Strida evo3 gearbox disassembled


I own a strida evo 3. Thanks to Bill Willby I repaired the back hinge last year.

For quite some time my gearbox made scratching noises while pedaling. Not often - and changing through the gears made the scratching disapear. Now, last friday it began to squeak. That was the point, when I decided to disassemble the gearbox. To loosen the lockring at the belt wheel I had a friend mill a tool: drawing for the strida lock ring tool is available here.

I tried to be very careful when I opened the gearbox. Nevertheless it sprung open and I had a nice 3D-puzzle and a lot of bearing balls on my kithchen table… The balls have three different sizes, it is not hard to figure were to place which. When I reassembled the box I found 3 or 4 of the smallest size missing. The grease used in the gearbox is black, which is not its initial color. It might be just wear and may be some of the grinded down balls.

Does anyone know the exact sizes of the different bearing balls?


*Edit: Yes, I’ll post pictures later, I need to clean out the grease first.

Hi Stephan,

welcome at Stridaforum :smiley:

Guess it’ll be tricky to get official info from Sturmey Archer; most likely they act like ATS and won’t support repairs. Perhaps a stupid question, but wouldn’t it be possible to measure the existing bearing balls?

Best regards,


Hi Chris,

thats no good news about Sturmey Archer :frowning:

I can use my calliper gauge - at least I’m not sure about the precision of my efforts… I guess I’ll just try and see what I can buy. If I have the new bearing balls on my table, I’ll roll them together with the old ones between two sheets of glas to see if they differ in size. Should be precise enought. I think…


I’m not sure about that - just my meaning.
(However I’ve tried already to ask a contact in Taiwan, maybe they can reach Sturmey.)

I do know that the official repairs way is the same at ATS and Sturmey Archer; they want the defective drives back to refurbish them in house.

Good idea with the glass plate, also I think that there are not that many sizes available and there must be recognizable, certain steps between the sizes.

Yes, they could talk to them and it is just as expected:
The KS3 drive is “exclusive” and therefore not any (technical) info available for the public!

I believe it could be also said like that:
“SA signed a contract with MC to manufacture the KS3 drives exclusively for them.
Part of the contract is also a big muzzle.

[size=85]Bad alter ego:
“How dare you - you’re a Westerner and want OUR technical data? No way!”
Very bad alter ego:
“That’s fine vice-versa only, hihihihihihi”

I thought I would re-ignite this thread because strida4ever never posted his pictures and I found his blogpost about how to disassemble the KS3 hub.

In the original German HERE

In GoogleTranslated English HERE

The only out-of-the-ordinary tool needed is the retaining ring tool which he posted further up the thread but here it is again:



Thanks very much!

…and big shame on me for not discovering that article by myself, the more as it is German…