Umbauten auf den starren Gang

Dieser Artikel beschäftigt sich mit den praxisbezogenen Arbeiten zum Umbau eines konventionellen Straßen- oder Mountainbikes zu einem Fixed Gear Fahrrad. Möglicherweise fragst Du Dich aber eher, warum man so einen Umbau wagen sollte. In diesem Fall ist der Artikel Starrer Gang für die Straße hilfreich.

Naben für Fixed Gear Fahrräder

Es gibt vier verschiedene Wege für den Umbau auf starren Gang, wenn man nur Naben betrachtet. Man kann Bahnnaben, Flip-Flop-Naben, Freilaufnaben oder Kassettennaben umbauen.

Der beste möglich Aufbau für eine Straßenfahrrad mit starrem Gang erreicht man unter Verwendung einer Bahnnabe oder eine Flip-Flop-Nabe.

Bahnnaben

Bahnnaben haben zwei abgestufte Gewinde. Das Hauptgewinde ist wie bei einem Freilauf das, auf welches das Ritzel geschraubt wird. Vorgelegart löiegt ein etwas kleineres Linksgewinde, auf das der Konterring geschraubt wird. Nachdem man das Ritzel aufgeschraubt und es fest angezogen hat, wird der Konterring aufgeschraubt und drückt gegen die Außenseite des Ritzels und sichert dieses gegen Losschrauben. Wenn das Ritzel von der Kette gelöst werden will, versucht es den Konterring im Uhrzeigersinn zu bewegen, so dass sich dieser noch weiter festschraubt. So kann das Ritzel - egal wie hart man pedaliert - nicht von der Kette abgeschraubt werden.

Es gibt mehrere unterschiedliche Gewindegrößen, die für den Konterring möglich sind:

Typ	Gewindespezifikation
Britisch/ISO	1,29 Zoll x 24 TPI
Campagnolo/Phil Wood	1,32 Zoll x 24 TPI
Altes französisches Maß	33 mm x 1,0 mm

Flip-Flop-Naben

Flip-flop, or double-sided hubs are threaded on both sides. Usually one side has a track-type threading, (with lockring) and the other side is threaded for a single-speed standard freewheel. It is possible to find them with track threading on both sides, but not easily.

The usual way to use a flip-flop hub is to have a fixed gear on one side, and a single speed freewheel on the other. Ideally, the freewheel sprocket would be one or two teeth larger than the fixed sprocket.

You would ride with the fixed gear most of the time (I hope!) and save the freewheel for longer rides, or for getting you home when you are tired. Having the freewheel a bit larger than the fixed sprocket gives you a lower gear when you are using the freewheel. This makes it easier to climb. Since you can coast when you are using the freewheel, the lower gear is no disadvantage on the descents.

Single-speed freewheels are commonly used on BMX bicycles: most shops that deal in BMX parts should stock them. The common size used for BMX is 16 tooth. Other sizes may be hard to find, especially for 3/32 chain.

If you are going to use a flip-flop hub with a freewheel, you should have two brakes on the bicycle.

Note, there are two types of hubs called "flip-flop":

Fixed/free, this is the type I speak of above, with a "track" side and a freewheel side.
BMX type...BMX flip-flop hubs have two different freewheel threads, a standard one on one side, and a special smaller-diameter freewheel thread on the other, designed to work with special small freewheels (14, 15 teeth.) These are now quite rare, but if you are calling around looking for "flip-flop" hubs, make sure you get the right kind.

Konventionelle Freilaufnaben

Der günstigste Weg zum Umbau eines Fahrrads mit Kettenschaltung zu einem Fixed Gear Fahrrad ist die Verwendung der originalen Hinterradnabe, wenn diese für konventionelle Freiläufe vorgesehen ist. Ein starres Ritzel lässt sich hier einfach aufschrauben. Es gibt jedoch keine Vorrichtung für einen Konterring.

Wenn man diesen Pfad betritt, sollte man einen Gewindekleber verwenden. Man kann den Konterring eines Innenlagers mit britischem Gewindemaß als zusätzliche Sicherheitsmaßnahme aufschrauben, weil die Gewinde zusammenpassen.

Obwohl man einfach das starre Ritzel aufschrauben kann und einfach alles zusammensetzt, wird wahrscheinlich die Kettenlinie nicht stimmen. Auf diesem Umbaupfad muss man die Achse umspacern, danach das Laufrad neu zentrieren um eine korrekte Kettenlinie zu erreichen.

Sheldon Brown merke an, dass es Leute gibt, die sagen, man solle keinen Konterring verwenden. Im theoretischen Fall, dass die Kette vom Kettenblatt springt und vom Ritzel mitgerissen wird, verhindert der Konterring, dass sich das Ritzel einfach abschraubt, statt das Hinterrad zu blockieren.

Sheldon meinte, dass es besser sei, einen Konterring zu verwenden, um ganz sicher zu sein, dass man nur mit den Füßen sein Fahrrad be- und entschleunigen kann. Das gilt insbesondere, wenn man nur mit einer Bremse am Vorderrad fährt. Wenn man keine Bahnnabe nutzt, sollte man überdenken, zwei handbetriebe Bremsen zu benutzen. Falls die vordere Bremse ausfällt und man mit den Beinen das Fahrrad bremsen möchte und dann noch durch den plötzlichen Ruck, das Ritzel losgeschraubt wird, ist man verloren!

Kassettennaben

It is also possible to convert a Shimano cassette Freehub ® for fixed-gear use. Quality Bicycle Products used to make the "Surly Fixxer (formerly Sub 11.0) Hub Converter", an adapter that replaces the Shimano Freehub body with a rigid aluminum block that is threaded for a fixed sprocket and lockring -- unfortunately, no longer made, though you might still snag one in old stock.

This device is mainly intended for use with disc wheels and the like. Although it works with most Shimano cassette Freehubs, it is expensive enough that it doesn't generally make sense unless you already have a very good wheel that you don't have any use for as a multispeed. Bruce Ingle, a fellow member of the Charles River Wheelers used a Shimano cassette hub, which he immobilized by brazing the ratchet mechanism together.

I rode with a brazed-up cassette hub for quite a while, and it worked fine.

Schnellspanner oder geschraubt?

Track hubs generally come with solid axles and track nuts. This is because most velodromes have rules requiring this type of wheel attachment.

As a result, it is widely believed that quick-release axles are not suitable for fixed-gear use. This is false!

It is my belief that the velodrome rule dates back to long before the invention of the quick-release, when the choices were standard nuts or wingnuts. The protruding "wings" of wingnuts might constitute a hazard in a crash, and I believe that's why the rule was instituted. Since quick-release skewers don't have any sharp projections, that becomes a non-issue in practice.

If you are going to use a quick release with a fixed gear, you should make sure to use a good quality enclosed-cam skewer.

Rahmen für Fixed Gear Umbauten

Straßenfahrräder

It is very desirable that a frame for fixed-gear use have "horizontal" rear dropouts: that is, the slots in the frame that hold the rear axle should run in a more-or-less horizontal direction. This allows you to move the axle back and forth as needed to adjust chain tension. This makes things much easier than if you try to convert a newer bike with vertical dropouts.

The most desirable bikes for fixed-gear conversion are 1970's road bikes. These usually have horizontal dropouts, and usually don't have unsightly shift-lever bosses. Frames of this era also tended to have more generous tire clearance than newer sport bikes, providing more versatility in the choice of tires, and the use of fenders.

Dreigang-Fahrräder

Old three-speeds can also make quite satisfactory fixed gear bikes, particularly English ones. The rear triangle is already just about perfect for a track hub; they usually have 110 mm spacing. The better English 3-speeds had pretty nice-riding frames, and can be very pleasant bikes for not a lot of money.

If you replace the 590 mm (26 x 1 3/8") wheels with 622 (700C) wheels, the bottom bracket gets raised a useful amount, providing good ground clearance. Using the larger wheels also allows you to install a better, shorter-reach brake caliper. There is a limit to the width of a 700C tire that will fit under the fork crown, especially with fenders, but relatively narrow tires are usual on a fixed-gear bicycle.

Eingang-Fahrräder

One-speed bikes are very easy to convert, since they usually already have 110 mm spacing. Unfortunately, most adult-sized one-speed bikes are not very good performers, and tend to be too heavy and sluggish for enjoyable fixed-gear riding. Some of the better-quality cruisers work OK as fixed gears, but watch out for low bottom brackets.

One of my favorite fixed-gear bikes is my 1916 Mead Ranger. This was originally built as a coaster-brake bike with 28-inch single-tube tires on wood rims. It was wheelless when I bought it at a flea market, so I set it up with some nice quality '70s vintage 630 mm (27") wheels and modern tires. It's surprisingly pleasant to ride.

Mountainbikes

A fixed-gear mountain bike may be the ultimate in heavy-duty urban transport, and, if you are adventurous enough, you can even take it to the woods. Mountain bikes tend to have adequate ground clearance, although most, alas, have vertical dropouts.

cb3 I have an old Bridgestone CB-3 set up for nasty winter conditions, with a 28/15. This gives a nice low gear, a 3.63 gain ratio (49" / 3.88 m) which will take me as fast as I care to go when the streets are snowy. A fixed gear this low makes the brake almost unnecessary: such a low gear lets me slow the bike down quickly by resisting, especially considering that it can't go very fast.

I have set up a couple of mountain bikes with flip-flop hubs, so that I get a fixed gear on one side and two different freewheel gears on the other. This is done with a double chainwheel and a two-speed freewheel. (The freewheel is actually an old 5- or 6-speed freewheel with 3 of the sprockets replaced by spacers.

In front, I have a 42/52 double, which I use with a 19 tooth fixed and a 20/30 freewheel. This gives 3 usable combinations: Gain Inches Meters 52/19 Fixed 5.45 71.2 5.70 General road use 52/20 Free 4.90 64.1 5.13 Road...when I'm tired, or hilly areas. 42/30 Free 2.64 34.4 2.75 Off-road. The 52/30 and 42/20 combinations are not usable due to chain length. I change gears manually...yes, I have to stop to do it, so I don't do it that often.

Bruce Ingle (also mentioned earlier) has gone me one better, and made a triple-fixed mountain bike. He used a Shimano cassette hub, which he immobilized by brazing the ratchet mechanism together. I am a bit nervous as to the long-term prospects for this hub, in particular the connection between the freehub body and the hub shell, but I think I will have to copy his setup. He's got: Gain Inches Meters 48/20 Fixed 4.65 62.4 4.99 42/26 Fixed 3.13 42 3.36 36/32 Fixed 2.18 29.3 2.34

Vertikale Ausfallenden

Most newer bikes (made since the late-1980's) have "vertical" rear dropouts, where the wheel slides upward as you install it. These are a problem when you want to dispense with a derailer, because you need some way to regulate chain tension. dropf-comp dropf-short dropf-semivert dropf-vert Horizontal Dropout Campagnolo 1010 Horizontal Dropout Short Semi-Vertical Dropout Vertical Dropout Spoke Divider dropf-stamp dropf-nohang dropf-raleigh dropf-sub With Hanger Without Hanger Raleigh 3-speed Track Fork End Not a dropout! You CanNOT use any sort of pulley type chain tensioner on a fixed gear bike!

You cannot use a derailer on a fixed gear bike, even as a chain tensioner, because when you resist the rotation of the pedals, you would bend the derailer. This presents a problem if you want to use a frame with vertical dropouts as a fixed gear, because there's no easy way to adjust the chain tension. This is also true of chain tensioners sold for singlespeed coasting bikes, such as the Surly Singleator.

Even the chain tensioners used for downhill mountain bike racing are not strong enough to withstand the stress of resisting the pedals. These tensioners have to clamp on to the chainstay, which is more or less round. There is no way to make one that would be secure, short of installing some sort of brazed-on fitting.

Solutions to this problem are described in a section of our article on non-derailer drivetrains. Please read the entire page, as it also describes other important topics with fixed gears.

Nabenbreiten/Rahmenweiten

Frames built originally to be used with 5-speed freewheels usually have 120 mm spacing between the rear dropouts. Fixed gear hubs are commonly available in this spacing, although they are more commonly found in the narrower, 110 mm spacing which is standard for track hubs. If you are using a newer frame, with wider spacing, you may want to replace the axle. You may want to replace the axle in any case, because fixed gear hubs generally come only with solid axles, not quick release.

Antriebsstrang

¹/₈ Zoll oder ³/₃₂ Zoll Ketten?

Many track bicycles use a wider chain than is common on multi-speed bicycles. Derailer-type chain has a nominal internal width of 3/32". Most bicycles without derailers, including most fixed-gear bicycles, use the wider 1/8" size. You can buy fixed-gear sprockets in both widths. There is more about chain in our article on non-derailer drivetrains. An important note: only master links for 1/8" chain can be detached and reattached without loosening the wheel -- so, 1/8" chains are easier to remove for cleaning.

Kettenlinie

Derailer bikes can work fairly well even with the chain running at a considerable angle, but this should not be done with a fixed-gear setup. It is quite important to get the chain line just right.

This topic is addressed at more length in our article on non-derailer drivetrains.

There is more detailed information on chainline in my Bicycle Glossary's Chainline Entry and even more in my Chainline Article.

Kettenspannung

The chain tension on a fixed gear is quite critical, and is regulated by moving the rear axle back and forth in the fork ends. If the chain is too tight, the drive train will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding. If the chain is too loose, it can fall off, which is quite dangerous on a fixed gear.

This topic is addressed at more length in our article on non-derailer drivetrains. Special equipment choices are required if the frame has vertical dropouts.

You need to pay more attention to chain wear on a fixed-gear bicycle than on others, because the consequences can be more serious if the chain falls off. If the chain is badly worn, adjusting it just short of binding will result in rough running and low efficiency, because the chain will not engage the teeth of the sprocket evenly. Check the chain for wear, readjust the position of the rear hub and replace the chain as needed.

Bezugsquellen für Fixed Gear Bauteile

Unfortunately, fixed-gear riding is somewhat of a fringe activity from a commercial point of view, and those who have not learned to love it tend to write fixed-gear fans of as nuts and fanatics.

If you have a local bike shop that stocks fixed-gear stuff, you are in a lucky minority, and I urge you to patronize them.

If you don't have such a shop nearby: See also "Fixed Gear on the Cheap" by Tom Deakins Fixed Gear Parts from Harris Cyclery

Siehe auch

Interested in multi-speed fixed gears? See: The Sturmey-Archer ASC Three-Speed Fixed-Gear Hub Converting a Sturmey-Archer AW to Fixed Gear

Quelle

Dieser Artikel basiert auf dem Artikel Fixed Gear Conversions von der Website Sheldon Browns. Originalautor des Artikels ist Sheldon Brown.

Weitere interessante Artikel zum Thema Singlespeed

Weitere interessante Artikel zum Thema Sheldon Brown

Weitere interessante Artikel zum Thema Workshop