optimal gear ratio for equalized steps between gears, smaller first gear for climbing steeper hills with increased range (303%), better shifting performance into first gear.
My SRAM S7 is fitted (since January 2008) to a bike I use for daily commuting. The principal advantage over derailleurs is the reduced maintenance requirement (less frequent lubrication, slower wear on chain and sprocket).
Inevitable drawbacks are in extra weight, and slightly slower wheel removal and replacement in case of puncture. More subjectively, I suspect greater system friction, particularly in the lower gears.
Unfortunately, access to all gears is erratic. Sometimes the unit is fine. Sometimes it will engage only one gear (either 1 (lowest) or 4, which I assume is the direct drive). Sometimes it will engage 1 and 4 only: sometimes 1, 4 and 7 only. Usually the loss of gears is linked to disengagement and reattachment of the click-box. Disengagement is either deliberate (removal of the wheel) or unintended (the knurled retaining screw to the clickbox works loose).
Replacement of the shift tube, shift rod and retaining circlet (the interface elements between the clickbox and the hub itself) has not cured the problem, nor return of the hub itself to SRAM's UK distributor for review / servicing.
I have stripped and reassembled all elements of a derailleur bike, so consider myself reasonably capable. However, this problem defeats me. In addition, even in London the installed base is not large: mechanics are generally unfamiliar with the unit and have proved unable to diagnose problems accurately and deal with them.
Weaknesses: Difficult to repair, parts aren't readily available, expensive, Heavy, harder to change flat
Bottom Line:
Last November (2006) I built up a commuter with SRAM Spectro S7 internal gears. I promised a 1000 mile update. The original thread is here: http://forums.roadbikereview.com/sho...ght=spectro+s7
The one line summary is that I will be converting this bike back to derailleur gears.
The primary problem is that the shifting has become very unreliable. For some reason I can’t get into 2nd and 4th gears, and these were gears I used a lot. Since this is a “black box” system to me, I don’t have confidence that I can trouble shoot and repair, and getting parts is a hassle.
Even if the hub and shifter worked perfectly, I would probably conclude that a derailleur system is a superior option. You can get a good hub, cassette and derailleur for much less money than an internal gear hub. You get a wider range of gears, and it is reliable, durable, and easy to repair. There are many shifter options, unlike the gear hub’s exclusive grip shifter. Changing a flat was an extra pain at a time when I really didn’t need the inconvenience.
I did go for 10 months and over 1000 miles in all weather with zero maintenance, not even oiling the chain. (The chain does show some rust, but it doesn’t squeak.) But, other than the chain abuse I could have done the same with derailleur gears and had a better outcome.
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Strengths: Easy installation and set up; low maintenance; no rear derailleur makes drive train cleaning a joy; no rear cassette allows for a symmetrical, and thus stronger and more durable rear wheel.
Weaknesses: Weight; rough first and second gears; low product demand means you will have to order it (if you don’t buy a bike which features it as original equipment); good luck if you absolutely have to have the latest, and best looking, version. The price I paid is much less than what a bike shop will ask to order the same components for you, however, it was ‘old stock’. I learned this when I received my order and couldn’t help but notice that the click box and grip shift were radically different in appearance from the ‘2003’ versions featured on Sram’s website. A fusillade of e-mails between me, WebCyclery, their supplier and Sram finally established that the updated versions on Sram’s website will not be imported until these current ‘old stock’ items are depleted. Sram assures me that my hub is identical in every respect and that the differences in the click box and grip shift are only cosmetic. Still, I am frustrated that I was not able to order the much more stylish products featured in Sram’s on line catalogue, although I certainly can’t argue with the price I paid.
Bottom Line:
I became interested internally geared hubs as an alternative to the rear derailleur arrangement (with it’s cassette and dished rear wheel) because I needed a stronger, longer lasting rear wheel for commuting in the city. I decided on the Sram because it is available in a ‘free wheel’ version without an internal brake. This is important when you consider the inevitable rear puncture. Not having a brake arm and cable to deal with can make the difference between making it to work on time and arriving late. The Sram click box (a quick release shift cable interface) further simplifies and speeds up rear wheel removal and installation. Even though proper chain tension requires traditional nuts, as opposed to modern quick release hubs, rear tire repairs take only a few minutes longer.
This hub is fabulous for the majority of my riding, which is commuting over relatively level urban terrain. The spread of gear ratios is more than adequate. And once you learn a little internal hub technique (you need to ease your pedaling during shifts under power) it changes gears very well - even while stopped at a traffic light. However, once the road turns upward you will become aware of two major weaknesses inherent to all internal hubs. The first is an annoying mechanical friction loss which plagues the lower gears. First gear is a real coffee grinder. Second is markedly better, but still feels fairly rough. This makes you feel slow, even if you’re not. The good news is that gears three through seven are as efficient as most cassette and derailleur set ups. Since I spend most of my time in gears four and five, this friction loss is not much of an issue for me.
The second negative factor is weight. There’s just no getting around the fact that this hub weighs over 3 lbs. As a result, my bike weighs 27 lbs before I put my panniers and water bottles on. This is 30% more than most road race bikes, but many mountain bikes weigh this much if not more. Did I mention I need the workout? Let’s just say I should loose 30 lbs before worrying about my bike loosing 5.
This set up is definitely not for racers or high mileage tourers. But if you’re a commuter or recreational rider without too many hills to worry about, this might be the ideal set up.
