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No Longer Made


MAVIC 845 MOUNTAIN REAR DERAILLEUR

The 845 weighs more than any other MTB rear we reviewed. The major reason, is the weight of the pulley cage, which is 5mm longer than the 841 and made of Black painted steel. The outer side, (away from the wheel), is made of 3mm thick stamped steel. The plate remains absolutely rigid even with the tension pulley removed while attempting to bend it. The inner plate is made of 2.5mm thick steel and does give slightly at the bottom, but only if the pulley is removed first. The cage is the most massive we've seen. The pulleys Mavic uses are very traditional, a nylon-like hard plastic outer pulley has a machined brass insert (bushing) that operates as an outer bearing race. The inner race which the axle passes through is made of smoothly machined steel. Aluminum plates surround this bearing assembly before the pulley is bolted into the cage. The pulley use the same steel bolts found in the 840 and 841 models. Cosmetically, the derailleur body has a colorful sticker over it, that identifies it as one of Mavic's ATB or "V.T.T." parts. The Mavic 845 rear weighs 295.5 grams, will accept cogs up to 32 teeth in size and is rated my Mavic at a 38 tooth capacity. The 845 weighs 294 grams. The 845 has been discontinued by Mavic but we have a few and there are likely to be other stores that also have them. No longer made, we sold the 845 for $109.99





In-depth Information About Metals

Aluminum
Aluminum is extracted electrolytically from bauxite ore. It is made by the electrolysis of aluminum oxide which is found in larger concentrations within bauxite ore. Bauxite is a mixture of the hydroxides of aluminum, together with other impurities such as oxides of iron, titanium, and silicon. Bauxite is produced by the weathering and change of aluminum silicate rocks usually found in tropical and semitropical regions where climate has produced an accelerated weathering process. Bauxite is not a rare ore and is widely available in the US, the Caribbean, and Europe. Approximately 4 pounds of read the full article...

Beryllium
Beryllium is a specialty metal that is steel-grey metal in color, with an extremely low density, making it very light weight. At 1.85 grams to the cubic centimeter, its density compares to that of magnesium. It is also a high strength metal, making it possible to design light weight, thin membered parts with ahigh stiffness. A column made of beryllium to support a load placed directly downward on top of it, will have a greater load carrying capacity, and be lower in weight than any other metal of equal size.

Until the 1950's beryllium was used read the full article...

Titanium
The element titanium was discovered in 1763 by an English cleric, William Gregor who was an amateur chemist with an inquiring mind. It was in the black sands of Cornwall that he discovered the new element that had up to that time, attracted little scientific interest. A few years later, an Austrian, Klaproth, extracted the same element from an ore widely known as "rutile", which is a mineral consisting of titanium dioxide (one titanium atom, two oxygen atoms), that is a reddish-brown substance with a slight metallic luster. While rutile is the highest grade read the full article...

Metallurgic Hardness Testing
There are three types of tests used with accuracy by the metals industry,they are the Brinell hardness test, the Rockwell hardness test, and the Vickers hardness test. Hardness is the property of a metal which gives it the ability to resist being permanently deformed (bent, broken, or have its shape changed), when a load is applied. The greater the hardness of the metal, the greater resistance it has to deformation. Since the definitions of metallurgic ultimate strength and hardness are rather similar, it can generally be assumed read the full article...


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