Front wheel 9mm across flats into 10mm drop outs

[PAB855]

I'm about to transfer a Swytch front wheel from a bike with 9mm drop outs to a bike with 10mm drop outs.
It's a bit frustrating because the wheel had 10mm across flats originally and had to be filed down which took time and patience. The result was a very snug fit with the torque washers in place.
I've swopped the Swytch wheel over into the 10mm gap and of course it was easy.

The question is, technically there's a 0.5mm gap on each side of the flat which should be filled .Any suggestions? A 0.5mm thick washer with lugs, on the same idea as the torque washers?
Or a 1mm single tab washer? I don't think so because the axle will 'settle' centrally when the wheel is fitted.
Or would you just tighten up and go. I must say, it's tempting

I thought this was more a technical question, that's why I didn't post it on the e bikes section.

Cheers

[531colin]

It’s the function of the torque washers to stop the axle turning in the dropouts. As you have been using it with the torque washers a sloppy fit on the filed down axle, I don’t think there’s much to be lost by carrying on doing that.
On a Rohloff where the torque reaction at the axle can be in either direction, depending on which gear is engaged, the reaction arm is particularly well secured to the axle assembly by 6 screws, it doesn’t rely on flats on the axle.

[Brucey]

if the front wheel is properly tightened the 0.5mm gap shouldn't matter. However, this is presumably a motor wheel and there is wheel retention to consider too. All front wheels (on bikes where it might be possible to ride them with the wheels not properly tightened) are now meant to have some form of secondary wheel retention, so that even a loose front wheel can't simply drop out of the bike over a bump.

Now it is entirely up to you if you have a secondary wheel retention system or not but should you ever sell a bike on having disabled it, there could be unfortunate repercussions. FWIW if the 9mm dia. axle is threaded where it passes through the dropouts, it should be possible to make some spacers that are threaded on the inside but are 10mm OD. With a motorised wheel, I much prefer to use a separate torque arm instead of just washers.

[PAB855]

It's always good to have your comments, Colin and Brucey.

Many thanks.

[PT1029]

Swytch also do a torque arm for better axle retention, said to be for carbon or alloy forks and forks "over 30 years old". If your axle isn't a snug fit in the dropouts, this might help.
https://www.swytchbike.com/accessories/ (scroll down to universal torque arm).