Mountain Bike Cable Tension

October 24, 2008 by  
Filed under Tips

rear derailleur closeup 300x225 Mountain Bike Cable TensionMany of us have the experience when we are on the trail and are transitioning into the big climb. Your fingers are poised over the shifters ready to rapid fire into the appropriate gear to ascend to the top of the climb. As your momentum starts to decrease your finger fires off a few clicks on the shifter you begin to pedal so the derailleur will shift your chain to your desired cog or gear and BAM! Your chest is thrown into your bars just before your front tire folds over and you are thinking “I hope I can get out of my clipless pedals before my bike hits the ground.” Your derailleur did it again, it missed your desired gear, didn’t shift, your chain came off, or…something else similar. The bottom line is your derailleur let you down. For years I rode under the assumption that if my derailleur was on the fritz then this is a task for a licensed professional and I either toughed it out with a bike shifting poorly or I did the hike a bike out. For all I knew a derailleur is not something that you can fix on the trail like a flat tire. However I was wrong.

When you encounter a shifting problem on the trail a lot of time it has to do with cable tension, which can be a very simple problem to remedy enough to get you back in the saddle to finish the ride. The cable in question is the one that runs from the shifter to the derailleur. On most mountain bikes there is a knob where this cable meets the shifter. This knob is one of the ways that you can fine tune cable tension on your bike. So if you are on the trail and you are having problems with your bike shifting properly simply identify which derailleur is having the problem. Then locate the cable for the corresponding derailleur and turn the knob no more than about 45 degrees. If problem still persists then go another 45 degrees in the same direction. Continue with this until you are able to shift your bike well enough that you can comfortably finish your ride. If the problem gets worse return the knob the original position. Once you are back at the original position turn the knob opposite of the way you originally turned it. I have found this to be a quick fix about 85% of my on the trail shifting problems. This is just a band-aid and if it works, I do strongly encourage you to seek out a professional to tune your bike. This is just some advice that I learned to pick up along the way to share with you to help you out when you are on the trail. Most of us do not ride with our bike mechanic to fix all our problems when they happen.

If this does not work for you another antidote that I have used more than once on the trail is to use an Allen wrench to manually adjust the cable tension at the derailleur. Sometimes I was able to adjust it so it would shift just fine. Most of the time, at least when it was a problem with just my front derailleur, I had to either adjust the tension so I could only use my bottom two sprockets. Occasionally when my cable tension was so bad (because I was too cheap to take it to a shop, I know this is my bad) that my chain was constantly falling off I had to adjust the cable tension at the front derailleur so it would not shift on the front derailleur at all. I was still able to use the rear, but my front derailleur was so out of tune that nothing else could have been done on the trail other than rigging it to stay in the smallest sprocket just to get back to the trailhead. This makes for a frustrating day of riding, do not let your bike get as out of tune as I did, but if you do, which I know some of you will, you will know what to do WHEN not if disaster strikes.

mountain biker in valley 204x300 Mountain Bike Cable TensionCable tension is a regular problem with mountain bikes, and you are not alone in the problems with shifting world. It is a problem that plagues both full suspension and hardtails alike. However I have found full suspensions to be more problematic with cable tension than the hardtails. Some of the things that cause cable tension problems are:

  1. Riding: mountain bikes take impact and abuse and this causes movable parts to move.
  2. Shifting: when you shift your cable moves and pulls your derailleur in one direction or another.
  3. Transport: we are all guilty of being too over zealous and throwing our steed into the back of a truck to hurry and get to the trail head as soon as possible and this can push your derailleur into a position that stretches your cable beyond where it is properly functioning.
  4. Storage: improperly storing your bike can make components shift and move and cause cable tension to be thrown off.

So take care of your bike and have it serviced by a professional regularly so you can minimize on the trail catastrophes. Because problems don’t occur in the parking lot or just after your ride is over. They happen when you are too committed to return the way you came or right before you get to the good part of the trail.