Dear List,
there are several issues here, many of which have been addressed. To summarize top vs. bottom bb cable guides:
- aesthetics 1: Which looks better? A matter of taste, it depends on whether you prefer traditional + ornate or modern + simple. - aesthetics 2: The top chain stay stop can get whacked and chipped by the chain.
- mechanical 1: The angle of cable deflection is less acute with top guides. Back in the early 80's when steel was still king and Eddy Merckx started producing his own frames, this was the reason his Italian advisors gave him for using top-mounted guides on Merckx frames. He did so, but other builders preferred the simplicity of bottom mounted guides. - mechanical 2: Modern shifting systems require low friction, which is easier achieved over short plastic or stainless bottom guides than relatively long ferrous, non-stainless top guides. Some people put plastic sheaths over the cable where they met the top guides, but this was a bit of a stop-gap measure. - mechanical 3: Top guides aren't always brazed on correctly, and can be bent. And they're heavier. - mechanical 4: Many modern frames have massive or strangely shaped tubes which would preclude the use of top guides. The bottom cylindrical half of the bottom bracket shell is one of the few remaining constants of most frames.
- maintenance: Top guides collect crud and are difficult to clean.
- economics 1: Once mounted, top guides are more difficult to paint. Which leads to what is probably the decisive reason, as has been noted: - economics 2: The efficiency of mass production, which is the same reason brazed-on clamps for the saddle tube died out. It's far cheaper to leave a simple slit tube for the saddle, and bung on a mass- produced taiwanese clamp, and it's far cheaper to bung on a plate than to braze or weld on two guides. As Tom Harriman said: "The bicycle industry is like all other businesses, it's always going to be looking for ways to cut cost and stay profitable."
Greets
Kai Hilbertz Munich, Germany
On 20.10.2008, at 16:38, Dale Brown wrote:
>
> (I waited to see if anyone gave an answer I agree with ! No one did,
> Ha!)
>
> Here's the deal... (as compared to under the bb shell guides):
>
> - They accumulate dirt and goo in the crevices that are extremely
> hard to thoroughly clean/and potentially rust. (It's actually hard
> to thoroughly get paint on them with all the angles and hidden areas.)
> - Many (!) are improperly brazed on, as to position & how they
> direct the cables.. A savvy frame builder can point out that
> immediately and novices are blissfully unaware.
> - They are heavier (OK, not by much, but nonetheless...)
> - The chain stay stop often gets whacked, and chipped by the chain.
>
> I still like them, but under-the-bb-shell routing is easier, no
> question. And "more modern!"?
>
>
>
>
>
> Dale Brown
> Greensboro, North Carolina? USA