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advise me on inexpensive bb + crankset combo

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advise me on inexpensive bb + crankset combo

Old 08-24-12, 08:19 PM
  #1  
BlaineHeadrick
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advise me on inexpensive bb + crankset combo

I bought this kind of folding bicycle off ebay (not from same seller as in link tho):
http://www.ebay.com/itm/New-26-Foldi...ht_2712wt_1035
Price: $174
Color: Pearl White
Super Light Weight: 36 LB
85% Factory Assembled
Shimano Folding Mountain Bike 6 Speed
Frame : Steel 3 pcs crank, 50.8x28.6x50.8mm, tig, head tube: 30*120mm
cup and cone bb spindle http://www.ebay.com/itm/Used-Steel-C...ht_2084wt_1139
Tires: 26"x 2.125, BK
Rear Derailleur : RD:TZ-50 6S (Shimano)
Derailleur Lever : right side: SL-RS35-6R 6S index left: nil (Shimano)
Freewheel : teeths x pieces: 1/2"x 3/32"x 14 - 28T, 6 piece index (Shimano)
Forks: 26"SUSP. FORK , 1-1/8" WIDE: 102mm - OD: 27mm ID: 22.2x 152mm
Stem: Folding 3PCS EXT:100 25 degree 22.2*150,with safe line。T=1.4
Brakes: alloy V brake F: 90 degree , R:110 brake calbe sheath ,brake 55
Tire: size: 26"x 1.95
Rim : Alloy 14Gx36H : 26"x1.5
After riding it about 8 times the left crank arm comes loose and falls off.

I took it into a bicycle store (Al's Bicycles - 2624 Broadway Court, Edmond, OK (405)341-4331) and this grey haired manager there said that the bicycle was worthless and I should just throw it away. I felt like I was marked as a pigeon and decided to get out of there.

The 2nd bicycle store I went to (Schelegel - 900 North Broadway, OKC 73102) had a similar outcome. The service director there went to great lengths to deprecate every aspect of the bicycle and said that since the frame was held together only by tack welds, and given that the bicycle was not properly adjusted when it was taken out of the box it was beyond salvaging and a death trap; they refused work on it, citing their policy of safety assurance on their work.

Heres a picture of the weld. Seriously, does it look that bad? I mean i'm not performing any acrobatic tricks or stunts, just leisure riding. And, only one side is tack welded. The other is metal on metal.


The only problem I see is a stripped crank thread and a rounded out arm hole. (Also, the left pedal plastic casing got torn opened somehow. But, I think I must have done that when I tried to remove the pedal with vice grips instead of properly with a pedal wrench.)


So, I ordered a crank arm off amazon and tried that out. But after about 800 meters it fell off too. So my dilemma remains: should I try to fix it or upgrade to a sealed cartridge bb and crankset?

I read that the ISIS sealed cartridge splined bb is able to handle much more torque than the square tapered bb.
If I just put another square tapper cup and cone bb on it whats to stop the same damned thing from happening again? I'm still not entirely sure what happened in the first place to cause it to break so fast. But, I've read alot of sour blogs about the bottom brackets that come with these cheap ebay bikes so its not just happening to me.

Also, if I upgrade to sealed cartridge bb I would need to get a new crankset too. Can someone point out an inexpensive crankset and bb that would go together? Preferably ISIS or octalink. I'm having trouble finding info on which are compatible with what.
I'm complete newbie so any thoughts are appreciated.
TIA


edit: for the sake of not bearing false witness I must add that the ebay seller, Hometroopers, just mailed me free of charge a spare bb spindle, crankset and folding pedals, many months after ebay buyer protection expired.

edit2: it wasn't a grey haired manager of Al's bikes that was trying to scam me, it was the grey haired owner.
Attached Images
File Type: jpg
tack weld.jpg (58.7 KB, 24 views)
File Type: jpg
pedal.jpg (88.7 KB, 17 views)

Last edited by BlaineHeadrick; 11-05-12 at 11:52 AM. Reason: owner of Al's bikes is a scammer
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Old 08-25-12, 10:47 AM
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sorry to tell you this, but the bike is a total piece of *****. its probably not worth your time fixing it. also (and not to be mean), it sounds like you dont have a great grasp on bicycle mechanics and parts etc.- thats why there are professionals.

that being said, I would encourage you to fix this for as cheaply as possible.

the arm probably keeps falling off because its under-torqued and/or the spindle is mushed and cannot hold the arm on any longer. I would try and get a real crankset by shimano or another "real" brand. DO NOT GET ISIS!!! they have a storied history of arms falling off and bearings wearing out in minimal time.

maybe http://www.nashbar.com/bikes/Product...36_-1___202345

or just a simple square taper double from a local shop's parts bin (or ebay if you must- but still support your local shop)
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Old 08-25-12, 12:00 PM
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It's uncommon for the BB axle to become deformed, almost always it's the arm's hole that gets rounded out. once the arm/axle looses their full surfaces contsct the arm will never stay tight. The common fix is to replace the arm (LH alloy are usually about $15/20), install it without lube on the hole/axle flats but with lube on the bolt/nut threads, torque the bolt/nut to about 33 ft lbs, ride it a little bit and retorque. Repeat the ride and torque over the next week.

Yes the bike's welding looks pretty crude and made for the least cost possible. Will the welds fail, only time will tell. The rest of the parts list follows this theme. Not surprised that the LBS didn't think much of your bike. Sad that they insulted you by how they explaned things. There are more tactful methods of calling out a pig. But one of the judgements shop HAS to make is the worthiness of a repair. Not in whether the customer thinks it's a good value, but if the repair never gets picked up and the shop has to sell it off to recoup their investment. This is where a cheap bike might not be worth fixing. Again how the shop educates the customer is the skill that some good service guys don't do well.

Your pedal looks like many i see. Very cheaply made, it's likely the plastic failed from the pressures of use. This type of pedal costs $10 or less. Generally the all plastic pedals that shops sell are a bit more robust but still being plastic do have a limited lifespan. Consider moving into a metal pedal, espically if you're big or tend to hit pedals on the ground. Andy.
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Old 08-25-12, 04:03 PM
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BlaineHeadrick
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Originally Posted by skeem View Post
also (and not to be mean), it sounds like you dont have a great grasp on bicycle mechanics and parts etc.- thats why there are professionals ... - support your local shop
Very true. I'm a newbie at this with a terrible grasp of mechanics and I believe I'm also a bit dyslexic so I thank you for your response and patience.

As to my local bike shop professionals, they simply refused to help me at all. Although, they'd likely show more of an amiable disposition if I'd bought their bikes at 4x the prices.


Is there perhaps a way to put an inexpensive single piece crank on this? At least I would know the arm wouldn't fall off when I'm in the middle of nowhere.


All comments appreciated. Thanks!
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Old 08-25-12, 05:31 PM
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Originally Posted by Andrew R Stewart View Post
install it without lube on the hole/axle flats but with lube on the bolt/nut threads
Shouldn't it be the other way around? Lube the hole/axle flats but no lube on bolt/nut threads?
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