limmiwinks23

i put a used BB on my nashbar atb frame(18") and it wont screw in all the way, it sticks out of the frame, how do i know what size i need? it only says 68mm but thats the diameter right?

cyclotoine

68 is the width of the BB shell on you bike, an ATB should take a 73mm. either way I don't know why it isn't screwing in all the way. At 68 should fit but then you will have the left pedal too close to the frame and possibly rubbing. how much is it sticking out? did you clean the threads well?

limmiwinks23

how do i clean the bb shell??, no i mean the frame specs say 68mm and it threads in until it just stops

mx_599

mine sticks out too. as long as it is tight, its okay

limmiwinks23

well, it wont go into the 3rd ring....??

mx_599

oh, i thought you meant the non drive side. well, take it out. use a metric ruler and visually inspect/measure the threaded distance on the cup and then the threads on the frame. ask yourself, "are there enough threads in the frame for this cup to seat all the way??"

if yes, then make sure both threads are clean like the above poster said. make sure no crushed threads are evident...this will surely cause resistance.

put a light lubricant on and try again. you might have simply hit a "false" tightness....and just need to put more torque into it assuming what i said above all checks out.