Joshman380

I have a Kent Mountain bike, not top quality I know, but it does the job..kinda.


Quick history, I bought this bike on Craigslist for a whopping $10. When I bought it the rear derailleur was hanging loose, missing the top screw (that keeps it from moving around), the right side nut for the rear wheel was missing, and there was a rusted chain.


I brought the bike home, got the derailleur mounted, new nut for the wheel, and I bought and installed a new chain. Here's where my problem is. I'm looking at another bike from the same manufacturer (just a different model, using all identical parts), and when the chain is on the smallest rear sprocket (both bikes in the same gear position), the rear derailleur is in a completely different position on my bike than on the other bike. I should note that when I installed the chain, I installed it on the biggest sprockets (front to rear) and when I linked the master link, the derailleur was nearly all the way forward. (stretched all the way out)


The other problem I'm having is when I try to pedal uphill, my chain slips a tooth. These problems may be related and possibly due to the following:


There is slack in the cable for the rear derailleur. Obviously I'm no bike mechanic, so I'm not sure if this particular cable can be replaced, or if I have to go out and buy a new shifter. I'm wondering if I can get by with just taking up the slack in the cable? Will doing this fix the chain slippage, or do I still have to remove a link?


The chain I bought was an SRAM chain for an 8 spd rear sprocket. Upon installing I noticed that I only had 7 speeds. Obviously this chain is too long to begin with. I took out 4 links when I installed the chain, thinking it's easier to remove a link than trying to re-link the chain.


Any help would be appreciated...I have two days to get this bike road ready..gonna be riding to work for a bit.

alcjphil

The most likely cause of the chain slip is worn teeth on the cogs of your freewheel. This frequently happens when an old worn chain is replaced. Solution to that is to change the freewheel

Joshman380

Could it also be too loose a chain? I feel like I intentionally left the chain a little longer because I don't want to try re-linking a chain if I cut it too short.

LesterOfPuppets

Sounds like you cut the chain a little short.

8-speed chain is good for 6,7,or 8 speed gears.

Skipping could be a lot of problems. Worn chainring, worn rear cog. If it's wanting to change gears in back it could be poorly adjusted rear derailleur.

Look for derailleur adjustment vids online. I like to release the cable, make sure center of top pulley aligns with outside face of small cog (using H limit screw)
Then pull cable and anchor it. Some low-end derailleurs seem to like the cable a little loose, so don't pull super tight before anchoring.

Then shift through gears, adjust cable tension til they work, shift to big cog, adjust L limit screw if needed.

​​​​

Joshman380

Cut the chain too short? That doesn't make sense...when the chain is on the smallest to smallest cog the chain looks like it could almost fall off. Is there supposed to be a ton of slack when installing on the biggest cogs? I was under the impression it was supposed to be tight on the biggest to biggest cogs. That's how my local bike shop told me to install it....

Incidentally, it's not wanting to change gears on it's own...It's just skipping a tooth when riding uphill.

Joshman380

Would this be a suitable replacement for the cassette?

https://www.ebay.com/itm/Seven-7-Speed-Freewheel-Screw-on-Bicycle-Cycling-Bike-14-28-Teeth-Universal/223479379231?epid=7028009711&hash=item340868b51f:gtYAAOSweqNciydC

Joshman380

Here's a picture of the rear cassette.

alcjphil

That link is to a freewheel, not a cassette. It is important to know the difference. Your bike probably has a freewheel

fietsbob

It's a freewheel not a cassette
and your $10 bike is just not made to any level of precision standards so I recommend:

realistic expectations .. now a 5678 speed uses same chain, 9,10 and more need narrower ines

yes any 7 speed freewheel will do , and buy a new chain at the same time..
and a freewheel remover , may have to buy 2..
one for what is on there and one that fits the replacement freewheel, to remove it in the future..




Or the latter part of catch & release , go shopping for a better bicycle.. leave that one by the curb with a free sign on it

(though unlocked & left with a higher for sale price has been shown to be taken faster.)





Reading books on bike repair is always a good thing..

....

LesterOfPuppets

The description of RD nearly straight out, just sounded like it might be too short. That would explain diff. RD position. Could be other things though.

LesterOfPuppets

looks like the RD cage is angled in a bit. Bent dropout, claw or cage possible.

Joshman380

I'm just gonna take it in to the bike shop and see what they tell me. Mountain bikes are a complicated beast compared to single speed bikes.

fietsbob

you at least will not have to buy a freewheel remover to use once. .. by having the shop use theirs..

JohnDThompson 

I agree with @alcjphil that a mismatch between a new chain and a worn freewheel/cassette is the most likely cause. An 8-speed chain should work fine on a 7-sprocket cluster, as long as both are in a similar wear state. Take the wheel in to your LBS and have them replace the freewheel with a new one of the same tooth counts (to avoid having to re-size the chain again).

Joshman380

Thank you sir. I'm no bike pro so I'm sure most of my terminology is off.

So according to the bike shop, my freewheel is done. Chain length is ok, everything else is good. As I suspected the teeth on the cogs are supposed to be straight, not angled as you can clearly see in the picture of my freewheel. I have to say I'm relieved..I'm not prepared to spend a TON of money fixing a bike that cost me $10.

So the question now is what freewheel to get. I'm looking at Shimano right now..I think I'd like a little better quality than the original. I wonder though...Shimano is a Chinese brand..although quality and very well known and widely used, I see other Chinese brands like Sunrace and Sunlite going for similar prices. What's the difference here?

Here's a link to one of the Shimano ones I'm looking at, but it seems there are different models for the 14-28t range:
https://www.ebay.com/itm/SHIMANO-TZ2...sAAOSwp5JWbdCz

fietsbob

yea then its time to shop for a new bike , since whos hour of time is worth Just U$D 10 these days...

Joshman380

I don't have even $100 to buy a new bike, so fixing is the alternative, and so far way cheaper.

fietsbob

time to get a 2nd job..?

NB: a bike repair book can be checked our from the public library for free..

Joshman380

Here's a full pic of the bike. Not bad looking..odd frame design IMO. It's the bike in the front.

Joshman380

I appreciate advice and helpful comments. Comments regarding my financial situation are not needed and are NOT helpful.

fietsbob

the reading part is free

LesterOfPuppets

twisted teeth are usually fine, as they're a common shifting aid.

If the previous owner spent all their time in the same cog and it only skips in one cog then it may be a worn cog. I doubt that thing has enough miles on it to have a waste freewheel already, though.

I'd guess rear derailleur alignment is needed.

frame is shaped like that cuz it's a full suspension front triangle with a rigid rear triangle welded to it.

hokiefyd 

A new Shimano freewheel will work just fine. Shimano is not a Chinese brand, though many of their lower end parts are made there. An MF-TZ21 freewheel would fix you right up, plus a standard freewheel removal socket tool.

Joshman380

That particular model did look like the best match.

Incidentally, I broke some of the old chain to use to make a whip tool to remove the old freewheel. Left the pieces I took in tubs of rust lime calcium (not to be confused with the more popular CLR) overnight and they came out pretty good. A wire brush to clean it off a bit and bam. Chain for the tool now usable.

hokiefyd 

Cool; nice work! It looks like a KMC chain, which is a good brand name. They're probably the largest producer of bike chains in the world, and have very popular offerings, from budget chains all the way up to top shelf stuff.