Thursday, December 23, 2010

Hubba, hubba!

You probably have never thought about the internal gear hub on your bike. I had a bunch of old 3 speeds when I was in school, and I know I never thought about them except to adjust that little screw thing on the cable. So you might be as surprised as we are to hear that hubs are actually really totally like, important and stuff?, and they make a big difference. On any bike. They are used on cargo and city bikes partly because they're reliable and maintenance free, but if they stop working, they've stopped being reliable and maintenance free too. So, when did you last grease yours?

So, last week I spent a bit over an hour trying to swap the summer tires on the box bike for a new set of Marathon Winter tires. Read the rest of the post before you try this at home. The Marathon Winter are the only ones we could find that have carbide studs and a 406 wheel size (the front wheel, 20 inch) available. (More info than you need about studded tires here.) I already put them on the Onderwater tandem, same tire sizes, and it gets around on the ice patches on the streets and the icebergs in the alleys much much better than the box bike with its regular Marathon tires. They went on quickly on the Onderwater and it's a great, stable bike now in all kinds of road conditions. It is true, though, what many people told us before we got the studded tires — they are louder than regular ones on clear pavement. Sort of like riding over sand in the road in summer or buzzing, depending on which one of us you ask.

Just like the Onderwater, the Bakfiets we have has a Nexus 8 speed rear hub and those semi-functional Shimano roller brakes. The chainguard is similar. So in about 5 or 10 minutes I was able to get the back wheel off. It took a little work forcing it off the frame. There’s a slightly optimistic how-to post on the Dutch Bike website which I found afterwards. The keys: yes, you have to take off the brake cable and unbolt the brake arm from the left chainstay, and the tension adjuster bolts (10 mm) on the back of the dropouts have to be almost fully taken apart too. Getting the shift cable off the drive side is also charming — shift to 1st, hold the hub shift ring tight while you unthread the cable, and it comes off easily enough.

Swapped the tire indoors where it was warm. The new tire went on fine, everything A-OK.

Then it was time to put the wheel back on. Wouldn’t fit. Just wouldn’t. The spacing between the dropouts was too narrow. By about 1.5 − 2 cm. I could get one side hooked in well enough, then there was no way to get the other one in. Infuriating. On top of the bad frame spacing, the soft steel dropouts were soft enough to bend slightly when they were half on the end of the hub and axle. (they didn't have "Campagnolo" stamped on them - I checked.) We have a first generation Bakfiets and apparently the newer ones don't have as much problem with frame spacing as ours, and they have the improved newer hub version too.

Rather than take a car jack or some boards to my frame and bend it open to fit the hub it had already had in it, I took an icy cold deep breath and took it off to the dealer. They are really nice and helpful, and we got it back on with three people pulling and pushing and grunting manfully, but something or another in the angle of the hub had changed, and after the surgery it wouldn't shift into 5th gear or above without a grinding feeling and a noise. It felt like a regular wheel that needs the bearings repacked, with choppy shifting. Could it be the kids jumping back and forth in the cargo box? The slush and winter road conditions? The new snow tires? Hard to diagnose.

It turns out after about a week of looking into it that the Nexus 8 speed hubs, especially the early versions like ours (SG-8R20), tend to get this problem often and it has something to do in our case with a slightly bent planetary gear, one of the little pieces that do the work inside the hub. I think mis-shifting is supposed to cause this, or bad installation, or maybe lack of lubrication, though it is supposedly sealed. Take it to the dealer if it doesn't just install itself. Shimano says on their website (see "note") that a dealer has to grease it every two years (with fancy Shimano grease). If that is what caused ours to go, I guess it's a good idea that whatever hub you have, you should be regreasing it according to the manufacturer's plan. Or look at Hubstripping for serious internal gear geekdom and better ways of doing it. Go on, just take a look. Because now you're part of the internal gear community, too. (it was better when Marco was still running it) (just kidding). Sheldon Brown's site is also full of great hub information and is now maintained partly by John Allen, one of the master hub senseis on Hubstripping (and a major advocate of "vehicular cycling" - the guy must not have kids).

The internal guts of the new Nexus hubs still fit in the old shell that's hooked on to our spokes and rim and tire and so on, so the easiest solution is probably to buy a new (SG-8R36) hub and use it as a refill. While thinking about that $300 investment, we took the Onderwater in with its functional SG-8R31 wheel (again, with that party-killing roller brake) to be the box bike's organ donor. Should be on it tomorrow. I'm not touching it. The other option is to choose a nice hub, a nice heavy duty rim, and get a good mechanic to build a heavy duty wheel with thick stainless spokes. Similar price, possibly.

There are a few other pretty good wide range hubs out there to use instead if we choose the nuclear option. SRAM makes a 9 speed, Sturmey-Archer an 8 speed, and Shimano even an 11 speed that take disc brakes. The S-A has a drum brake option. No roller brakes! But, as far as I know, none of these are really rated for the weight of the cargo bike. There's a guy in Chicago we heard about who installed all of these hubs over the course of a year or two on a regular bike (I think - third hand story) and kept burning them out. He wound up buying a fancy Rohloff, and according to the legend, it's still working. It's the Lamborghini of bike hubs (like their sports cars and also like their tractors). In Chicago it's so flat we could probably get by with 3 or 4 speeds if they were the right ones, but more is better. Fourteen precision machined, evenly spaced gears crafted in the Black Forest's Daimler Benz transmission factory might be overkill... I think some 3 and 5 speed Sturmey Archer hubs are also rated for this weight, though it's hard to get this information on line. And I just saw pictures of a bike made in Oregon with a NuVinci hub - I wonder if that would work well?

So, er, grease those hubs, y'all.


  1. Some additional information: The Shimano representative I spoke to recently told me that all current Shimano internal gear hubs are rated for the weight of the loaded cargobike. They suggest the Red Line premium model which has better bearings on the planetary gears but all are OK. Also, the SG-8R36 and -8R31 internal parts will not fit in a -8R20 housing because the non drive side used to use pawls but now uses clutches, and they aren't compatible. I think the 8R30 guts might fit in the 8R20.

    We are temporarily on the road again with a borrowed rear wheel. This should hold us for awhile. I still think I might have a good look at other hubs before building a new wheel with a Nexus, though.

  2. There is more info on hubs in the comments to part 1 of the Cargobike primer post.

  3. Shimano suggested replacing the guts of our hub with the original 8R20 version to make sure everything would fit. It'll cost less than $150 including installation and so that's what we're doing. If anyone has a Rohloff hub to sell me for a comparable price now is the time to let me know!

  4. Shimano sent the 8R25 internal parts and Dutch Bike got them installed quickly and (so far) functionally in the 8R20 hub body about a month ago. Back onto the tandem it goes (swapping the rear wheels between tandem and box bike). In the end it did cost about $150 to fix. Still not sure why it failed, and "they always do that" isn't a very helpful explanation from the manufacturer. After this episode and the broken axle in the front dynamo hub last year, we'll do a lot of comparison before buying another Shimano internal gear hub. Do you think anyone makes a better one?


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