# bmx crank woes...any advise?



## climbingbubba (Jan 10, 2007)

well i broke down and got some bmx cranks and now i can't get them to go on right. the issue i have is that i get them all on there snug and then i try to tighten the bolt to lock down the sprocket and it bends the sprocket towards the cank and puts pressure on the BB bearings and the cranks don't turn more than half a turn on when i spin them. 
i tried putting a 1mm thick washer in and it was too big.
when i loosen the bolt the cranks move free but there is play with the sprocket.

for refference i have wethepeople royal cranks with a profile 23t sprocket.

anyone else have this problem? i was thinking next i would try to

1. find a rubber washer that would squish down more than the metal one.
2. turn the sprocket around so its the flush back side would be against the crank instead of the fancy designs on the front side.

what do you guys think?
anyone else run into this problem with their cranks?

thanks


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## A Grove (Nov 12, 2006)

Dremel


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## boyfromthelak (Feb 16, 2004)

my cranks also put a little bend in the sprocket(well my profiles but not my flys on the bmx bike) never had a problem with it. and i don't think my cranks spin more then one revolution but they are buttery smooth


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## Dave Moore (Apr 15, 2004)

If money isn't an issue, you could go with a tree splined sprocket and forget about the bolt.
Are you absolutely sure you installed everything correctly? No offense intended, I have no idea about your mechanical ability.

If all else fails then dremel as mentioned or find a thinner washer.


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## sittingduck (Apr 26, 2005)

Sounds like you have failed to properly install the cranks. With the bolt in the arm removed, there should be no play in the sprocket. Also, unless the arm is defective, the inside faces of the arm at the spindle and at the sprocket bolt threads should be flush. Do you have an adapter or other spacer that prevents the sprocket from sitting flush to the crank arm?


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## climbingbubba (Jan 10, 2007)

im pretty sure i got them in there right. what i have tried is tightening it down all the way til the sprocket doesn't move but then it puts too much preload on the bearings and it doesn't spin well. if this is not a bad thing then i should be ok. i usually tighten it until right before the spinning becomes impared then i tighten the bolt on the sprocket. when i get to that point either the sprocket has play cause the bolt is too loose or it bends a little and puts pressure on the bearings and once again it doesn't spin right.

as for the dremmel part. dremmel what? the washer? the gap that causes it to bend is inbetween the sprocket and the crankarm.


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## sittingduck (Apr 26, 2005)

Sounds like you might need another spacer in between the bearings. If you are able to preload the bearings by tightening the crank arms, you have definitely failed to properly install the cranks. You DID put the spacer between the bearings, right? And checked to make sure it was the proper length by putting the cups and spacer on the spindle and checking the width on the outside of the BB?
You never answered my question: "Do you have an adapter or other spacer that prevents the sprocket from sitting flush to the crank arm?"


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## climbingbubba (Jan 10, 2007)

sittingduck said:


> You DID put the spacer between the bearings, right? And checked to make sure it was the proper length by putting the cups and spacer on the spindle and checking the width on the outside of the BB?


yes i did put the spacer between the bearings and NO i did not check it first. if it is the wrong size then where can i get another one? would a LBS have one?



sittingduck said:


> "Do you have an adapter or other spacer that prevents the sprocket from sitting flush to the crank arm?"


i do have an adapter that i pressed into the sprocket but i made sure that the part that sticks out is facing the bb and not the crank arm.


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## BikeSATORI (Mar 20, 2004)

I've got some wethepeople royal cranks as well.... but not that problem.

The part where you say the cranks won't spin is 99% more likely the lack of enough spacer width in between the bearings (or maybe too much???)... but it sounds odd how you relate it to the sprocket bolt... that shouldn't have an effect on binding bearings. Yes, some sprockets do bend a hair when tightened down, but not as much as it seems you are attempting to explain... Are you sure you have the adapter/top-hat spacer installed correcting into the inner bore of the sprocket? probably goes from 22mm down to 19mm... Does your sprocket rattle around on the spindle, or sit there snug?
I've never run my cranks with a profile sprocket, nor anything under 25t, but that shouldnt' be very relevant to your problem....
if adding the proper amount of spacer width inside your bb shell doesn't work to keep your cranks spinning when preloaded properly and tightened down.... I'd agree with sittingduck, it sounds like something must be defective,.although that's just an easy thing to suggest without really knowing.

A rubber washer isn't going to solve any problems.
If you got the wrong size tube spacer for the middle, you would know it, there are like 5mm + differences between the different sizes. Usually you just add very thin spacers until it works out fine if the tube spacer rattles between when everything is loosened. It shouldn't move back and forth between the bearings too much when loose....


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## sittingduck (Apr 26, 2005)

Very puzzling.... Try putting a straight edge on the inside of the crank arm, to see if it's flush with the surface of the sprocket bolt hole. It sounds like maybe your crank skipped quality control before it shipped.  
I have a washer on the inside, giving the adapter a little more length. Otherwise I don't have enough thread to get the lockring onto the left bb cup. You should be able to snug up the cups without the arms on, so that there is a slight resistance in the bearings. (tight to the inner spacer) Then you can crank down the arms and it should still spin smoothly. If there is a gap between the arm and your sprocket, either get a new arm, or have someone make you a really thin washer.


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## boyfromthelak (Feb 16, 2004)

didn't notice you said you have a 23t sprocket you need one of these

http://www.danscomp.com/457002.php?cat=PARTS

other wise you'll drop the chain anyways


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## climbingbubba (Jan 10, 2007)

ok to answer the new questions.

1. yes i have the sprocket insert in right.
2. i can't tighten the crank arms enough to make the sprocket not move cause then the crank arms don't spin. 

im not so concerned with the fact that it is bent a little as i am with the fact that when i tighten the bolt it puts pressure on the BB. it don't make sense to me.

as for the middle insert. is there other spacers i can use to adjust (like the little ones that came with the cranks) it or do i just need to order a larger one if the one i have is too small?

thanks for the advise so far. i have my bike at my parents cause they have all the tools and work space so when i get there ill tear it all apart and check it out.


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## combatkimura (Jul 17, 2007)

it sounds like you are side loading the BB bearings because the spacer inside isn't long enough. I had to use some washers inside mine to get the right length on my 83mm bb shell. What BB did you get for it? When you install the BB you should be able to take out the spindle and the spacer shouldn't move (fall down) and should be pressed between the bearings. The BB needs to be tightened down on the spacer (not crazy tight) and the crank arms press on the outside of the bearings to make it one solid spinning mass. If your sure everything is installed correctly you may need to have the BB shell faced and chased.


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## boyfromthelak (Feb 16, 2004)

also you will need the bolt showed you or to dremel yours down otherwise the chain will hit the sprocket bolt result in a broken chain or a dropped chain even on a singlespeed bike


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## sittingduck (Apr 26, 2005)

climbingbubba said:


> ok to answer the new questions.
> 
> 1. yes i have the sprocket insert in right.
> 2. i can't tighten the crank arms enough to make the sprocket not move cause then the crank arms don't spin.
> ...


You can just add some small spindle washers next to the spacer if It's too short.
If I were you, I would take it all back apart, and assemble the bb on the spindle, then check the width on the outside of the BB. Check the right arm by placing it flush on a flat surface and see if the crank mounting bolt hole is where it should be. If everything checks out, it may be time for a chase and face job, or for an experienced mechanic to take a look for you.
Good luck.


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## Axis (Mar 11, 2004)

fyi with the imperial 23t and a standard profile sprocket bolt I have no issues witht he chain hitting the bolt.


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## boyfromthelak (Feb 16, 2004)

that good to kno all my friends rock primos that run the smaller chainrings so i just new from there expierience


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## joelalamo45 (Aug 3, 2006)

My advice would be to take your bike to your LBS and have them check it out. Chances are they could fix it for you in about 5 minutes.


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