How to replace a broken front hub on a vintage steel wheel from a vintage steel bike?

Question

My mother's old bike is being used as a 'spare bike' for various of the kids. It's from the '70s, a steel framed, steel wheeled, dynamo lit, sit up and beg granny bike with a sturmey archer three speed rear hub.

Surprisingly, the kids all like it.

However, the front hub (also a sturmey archer) has a big bad crack in it. So I'd like to replace it, but keep the wheel. Yes, it's steel, but it's a very high quality wheel and very pretty. The bike is still in use with a wheel from another bike, but the original wheel is so pretty. Everything's in good condition apart from the broken hub. Steel spokes have spoke nipples that all turn.

Is there a clever way of replacing the hub? Or is this a full-on wheel build? And if so, any advice?

H

Answer 1

If the hub is broken you’ll have to replace it and rebuild the wheel. (or replace the whole wheel)

The good news is that front wheels are relatively easy to build and more forgiving. All you really need is a good nipple spanner which fits the existing nipples. You can use the fork and rim brakes to true the wheel. It helps to have a second, similar wheel as a template for the lacing pattern and to compare spoke tension. For best results you’d need a truing stand and spoke tension meter.

If the new hub has the same flange diameter you can re-use the spokes.

Answer 2

Sounds achievable, given some patience, mechanical aptitude and a couple of special tools.

Easy+cheap option A front wheel is relatively common and can be sourced used cheap. If you can find a complete one that suits the bike, just buy it. Most bikes have an Over Locknut dimension (or OLD) of 100 mm, meaning the horizontal gap between the insides of the fork's dropouts. You may have to realign brake pads too. Make sure the replacement wheel is the same diameter as the old, could be any number of sizes.

Easy, more expensive Buy a brand new wheel of the right diameter for this bike. It will very likely be an aluminium rim instead of a steel rim, but that will result in better front braking. Make sure you get the same size, to reuse the existing tyre and to match the front rim brake.

Harder If the hub itself is dead/dying, you can fit the other good parts to a replacement hub. There are a lot of numbers, and they all have to match to be a good fit.

• OLD needs to be the same, else you might need to shim things.
• Number of spoke holes needs to match whatever the rim has. Its likely 32 or 36 holes, guaranteed to be a multiple of 4. You cannot safely miss any holes in the rim or the hub when lacing.
• Flange size - this relates to the length of the spoke that is required to match the rim size. An identical hub makes this so much easier - if you get something radically different then you might need a whole set of new spokes and nipples too. That adds up.

It could work to source a replacement hub from a used wheel that can't fit directly, perhaps a damaged rim or similar.

Buying a hub off ebay or similar is also a valid solution, but prices can vary wildly especially if it was unusual, superlative, or historic.

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Once you've got a hub, assembling it should be no harder than building any other wheel from scratch. The nipple spanner is vital. Some way to "true" the wheel, which might just be using the bike grame's front fork and a couple fingers. If you get into the axle, then you'll need at least one cone spanner of the right size. And a series of common hand tools like spanners and screwdrivers too. Plenty of existing questions go into wheel-building in more detail.

Answer 3

If the crack is in the shell, there is no option but replacing the hub or wheel. (It's true that almost anything can be repaired for a price, but welding and re-plating a generator hub shell while also maintaining the precision needs of a generator hub would be quite an endeavor).

If it's some other component cracking, you could consider getting a donor hub and switching in whatever needs it. Extreme care has to be taken with Sturmey Dynohubs to not demagnetize them when doing internal service. I've heard people talk about ways to remagnetize them once something goes wrong, but basically you have a new hobby in front of you if you needed to do that.

For a new hub, there's a little bit of an impasse between inexpensive generator hubs that mostly won't be a good aesthetic match unless a lot of extra handwork went into the finish and polish, or a handful of expensive ones that are available in mirror polish (which usually looks closer to right on older bikes even if the patina doesn't match).

Sturmey-Archer Dynohubs have a lower power output than modern 3W hubs, and the original lights probably won't fare well when paired with a new hub. Putting on a new generator hub will probably require new lights. There are some available with reasonable vintage looks. One idea there is getting a Schmidt E6, which were built to last forever but are available used for (relatively) cheap now because they're halogen and now LED rules everything. E6s blend in well on older bikes when paired with any kind of shiney metal bracket. There are some other vintage-look generator lights out there as well.

Of course the simple thing would just be finding another of the same hub in good condition, and then it will work with the lights without issue.

There's also the consideration that if this is a bike that gets ridden in conditions where the lighting is even relevant, just getting a basic Japanese or Dutch shopping bike style modern hub (a cheap Sanyo/Panasonic one for example) and some basic modern LED generator lights is going to represent a considerable safety/usability improvement. You might be able to find some vintage look LED generator lights for not terribly expensive.

Answer 4

Just to say that I rebuilt the wheel very successfully and easily while watching a movie one evening.

After I'd roughly put the spokes and hub and wheel together, I put the wheel onto the outside of the front fork of the bike (which I had upside down on the floor beside me) and used that guide to keep the wheel straight. And I just worked around and around and around and tightened the spokes and it all just worked.

Oh - do NOT try this without a spoke wrench. Just don't!

And thanks for the advice. A 1970s or even 1960s bike is still in service.