cant adjust rear gears

[andy765gtr]

need some advice please. im a bit of a newbie to cycling and ive been trying for hours to fix an old Marin hawkhill MB's rear deraileur but cant seem to get the gears right.

when i adjust it to get the gears to down-shift through all the cogs properly, it wont up-shift properly; it kind of hesitates like it needs more cable pulled. but i can then easily adjust the deraileur so it does up-shift easily, only it then annoyingly sticks on some of the down shifts instead. so in effect i cant get a perfect gear change; its almost as if the shifter doesnt pull enough cable through or something.

admittedly the bikes well used and had a hard life, and ive done a big mileage the last year comuting on it, so probably its just got worn out; but seems to work fine apart from this fault. i havnt seen these particular symptoms mentioned anywhere ive looked on the internet. experts seem to imply that if you can get it indexed right in one direction it will be fine in the other direction as well.

is there a way of making the deraileur mech to move a bit further sideways each shift? its like its not moving far enough to work properly; or make it catch onto the sprockets by 'bending' something abit (look i said i was a newbie ok!)

or if i jus need new parts, what do i get, and how much is it gonna cost? cycling was supposed to save me money as well as the planet lol cheers,andy

 

[cruisin]

Try lubing the derrailieur and adding new inner and outer cables as it sounds like a cable problem to me.

 

[andy765gtr]

Try lubing the derrailieur and adding new inner and outer cables as it sounds like a cable problem to me.

hi, yes maybe the cable.

not having access to a new cable at the mo, i had a bit of success yesterday by close examination of the inter action of the gear tooth angles and chain (interesting), and then dremelling one or two of the cog teeth on each cog shorter so they start gripping onto the chain edge when the mechanism pushes it over, thus allowing the next teeth in line to eventually fall into the chain slots. before each one was sliding off the edge and going down the wrong side of the chain - the worn rounded edge of the chain wasnt helping. the cogs have a number of teeth missing, so im not to worried about causing more it more damage.

the gears are a somewhat better in just in a few minutes work. so maybe its partly a wear issue, plus cable not pulling it over enough

 

[garage sale GT]

In addition to the obvious fact that your drivetrain is worn out, the bike may have been fitted with a chain that is too narrow, so the cage can't push it far enough. Or, the derailleur cage may have been bent so it is wider than it should be. Or, perhaps the pins and their holes in the derailleur have worn out until there is too much slop in the unit. both conditions would cause the bike to shift fine one way but not the other.

These ideas are only suspicions. I do not know if it is actually possible to wear a derailleur's pivots that much.

 

[andy765gtr]

yes all that is probably true of my setup. very worn!

any idea how i upgrade these things. do i have to buy a set of rear cog wheels(not sure of the proper name of that sorry), a new derailleur and a new chain, but make sure they are all compatable, right? do i also need new chainwheels and shifters too? sounds like a right nightmare matching all them up as they are normally offered as individual components on ebay (im pretty much DIY if possible). cheers andy

 

[garage sale GT]

1. Does the frame fit? Do you like the bike?

2. check if the wheels, steering, or pedals wobble without turning, i.e. if they're loose. if they do, you may need new wheels or the other parts will need new bearings put in. If those parts are not sealed, they probably need a repack with fresh grease. A wheel which wobbles because it's turning, on the other hand, just needs a bit of straightening with a spoke wrench.


Assess what's wrong with the bike. It may just need new rear cog wheels (there's 2 different systems with different names) and chain, and maybe new cables.

Get a book or check out sheldonbrown.com or parktool.com.