Any bike that doesn’t have a derailleur needs a way to tension the chain or belt. The various methods include: horizontal dropouts or rear-facing track-style fork-ends, with or without tensioners; sliding vertical dropouts; spring-loaded derailleur-type tensioners; eccentric bottom brackets; and, eccentric hubs.
Bikes with internal gear hubs and/or hub brakes also require some way to keep the hub from rotating within the dropouts. In most cases, this is accomplished with what is called an anti-rotation washer. An anti-rotation washer is a heavy washer with a slotted opening that matches the flat faces of the axle, and a tab that fits within the dropout opening to prevent rotation. In other cases, the hub is held in place with a reaction arm attached to the frame.
Belt driven bikes are somewhat sensitive to the type of dropout and tensioning device used. On a belt bike, as little as a 1/2 turn on an adjuster can be the difference between being in or out of the recommended belt tension range. And as with belts in other applications, precise pulley alignment is required to keep a belt running on center.
My favorite set-up for belt bikes is the sliding vertical dropout. With this design, the axle stays locked within the vertical dropout slot while the entire dropout itself slides fore-and-aft within the frame. Besides providing the ability to make fine adjustments, once the dropouts are locked in position, no adjustments are required, even after removing the wheel for flat repairs or other maintenance. I’d venture that most belt drive bikes will feature some variant of this design in the future.
My Civia Bryant uses horizontal, rear-facing, track-style fork-ends combined with a pair of tensioners. The right hand tensioner has an anti-rotation plate attached (see the black plate in the photo above). Bryants prior to this year’s model were spec’d with a single tensioner on the drive side and an anti-rotation washer on the non-drive side. This new set-up is cleaner and much easier to use. If you have an older Bryant with the single tensioner and an a/r washer, these new tensioners can be purchased from Quality Bicycle Parts through your local dealer (QBP part number CH5400, retail price $30 pr).
SRAM is introducing a two-speed auto-shift internal gear hub to the European market this summer. It’s my understanding that the internal shifting mechanism is controlled by centrifugal force; when you reach a certain speed the hub automatically shifts to a higher gear, and when you slow down, it automatically shifts down (the shifting points can be preset at 7.5, 8.7 or 11.2 mph). Specs as follows:
- Speeds: 2
- Gear Ratios: 1:1 and 1:1,37 = 124%
- Spoke Holes: 28 or 36
- Sprockets: 15, 16, 17, 18, 19, 20, 21
- Finish: Ni-Chrome-plated
- Weight: 980 gr
- Shifting points: 7.5, 8.7 or 11.2 mph
- Brake: Coaster
Automatic shifting is nothing new. From what I can discern, this hub is based upon the rare Sachs Torpedo-Automatic. Then there was Shimano’s ill-fated 3-speed auto-shift “Coasting” drivetrain. And though it’s not exactly an automatic, Sturmey Archer seems to be doing well with their 2-speed kick-shift hub.
I’m not convinced we really need automatic shifting on bikes when we already have indexed internal gear hubs, but for those who want the simplicity and clean lines of a single speed while needing the advantages of a second gear, this is an interesting alternative.
There’s no word yet on price or whether it will be imported into the U.S. The Automatix is the first among other new IGHs from SRAM due out later this year.
View the Spec Sheet [PDF] →
[Hat tip to Jeff L. —ed.]
Let’s see, I’ve either owned or had on loan five bikes with Shimano Alfine 8 hubs, four with Shimano Nexus 8 hubs, two with Sturmey Archer 5 hubs, three with Sturmey Archer 3 hubs, one with a Nexus 7 hub, one with a Nexus 3 hub, and one with an SRAM iMotion 9 hub. Among all of those internal gear hubs, I’ve never had an issue until the most recent Alfine 8 on my Civia Bryant.
It’s not unusual for internal gear hubs to make some noise when they’re new, but they almost always quiet down after a brief break-in period. This particular Alfine 8 started out noisier than most, and it’s only gotten louder over time, to a point where it was obvious something was not quite right. I finally consulted an expert on internal gear hubs who recommended I have it serviced. Being the sucker-for-a-good-bike-maintenance-project that I am, I decided to take it on myself.
The recommended process involved removing the internal parts of the hub (they come out in one piece), briefly soaking them in Shimano’s special IGH oil, then reassembling everything (while I had it open, I also added some grease to the bearing races and around the seals). The specific steps included removing the cassette joint, sprocket, and dust cap on the drive side, then removing the disc caliper and bearing cone on the non-drive side. Once the external parts were removed, the innards of the hub slid out toward the drive side in one piece. Once the internal parts were free from the hub body, it was simply a matter of dunking the whole thing in Shimano’s oil bath as per their instructions, then reassembling.
I’m happy to report the service worked. The snapping/clunking sounds I was hearing while pedaling lightly are now gone. It’s my understanding that the purpose of the oil is not so much to act as a lubricant as it is to refresh the grease within the internal parts of the hub. It appears either the hub was not lubricated sufficiently from the factory or it sat dormant long enough that the grease had started to dry out (my bike is a NOS 2009/2010 model). Whatever the case, everything is smooth and quiet now and I should be good to go for at least another couple of years.
This was the first time I’ve opened up an IGH. The process was less daunting than anticipated, though I wouldn’t recommend it for anyone other than the experienced home mechanic who enjoys a challenge and is willing to do his/her homework. For those who don’t have the experience to undertake such a process, dealers who regularly service IG hubs should be able to do a service like this in under an hour (assuming no other issues). Of course, if there is actual damage to the hub, the time it takes to do the repair may be significantly longer with correspondingly higher costs.
Gates recently released their Carbon Drive Calculator (CDC) for the iPhone. The CDC just might be the ultimate app for the combo tech-nerd/bike-geeks in the crowd. Besides calculating center distance, drive speed ratios, and optimum pulley size, the app uses the iPhone microphone to test belt tension. Yup, believe it or not, you pluck the belt like a string and the CDC estimates belt tension by pitch. I haven’t tested it yet (I’m not an iPhone user), but it sounds way cool if it actually works. If there are any iPhone users in the crowd who also run a Gates Carbon Drive, I’d love to hear how it works for you.
I recently upgraded the brakes on my Civia from Avid BB5 Road discs to Avid BB7 Road discs. I’ve had good luck with BB5′s in the past and they were performing well on this bike, but when an opportunity arose to sell my existing brakes, I went ahead and made the switch.
The differences between these two brakes are subtle. The main difference is that the BB5 has a pad adjustment knob only on the inboard pad, whereas the BB7 has adjustment knobs on both pads. The ability to adjust both pads makes the BB7 slightly easier to set-up and keep adjusted properly.
The BB7 also has larger brake pads which provide slightly more braking power and what feels to me like slightly better modulation. They should be less likely to overheat in touring conditions, though that’s a moot point for commuting. Probably the biggest advantage of the larger pads is that, due to their larger surface area, they don’t need to be replaced as often as the smaller pads in the BB5.
One disadvantage of the BB7 is that is doesn’t have a barrel adjuster on the brake. It’s a bit perplexing that the BB5 is supplied with a barrel adjuster, but the more expensive BB7 only has a stationary stop. Avid does supply an inline barrel adjuster with the brake that can be inserted into the housing up near the handlebar, but an adjuster on the brake would make more sense, at least on the road version of the brake.
The BB7 comes supplied with metallic brake pads designed for use with their rotors. My bike is outfitted with Shimano rotors which are not recommended for use with metallic pads. I could have swapped the stock rotors for the Avid rotors that came with the brakes, but it would have required an adaptor for the Center Lock disc mount on the Alfine hub, so I opted to stay with the Shimanos. Because of this, I also ordered a set of Avid Organic brake pads for the BB7 calipers. It’s my understanding that the organic pads are a little grabbier than the metallic pads, though they feel great to me. They also wear a little faster than the metallic pads, though that’s not a serious concern for commuting.
There are a few other subtle differences between these brakes, none of which have much of an effect on performance.
Overall, this was not a bad upgrade. If I was building a new bike from scratch, I’d certainly spend the extra for the BB7′s over the BB5′s, but if I didn’t have an opportunity to sell my existing brakes, I can’t say the subtle advantages would be worth the full price of a new brake set.
Who’s riding one? How’s it going so far?