Bicycle Help?

[TWBryan]

Hope this is the right place to ask,if not ,mods please move to where it needs to be. I'm hoping someone here can help me out. I'm working on an old bicycle given to me by a friend. It's an old Walmart (china made Mongoose MGX DXR) mountain bike, when I got it I replaced the tubes,tires ,and rim tape. The chain slips,so I did some research,I believe the issue is in the cassette gears. I bought the tool (FRM-1) and removed the cassette,it threads onto the wheel. Some of the gears are fin shaped so I figure that is the issue.
So I ordered one of these from Ebay.

http://cgi.ebay.com/Shimano-7-Speed...1QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

I'm hoping this is the correct one. It threads on anyway. I'm now wondering if
I should buy a replacement crank set.Perhaps this one?

http://www.nashbar.com/bikes/Product_10053_10052_174926_-1_200294_200276_200374

And what type of chain do I need?

I know this is a china made hunk a junk,but this kinda devolved into
a grudge fight between me and the bicycle,and I'm determined to win. I'm hoping some knowledgeable soul will be able to at least tell me where to look for the answers.

Thanks For Looking

 

[BlackHills]

Hope this is the right place to ask,if not ,mods please move to where it needs to be.

Gadgets and Gear is where it should be.

The chain slips,so I did some research,I believe the issue is in the cassette gears. I bought the tool (FRM-1) and removed the cassette,it threads onto the wheel. Some of the gears are fin shaped so I figure that is the issue. So I ordered one of these from Ebay.

http://cgi.ebay.com/Shimano-7-Speed...1QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

I'm hoping this is the correct one. It threads on anyway.

That freewheel should work fine. Some of the gears being 'fin-shaped' on the old one doesn't necessarily mean they were worn as some look that way new. If I had to guess the chain was the problem and not the freewheel, but the one you bought is surely better than the one that was on it. You will probably have to adjust the rear derailleur as well once you have it back together as the spacing is likely different. BTW, it is a freewheel not a cassette, they're similar animals but not exactly the same.

I'm now wondering if I should buy a replacement crank set. Perhaps this one?

http://www.nashbar.com/bikes/Product_10053_10052_174926_-1_200294_200276_200374

You could buy that but I doubt you need to. You could also run into problems mounting it on your bottom bracket or have clearance problems. I wouldn't spend the money for a new crank unless I had to.

And what type of chain do I need?

A chain made for 7 or 8 speed would be best. On the Nashbar site I'd buy the Wipperman 6/7/8 chain or the SRAM 8sp chain, they'll be higher quality than the Nashbar one and easier to install with the Connex link/Powerlink. You'll need a chain-breaker to get the length right and to take the old chain off, a cheap one will work fine for your purposes.

I'm hoping some knowledgeable soul will be able to at least tell me where to look for the answers.

Here's a good place to learn all about how to work on bikes. Poke around the ones in the yellow box, "Articles by Sheldon Brown and others", particularly the "Gears and Drivetrain". http://www.sheldonbrown.com/

 

[TWBryan]

Blackhills,
Thanks so much for your response. I won't mess with the crank if I don't have to. I've already taken it apart and cleaned it and re-greased it so i don't see a need to do anymore. The old chain (maybe original chain) was slipping. I replaced it with a walmart bike chain (only one they had) ,it slips too.Neither chain seems to match up to the gears very well. So I guess I need to get a new chain and the tool(s) I need to shorten or lengthen it ,or at least join the darn thing. The front and rear derailleur pieces seem to move back and forth ok. Front derailleur seems to be too wide to shift the chain well,but maybe that's normal. Which chain tool should I get?

Thanks Again !!

 

[BlackHills]

You're welcome. It's pretty unusual for a freewheel to wear that fast but I suppose it's possible.

How did you attach the new chain without a tool? The length has to be correct or it won't shift properly and would probably skip. A new chain comes long so it will fit a variety of bikes, it's normal to have to take out several links when you install one. Both chains I mentioned don't require a tool to attach, the master links are designed to snap together. There is a section on how to get the proper length on that site I linked. As for the tool, if you do decide to order from Nashbar I'd just get the cheapest one they have. If you have a decent local bike shop (not Walmart) you could get the chain and tool there.

Regarding the cage on the front derailleur being wide that is normal. The chain is on one ring in the front but has to move back and forth over several cogs in the back so it needs some room to bend a little without rubbing the FD. IF it wasn't that way you'd have to 'trim' the FD after nearly every shift.

 

[TWBryan]

Well,the friend I got it from rode it for several years. When I received it I had to clean the caked on dirt and gravel out of the drive train. The rear derailleur was completely clogged. I think it quite likely he rode the thing to "death".
I've no idea,how long the chain is supposed to be,I just put it on without shortening it. I've considered taking it to a local bike shop and having the chain fitted. It might be the easiest and cheapest way out.

 

[BlackHills]

Well,the friend I got it from rode it for several years. When I received it I had to clean the caked on dirt and gravel out of the drive train. The rear derailleur was completely clogged. I think it quite likely he rode the thing to "death".

That would certainly cause things to wear out quickly.

I've no idea,how long the chain is supposed to be,I just put it on without shortening it. I've considered taking it to a local bike shop and having the chain fitted. It might be the easiest and cheapest way out.

Here's an explanation of the chain length. If you didn't shorten the new one that was a huge part of why it didn't seem to work. You're right that taking it to the shop might be the easiest way, though it's not hard to do yourself and it's always nice to know how to do something for future reference. As for the price, the tool you need is only around $15.

 

[TWBryan]

Blackhills,
Thanks again,yes bike was in extreme state of neglect. Apparently he used the wrong lube on the chain and gears in an attempt to resolve the slipping. Rear derailleur gears were clogged with dirt and gravel. So I suspect gears were worse for wear. Orderd a Park chain tool (ct 5 I think) and a Shimano HG50 7/8 chain.
I have read some of Mr. Brown's articles,and now that I have better idea of what I am dealing with,will go back through them again. I probably have more invested in tools and parts then the bike is worth,but as I said I am determined to get it functioning.

Thanks Again

 

[BlackHills]

Blackhills,
Thanks again,yes bike was in extreme state of neglect. Apparently he used the wrong lube on the chain and gears in an attempt to resolve the slipping. Rear derailleur gears were clogged with dirt and gravel. So I suspect gears were worse for wear. Orderd a Park chain tool (ct 5 I think) and a Shimano HG50 7/8 chain.

You're welcome once more. Yes, if it wasn't lubed/maintained properly things wear fast. That tool should work fine but the chain...eh, I'd have went with the Wippermann or SRAM. The Hyperglide (HG) series is a bit of a pain to work with, they require using a special pin to join together and you can't reuse that pin. Make sure you get the length right the first time. The other two have a master link that snaps together, they can be taken apart/reused easily.

I have read some of Mr. Brown's articles,and now that I have better idea of what I am dealing with,will go back through them again. I probably have more invested in tools and parts then the bike is worth,but as I said I am determined to get it functioning.

He was a fountain of knowledge and is sadly missed. It's a good place to learn how to work on the bike, they are pretty simple to fix. I'd agree with your last sentence, you probably do but chalk it up as a learning experience.

Good luck with getting that Mongoose up and running.

 

[TWBryan]

Blackhills,
I wondered about the chain,but was led astray,by the lure of Free Shipping. Had no idea Mr.Brown was deceased,that is sad. Thanks for moving me a little further along on this project.