Jackyll the Tandem Part 3: Stopping the rumbles

It's now been about a month since we've had the tandem, and so far we've sorted through many of the important bits.  Almost all the moving parts have been pulled apart and relubricated, still the front hub, the drum brake and a few other bits and pieces still need to be sorted out.  Slowly but surely it is getting there.

The curious case of the Maxi-Car Front hub

This has given me a bit of strife since I picked up the bike, as there was always a telltale grumble and bump, it took me a little while to realise that it was from the front hub.  The front hub is a bit of a special case, it is a Maxi-Car unit which have a nearly cult status amongst retro-grouches and Francophile cyclists.  Their high quality and idiosyncratic construction has created a bit of a following, however they have been out of production for a little while so spare parts are a little thin on the ground.

Since I discovered the utter and total failure of the seals in the front hub, which allowed the insides to get completely corroded, I have managed to disassemble the hub and assess its condition.  The bearings are totally shot with severe pitting, one of the cups is badly pitted and the other one is not too bad.

After consulting on the CTC forum the easiest option to restore smoothness to the bearings was to grind them back in-situ using the old bearings and some valve grinding paste.  This is normally used to grind car valves and valve seats to give them a tight fit, however this comes in useful for jobs like this.  The technique is a bit of an old school one, and I'm quite aware that it isn't a long term solution.  Long term I either find some way of removing and replacing the bearings cups with new (potentially very difficult) or I just replace the hub completely.  Part of the problem is that the hub and fork are made to a non-standard 110mm spacing, so to replace the front hub I would either have to respace the fork or respace a hub to suit.

The technique involves using the axle and the old bearings fixed into the chuck of a drill.  This is then used with some of the grinding paste and then spun around for a while until most of the pitting is removed.  The first step involves grinding it with the coarse paste, the side which was more heavily pitted took quite a while to grind through.  One of my concerns was that the cups were only case hardened on the top surface and once you cut through that it would be relatively soft metal which wouldn't last as a bearing surface.  However despite this, even if the hub spun more smoothly for a little while it'd be better than it was currently, I had nothing to lose really.

After a fair bit of grinding I managed to grind away most of the pitting on the bad side, although there was still a bit of roughness.  The old bearings I was using to grind were starting to give way so I wasn't really able to use them to grind properly.  Ideally it would be better to use a lathe or some other more proper cutting tool to grind away at the bearings.  A spin with the fine paste after to smooth things out was the next step.

Now I had a final go with some toothpaste

One side came out quite nicely, however the other side still had some pitting in it.  At this point however the old bearing which I was using as a grinding tool had completely given out, and I had resigned myself to the fact that this was only ever going to be a temporary solution so I stopped.  I gave the hub a very, very thorough clean; this is important as any grinding paste left in there would just tear away at the bearings in no time.

I popped in the new bearings that I bought online and tightened her up.  The hub is slightly unusual in the way the bearings are installed and adjusted,  however it allows you to set the tightness of the bearings instead of pre-loading them like most cartridge bearing hubs.  Once it was greased up and assembled I gave the wheel a spin, it was a lot smoother than before and I had got rid of the loud rumble.  While still not perfectly smooth, this should give the front hub a little bit more life.


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