Why does my left-crank arm come loose every.time.I.ride?!?!

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8/2/2014 5:00 PM

it's only my left (non-drive side) crank arm, and the f'er comes loose (to the point of falling off the spindle) every time i ride for over 10min...
I carry a wrench and an allen key when riding, and have to constantly tighten the spindle's bolt then the crank-arm pinch-bolt.

Alignment looks great yet the thing constantly falls off desapite how tight i put it. I don't know what to check... can the spindle's teeth get chipped/bad and cause this? everything in the drivetrain looks great and i'm just at a loss as to why this happens, i mean it looks so perfect that even half-way loose nuts shouldn't cause this floppy crank/spindle connection, yet i can tighten them to hell and they still separate after a minimal amount of riding sad

any thoughts/tips/suggestions on what to check are incredibly appreciated!!

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8/2/2014 5:03 PM

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YOU AVIN A LAUGH M8?
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The Trailest Bike On Vital

8/2/2014 5:21 PM

What cranks?

If they have a pinch bolt, tighten that.

If they don't, then make sure you have a spacer between your bearings, crank it down and USE BLUE LOCTITE.

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"Hey anybody ever make that mistake like right when you wake up in the morning and you believe in yourself?" -Kyle Kinane

"BIKES!" -Tom Segura

8/2/2014 5:25 PM
Edited Date/Time: 8/2/2014 5:26 PM

dave lawrence wrote:

What cranks?

If they have a pinch bolt, tighten that.

If they don't, then make sure you have a spacer between your bearings, ...more

if you use red it will never come off , unless you use a blowtorch

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8/2/2014 6:08 PM

bmxsteve99 wrote:

if you use red it will never come off , unless you use a blowtorch

Not always, my friend has the Animal BPE pedals and he used red loc-tite on the threads because they kept coming loose, and they STILL came loose even when we caked that shit on and let it sit for awhile. I know it wasn't the loc-tite's fault cause it's the same stuff I've used on other stuff that needed a blowtorch to take off.



As for the original question, a lot of factors can be the issue, check the following

-if you don't have an internal BB spacer, they can come loose
-if your crank arm isn't on the spindle enough or too much, it can come loose (you want the arm to be at least 3/4 the way on the spindle, but not on so much that the spindle pushes through the other side & bottoms out.)
-if your crank is developing the "profile wobble", check and see if when the bolts are tight, if the crank arm can be moved up & down on the spindle slightly (not side to side), this indicates that your splines are wearing out & is why it keeps coming loose
-if your threads in the spindle and the bolt are still good and not stripped
-if your bearings are still good, bad bearings can cause wobble and wiggle the cranks loose overtime


check those & report back.

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8/2/2014 7:41 PM

Blue loctite, Grease the bolts, tighten the compression bolt first then the pinch bolt. If those methods don't work, I would get some new cranks (if it were me)

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I ride to stay on two wheels and have fun!
BIKE CHECK

8/2/2014 8:56 PM

your having problems with it staying on, and repeatedly reattaching it, did you install the spindle and cranks yourself or did a bikeshop? seems to me the most likely situation is that your spindle's threading is stripped.

take your cranks off, and screw the bolt in, then tie a rope around the bolt head and try pulling, if u feel it give, its stripped.

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8/3/2014 1:24 AM

I have an idea but you probably have it right.

make sure they aren't on back to front. If they are they will always come loose

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The first breath is the beginning of death

8/3/2014 12:18 PM

If it keeps coming loose and you've ridden it this way, the splines on the arms and spindle are likely to be pretty worn.

If this is the case, it will probably keep coming loose.

It might be time for a new crank.

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Chris

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8/7/2014 1:53 PM

what i'm thinking :/ thanks

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8/7/2014 5:05 PM

Now that I saw this post, my 48 spline cranks are coming loose every once in a while. damit

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I ride to stay on two wheels and have fun!
BIKE CHECK

8/7/2014 5:10 PM

MidWestBMX wrote:

Now that I saw this post, my 48 spline cranks are coming loose every once in a while. damit

thats profile wobble, and nothing short of welding the crank boss to the spindle is going to stop the wobble after it develops fully

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refs: hookjrclc, hardbmxtim, hatchmoses for sale and trade, kymike for sale and trade, blizzbikes for trade, and some other dude i cant remember his username, vrsapat956, colonydirt94, mario.villegas90, wolfen
Camera Setup: Panasonic HMC150, Panasonic GH2, Canon FTBn, Yashica Lynx 5000e, Canon 28mm f/2.8, Canon 50mm f1.4, Rokinon 7.5mm f/3.5

8/7/2014 5:42 PM

good thing they are 2 pc cranks and the left is coming loose!
great. -_-

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I ride to stay on two wheels and have fun!
BIKE CHECK

8/8/2014 12:25 PM
Edited Date/Time: 8/8/2014 12:32 PM

MidWestBMX wrote:

good thing they are 2 pc cranks and the left is coming loose!
great. -_-

Is the left the removable arm or is the right?

Snug them. Add a BB spacer so you can crank em tight. Add spindle spacer if your bolt bottoms out.

My 48 spline 1948s loosen up about once a month or so.

Just give your bike a good check over once a week, and carry some basics to check it when out and about.

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"Hey anybody ever make that mistake like right when you wake up in the morning and you believe in yourself?" -Kyle Kinane

"BIKES!" -Tom Segura

9/4/2017 3:34 PM

MidWestBMX wrote:

Now that I saw this post, my 48 spline cranks are coming loose every once in a while. damit

bmxsteve99 wrote:

thats profile wobble, and nothing short of welding the crank boss to the spindle is going to stop the wobble after it develops ...more

Call Profile, they will hook you up IF you have Profiles. I have always just called Mat and he sends me a new arm/spindle/bearings whatever the problem is.

If they aren't Profiles, what type spindle and what brand? Example: Spline 48/Kink...if I know the information I might be able to help you out. Thanks to how long I have rode, I have some friends at nearly every company. They really come in handy

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9/4/2017 4:29 PM

Mine did that but I changed the bolt to another one and it was fine. Mabey just by new bolt.

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