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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 01-07-09, 05:53 PM   #1
ilikebikes
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Machined VS Non-Machined

This is something I found on the C-List of all places, thought it was a bit interesting and wondered if anyone can say for sure that this is indeed a fact. ================ From Jobst Brandt the author of The Bicycle Wheel:

Question: Just wondering if it really makes any difference. Some manufacturers don't even advertise whether the sidewalls are machined; others do. Velocity for example, makes both, but I believe they're the same price. What gives? Just marketing hype?


Answer: What you hear and read is mostly marketing hyperbole, but machining rims has its reason, and it isn't for your benefit. If you inspect a machined rim closely, you'll find a surface that looks as though made by a thread cutting tool. The purpose is not to get a flat braking surface, but rather to produce a series of fine grooves to prevent brake squeal on new bicycle test rides.

The machined grooves, about the texture of LP vinyl record grooves, can be felt by running a fingernail across the rim. These fine grooves usually wear off on the first braking descent in wet weather, the condition that causes rim wear in the first place. Even anodizing, which is a hard ceramic, whether thick or thin, is more durable than the machined rim. However, anodizing is not the solution to wear, because it degrades braking. Anodizing being an insulator that overheats brake pads and causes brake fade.

The claim that machining is for purposes other than suppressing brake squeal is far fetched. For instance, rim joints have been made with no perceptible discontinuity almost as long as aluminum rims have been made. Unfortunately, some people in marketing believe that rims will separate if not riveted (or welded) and introduced riveting that usually distorts rim joints. Fortunately, that rims were made for many years without rivets and had flawless joints proves otherwise.

In practice, machining solves the new-rim squeal problem at the cost of a rim wall of unknown thickness. It also adds a bit of sparkle to the new product by giving rainbow reflections in showrooms. Mavic, for instance, has rims listed as having "CERAMIC2", "SUP, "CD", "UB", MAXTAL", all features that substantially increase cost over plain aluminum rims that were offered at about 1/4 the price not long ago.

The web site explains that "CERAMIC2" is an insulator that improves braking even though the rim is "UB" machined, ostensibly for the same purpose, before ceramic coating. This is a tipoff, because without special brake pads, this feature overheats pads causing them to wear rapidly while degrading performance. Not mentioned is that it's main purpose is to reduce rim wear in wet and gritty conditions.
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Old 01-07-09, 06:13 PM   #2
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Brandt is kind of insane about certain things, and this is one of them. The two things that I believe is that braking in wet weather wears rims, and that you can brake on an unmachined rim. Also, I believe that machined rims cause brake pads to wear faster, but that's because the machining makes stopping much more efficient.
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Old 01-07-09, 06:25 PM   #3
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Originally Posted by dmg View Post
brandt is kind of insane about certain things, and this is one of them. The two things that i believe is that braking in wet weather wears rims, and that you can brake on an unmachined rim. also, i believe that machined rims cause brake pads to wear faster, but that's because the machining makes stopping much more efficient.

ditto
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Old 01-07-09, 06:42 PM   #4
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Originally Posted by ilikebikes View Post
What you hear and read is mostly marketing hyperbole, but machining rims has its reason, and it isn't for your benefit.


However, anodizing is not the solution to wear, because it degrades braking. Anodizing being an insulator that overheats brake pads and causes brake fade.
sounds like it's for my benefit to me...
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Old 01-07-09, 06:57 PM   #5
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I honestly have seen no real testing between the two ... so I don't know. But from my own personal experience the only difference I see is that braking on a painted surface would suck (if it is powder coated).
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