Merkblätter zur Restaurierung der überschweren Kräder BMW R75 und Zündapp KS 750.
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Thema
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The Wheel
To get good wheels today is quite problematic.
The gearing of the wheel is worn out.
Worn out gearings of the wheel have the effect that at every change of load heavy hits occur in the drive system to the transmission. With a worn out gearing the wheel can be freely moved up to 40 mm at its outer diameter . On strain a sudden shear blasting of the gearing is quite often the end of the gearing of the wheel.
The rims are laterally or radialy deformed.
The reason for flittering steering, vibrations and a turbulent driving style of the bike is mostly the gearing of the wheels.
The lateral / radial deformation should not be more than 1,0 mm according to the BMW manual.
With more than 2,0 mm you should seriously consider to change something. But in most cases an adjustment of old worn out rims is not possible without taking all the spokes out and adjust the rim.
The brake drum
The brake drum is often damaged or corroded at the brake surface.
The diameter is too large or the brake surface is warped.
It has a standard inner diameter of 250 mm.
A machining up to 252 mm is permitted. A lateral / radial deformation of 1,0 mm is permitted.
A machining over 252 mm should not be made because the material of the wall is too thin which leads to a warping when heated.
All these mistakes lead to a dramatic reduction of the braking performance.
After machining a brake drum the brake pad – produced for 250 mm – does not fit anymore.
You need to use an oversize brake pad. In between these dimension it must be adjusted accordingly.
The spokes are often seized up in the threads so that you cannot tension them anymore.
There are 20 long and 20 short spokes.
The thread is rolled up, not cut and at the end there are two thickenings towards the spoke head.
This kind of spokes is called thick end spokes. Other spokes should not be mounted because otherwise there is the danger of breaking.
Paintwork
The first version of the wheels was painted in the same color as the bike. Often the paint comes off the brake drum because of the heat during braking. From 1943 the brake drum and the spokes are painting in black thermal coating. The rim is still kept in the same color as the bike.
If you have a defective wheel today you have to think about it whether it is worth to be restored as the labor and material costs exceed the price of a new wheel.
Work:
Dismantle the wheel and sandblast it
How is the gearing towards the gearing inside the wheel?
Can I repair the damaged brake drum at all?
When the rim has a deformation it is impossible to eliminate it by tensioning the spokes. Therefore the rim is too solid.
| Spoke set order no.3323 | Rim order No. 3337 | Wheel order no. 3337-1 |
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Wir bieten an: Ersatzteile + Instandsetzungsarbeiten |
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Wir bieten an: Ersatzteile + Instandsetzungsarbeiten . für |
H-P Hommes Ersatzteil-Dienst
Ersatzteile + Instandsetzungen
repairing + restoring