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Tech & Wearables

Technical FAQ: Internal cable routing tips, more on oversized pulley wheels and gearing

VeloNews' technical expert offers suggestions for fishing internally-routed cables and further discussion about chain tension with oversize pulley wheels.

Have a question for Lennard? Please email him at veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
My local bike shop was unable to restore the rear brake cable through the internal housing of my Klein Reve top tube. Is there a special trick that you can suggest to route it? The best they could do was to use zip ties to hold it in place on the outside of the top tube, but needless to say that is suboptimal. Here’s hoping you can give me some ideas.
— Bob

Dear Bob,
With most bikes, I would say to get one of these IR 1.2 kits from Park Tool. It works wonders for routing internal cables and hoses.

Your particular bike creates more problems, however, which is why I’m sure your shop was stymied. That internal cable design was intended to run bare cable inside; the insert into the tube is a housing stop. The hole into the frame at each end is thus hardly bigger than the cable itself, which is insufficient for the end on the Park IR-1.2 lead wires to fit through.

The opportunity to solder the new cable end-to-end to the old cable before removing it and pulling the new cable through with it was lost when the old cable was removed. That was the method we would use back in the 1980s and 1990s when we ran into bikes with internal routing like this.

Since you can’t use the Park IR-1.2 tool, you will be stuck with trying to fish cables through by themselves (put a bend in the end so that you can twist the cable when the end gets to the hole until it pops out). Alternatively, you can try fishing a stiff wire through whose other ends you solder end-to-end to the cable; don’t bother soldering it unless you are successful in getting the other end to pop out of that tiny hole.

Another method that might work is to vacuum it through. Crimp a piece of string to the end of the cable with a cable-end crimp cap, drop the string in the hole in one end of the frame, and suck its end out the other hole with the narrow edging tip of a vacuum cleaner. Tip the frame in the bike stand to get the assistance of gravity. You may need to file down the soft aluminum crimp cap (after it’s crimped onto the cable and string) to make it small enough to fit into the tiny holes in the frame. This method works surprisingly well, and I describe it in the 6th edition of Zinn and the Art of Mountain Bike Maintenance.
― Lennard

Dear Lennard,
With the recommendation to replace carbon fiber forks every five years, where can we get them with a 1 1/8” steerer with 50mm rake that will accept a minimum 28mm tire? The only one I have found is a Columbus Caliper SL.
— Christian

Dear Christian,
That one should work. Otherwise, WoundUp offers up to 48mm rake in such a fork.
― Lennard

Regarding chain tension and oversized pulley wheels as well as chainring questions from last week’s column:

Dear Lennard,
Thanks for such an in-depth response to my questions. After reading it a few times, I don’t have a very technical mind but more of an inquisitive mind, which leads me to another question. Does low cadence pedaling (my style and hence the need for larger big chainrings) yield higher tensions on the loaded part of the chain and therefore increased drag? My assumption is yes, but I figured I would ask.
— Scott

Shimano
Chain tension is inversely proportional to chainring diameter. Photo: Lennard Zinn | VeloNews.com

Dear Scott,
Since chain tension is inversely proportional to chainring diameter as I explained in a previous column, you would not expect to have higher chain tension. Even though you are pedaling at a lower cadence and a higher load on the pedal with each stroke, the increase in chain tension due to that is counterbalanced by a drop in chain tension due to an increase in chainring size.
― Lennard

Dear Lennard,
One thing I don’t understand about your answer on the oversized pulley wheels: how do larger pulley wheels decreases the spring force applied at the cage? And does the chain length have to be increased just to get around the bigger wheels and new cage?
— JP

Dear JP,
CeramicSpeed’s rear derailleur jockey-wheel cage for oversized pulley wheels (OSPW) has repositioned spring holes. Due to that, the angular position of the spring attachment point to the cage is rotated slightly, causing the torsional spring to not wind as far, therefore creating lower spring tension.

Furthermore, the CeramicSpeed OSPW cage has multiple spring attachment holes. This allows the user to adjust the cage tension from stock-level tension (already lower than with the original jockey-wheel cage and pulley wheels) to a lower tension, depending on which hole is used.

Typically, a longer chain length is needed to accommodate the larger pulley wheels. However, it depends on the starting chain length with the stock derailleur set up prior to installing the OSPW cage and pulley wheels.
― Lennard

Dear Lennard,
When it comes to crank arms, I agree: “That said, things were simpler 11 years ago in this regard.”

I am a Shimano guy, but when the first Dura-Ace 4-armed crankset came out, I knew it was the beginning of the end. About a year ago, I purchased a 105, 110 BCD, 175mm crankset “just in case.” After seeing all those videos on the un-bonding of those Hollowtech cranks, I’m glad I did.
— John

Dear Lennard,
Regarding Scott’s email on gearing, and as you alluded to, newer (7900 and beyond?) chainrings really seem to be “pair specific”. I tried a 50/42 combo, as well as 53/38, both of which were non-matching A/B types I tried to match that didn’t play nice with the ramps on the big chainring. On the 50/42 combo, I was going for a good time at the Mt. Fuji hill climb, which is relatively tame at 5.4 percent average for 23-24km, and wanted a tight combo up front. Either way, didn’t shift well.

This resulted in noticeably slower shifts from the small/big chainring, and I went back to the Shimano-specified combo. Tried this on 9000 as well as 9100 Dura-Ace.

On the topic of gearing, for those that prefer smaller jumps in the cassette, check out the Shimano “junior gears” Ultegra 14-28 cassette. Great climbing cassette if you don’t like big jumps, and I even used it for a rolling TT with a 55/42 up front. Only wish they now made a 14-30 or 32 to go with the larger capacity of newer generation RD`s.
— David


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of The Haywire Heart,” and author of many bicycle books including Zinn and the Art of Road Bike Maintenance,”DVD, as well as Zinn and the Art of Triathlon Bikesand Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn on Twitter.