Can i replace the 19mm nuts on my ebike's rear axle with 18mm nuts?
Context: my ebike has 19mm nuts on the rear axle (and 15mm on the front). I have an old Proto wrench that’s a 15mm/18mm, so i’m wondering if i could replace the rear nuts with 18mm nuts instead, so i can carry around one less wrench.
The bike is an Eahora Cupid with a 1000w motor if that makes any difference.
That’s a 90Nm motor according to the spec sheet which is somewhat realistic for 1000W hub. Unless it’s got a torque arm, you need every bit of clamping force you can get to keep that axle from rocking or spinning out under load. This is controlled by the nut surface area and material. If there’s no torque arm, I wouldn’t fuck with it.
thank you! this was the answer i was hoping to find. there’s no torque arm, so I’ll stick with carrying two wrenches.
as an aside, does anyone have any recommendations for cranksets for a '92 rockhopper? it’s got shimano biopace on it (what it came with) which is now warped after years of abuse, and I’m hoping to turn that into a commuter for the days I don’t like taking the ebike.
In order to avoid having to remove the rear wheel often, I’d buy a rear tire with really good puncture protection. I had an episode when I had to remove my rear hub several times in a month because I used Panaracer GravelKing which turned out to have really weak protection. I switched to a version with protection and I haven’t had to remove my hub due to punctures. Having to torque the nuts to 50Nm isn’t fun.
Not familiar with the bike but what could it be - square taper, ISIS? Not sure if ISIS is that old. If it’s square taper, there’s plenty of options. The lower end Shimano cranks (Alivio, Acera) used to use square taper. They probably still do.
Looked at a pic of Biopace, looks like square taper.
Some locknuts have a different size hex flat than a standard size and can be sourced locally. There are not “custom” sizes for the most part, and if you find something like that, you should be extremely skeptical of what you find.
Generally, hardware should always fall inside an engineering standard size. This will be like an ISO, DIN, or JIS number. This standards number will specify all of the material properties and tolerances. While you may not be interested in these details, their existence helps to verify you’re buying something relatively safe. Failure at the rear is not as bad as the front, but it can still make a really bad day.
There are some options for oddball hardware out there if you know where to look and probably spend a little more. You just need to match the thread pitch and whatever other features the nut has (flared, serrated, nylock, whatever). In the US I use McMaster-Carr, they might ship overseas. Just go through the parameter list and pick what you want.
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