[JStergis]

Gotta see if I can snag some advice from the bike experts here.

I've got a 2009 Giant Boulder, with a Shimano Altus rear derailleur, it's got approximately 1000 miles on it.

I started noticing about 100 miles ago that if I was climbing a rocky dirt road or trail in a higher gear and putting a lot of effort in, the chain would "slip," basically causing my foot to go straight down to the ground, at which point I've probably lost enough speed where I have to start back over. It only seemed to do it on bumpy roads in high gears, and very rarely.

Now 100 miles later, it's gotten much worse, I basically ignored it before because it was such a rare occurrence, but now I can't. On smooth pavement, it has no problems at all, but if I'm putting any effort whatsoever into the pedals and I hit the slightest crack in the road, it will skip, mostly in gear 3+ in the back, the front will do it in any gear. I took it 20 miles yesterday, and didn't notice it until I started climbing back up the hill home. Every single time I was giving it power on a hill it would slip on any little bump. It was extremely frustrating, and I ended up putting it into 1st and 2nd and climbing back up slowly that way, since it seems like it almost never has an issue with 2nd, and never does in 1st.

I can't figure out the issue. I re-tightened the cable to take out any slack and adjusted the derailleur so it shifts nicely, but the problem is still there. I also found what is supposedly a tension screw, and adjusted that thinking that it would put more tension on the derailleur preventing the chain from slipping, but it made absolutely no difference.

Someone brought up that it's possible that the chain stretched, but they seemed to think that it wasn't too likely in only 1000 miles. Where I live is very mountainous, and you can at times be climbing one second and descending the next, so I do shift a lot, which I imagine could stress the chain. I also noticed that the two gear cogs on the derailleur looked a bit worn down, but I wasn't totally sure what they used to look like, so I can't be sure. The main 7-speed cogs on the back and the three on the front are definitely not stripped. I posted a few pictures of it, including what I think is worn down so you can have an idea what it looks like.

Thanks in advance for any tips!

Joe

[leroys1000]

Looks like there is quite a bit of wear on all the sprockets.
That idler sprocket looks like it is made of aluminum and is
pretty well chewed up.
There is aluminum dust on everything.
The sprockets on the rear don't look all that great either.
Looks like time for an overhaul.

[JStergis]

Thanks for the reply.

Do you think replacing the derailleur would be a good plan, or should I do the chain and rear sprockets as well? I don't think they're all that expensive. Correct me if I'm wrong, but I think I've seen the Altus for around $25 new.

Is it typical for the drive train to wear down in about 1000 miles? Granted, I do drive it hard and it was the bottom of Giant's line, but so far it's caused me no problems. I've had to replace the brake pads, but other than that, it's been solid until this.

Also, I know I can do the derailleur myself, I have replaced them before, but I know I have no way of replacing the sprockets, so I'd probably have to have the bike shop do that. The chain is probably a link, but if I'm having them do one thing, they might as well do everything.

[leroys1000]

Probably a good idea to replace the derailer assembly
and the rear sprockets.
The way you push the bike,I suggest you avoid using aluminum
and go all steel.
After it's repaired,try to remember to oil the chain about once
a week.
Should last longer with steel sprockets and regular maintenance.
Might check the main sprocket condition too.

[deluxnate]

Oiling once a week seems like overkill to me, but I agree. If you went steel you 'd probably notice a lot better longevity and performance.
Not being snobby, but I'm surprised you got 1000 in on a Altus group. If you fetched a little bit to replace for say a Deore you'd probably get plenty more miles out of it than this.
Good luck

[JStergis]

I still haven't given it to the shop to fix, since I'll miss it during decent weather. It looks like next week is pretty awful looking though, so I'll do it then.

So, 1000 is a lot of miles for an Altus to live through? I guess that makes me feel a little better about it. The gears on the derailleur are pretty obviously of weak material, they almost feel plasticy.

It goes fine if I drive it really gently, and stay in low gears so I'm pedaling quicker than I normally would (less force on the drivetrain that way), If I drive it normally, it's frustrating. It's tough to train myself to use such low gears! Normally, I shift it up pretty high, because I typically will accelerate pretty quickly to, say, 15-20 MPH, then get into one of the top gears and just maintain the speed at a slow pedaling speed.