Shimano SG 7R-46, 7 speed hub

Shimno SG7 R46One has to be a real bike-geek to get excited about internally geared bicycle hubs. Those CAD drawings showing an exploded view of the planetary gear system are like porn to some. I had wanted to lace up a wheel for years using one of these hubs, but just never got around to it. Finally I decided to take the plung and purchase the Shimano Nexus7.

There are many different manufacturers of internally geared hubs I could have chosen, including Shimano, Sturmey-Archer, Rohloff, and others.

I selected the Shimano hub for several reasons: reputation, reasonable cost, and gearing. If money were no object I would have chosen the Rohloff 14 speed, but the hub would have been more expensive than every other part combined. I just couldn’t justify spending over $1200 for one component of a utility bike

I chose to order the optional roller brake mechanism for the hub. The rim I selected was a very sturdy Sun-Rhino downhill rim designed for disk brakes, hence no braking surface. I am little disappointed with the performance of the roller brake. Not only is it heavy, but it isn’t really that great at stopping the bike. Of course it can be made to lock up the rear wheel, but the braking quality feels a bit mushy. Apparently the manual suggests not overusing the brake on hills. What?! That’s not too good when one lives in  San Francisco where steep hills are inevitable. However the tradeoff in reliability seems to be worth it. A really great thing about the roller brake is that it’s rain proof and practically maintenance free. I simply adjusted it once and I haven’t touched it since. That was over 1500 miles ago. Another nice thing about this configuration is that there will be no wear and tear on the rim from the brake pads slowly eating away at the sidewalls. I set out to build a wheel for the long haul and I think I’ve done that. I have a feeling that this wheel (with a little bit of maintenance) will last at least a couple of decades. So far, I’ve not had to true the wheel. The hub itself has met all my expectations. It’s durable, maintenance free, easy to adjust and fun to use. Although it seems somewhat heavy, it is actually comparable in weight to an average derailleur and cassette system.

I settled on the indexed rapidfire shifter which works very well, but is rather slow to click from 1st to 7th, something I often do when cresting a hill. I had originally installed a clunky looking twist shifter which I actually prefer because any gear is accessible with one small flick of the wrist. However, because of the curve of the handlebars, I just couldn’t cram in a grip, brake lever, and a twist shifter without compromising comfortable hand positioning.

One nice thing about the hub is that it can shift to any gear while the bike is stationary, making it ideal for stop and start city riding. Shifting under power is a little tricky. When shifting using a modern derailleur and cassette system the act of pedaling helps move the chain to a different cog. Today’s cassettes have little ramps that assist with this and allow for shifting under some fairly strong forces, such as when going up a steep hill. The Nexus-7, however, requires that the rider ease off the pedaling quite a bit in order for the shifting to take place. This is a little bit of a drawback when trying to keep momentum up a sharp incline. Unfortunately, shifting under max power does not work. The hub simply stays in gear and won’t disengage.

Although this can be slightly annoying, I quickly became used to this and have learned to shift in advance of a steep hill.

That being said, the shifting works great on moderate hills and flat terrain.

I’ve heard some people complain about the drag created by all those gears grinding together; sure I can feel it little bit, especially when I’m in third. For some reason third gear transmits a noticeable vibrating sensation through the chain all the way through to the pedals. It’s sort of weird, but easy to get used to. The rest of the gears have their own feel. Fourth has almost no drag whatsoever, because that gear ratio is almost 1:1. So if you have a 42 tooth cog in front and the standard 20 tooth cog in back that’s what you get: 42/20.2.


Here are the gear ratios taken from the Shimano site:

Total : 244%

1 : 0.632

2 : 0.741

3 : 0.843

4 : 0.989

5 : 1.145

6 : 1.335

7 : 1.545

I look at the Shimano hub this way: let’s say you have a bunch of furniture to move, do you choose a Ferrari or a Toyota pickup? Well the answer is obvious. I apply the same idea to bicycles. If I had to make a trip to the grocery store for the 3 bags groceries, I would rather take out my Nexus-7 equipped basket bike than my svelte, Ultegra equipped racing machine

For what it is I really love this hub and I would certainly recommend it for anyone building a fun, maintenance free utility bike.

The late website of the late Sheldon Brown has a lot to say about internally geared hubs, including the Shimano Nexus-7. Be sure to check it out.