Bicycle Mechanics - Chain Skipping...

Hello,

I am new to biking. I just bought an used Trek 6500. The only problem is that in certain gears it seems that the chain is skipping. What I think it seems to be is one of the derailleurs is not positioned completely right so in certain gears the chain is hitting the derailleur and it is almost trying to switch gears when it isn't supposed to.

Is this a common problem? Is it difficult to adjust the derailleurs? Any advice would be great.

Thanks

Do a search on you-tube for adjusting derailleurs and the barrel adjuster -- lots of good instruction videos on how to do it.

www.parktool.com has repair instructions online. Chain skipping is also a symptom of excessive chain/chainring/rear cog wear. If it only does it for certain chainrings or cogs, that suggests the chainring or cog is worn. You can also directly measure the chain to check if it's "stretched" (acually, worn).

.75mm or 1.0mm FTW!

Also, can anyone tell me the year of this bike? Its a yellow frame and purple lettering. Trek 6500 Alpha ZX. Has mostly bontrager and shimano components.

It is the one with a Manitou front shock

Try bikepedia

Specifically, this entry: http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?Year=2001&Brand=Trek&Model=6500&Type=bike

So I pinned down what gears skip. On the rear cassette it is gear 5, 6, and 7. So now I don't think its the derailleurs... Where should I start? The chain? Rear cassette? Any more ideas?

Almost certainly, you have a worn cassette. On a cassette worn enough to skip, you almost certainly need a new chain too since your old worn chain will skip in most gears of a new cassette.

Almost certainly, you have a worn cassette. On a cassette worn enough to skip, you almost certainly need a new chain too since your old worn chain will skip in most gears of a new cassette.

Agreed. The chain skipped on my 1972 last night as I crossed a very busy thoroughfare...not a good feeling. I replaced the chain which was worn and had streched, but the chain skip became worse, such that I could sit on the side of the road and turn the pedals watching the chain dragging over the 20-tooth cog. A new freewheel is on the way.

The type of skipping that the OP described may be due to a poorly adjusted rear derailleur cable tension, not necessarily a worn cassette or freewheel cog. Or it could be both. Adjusting the derailleur(s) should be tried first.

The type of skipping that the OP described may be due to a poorly adjusted rear derailleur cable tension, not necessarily a worn cassette or freewheel cog. Or it could be both. Adjusting the derailleur(s) should be tried first.I Re-read and agree. Try adjustments to fine tune first. If it shifts better but still skips, chain and cassette are next. If you are not comfortable doing this work with the help of the park tools web site or youtube videos, a local shop should be able to help you out.

Agreed. The chain skipped on my 1972 last night as I crossed a very busy thoroughfare...not a good feeling. I replaced the chain which was worn and had streched, but the chain skip became worse, such that I could sit on the side of the road and turn the pedals watching the chain dragging over the 20-tooth cog. A new freewheel is on the way.

As you found, putting a new chain on a very old cassette or freewheel can cause skipping.

OP, follow the suggestions about derailleur adjustment first.

Thanks.

If I am to replace the cassette, what tools with I need? Are there any special lockrings or chain tools I will need?

http://www.parktool.com/blog/repair-help/cassette-and-freewheel-removal Add a chain tool because that will be next. If your are buying on the internet, you will save shipping by buying at the same time.

Well I adjusted the front derailleur - which is the one that I knew was off. The back seems aligned according to the videos on youtube. But it is still skipping. I am looking for a new rear cassette, any suggestions. All my components are Shimano deore, 9 speed, 11-32 teath, chain size is 1/2 x 3/32. I am looking for a decent good priced cassette. I don't want to put a lot of money into it. I also will need a chain. Is it a bad idea looking into an used one? Any advice would be great!

For the parts you need go to Amazon.com
I get a lot of my parts here.Don't get a used chain get all new parts.Good Luck

This may be cheaper:
cassette:
http://www.jensonusa.com/store/product/CS408B08-Sram+Pg+950+9+Speed+Cassette+10.aspx

chain:
http://www.jensonusa.com/store/product/CH411B00-Sram+Pc-951+9Sp+Chain+10.aspx

New chains are some of the cheapest bike parts, and far too critical (and quick wearing) to consider used. As for tools, you will need a chain tool, a chain whip, and a cassette tool (make sure you get one for shimano cassettes). Also a large-ish adjustable wrench will be useful. I would expect it to run $50ish in parts (depending on how high-quality you get), and $40-$50 in tools (again, depending on how high quality you get).

I just ordered a Sram PG970 cassette with a Sram PG971 chain. Sram is compatible with shimano correct? I also bought the parktool FR-5 cassette lockring tool. I have a chain tool, and a chain whip. I hope it goes well...

I just ordered a Sram PG970 cassette with a Sram PG971 chain. Sram is compatible with shimano correct? I also bought the parktool FR-5 cassette lockring tool. I have a chain tool, and a chain whip. I hope it goes well...

correct

In my case, my skipping was the freehub and not the cassette. If the teeth aren't heavily worn, you may need to service or replace the free hub (assuming all of the above advice about trying the easy stuff first doesn't fix the problem)

FYI: I replaced the 14-24 freewheel on my 1972 International and it is like riding a new bike...a 180 degree turnaround in shifting!

Hey I'm running into a new problem why I'm waiting for the parts. My front tube keeps popping. I've on my third already. The last one lasted one day. I'm not even using for mountain biking right now, just commuting. The front tire looks really worn out... Is it commonly the tire or I have been reading that sometimes its bad tape on the rim, or something along those lines. Any advice on where to start would be great!

First, dismount the tire and inspect the rim. Make sure your rims are smooth with no burs that could cause a small puncture. The tape should be in good condition with no gaps or holes, otherwise the tube can blow out around a spoke. If in bad shape, replace it on both wheels. Inspect your tires and be sure there is no debris inside such as a small stone or the end of a thorn sticking out of the inside of the tire against the tube, aside from that, your worn tires may be too thin and allowing small punctures so replace them. Now, if you are using Continental inner tubes, my experience with them is that they sometimes have leaks in the rubber around the stem when brand new, an obvious defect.

I hope this helps!