Antriebssysteme ohne Umwerfer: Unterschied zwischen den Versionen

Diese auf dem [[Ersatzteilmarkt]] verfügbaren exzentrischen Innenlager sind meist recht teuer, funktionieren jedoch mit jeder Hinterradnabe.

Fortunately, most "vertical" dropouts are not exactly vertical: they usually have a bit of a slant to them. You may have to play games with chainwheel sizes. One of my fixed-gear bicycles is based on a Cannondale touring frame. It happens that there is just enough adjustment to make it work with my preferred 42/15 combination. If the chainstays were a bit different in length, I could replace the 42 with a 41 or 43.

Adding or subtracting a link in the chain will move the axle 1/2". Changing either sprocket size by one tooth will move the axle 1/8" (3.2 mm). Thus, if I wanted a 5.75 gain ratio (75" / 6 meter gear), I might first try a 42/15: this gives a gain ratio of 5.77 (75.6" / 6.05 m gear). If the chain was too loose, I could take up 1/8" (3.2 mm) of axle movement by replacing the 42 with a 43. This 43/15 combination would raise my gain ratio to 5.91 (77.4" / 6.19 m). Alternately, I could get the same axle position with a 42/16 --5.41 (70.9" / 5.67 m).

If I was not happy with these choices, I could add a link to the chain and switch to a 45/17 --5.45 (71.5" / 5.72 m) If I added two links to the chain, I could get the same axle position with a 48/18 --5.49 (72.0" / 5.76 m)

[[Datei:Half-link.jpg|right|Halflink einer Kette]] It is also possible to use a special "half link" or "offset link" to lengthen or shorten your chain by only 1/2", and adjust the sprocket-to chainwheel distance by 1/4". Half links are available for both 1/8" and 3/32" chain. Not all chains have the same diameter rivet pins: use a half-link of the same brand as the chain, or at least check.

Another possibility would be to do a little bit of filing at the back of the dropout to let the axle move back just a bit.

[[Datei:Sovos flat axle.png|center|Nabe mit flachgefeilter Achse]]

I used a more drastic solution on my Bianchi Osprey. I cut the rear axle short so that it didn't protrude past the surfaces of the locknuts. Thus, only the quick-release skewer went through the dropouts. Since the skewer is quite a bit thinner than the actual axle, this gives me considerably more adjustment room.

I rode that setup for a couple of years with no problems, but later got a deal on a Bianchi B.a.S.S. purpose-built singlespeed frame that fits me better, is lighter and has horizontal track-type forkends, so I'm no longer using that setup.

Quite a fine adjustment is possible positioning a "ghost chainwheel", as shown on our home-built tandem page. It does reduce drive efficiency slightly. The larger it is, and the closer to the rear hub, the more slack it takes up, the smaller the risk of its falling out, and the less likely it will rub on the chainstay. The range of adjustment with a "ghost" chainwheel is greater than with the other "kludge" solutions described here.

As the chain wears, it lengthens, and to keep it from falling off the sprockets, it should be adjusted a couple of times before it needs to be replaced. The limited range of adjustment possible with the kludge solutions may require replacement of a chain sooner than otherwise.

Eric House has prepared a whole web site devoted to the problem of finding sprocket combinations that will work with vertical dropouts. He has developed charts and Java applets that show the options available for particular chainstay lengths.