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Discussion Starter · #1 ·
I just bought a Mongoose XR-75 and am having problems with the chain slipping over the sprockets. Seems like there isn't enough tension on the rear derailer. Any time I really put pressure on the peddles, it slips. I am having a hard time seeing what exactly is happening, but one thing I did see was that it looked like the chain bunched up as it was traveling toward the front sprocket. Doesn't matter what range I am in or what gear.
I am a noob at adjusting these things. Is there any way to do this to put more tension on it?
Larry
 

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Single(Pivot)and Happy
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Go to parktool.com, buy a bike repair book, or take your bike to a bike shop.
 

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~Disc~Golf~
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LarryGScott said:
I just bought a Mongoose XR-75 ...
not to be a dick, but there's your problem.

BTW the ParkTool recommendation that Boulder Pilot said is excellent advice.
I'm sure he knows, but why try to explain everything about tuning your drive train here, when it's better detailed there?

Or take it to the shop
 

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You were given three answers to your question.

You've got a little learning to do, to be able to provide enough information for anyone to help you.

If you've got a short attention span, going to a bike shop may be best, and they can show you what to do.
 

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Discussion Starter · #6 ·
I just wanted an answer to point me in the right direction. To quote highdelll "not to be a dick", but I bought this bike for not so much riding downhill or even offroad in general, but to get exercise.
I will look elsewhere for my answer.
 

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~Disc~Golf~
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Upon reflection, I thought I should repost and do a little clarification/ explanation...
the XR-75 is about as low in quality of componentry and build as you can go. (nothin against you personally)
The bike will simply not perform nicely - it's the nature of the beast

that being said, here's the link to exactly where you need to go:
http://www.parktool.com/repair/byregion.asp?catid=53&imageField2.x=17&imageField2.y=5

just follow all the directions for tuning the derailleurs step by step and you can't go wrong.

ALSO, per your description of your problem (chain skipping/ 'bunching') it sounds like you may have a stiff link/s. Cycle your chain around by back pedaling - when/if you see it 'bunching-up', grab that section with you hands and feel if the link/s are stiff.
If so, you'll need a chain-breaker to work the pin back and forth slightly to loosen it (it will also help to drop some oil on as you do this)

Good Luck :thumbsup:
 

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I'm an LBS mechanic and there are three main things that can be happening in this case.

1. If the slipping and popping is coming from the rear, it is the cassette and it will need replacing.

2. If the slipping and popping is coming from the front, it will be the chainrings... these can be replaced individually, so narrow it down to where the issue is.

3. One or more chain links may be siezed up and this can be alleviated by pin pointing the links and freeing them up via lube and or wiggling them back and forthe from side to side. It may take a little more if they're really siezed, but worst comes to worse you replace the whole chain.

These are the main causes of slipping and popping, start with these and go from there.
 

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~Disc~Golf~
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Like I said 'not to be a dick' - I wasn't homie
you said "I just wanted an answer to point me in the right direction."
the first reply was: "Go to parktool.com, buy a bike repair book, or take your bike to a bike shop"
now, how is that not pointing you in the right direction?
noone was suggesting that wanted to go DH'ing - just offering the appropriate advice as to what to do.
 

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~Disc~Golf~
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BigRedFSR08 said:
I...

2. If the slipping and popping is coming from the front, it will be the chainrings... these can be replaced individually, so narrow it down to where the issue is.

...
I believe the XR-75's are riveted
-just pointing that out
 

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Sorry, I didn't even look at the details... I guess its just a habit to recite the three main causes of slipping and popping. Most of the time the chainrings are bolt on... sorry
 

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highdelll said:
Like I said 'not to be a dick' - I wasn't homie
you said "I just wanted an answer to point me in the right direction."
the first reply was: "Go to parktool.com, buy a bike repair book, or take your bike to a bike shop"
now, how is that not pointing you in the right direction?
noone was suggesting that wanted to go DH'ing - just offering the appropriate advice as to what to do.
No, you just don't understand. He just wants to ride for exercise, which makes it totally different :rolleyes: Why would he want to exercise both the body and mind?
 

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Discussion Starter · #13 ·
Thank you for this info, I guess I could have been nicer in my response. Especially since I am the new guy here.
Thanks again,
Larry
 

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~Disc~Golf~
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BigRedFSR08 said:
Sorry, I didn't even look at the details... I guess its just a habit to recite the three main causes of slipping and popping. Most of the time the chainrings are bolt on... sorry
no apologies necessary mate :D
 

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~Disc~Golf~
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LarryGScott said:
Thank you for this info, I guess I could have been nicer in my response. Especially since I am the new guy here.
Thanks again,
Larry
Welcome to MTBR dood! ;)
 

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Discussion Starter · #17 ·
I checked the chain a little while ago and it's got about 2 inches of slack before the derailer moves. The derailer just doesn't seem to have enough tension to do its job. That is as far as keeping the chain tensioned. It almost seems like the chain is about 4 or 5 links too long.
 

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LarryGScott said:
I checked the chain a little while ago and it's got about 2 inches of slack before the derailer moves. The derailer just doesn't seem to have enough tension to do its job. That is as far as keeping the chain tensioned. It almost seems like the chain is about 4 or 5 links too long.
What combination of chainring and cog? Makes a difference...

Could be the chain's too long, could be the derailleur just doesn't have a very strong spring, or it's not set up correctly, etc. Is this a brand new bike?
 

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LarryGScott said:
I checked the chain a little while ago and it's got about 2 inches of slack before the derailer moves. The derailer just doesn't seem to have enough tension to do its job. That is as far as keeping the chain tensioned. It almost seems like the chain is about 4 or 5 links too long.
This does not really make sense.

One of the reasons the local bike shop (LBS) was suggested is it near impossible to fix such issues without being able to see the problem.
 

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Discussion Starter · #20 ·
It's not a new bike.
It happens on any combination of chainring and cogs. All the way from 1st gear to 21st gear.
I really don't think the derailer has a strong enough spring.

I guess I should clarify this. It isn't skipping from one to the next, it is jumping over the teeth.
 
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