Megawolf

Yesterday, I bought a Diamondback Apex secondhand for $75. The man I bought it from said that it might need new tires and the gears could use some oiling, but that the bike was in good condition other than that. Seemed like a good deal, so I took it.

The tires just needed to be aired up, and the chain definitely needs to be lubricated or possibly replaced (kind of rusty). I decided to ride it a bit, and discovered that the gear shifter seemed to treat the third gear as first. Shifting higher than 5th gear causes the chain to come off. I played with the derailer and derailer cable a bit, but the best I could get it to was second gear. I have considered taking it to a bike shop for a tune up, but the nearest one is over an hour away. I've also heard that the problem could be inside the shifter itself, but I haven't tried taking it apart yet. Any ideas?

DX-MAN

Inside the shifter is the last place you look before replacing the shifter. Cables are likely not only out of adjustment, but needing lube, themselves. (I use Slick 50 One grease, wiping a thin layer over the length of each cable -- works wonders) If you can't get that grease (dunno if it's still sold, I bought two tubs of it years ago, still have plenty left), Mobil 1 in a mid-grade weight would do well, also. I'd say, just go ahead and lube the cables, it can't hurt.

There are a lot of things that can cause your shifting woes; is the derailleur or its hanger bent? Is the cage bent?

I would definitely spend some time fiddling with cable adjustment; if you're familiar with it, you know it's not rocket science, just needs care and attention to detail. If you're not, though, I'd look at the trip to the LBS.

I could walk you through it, but as slow as I type, I could build an entire bike in the same amount of time! Not feasible for me.......Sorry.

cny-bikeman

"Fiddling" with the gears will just waste more time than you have already spent. If by 5th gear you mean the smallest cog in the back, then the high limit screw needs adjustment, then the cable needs correct tension. Check the Park tool site for the correct procedure. A bent hanger typically would cause the opposite problem - the chain would go into the spokes if you shifted to a low gear (larger cog).

CACycling

Older STI shifters can often use a good flusing (WD40 or penetrating oil) to return them to good working condition. The Apex was one of DB's best of that era and will make a great bike.

Megawolf

I should have mentioned this earlier, but it's a 21 speed bike. The rear gearset has 7 gears. Setting the shifter to first gear puts the bike into third. The chain is on the seventh gear when I set the shifter to fifth. Therefor, shifting higher than fifth causes the chain to slip off.

I am not sure how to determine if the derailer is bent, but it seems to work well. Cable tension seems the most likely culprit to me, but I don't know a whole lot about bike maintenance. I was considering looking inside the shifter to see if maybe the tension or gear setting is off inside there, but that seems to be a last resort option.

wrk101

Read the step by step instructions on rear derailleur adjustment at the Park Tool site. It is outstanding, and will walk you through the entire process. Way too early to be looking inside the shifter.

Megawolf

I will follow the instructions and post back here with the results after I finish. Thanks for all the help, everyone!

AlphaDogg

I have a feeling that the hanger is bent.

FastJake

+1

If the chain is rusty there's a good chance the cables are too. Replace any rusty/frayed/corroded cables and the housing too. Then read step-by-step instructions for setting up the derailers. If the shifter clicks through all 7 gears it works and does not need replacement.

cny-bikeman

The hanger would have to be bent outward in order to produce the symptoms the OP describes. I'm don't think I saw that more than once in over 20 years of working on bikes (someone had yanked way too hard to remove a stored bike, and the derailleur was caught on a solid object).

If the derailleur overshifts past the high gear then the outer limit screw needs to be adjusted (tightened) - that's the sole purpose of the limit screw. Then make sure the cable is running smoothly, and if not replace it. Next is proper cable tensioning. If it then won't shift up to the large cog the inner limit screw needs to be adjusted. Other than a few other details that will most likely resolve the problem.

Megawolf

I followed the directions from Park Tool, and it's better. Still needs some fine tuning, but it looks like everything will work properly once that is done. Once again, thanks for all the help!

I'm planning a trip to a LBS this Saturday. Considering that I did not buy this bike new, a full tune-up from someone who knows exactly what they are doing seems like a good idea to me.