HELP bottom bracket?
 

hi all, i have a barracuda oblivion that my brother striped and now im trying to put it back together and fix it.

before it was stripped, when pedaling the pedals would come loose then fall off unless tightened.

if i hold both pedals the bottom bracket moves when i lift or push down on the pedals.

am i right that i need a new one?

do they come in different sizes? what part do i need to measure if i take this apart to get a new one?

sorry im new to this

thanks in advance

Maybe you need a whole new crank and bottom bracket. Do the pedals thread in and stay tightened now? Sounds like a lot of play in either your pedals or bottom bracket or both. Bottom brackets are mostly crank-specific, though, so hard to say what you might need to shop for. I tried looking up a Barracuda Oblviion on bikepedia.com but don't see that model. What make and model of cranks are they? You might find info on the backs of the crank arms.

Hello minibeefy, welcome to the forums. I agree witht he above, sounds like it is time for new bottom bracket and cranks. however, when you say the pedals fall off, do mean the crankarms yes?

well the crank is all bent aswell from being stuck in the garage so im goin to need a new one of those too, im thinking i need to replace the whole pedal system. if i remove it all will there be some kind of markings to show me what size they are????

its not yet ridable as there are other parts missing but im assuming they will come undone like they did before.

sorry yes i mean the crankarms, sorry didnt know there name .

Might be time to seriously consider whether the bike is worth putting back together or not. You might be needing lots of new parts. bk

well it was like a £500 quid bike and is probably the best bike iv ever ridden so i do wanna get it back up and working and if it cost me £100 to get this working its better then spending £200 on a new one lol.

iv had a look and seen bottom brackets and cranks fairly cheap on ebay, just need to find out what i need, i.e sizes

what sizes do these come in and how do i find out what mine is?

Best bet is to take your parts to your favorite bike shop, and get them to order replacements for you. ebay is a crapshoot product wise, and best suited for buyers who know exactly what they want. And ebay sellers often mismeasure or mislabel parts, making it even more difficult.

If you want to continue on this path instead, post pictures on all of the parts you want to replace, and close ups on any/all markings.

ok, thanks very much for your help guys, i will crack out the spanners and socket sets tomo and get cracking on taking it apart

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hey guys, these are pictures of the parts iv taken off of my bike that i need to replace, any help would be appriciated

i took them to a bike shop near me, he said i can get any bottom bracket that is a 68mm and has square ends like the one i have and that the crank that i need is any of the square type cranks with the offset pedals.

Well, almost. BBs can have different shell widths, different axle lengths, different threadings and different axle ends. Right now you've got the shell width and the axle ends.

Pretty basic square taper crank. Is it the arm not pictured that's been bent? Rather than change to a square taper it might be time to think about a different crank, too. Perhaps one of the current "standard" external type bottom bracket types. Basically square tapers are still around and work fine, although choice in bottom brackets isn't what it once was. The two splined interface systems (Shimano's Octalink or ISIS) have also largely gone by the wayside in favor of the outboard bearing type cranks. There were some awesome deals going around on the Shimano LX M582 for a while at closeout (they're revamping the LX lineup in favor of SLX for the most part); I see SLX crank & bb (they normally come as a set, no need to shop for a separate bottom bracket) at CRC for 90 pounds. http://www.chainreactioncycles.com/M...?ModelID=28020

its not the arm thats bent its the bit that the chain runs on (crank?) thats all bent up so when riding the chain comes off,

iv had a look around and found some fairly cheap bb and cranksets,

iv measured the bb and it 113mm long, so am i right that its a 68x113 bb that i want?

im a student so looking for a quick fix for now and then upgrade later when i have more money, just need a bike to use at the moment to get to uni and back

It is the chainring that is bent. These can be replace on the cranks you have. But your cranks need to be replaced because they wont stay tight on the BB spindle. The cheapest cranksets come with the chainrings riveted to the cranks. Better ones have chainrings bolted on, which allows you to select chainring sizes to suit your riding conditions.

That would be a chainring that's bent then. You might be able to simply straighten it with some patience and a set of pliers. Looks like those are chainring bolts, so an alternative would be to replace the offending chainring, too (looks like a fairly standard 4 bolt 64/104 mm bolt circle diameter set).

Like andrewp said, concern is what you meant by pedals falling off before...was it the crank arms that kept falling off or did the pedals come loose in the crank arms themselves? If the crank arms kept coming off the chances are you've damaged the softer square tapered interface in the arm rather than the harder taper on the bottom bracket itself, and a new bottom bracket alone may not solve your problem. You seem to have the sizing down (there's two other factors, the type of threading and the degree of the taper, but with a 68mm shell it's most likely English threading (1.37 x 24) and a JIS taper (common with a crank like yours).

You might want to look at this article http://sheldonbrown.com/bbsize.html

sorry

right its the crank arm that falls off, the bolt that connects it comes loose then it falls off, its only of the side opposite to the crank, there is also play in the bottom bracket which is why i figured this would need changing,

i already replaced the crankarm before and it still happened

Replaced as in bought another? Are you torquing the bolts to spec?

yea i bought a new one, yea iv made sure they where done up properly, thats why im thinking if i replace the whole lot it should then work

How did you do that? torque wrench properly, or backyard mechanic guesstimate properly? Cranks needs to torqued fairly hard, and people doing them up by feel have a high failure rate.

Don't count on it. It's pretty much impossible to damage the hardened steel in the bb spindle with the ever so much softer aluminium alloy in the cranks. All brand new bits will fail just as readily unless they're assembled right.

yea i used a torque wrench and also took it to a local bike shop and they tightend it for me before

Curious, what value did you torque it to?

if im honest i cant remember now but the bike shop had told me and i tried then took it to the bike store for them to do it and it still didnt work.