But more likely, it will just help you avoid some inconvenience and complete a ride when you otherwise would have needed to abandon and find an alternate way to get home.
Of course, if you regularly ride a fixed gear bike over Kazahari Pass, or if you live in northern Germany or central Nebraska where there are not any real hills, then you can stop reading.
On the Rocky Mountain 1200 we faced some difficult conditions, which caused mechanical problems for many riders. For me, these:
-- completely shredded my Vittoria Open Pave tires, rear and then front (rumble strips, debris, etc.),
-- resulted in a broken rear derailleur cable and unusable right shifter, 380 kms into the 1200 km event,
-- caused a broken rear spoke at around 620 kms (same old, same old -- and I'm ready for these with a spoke wrench and had no problem riding home with 35 spokes remaining),
-- resulted in lots of roadside debris sticking to my tires, triggering at least 3~4 flat tubes over the course of the event (after NO flats on Tohoku 1700 or Cascade 1200),
-- broke the base mount of my Phillips Saferide LED light -- it snapped off during the final descent, I think from the combination of violent shaking (rumble strips) maybe added to the metal fatigue of repeated adjustments,
-- contributed to a broken closure/snap on my 4-month old Ortlieb handlebar bag, as I fumbled in the cold to open and close it too many times,
... and on and on.
The largest single mechanical difficulty was the broken rear derailleur cable and shifter.
Like any sensible randonneur on a 600 km or longer event, of course I carried a spare shifter cable. But in the near-freezing rain, wind and gathering dark of the Yellowhead Highway early evening on Monday July 24, about 65 kilometers west of Jasper, Alberta, I could not get the replacement cable properly threaded in the Shimano 7800 STI shifter. Maybe some of the old cable was still jammed inside. Or maybe I did not properly set the shifter to the lowest gear by pushing the small paddle repeatedly before I threaded the new cable. I do not know. Whatever the cause, the new cable was quickly tied in knots inside the shifter and the shifter was non-functional. So I rode the bike in 34x11 gearing the rest of the way to Jasper.
At the Jasper control, Patrick was offering mechanical assistance, and had a nice big tool kit next to the check-in desk. But he also was checking in riders, signing brevet cards, checking out riders, offering information, pointing people to the showers, food and sleeping accommodations, and dealing with emergencies such as randonneur hypothermia (like the rider I saw in the back seat of a good Samaritans' van that had stopped and picked him up in response to his plea as he froze at roadside on the descent from Yellowhead Pass -- which van then had followed me all the way in to the control, stopping and waiting patiently as I hunted, pecked and backtracked through the last few turns in town).
At first, Patrick gave me the bad news. He said there was no way to fix the shifter, at least not on site and not in time for me to continue. He said he had taken apart an STI shifter once several years ago, using a very complex rig so that springs did not go flying all over the shop floor. Not something that would be possible in the Jasper control. I was resigned to the possibility of a DNF.
A few minutes later, as I ate, Patrick came over and said that he thought he could rig the bike so I would have a 2-speed, with a fixed rear cog (of my choice), and the ability to shift between the 50 and 34 rings with the still-functioning front derailleur. If I wanted to change the rear cog, I would need to get off the bike, get out an allen wrench, force the derailleur into position and re-set the cable either shorter or longer than before. I was elated -- he was offering a way to continue!
The elation wore off as I realized it might be a very long 750 kms, riding a 2-speed bike. Still, if I could set the gears low for the big climbs ahead -- Sunwapta Pass and Bow Summit -- then I could limp along much of the way thereafter. A 1200 km randonee with a 90 hour limit requires that one complete the first 600 kms in 40 hours, allowing 50 hours for the second 600 kms. And everyone I had spoken to advised me that for the RM 1200, you just need to make sure to get over the big hills within the time limit, and then the second half would be much easier.
Anyway, enough of a prelude, and on to the lesson. What to do when your rear derailleur cable breaks?
First, remove all the pieces of "outer" cable lining and the broken "inner" cable. Stow the outer cable for future use.
Cut a length from the broken inner cable approximately 20 cms / 8 inches in length. Tie a knot near one end of this length. It will look something like this:
(If you happen to have a cable or portion at least 6 inches long that still has the "knob" on one end, then you can use that instead.) It would then look something like this:
Once you have this piece prepared, you thread it through the barrel adjuster on the rear derailleur, from the rear, with the knot/knob stopped up against the rear side of the adjuster.
You then shift the derailleur/chain -- with your hands -- so that it is on the desired rear cog, and tighten the bolt and plate to the unknotted portion of your cable. I don't have a photo of this, exactly, given a subsequent improvement on the repair, but the relevant part of the bicycle looks like this:
The "knot" or "knob" would come into and rest against the barrel adjuster from the bottom of the photo, and the other end of the cable piece would be secured under the bolt and plate toward the top of the photo.
Using this method, the derailleur can be "fixed" to any gear if you use your hands to move the derailleur and chain into position (preferably while spinning the crank) then tighten the cable at the proper length.
You can even adjust the setting slightly by turning the barrel adjuster. Maybe you will get a 4 speed rather than a 2 speed without getting out the wrench. If you use a knot, however, you will find that the knot sticks somewhat at the adjuster and the cable twists as you try to turn the adjuster, so it may not be easy to turn the adjuster very far, or it may spring back when you release it. At least I was able to turn the adjuster enough to "fine tune" and have the chain set directly over a cog. Twisting cable is not an issue with the knob.
After another 300-400 kms, John B. did a better jury-rig using a longer spare cable that had the knob still on the end, threaded that all the way from the barrel adjuster on my downtube and reinstalled the "outer" cable that you see in the photo. So I was able to shift one or two cogs on the rear cassette just by turning that barrel adjuster on the downtube -- without getting off the bicycle -- for a real 4 or 6 speeder!
This is a trick I will never forget.
No comments:
Post a Comment