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Clear coat is completely sufficient, as long as the magnets are free of iron debris and the surface carefully degreased.

It's the cleaning that takes the long time!

I did a batch today with primer.

I mean, I can't tell if there is full coverage, if it's clear! That's me painting them, but also if they 'click' onto another magnet it might knock off the coating.

I'll take a view when they are dry tomorrow.

That Is why I would wait until all magnets are back in their spot on the rotor, THEN clean them and paint them. Not individually.

I considered that, but it is more controlled this way and I can 'quality check' the coverage on the edges closely. and pick the magnets that appear to have the best protection, in case the cover doesn't adhere to the surface properly (where there is missing plating).

I don't know. There are many ways to do this better. I'm just trying to get on in a direction that puts the bike back on the road!

I would still need to clean them as good as I have been doing before installing them. This painting step is simple enough.

One thing I have considered is if there is less space to fit the magnets in if they have a layer at the edge. I am aiming to take advantage of the replacement magnets by installing them in a particular order so that small differences can be 'lost' in the gaps between the smaller magnets.

I have ordered a 10cm 'finger' belt sander to clean up the inside of the rim and take off the glue residues. I was getting bored with sanding them off by hand!

Nightmare day today.

Neither the lacquer nor paint would stick to the magnets, it flakes off. Though it does seem to stay on the exposed zinc. I think better to learn this now than fill the wheel with flakes of paint. I have to clean them up.

My finger sander arrived, but will not work between the magnets.

I cannot manually clean up all the glue with every other magnet in place. I think I have to remove large sequences of magnets so that it is an open area to sand down. I was worried to do this, in case I lost the accurate placement, but I think it will be OK by using the replacement magnets to 'absorb' position inaccuracies.

I seem to be able to place several at once next to each other, I think this is OK I just need to be careful and make a plan so I leave enough magnets in key positions to make sure I can put the rest back in the right place.

The wheel is a total mess at the moment.

bob2.0 hat geschrieben: Di 8. Apr 2025, 18:14 ...
My finger sander arrived, but will not work between the magnets.
...

Why that, is it wider than 15mm?
I thought these finger grinders are only 10mm wide (usual belt size is 10mm x 330mm).

Furthermore: I still can't get the point of using lacquer or paint on the magnets.
Most important point is to glue them "watertight" onto the rim, so that there will never grow any rust underneath them again.
From my point of view: everything else is more or less cosmetics.

I fear that rust may start at the edges and then work its way under the magnets.

The first two worst ones that caused the initial problem appeared that this is what happened. Maybe it did, I can't tell, they were a mess. So, it is mainly the edges that concern me, with the potential for rust to work its way under.


The finger sander is made of steel, and it is pulled this way and that. I did get it into position, but then it won't start running because it's pulled tight down to the rim by the magnets.

Once I remove them 'all', I will remove a quarter of the whole rim at a time, then I can get it in there. The rust is easy to clean, it is just sitting loose on the surface, the issue is removing the previous dried glue that is still there. I'll show some pictures, so if anyone does this they can plan their own approach to it.

I realised I could mount several magnets at once (I originally thought that would be difficult, but seems OK), so I stripped all but a few remaining magnets (for the other magnets to key with).

I realised as I tapped the first few off that most of the magnets sitting on their own no longer had any significant adhesion! I simply pushed the rest off by hand! (Apart from the one I chipped, below.)

I had a go with the finger sander but it was too aggressive, and after I finished by hand you can see the dents it made even though I was trying to be super careful.


Then I moved on to the next 'quarter' and where the glue was put in better and there was less rust. I'm a bit dumb, I started with the better-glued end and chipped the magnet.


But at least it is cleared up now. Removing that glue was hard. I had to do it by hand and resorted to 80 grit, which I don't like getting near aluminium but it was taking too long to work off that glue with finer paper.

I have now taken the rust off 38 magnets, 5 remain on the rim, 1 snapped, 2 chipped, 2 demagnetised.



My key finding is that if the magnet(s) have gone rusty they are easy to remove and easy to clean up.

If they have been glued properly then
a) you will break them trying to get them off, and
b) it is a lot of hand sanding to remove the glue, nothing other than 'elbow grease' seems to work.

This is a dilemma because there is no way to know if a given magnet is good and solid, or rusty, until you try to take it off, and by then you will have damaged it if it was any good to begin with!

I think my advice has to be to NOT do what I have done as a pro-active step. There is no point attempting this unless and until you experience swollen magnets, because (ironically) you have to wait until they become rusty before you can take them off!

I can imagine that the glue I am about to use to put these back will never let go of the magnets again. If there are any more future problems, then I will have to make sure I have replacement magnets ready, because I am pretty sure they will not come off in one piece ever again!

It'll take several days now to clean everything up ready for reinstallation and get them glued in because I will do them slowly, in sectors. I think the whole problem has been that in manufacture the glue was allowed to flow downwards and to one side. So, that region of 'good glue' (where I chipped a few magnets) was where more of the glue ended up drying. I will try to avoid this happening again.

First batch of 6 glued in so far.

I'll check how they all are tomorrow, and if they seem OK then battle on and do the rest.

Looks tidy.
Think at least twice before gluing the magnets back to the rim, just to make sure that there is a steady alteration of field direction .
It would be a nightmare when you end up with two magnets beneath each other, oriented with the same direction of flux.