Anyone know anything about bikes?

[triggrhappy94]

I've started biking again to try to save money. Unfortunately, my old bike isn't in the best condition. When taking off from a complete stop, if I put too much force on the peddles the chain locks up for a second. It's not like I'm stomping it or anything. I'm pretty sure there's a problem with the back derailer, because I've been having some problems changing gear and it always feels like it changes gears when it gets unjammed.
It doesn't jam if I get a good rolling start before peddling (like rolling down hill) or if I go really easy when starting--which I've never had to do before.

Can someone help me diagnose my problem and, if possible, fix it?

 

[Dirty Hipsters]

A problem with the rear derailer could be possible. It also could be possible that your chain and gears just haven't been oiled properly. I'd say start with oiling (or re-oiling) the chain and gears and see if that solves the problem. If that doesn't help I would start thinking it could be a more serious mechanical problem like the rear dereailer.

Do you have any bicycle shops in town that do free diagnostics?

 

[Laughing Man]

Stiff link, to be honest it's hard to say without seeing the bike but a bike that has been lying around for a while not doing much is going to suffer from a few very distinct things.

Rust / corrosion or other stiff or bound parts.
Depending upon how the bike was left it could have a bent or mis shaped derailleur.

Both are easdy to spot and both are easy to fix

A stiff link can be spotted by running the chain through the rear derailleur and keeping an eye on the chain's movement through the jockey wheels (the small usually black wheels on the derailleur) you're looking for any skipping or any locations where the chain lifts or moves away from it's normal movement.

Solution is as simple as locating the split link getting a flat head screw driver, stick it in the gap in the stiff link and turning the screw drive with a little force to just open the link ever so slightly and then applying some suitable lubricant to the area. You need to apply just a bit of force and you want to try and hold the chain firmly so as not to twist or introduce a bend in to the chain.

A mis shaped derailleur can be spotted by putting the bike in 1st or last gear and looking at the rear derailleur angle and location in reference to the cog the chain is sitting on on the rear freewheel or cassette. A correctly aligned derailleur should point straight down this picture shows a mis alligned rear derailleur

A mis shaped derailleur can usually be sorted by grasping the derailleur firmly and then very gently bending it until it is correctly aligned. Their are special tools to do this but this is a quick and cheap way that for the most part will work

As you can see it is bent quite badily in towards the rear wheel.

 

[Trivun]

I've started biking again to try to save money. Unfortunately, my old bike isn't in the best condition. When taking off from a complete stop, if I put too much force on the peddles the chain locks up for a second. It's not like I'm stomping it or anything. I'm pretty sure there's a problem with the back derailer, because I've been having some problems changing gear and it always feels like it changes gears when it gets unjammed.
It doesn't jam if I get a good rolling start before peddling (like rolling down hill) or if I go really easy when starting--which I've never had to do before.

Can someone help me diagnose my problem and, if possible, fix it?

I'd recommend you take it to Halfords (or your equivalent if you're not from the UK), and sk for them to service it. It'll cost money, but it's better to spend less getting it checked than to spend the same amount plus parts and labour in a week's time when the bike is damaged. I don't know a massive amount about bikes myself, but this sounds similar to what happened to my bike twice. On both occasions (within weeks of each other, no less), the gear chain completely snapped. Both times I had to get a new chain fitted, and it cost me parts and labour which as a student at the time I couldn't really afford much. Just last week I had to have a new rear mechanism fitted because the original had snapped (the spring tension was completely shot and it was just hanging limply, meaning the gears and pedals didn't work and the bike was useless). Either way, I'd recommend you get professional help before you do some actual damage to it. Explain your problem to them and they should be able to help.

 

[triggrhappy94]

I think I may have fixed it. I'm going to take it out on a trial run soon to make sure.

I feel really dumb about what the actual problem was.
When I put the back tire on after fixing a flat, I hadn't tightened it all the way--I think it was because one side of the wheel didn't want to fit in the rest on the frame. While I was messing with my bike in my garage, I actually got the back wheel to pop all the way off.

Like I said though, I'm not 100% about this fix, so I'm going to test it some more before taking it out on busy streets again.
Thanks for all the advice. I'm definitely going to look into re-oiling the chain--it looks dirty and dry as a bone.