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Mongoose Consistent Front Derailleur Issue
#1
So I am currently working as a bike assembler at a Walmart, and though I know these are not even close to really being "bikes" they are what they are. However, I recently have had an issue, where I know that every Mongoose that we have in stock, and the new ones coming in, I'm sure will have the same issue over and over with the front derailleur being unable to shift onto it's largest gear with how they have sent it to me. This seems to be present on every model of Mongoose that we have, not just a single model, but we sell about 6 or 7, male and female, and all of them have this issue.

I am finding that I am spending what seems to be far too much time simply trying to fix this one problem, that I am now asking for help with what I can do to make my efforts more efficient. For the most of them, after some work, I manage to get it reliably shifting, however on a couple so far, I have had to abandon the process, as it just would not work at all.

These also use a grip shifter, which makes it extremely tough to shift at times even when I do get the highest gear working, often not even aligning with the numbers, or having to hold it just for a moment past where it'll stop turning to get it to shift over.

Is there anything I may be doing wrong, or any tips on dealing with this issue that'll make it more of a process that I can manage to get through with less fumbling about, hoping that this minor adjustment will work? It seems as if the derailleur on these Mongoose are just made in such a way that they are not designed to be able to push the chain onto the largest gear.
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#2
is the H limit screw set correctly?

Is the FD cage parallel to the chain rings?

Does the FD cage clear the large chain ring by 2 to 3 mm?

Is the FD tightly clamped to the post?
Nigel
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#3
I am having the same exact problem with both of the bikes I purchased for my son. He likes this one and won't let me buy him a better one. Derailleur will not go out far enough to reach outer/larger ring even with cable detached and H adjustment screw all the way out (and me pulling as hard as I can). No obvious obstructions. Looks like they came with the wrong derailleur. Mongoose is sending me another, but I am not optimistic.

Jaline - Did you get this figured out?

Any help/thoughts with this issue (besides buying a better bike) will be sincerely appreciated!
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#4
Replace the FD.

My favorite 48T and under FD is this one:
http://www.ebay.com/itm/2008-SHIMANO-ALIVIO-FD-M413-8-Speed-34-9-Front-Derailleur-High-Clamp-Alloy-NEW-/130931336391?pt=Cycling_Parts_Accessories&hash=item1e7c1da4c7

For smaller diameter seat tubes, I bought a short section of 1 3/8 inch OD aluminum tube with 1/8 inch wall, cut off a piece about an inch long, then section it into two half circles. Take a look at the pictures here: http://forums.bicycletutor.com/thread-3167-page-1.html

The M413 has lots of travel, at both the small end and the big end. The 34.9 version is so inexpensive because of lack of demand, people with 34.9 seat posts want a higher end FD; those of us with a little ingenuity get a very nice upper-mid range FD for a song.
Nigel
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#5
If the shifter just doesn't pull enough cable to get the derailleur over, one hack is to clamp the cable on the fr der slightly closer to the pivot point. This will change the geometry of the shifting so that the shifter will act like it is pulling more cable than it was before. Note however, that this could mess up other aspects of the shifting. Note also that if the der is hitting the outer limit, this won't achieve anything.

Finally, it's not uncommon in my experience with lower end bikes to have to overshift a little to get it in gear before you can let go of the shifter. Doesn't mean that it's "OK", but it's reasonably common.

It does sound like the bikes were assembled with parts that didn't quite match the design spec. You should probably pass that back up the supply chain. But I'm assuming that unless its a safety issue the store could get sued for, not much is going to happen.
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#6
Thanks Guys!

Will try the FD the Mongoose/Pacific Rep is sending since she was "confident" that it would work (hopefully different than the one already on the bike). Otherwise, I will order the M413 (< $15 shipped) since original FD hitting the outer limit and not close to reaching large ring.

Will update when able. Thanks again!
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#7
Not considering myself an expert on Walmart bike's. but from what I have seen of them, the ones that use a Falcon all stamped steel and clamp front derailleur, forget it they are junk. the inner plates and outer plates are ill formed and with indexed shifting are even wourse for the applied use. Measure your tube and go up to Shimano grade acera or alivio will make the world of difference in performance. honestly $15 to $30 upgrade. Shop around you will see
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#8
Shimano M413 - excellent; M412 - avoid.
Nigel
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#9
I had the same frustrating problem with a Mongoose Ledge 2.1 Mountain Bike.

My Solution - Raise the Front Derailler on the Frame Bar. It was too low, and hitting the side of the large front sprocket - preventing the derailer from moving fully to the right and using this gear.

This did, however, require new adjustments and calibrations as it affected the length of the cable travel and it's tension.

Good luck !!!
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#10
I had the same problem too. After racking my brains, this is what worked for me:

1st - Put the front derailleur into low gear. Then, make sure that the derailleur is properly aligned over the low gear by adjusting the low side adjustment if necessary. Then, make sure that the cable is tight.

2nd - If that didn't fix it, and it continues to not shift in to high or hesitates too much, put the front derailleur into high gear. Then, unscrewed the high side adjustment to let the front derailleur extend further out, letting the gear bite into the chain easier. Do not unscrew all the way, just enough to let the gear shift. Now it should shifts into high with no problem. That's what worked for me.

I don't know if it comes from the factory like that, or the Walmart assembler where I picked it up set it like that. All I know is when I picked mine up at Walmart, I had tune both front and real derailleurs and the front brake. It was horrible.

Also after 2 months, my rear tube just split. After 4 months my front grip shift went out. Horrible. Luckily, I bought the extended warranty and they took care of that with no hassle.
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