully they will chime in as well....
regards and apologies for being so nosy
Andy