Rear deraileur won't shift to lower (more speed/revolution) cogs.

Could be a few things. Either are common on a bike with this amount of use.

1. If you have been adjusting the tension of the shift cable, it may be a little too tight. This will provide the snappy up-shift but not allow the derailleur to travel outboard enough to execute the down shift. Loosen the cable by turning the barrel adjuster to the right a notch or two until the shifting is satisfactory.
2. The shift cable may also be rusted or oxidized. It is common for galvanized cables to be used to cut costs on a new bike and they eventually rust or corrode. These do not provide smooth shifting operation and will eventually result in sluggish down shifting due to increased friction. Replacement is the solution.
3. The cable housing (black casing that the silver inner wire runs through) may have gotten some dirt or other contaminant inside of it increasing friction. Cleaning or replacement is the solution.
4. The inner cable may have become kinked - also increasing friction. Usually this results in slow shifting both directions; so this is the least likely. Replacement is the solution.

Stainless steel shift cables are the best to use and run about $5-10 each. New sections of cable housing usually run about $2 per foot.


I hope this helps!


Matt @ roadragecycling.com

the derailleur cable is too loose. Shift the shifter into the smallest cog, make sure the chain is on the smallest cog. The derailleur cable will most likely be very slack now. At the rear derailleur, there will be a nut or a allen bolt pinching the cable to the derailleur. loosen this, pull the cable finger tight, tighten the nut or bolt again and then try shifting again. You can dial it in using the barrel adjuster on the derailleur or the shifter.

I would lube everything and check the derailleur adjustments and cable tension. Some Campy chains are 'notchy/clunky' all the time. It's just the way they are. If the bike is low mileage most likely nothing major is wrong. Check the derailleur hanger too just in case you dropped the bike and bent it or something. The shifter 'G' springs will wear out before the derailleur. When the springs are worn, the shifts will be imprecise and will jump from gear to gear without shifting. One thing with Campy stuff...it DOES take awhile to break in. Unless the shifting is horribly off, I wouldn't worry about it - just ride it more - and see what happens. Mirage is a good product, I think inline with Shimano 105 stuff.

http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

Search the web for "adjust rear deraiileur" for video help.

There are two screws that limit the "travel" of the deraileur. They will be about 3/4 inch apart. One screw limits how far OUT the derailler will travel (for the smallest cog) the other limits how far IN (for the largest cog). Loosening (turning it to the left a little) either screw will allow the deraileur to travel a little further. If it travels too far, your chain will overshoot the last cog. You might be able to see which screw to adjust, or just do it by trial and error. There is more in-depth at http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur they make great tools and have a terrific site with how-to videos and diagrams.

Bicycles have two sets of gears (front and back). The 6 position control slides the chain between the 6 sprockets (cogs) on the back. The 3 gears are for the front set of cogs. Between the two sets of sprockets, you get 18 (theoretical) different rates of chain movement per turn of the pedals. In fact some of the settings overlap. (However some of these should not be used. Do not use the settings that pull the chain to the furthest inside of one derailleur and the furthest outside of the other. This diagonal between the biggest and biggest sprockets (or smallest to smallest) puts extra strain on the chain.) The back derailleur is in the lowest gear when on the biggest sprocker. The front low gear is on the smallest cog. The highest gear possible is on the smallest rear cog and the largest front cog.

By planning the shifts in gears, you can maintain the same speed and cadence (rate of pedalling) on different terrains. (For going up a hill, use a lower gear than on flat terrain. However don't go to low or the bike may not balance well.) To shift through a large range of gears, you must be pedalling and then move the rear derailleur control followed by the front derailleur then the back again. (For faster shifts to a low speed, you can shift the front derailleur first but that can stress the system.)

For a guide to using the gears: http://www.southcoastbikes.co.uk/articles.asp?article=Gears .

I hope this helps.

Cindy Wells

Google bicycle shifting technique, for example:

http://coachlevi.com/cycling/complete-beginner-guide-to-bicycle-gears-shifting/

The basics of shifting are these:

1) The big ring and right side of the cassette in back are for speed.

2) The small ring and the left side of the cassette are for high torque, lower speed

3) The middle ring works with all rear cogs.

Avoid crossing left front to right rear and vice-cersa. It cause excess side loads on the chain.

With the wheel off remove the two pins which locate the guide wheels on the deraileur. Take off the guide wheels and the guide plate. Now straighten the chain and unwind the snarled area. Locate the chain around the smallest cog wheel on the back wheel and mount the wheel to the bike. The chain will hang slack. Now mount the upper guide wheel and guide plate to the deraileur making sure that the chain feeds off the rear cog and passes around the guide wheel towards the front of the bike. Push the deraileur forwards relative to the chain and slip the lower guide wheel in between the guide plates and pushing the chain back in the guides & fasten with the pin. As you reassemble the plates and wheels on the deraileur be sure to observe carefully which way the chain is running. It is quite logical and this should prevent mistakes being made

Try this first:
Shift into the little ring and release the cable. Pull it tight (with pliers) and re-tighten the cable. It should shift now. If it doesn't, the solution is a little time consuming, so i apologize in advance.
First, flip your bike onto the bars and saddle. Now shift into the small chainring and your lowest cassette cog (the largest in number of teeth). Release the cable from the front derailleur and set the adjustment knob for the front derailleur to its center point. You should find it on your down tube. Now adjust the "L" setting on the derailleur while turning the crank so that its stop sets it in a position where it just skims the chain but does not touch it. Now pull the cable taut and re-clamp the cable. Shift into the middle ring and shift the rear derailleur to its highest and lowest gears, making sure the chain does not rub the front derailleur. If it does rub (it will be in either the lowest or highest cog on the cassette), adjust the front derailleur by way of the adjustment knob to clear the rub. Then shift into the big ring and you should have no problem. Set the "H" stop if necessary.

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