Mountain Biking - Why does Specialized route the rear derailleur cable from the bottom tube?

Why does Specialized route the rear derailleur cable from the bottom tube while most manufactures route it from the top tube? ie. Klein, Giant, Trek...

Are they trying to be different? Is it that much more efficient as to expose the cable to the elements from the road?

I have an old Trek and compared to my friend's old Stumpjumper, his rear derailleur cable routed from the bottom tube is in a lot worse shape than mine.

This is why reason why my current search for a new bike does not include Specialized. Another reason being that ugly downtube bend in their Stumpjumper/S-works 2003 models.

Well if you replace your cables as often as is recommended then it's a non-issue, also there are ferrules availiable that make the crud factor even more of a non-issue..

From sheldonbrown.com
Over or Under the Bottom Bracket?
Over
Up until the mid-1980's, the usual way to run gear cables was above the bottom bracket, either using short pieces of cable housing, or, more commonly, simple guides, either brazed on to the bottom bracket shell, or clamped to the frame. From the guide, the rear cable would run along the top of the right chain stay to a cable stop at the rear of the stay, for the final loop to the rear derailer.
This worked quite well, until mountain bikes came on the scene and made granny gears a standard item. The problem was that the extended cage of a wide-range front derailer would interfere with the rear gear cable.


Under
The popular solution to this problem was to run the cable under the bottom bracket shell, and move the chainstay cable stop to the underside of the chainstay. This had the added advantage of being cheaper--a simple plastic block bolted or rivetted to the underside of the bottom bracket shell took the place of a brazed on or clamped on set of guides. Most multi-speed bicycles are now made this way.
Unfortunately, this routing tends to degrade shifting somewhat. Locating the chainstay cable stop down below creates a sharper curve for the final loop of housing, and also exposes the entrance to that loop to crud splashed up by the front wheel. The bottom-bracket guide, whether over or under the bottom bracket, is also exposed to sprayed mud and crud from the front wheel...a particular problem for off-road cyclists.


Top routing
The third option, increasingly popular for mountain bikes, involves bypassing the bottom bracket altogether, and running both gear cables along the top tube.
The rear runs down along the seat stay, and the front runs down the back of the seat tube. When this style first arose, in the early '90's, the front derailer was a problem, since existing front derailers were intended to be operated by a cable pulled from below. Early top-routing schemes used brazed-on pulleys on the back of the seat tube, a rather mono-buttocked solution, in my opinion. This problem has been solved by the ready availability of "top-pull" front derailers.

Having said that I have a Bottom routed Specialized hardtail and a Top routed Specialized FSR. I haven't had a problem with either of them. Heck the hardtail is still running the original cables and they still look fine.

Thx for the feedback.

I guess I'm more curious as to why bike manufactures have not taken advantage of routing through the top tube yet. While there is no harm routing it from the bottom tube, it's certainly a benefit to reroute it.

From an engineering perspective, I would think the bike design engineers would of picked up this improvement by now. Is it the cost of design change or are there loyalists that they're trying to please.

Design change costs. You'll see more top route cables as new frame styles come and go. Also, the top pull front D' is starting to gain popularity over the traditional bottom pull design - to the extent that the bottom pull design is on the way out in drivetrain manufacturer's higher-end lines.

The rear is typically routed in similar fashion to the front for design cleanliness

Most of Specialized's 03 bikes are "Monocoque" or "Semi-Monocoque" frames....

there's simply no other way to route the cables cleanly. If they were on top, you'd rip your knees apart (as well as if they were on the sides of the top "tube").

Not just Specialized, but almost any manufacturer with "folded aluminum frame masts" is going to be forced to run the cables on the bottom.

Klein and Maverick have *Internal* Cable routing.. but when that stuff goes wrong... don't expect it to be fixed easily, cheaply, or anytime soon. That design is an absolute NIGHTMARE to work on. (ask your LBS's main mechanic). They'd probably charge you double because it was such a thorn in their side to get'er' done!

The coolest thing about the higher-end 03' Specialized's though is the Full-Length-Housing. Yes it shifts a little "mushier" , but the pay-back is SOOOO worth it. An always clean set of cables that are never exposed to the trail poop you ride through. If / When your cables ever need to be replaced, drop a few *liberal* drops down inside the housing... let it soak in.. then thread the new cable in. It'll pull the lube with it, and make everything super slick and happy.


Hope that helps.

-Matt :beer:

I hate anything with internally routed cables. It sucks to work on (I work at a shop) and most such designs involve using housing throughout the run of the cable, resulting in degraded shifting or braking performance. Nearly all bikes I see in our shop route the derailleur cable along the chainstay. If you notice that neither Trek nor Giant does this, that's because Giant is making the Treks that would be comparable to the Stumpy. As was previously mentioned, if you replace your cables at proper intervals it's a non-issue.
The bend in the new Specialized frames is there for strength. You might want to visit their website and read up about why the feel it's a superior design. Go to http://www.specialized.com/SBCBkModel.jsp?san=03Stumpjumper&bl=mountain&my=2003 and click on the "ORE" logo.

The Specialized FSR's are routed on the top. The hardtails look like they route on the bottom.

Originally posted by Waldo
I hate anything with internally routed cables. It sucks to work on (I work at a shop) and most such designs involve using housing throughout the run of the cable, resulting in degraded shifting or braking performance. Nearly all bikes I see in our shop route the derailleur cable along the chainstay. If you notice that neither Trek nor Giant does this, that's because Giant is making the Treks that would be comparable to the Stumpy. As was previously mentioned, if you replace your cables at proper intervals it's a non-issue.
The bend in the new Specialized frames is there for strength. You might want to visit their website and read up about why the feel it's a superior design. Go to http://www.specialized.com/SBCBkModel.jsp?san=03Stumpjumper&bl=mountain&my=2003 and click on the "ORE" logo.

Can you give me some documentation on your statement that Giant is making Treks?:confused:

Yes, they have a manufacturing alliance that was mentioned in a recent issue of Bicycle Retailer and Industry News (page 25 of the March 1 issue). Aside from that, it's common knowledge.
Here's just one mention, though Giant is no longer making bikes for Specialized-Merida makes them. You'll need to scroll through a bit of the article.
http://www.dailypeloton.com/displayarticle.asp?pk=2451

Top tube cable routing has an inherent problem that nobody has mentioned yet.

Everytime you ride through a puddle, the water that splashes onto your shift cable runs down the cable and eventually can collect in the rear derailleur housing loop. Shimano provides a couple of rubber straw bushings to minimize this problem.

Honestly, on a reasonably maintained bike, I can't see any difference in performance. I personally prefer under the bottom bracket routing, but then I'm a retro grouch.

Giant makes the vaaaaast majority of asian-made alumunum frames under a certain pricepoint.

That aside, here's an interesting item...
Raiyn makes an interesting point about design changes costing money. Think about this: Ever notice the *third* area to route a cable through on the plastic thingie at bottom bracket? ever wonder what its for? It does not route to bottom pull front deraileurs or rears cleanly...

Its actualy a vestigial feature from back in the mid 80's when alot of mountainbikes had U-brakes brazed to the BOTTOM on the chainstays. Yep, thats a brake cable routing. No one uses u-brakes under the stays anymore, but changing the design on a cheap piece of plastic for no noticible return in value or performance is kinda dumb, so there it remains.....

Just in interesting historical note ;)

Originally posted by Waldo
Yes, they have a manufacturing alliance that was mentioned in a recent issue of Bicycle Retailer and Industry News (page 25 of the March 1 issue). Aside from that, it's common knowledge.
Here's just one mention, though Giant is no longer making bikes for Specialized-Merida makes them. You'll need to scroll through a bit of the article.
http://www.dailypeloton.com/displayarticle.asp?pk=2451

Thanks for that info. How can I find who makes a particular model? (Navigator 300)?

That is interesting, Stumpjumper.
Robert-I am not aware of any model-by-model reference and with our shop not being a Trek or Giant shop I can't really look into it further, but I would almost guarantee Giant made that bike.