Saturday, May 16, 2015

Satanic Serpent

Jake the Satanic Serpent came back to the workshop about three weeks ago because the shifting had gone crunchy again after another abusive mud wallow.

"Gloucester isn't until late September," said the owner. "I don't plan on riding it until a couple of weeks before that." He was referring to the big cyclocross race in Gloucester, Mass. in the fall. He said he would be riding his road bike for the spring and summer, so not to rush the 'cross bike.

I gratefully triaged around the Satanic Serpent, grappling with more urgent repairs for people who wanted their bikes now, not four months from now. I knew the urgent work would let up at some point in the summer so I could spend the hours of brain-frying quality time the Kona would demand.

Today the Serpent's owner called requesting the bike be ready for him to ride tomorrow. And he didn't call first thing in the morning, either. It was mid afternoon and I was still finishing a repair for someone who expected it today. So at 3:30 p.m. I started on the grungy 'cross bike.

The rear shifting was all out of whack. Mere silt and grime could account for all the symptoms. With every cog the industry adds to a cassette the shifting gets more sensitive to minuscule variations in cable tension. And somehow the rider had managed to get a kink in the rear derailleur cable about an inch above the anchor bolt. This would actually come into play when shifting to the lowest gear.

The first time around I had left one piece of 4mm cable housing -- the section from the brifter to the inline adjuster -- because it was under the tape. Reevaluating the cable routing I decided to replace it with a longer section of 5 mm to move the inline adjuster from a high position near the bar to a low position. The high position had almost eliminated a kink where the housing entered the adjuster, but a much lower position would eliminate it entirely. And the new housing would be 5mm with brass ferrules, so the cable should slide more easily through it.

With all the usual rigamarole, I removed the old cable, leaving a guiding sheath in place through the down tube.  I untaped the bars far enough to remove the 4mm housing and slid the old cable out of the brifter. I measured new housing, cut it, and slid the cable through it. Fed the cable through the guiding sheath. Pulled the sheath. Slid on the little chafe-guard that covers the cable where it emerges from the down tube. Ran the cable to the rear derailleur and anchored it. Then messed, messed, messed with the tension. And messed with it some more. Couldn't get it to shift up the cassette to lower gears. More tension...until it finally lifts, one cog at a time, will not shift into low gear no matter what. Check the limit screw, okay. More tension. More tension. More tension. It makes the last shift.

Hit the return lever. Nothing. Three clicks to get it to drop one cog. Ratchet ratchet ratchet it down to the bottom. Ease off some tension. It sort of works through nine cogs, just gets ten. Eleven? Absolutely not. Big ring, small ring, makes no difference. It either shifts pretty badly or really badly.

I pulled the cable again to make further refinements to the housing to get the smoothest curve with no tight bends or kinks. That didn't help. Changed the chain from a KMC to a brand-name Shi-no, just in case the derailleur and cassette were particularly loyal. Another waste of time.

From the beginning, the cables have had a raspy sound and feel as they pass into and out of the down tube. The entry and exit holes are just big enough for the cable. I can't shine a light and paste an eyeball up there to see what might be snagging things in the interior. Really skinny fiber optic cameras cost some serious coin.

By 6 p.m. I was ready to use a fire ax to open it up. I called the customer about twenty minutes later to tell him he could ride it this way if he really wanted to use it now, and bring it back midweek and forget about it for a while. I need to be able to spend several hours with this piece of crap, figuring out where the drag is coming from.

By 6:30 I headed out into the cloudy evening to trudge home.


NHcycler said...

Damn! I wish your shop weren't a 4 hour round trip from where I live. There's no way I could get that type of service from the shops in NH's balmy southern latitudes.

Of course, I could tap into my trust fund and purchase a vacation home on the lake...

cafiend said...

You'd want to be an inland property owner in Wolfeboro or Tuftonboro. The way the tax system in NH is set up and this school district is organized, those are the catbird seats.