Wartung von Naben
Um aus Naben die löngste Lebensdauer und den geringsten Reibungswiderstand herauszuholen, müssen diese regelmäßig auseinandergebaut, gereinigt, wiedereingepackt (Fett) und neu eingestellt werden.
Werkzeuge und Materialien
Falls möglich sollte man immer zwei spezielle Konusschlüssel für jede an Deinen Naben notwendige Größe zur Hand haben. Normalerweise heißt das dass man zwei Sätze Konusschlüssel haben. Ein Satz deckt die Größen 13, 14, 15 und 16 mm ab, wobei einige Konen nicht in diese Größen passen. Eine der Ausnahmen sind 1970er Jahre Dura Ace Naben, die 17er Schlüssel benötigen. Mann kann auch mit einem Konusschlüssel und einem Maulschlüssel (oder Engländer) für die Kontermutter auskommen. Die endgültige Einstellarbeit fällt aber mit zwei passenden Konusschlüsseln leichter. Normalerweise bekommt man diese Konusschlüssel nur im Fachhandel.
- Siehe auch
Um die Einzelteile zu reinigen, benötigt man eine alte Zahnbürste, ein paar Lumpen zur Reinigung oder Papiertücher und einen guten Entfetter. Entfetter sind im gut sortierten Baumärkten oder im Autofachhandel zu finden. Beachte genau die Bedienungsanleitung des Entfetters. Die besten Entfetter verlangen nach einer Spülung mit Wasser sobald das Fett vom Lösungsmittel aufgelöst wurde. Statt eines Entfetters kann man auch WD-40, LPS-1, Farbverdünner oder Kerosin nehmen. Dann muss man allerdings sehr viel von Hand schrubben, falls das alte Fett an der Nabe festgebacken ist. Nimm niemals (Reinigungs-)benzin. Das ist ein echtes Risiko für Leib und Leben, weil die Dämpfe am Boden entlangkriechen können und beim kleinsten Funken entzünden sich diese Gase. Stärkere Lösungsmittel verpesten mit Ihrem Gestank das ganze Haus - daher sollten sie ausschließlich draußen oder eine getrennten Garage benutzt werden. Es gibt auch ungiftige Lösungsmittel wie Citrasolv, die recht effektiv sind und weniger Probleme bereiten.
Zusätzlich benötigt man etwas Fett. Das beste Fett nach Sheldon Browns Meinung ist das Phil Wood Fahrradfett, das es im gut sortierten Fahrradfachhandel geben sollte. Es ist recht zähes Fett, das den Zusammenbau vereinfacht, weil es die Lagerkugeln an Ort und Stelle hält, während man Achse und Konus montiert. Dieses Fett ist sehr langlebig und wasserresistent. Mancher bevorzugt ein leichteres Fett wie dasjenige von Campagnolo oder das Lubriplate #105. Diese Fette haben etwas weniger Reibung, scheinen aber nicht so langlebig zu sein. Man kann auch Fett aus dem Automobilbereich nehmen. Ein Fett aus dem Bootsanhängerbereich kann bei Fahrrädern, die oft in feuchten Bedingungen unterwegs sind, hilfreich sein.
Der Unterschied zwischen Fett und Öl ist eine Frage der Gradmessung. Fett ist ein sehr dickes Öl, Öl ist ein sehr dünnflüssiges Fett.
Manche Rennfahrer nehmen lieber Öl statt Fett, damit sie im System weniger Reibung haben. Wenn man Öl einsetzt, müssen die Naben alle ein bis zwei Wochen nachgeölt werden, da die Naben sonst ernsthaft Schaden nehmen können. Das ist im Allgemeinen nicht den Aufwand wert! Den Unterschied kann man leicht spüren, wenn man die Nabe mit den Fingern hält und um die Achse dreht. Wenn das Laufrad montiert ist, ist der Unterschied nicht signifikant. Zum einen drehen sich die Lager recht langsam im Zentrum des Laufrads. Die Reibung durch Last ist um Längen größer als durch die Viskosität des Schmiermittels. Die Reibung in einer guten Nabe ist minimal im Vergleich zum Rollwiderstand der Reifen. Fett kann sogar zu weniger Reibung führen, weil es einen robusteren Schmierfilm bildet.
Zusätzlich sollte man einen Satz neue Lagerkugeln bereit legen. Sie sind sowohl im Fachhandel als auch im Internet leicht zu erwerben. Ein paar Ersatzkugeln sind auch sinnvoll, weil sie wie kleine flüchtige Teufel sind. Ohne neue Lagerkugeln sollte man eine Nabe nicht wieder zusammenbauen. Die meisten Vorderradnaben haben 10 3/16 Zoll Kugeln je Seite. (Ausnahme: Capagnolo Record, Nuovo Record und Super Record, die 7/32 Zoll Kugeln haben). So gut wie alle Hinterradnaben haben neun 1/4 Zoll Lagerkugeln je Seite.
Demontage
I would suggest that you start with the front wheel if you have not done this job before, because there are fewer complications. Before you remove the axle, check to see if it is bent. Remove the axle nuts or quick-release skewer that holds the wheel to the fork. Now if you rotate the axle and look at each end of it in turn you should be able to tell if the axle is bent. If it is, one end or both will wobble back and forth as it is turned.
Newer Shimano hubs have rubber dustcaps which you must pop off before you can do any further disassembly. Otherwise, your first step is to loosen one locknut.
If one locknut breaks free, fine -- some hubs use a keyed washer between each cone and locknut. The washer has a "key" or tab which slides in a groove cut in the threads of the axle. This washer will keep the cone from turning with the locknut. With such a hub, you might put a wrench on the locknut at each end of the axle and unscrew one from the other. Many newer hubs leave out the keyed washer, and so, use a cone wrench on the cone, and another wrench on the locknut on the same end of the hub. Otherwise, they are likely to turn together and be hard to turn. Also see special instructions for Raleigh front hubs.
There is an additional complication when you are working on a freewheel rear hub, because the freewheel block gets in the way. If you have the necessary tools (a freewheel puller to fit your brand of freewheel and a sturdy vise mounted on a solid workbench, or large -- additional advice is in the article on freewheels), the easiest approach is to remove the freewheel first. If this is not possible, you can do the job without removing the freewheel. Remove the locknut and cone on the left side of the hub and pull the axle out from the right side. You will just be able to get at the right bearing cup through the center of the freewheel.
On a cassette Freehub, the right-side bearing is more accessible, but it is easier to clean out the right-side bearing if you remove the lockring first. Instructions are in my article on cassettes.
It will not be nearly as easy to clean the right cup with the freewheel or cassette lockring in your way, but fortunately that side rarely gets dirty, because these parts make it harder for dirt to get in. Be careful not to get solvent inside of the freewheel or Freehub mechanism While you have the axle out of the hub, tighten the spacer for the right end of the axle tightly against the locknut and cone so you will be able to use a wrench on the locknut to hold the axle when you are adjusting the cone on the left. If you have put a new axle on a rear quick-release hub, it likely will be too long for the quick release to work properly. If so, it is easiest to cut it down after it is installed in the hub.
Lift off the washer, if present, and unscrew the cone. Once the cone has been removed from one end of the axle, the axle can be pulled out of `the hub, and the ball bearings will fall out. There is no need to remove the other cone and locknut that are still on the axle, so save yourself a lot of trouble and leave them on the axle, unless your old axle is bent and has to be replaced anyway. Remove the dustcaps by carefully prying them up with a screwdriver. If you have trouble getting the dustcaps off, leave them on rather than bending them. This will make it a bit harder to clean out the hub.
Reinigung
Der wichtigste Teil der Arbeit ist es, die ganzen inneren Bauteile so sauber wie menschenmöglich zu bekommen. Die Innenseite des Nabenkörper, die Achse, Konen und Lagerkugeln müssen vollständig von altem Fett, Schmutz, Staub und Lösungsmittel sein. Wenn man nicht auch die letzten Reste des Lösungsmittels entfernt, wird es das neue Fett aus dem Zusammenbau angreifen und man muss die ganze Prozedur viel zu früh von vorne beginnen.
Man kann sogar so weit gehen, dass man ein Bündel Papierküchentücher durch den Nabenkörper zieht und Reste mit einem Wattestäbchen reinigt. Falls die Nabe einen Ölauslass hat, nimm den Verschluss heraus, reinige ihn und das Ölloch. Wenn man einen keinen Entfetter benutzt, der eine Wasserspülung als Abschluss verlangt, kann man stattdessen auch die Teile in Spülwasser reinigen, danach mit klarem Wasser abspülen und leicht erhitzen, damit sie schneller trocknen und nicht so schnell Rost ansetzen.
Wenn man mit der Zahnbürste fertig ist, sollte man diese sehr gründlich reinigen, bevor man sich mit ihr wieder die Zähne putzt.
Now that the parts are clean, they should be carefully examined for wear. The cones should have a shiny track running around them where the balls roll against them. Examine this track very carefully to see if there are any irregularities or pits. A magnifying glass may be of help here. If there is any sign of a flaw, no matter how small, a cone should be replaced.
Examine the cups (in the hub shell) in the same way. In most cases it is not possible to replace the cups without replacing the whole hub, but fortunately the cups usually are the last parts to wear out. If the hub is cleaned regularly, lubricated and kept in good adjustment, the cups should last indefinitely.
One of the reasons why I suggest routinely replacing the balls is that it is very easy to fall to see pitting or crud on a ball, since you can't be sure that you have seen every side of it. When I am repacking a hub, if I drop one of the new balls on the floor, I don't even bother to pick it up. I use another new one rather than contaminate the bearing by putting in a possibly dirty one.
It is particularly important that all of the balls in a given race come from the same production run. They are made to tolerances of 3 or 4 millionths of an inch. One batch may be oversize, while the next batch may be several millionths undersize. If some of the balls in a race are that much smaller than others, the smaller ones might just as well not be there, because only the larger ones will be taking the load.
The balls need to fit easily into the race. If there is one too many, the wheel will tilt slightly one way and another after installation, and can not be trued.
Zusammenbau
If you removed the dustcaps, the first step in reassembly is to put them back in, unless they are the rubber dustcaps. Gently tap them into the hub shell with a hammer, working your way around the outer edge of the cap. Then line both cups in the hub shell with grease. Don't worry about using too much. It is not possible. If in doubt, use more.
Next, lay the wheel on its side, and insert the end of the axle that does not have a cone on it part way into the hub from above. (If you are doing a rear hub, make sure that the axle is going in the same way it came out, so that the long end will be on the freewheel side.) With the axle blocking the hole in the barrel of the hub, you can install the balls in the upper cup without any risk of having them fall through.
Now, lift up the wheel and let the axle drop down so that the cone rests on the balls that have just been installed in the cup. Hold onto the axle and turn over the wheel. Don't let go of the axle until it is resting on your work surface, or the balls may fall out. Install the balls in the other cup and screw the remaining cone onto the axle hand tight. This will secure the assembly so that you can now handle it without risk of dropping bearing balls on the floor. Install the lockwasher and locknut, and you are ready to adjust the bearing.
Adjusting ball bearings of the type used on bicycles is not difficult, but if you haven't done it before it is likely to take some time and patience. Don't be in a hurry.
What is meant by "adjustment of bearings" in the case of hubs is basically how far apart the cones are from one another on the axle. If they are too close together, they will pinch and bind against the balls, and the axle will be difficult to turn. The bearing will have too much friction and the parts will wear out prematurely. If the cones are too far apart, everything may roll freely enough, but there will be looseness or play in the bearing, and your wheel will wobble from side to side like loose tooth. The ideal is to find the point where the cones are loose enough that the axle turns as freely as it does when the cones are too loose, but with as little play as possible.
It is meaningless to try to judge the cone adjustment when the locknuts are not tight, because when you tighten the locknut, it changes the cone adjustment. What you have to do is to try different adjustments, checking each time for two things--friction and play.
To check for friction, pretend you are a safecracker and the axle is the knob of a safe. Turn it slowly and smoothly, several revolutions in each direction. It should move with the gentlest pressure, without any unevenness or binding. If you are not sure whether it is binding or not, try loosening one of the cones a bit. If it turns any easier, the previous adjustment was too tight.
To check for play, see if you can get the end of the axle to wiggle up and down or side to side. If there is play, you should be able to feel it with your fingers. There is a more detailed article about cone adjustment on this site. It descdribes some useful tricks to fine-tune the adjustment
It should be possible to adjust a good-quality hub so that there is no perceptible play, with no more friction than is present when the cones are too loose. If you are unable to get the hub to pass both tests with the same cone adjustment, take it apart again and repeat the whole procedure. Your problem is either attributable to dirt in the races (even a single dust particle can cause trouble), pitting on the bearing surfaces, a bent axle, or a basically poor-quality hub (such as the pressed-steel hubs that come on cheap bicycles). Also check whether you might have installed one too many bearing balls. If nothing you can do will eliminate both the binding and the play at the same time, it is better to adjust a little loose and accept a slight amount of play then to have the hub bind.
No binding with no play is the proper adjustment for solid-axle hubs, but if you have quick-release hubs, there is an additional, complicating factor. When you tighten the quick-release lever, it tends to compress the axle just a little bit. If the adjustment was just right with the wheel on your bench, it will be too tight when the wheel is installed and the quick release tightened. For this reason, quick-release hubs should be adjusted so that there is a very sight amount of play in the axle when the wheel is not installed. This play should disappear when the quick release is tightened to the dropouts. My article on cone adjustment describes a special home-made tool lets you get the adjustment right when the wheel is off the bicycle. You might also keep a pair of dropouts sawn off a junk fork, so you can tighten the quick release on them and still spin the axle to check for binding.
Bearing adjustment also can be checked by lifting the bicycle off the ground and trying to wiggle the rim back and forth between the brake shoes. There should be no rattling sensation. Now keep the bike off the ground and let go of the wheel. The weight of the valve should be sufficient to cause the wheel to swing back and forth several times before the wheel comes to a stop with the valve (or whatever part of the rim-tire-tube combination is heaviest) at the bottom. This test will not work on the rear wheel unless the chain is disengaged from the rear sprockets.
The hubs should be repacked at regular intervals as part of the normal maintenance of your bicycle. How often it is necessary will depend on how much you use your bike and under what conditions. If you only ride on sunny days and have good luck, you might be ,able to go a couple of years, but if you ride in the rain, or if you live in a sandy or dusty area, you may have to repack your hubs every couple of months. The interval can be extended considerably by installing external seals to block the entry of dirt. (See Sealing Your Bike Components for Under $ 10 by John Allen, July 1977 Bike World.) [But also see Jobst Brandt's comments on sealed bearings, on this site. -- John Allen]
Rather than repacking your hubs on a fixed schedule, I recommend that you periodically check the condition of your hubs by removing the wheels and feeling how freely you can turn the axles (in the same manner described previously). Do not be fooled because your hub may seem to have "just a little" friction. Frictional drag depends on the load on the bearing. When you are holding the wheel and turning the axle by hand, the only load is the weight of the axle set and the viscosity of the lubricant. When you are riding your bike, the load is the weight of you and your machine, and the frictional drag is increased by many times. You can feel the difference.
Siehe auch
Quelle
Dieser Artikel basiert auf dem Artikel Tool Tips Hub Overhaul von der Website Sheldon Browns. Originalautor des Artikels ist Sheldon Brown.
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