Author Topic: Aargh! Chainring nut stuck.  (Read 3386 times)

Andre Jute

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Aargh! Chainring nut stuck.
« on: January 20, 2012, 11:45:56 PM »
On a new Stronglight Impact Compact/Sugino Cospea crankset I was taking off the chainrings it came with preparatory to fitting a stainless steel chainring, when one of the chainring nuts gave a turn or two, and then stuck. The LBS also failed to shift it. The back of the steel chainring nut is already pretty mangled but doesn't stick out far enough to grab with a vise-grip. I don't care about the chainrings and new nuts can be bought. But I'd like to save the crank arms, which is what I bought the set for. What can I do? -- Hobbes

Hamish

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Re: Aargh! Chainring nut stuck.
« Reply #1 on: January 21, 2012, 12:06:57 AM »
I have drilled out chainring bolts before - easy on the middle/outer ring....hard on the inner ring.
 

JimK

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Re: Aargh! Chainring nut stuck.
« Reply #2 on: January 21, 2012, 12:09:45 AM »
Have you soaked the mess in WD-40 or some such unsticking fluid?

I stripped the chainring threads on a bike a year ago or so. That inspired me to apply some copper grease there on my Thorn. Avoid such nastiness if possible!

Danneaux

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Re: Aargh! Chainring nut stuck.
« Reply #3 on: January 21, 2012, 01:02:51 AM »
Hi Andre,

I'm surely sorry you're having trouble.  Bring it by my (home) machine shop and I'll make it right for you in a blink!

Lacking that (I'm a ways from you...), you have a number of options, any or all of which are likely to work.

1) I agree with Hamish; drill it out.  It is possible the fasteners were cross-threaded in factory assembly.  It happens. If you go this route, I would start from the backside. The best way is to size the bit so it is equal to the OD of the chainring bolt shaft. It doesn't take much, and should do the job. I would place a hex key in the bolt socket to stabilize it while you drill; hold it, else the whole assembly will spin uselessly.  Pad the crankarm to avoid marring. Done with care, your arms will be unmarked and all you will need to replace is the chainring bolt/sleeve nut set, salvaging even the rings in as-new condition.

2) In the event you're dealing with galvanic corrosion (unlikely since you were able to turn the fasteners a couple turns), use a penetrating oil, solvent, or spray. My favorite is a co-polymer called PB Penetrating Catalyst ( http://www.blastercorporation.com/PB_Blaster.html ).  It will work when others don't, particularly on Honda and BMW fasteners, which are unusually prone to galvanic corrosion in their 10th year or so.  Liquid Wrench is another popular on my side of the pond, though doesn't work as well.  Lacking those, you might try opening a fresh can or bottle of Coca-Cola (Dr. Pepper will work in a pinch) and pouring it on the fasteners while periodically tapping lightly on the fastener itself.  The drinks are carbonated and contain traces of phosphoric acid (that's why they eat tooth enamel) and do a surprisingly good job at loosening stuck fasteners when more formal means are absent.  You may be tempted to use ammonia as when removing a seized quill stem or seatpost, but it will damage the aluminum.  So will lye.  

3) Often, the chainring bolts fail to fully penetrate the sleeve nut, leaving a small flange that will take a blunt-flush screw/bolt extractor (often referred to as an "Easy Out"). This can be used to stabilize the sleeve nut while you go at the bolt from the front.  If you've also managed to strip out the hex fitting, then another will work in the former socket.  The extractor will often work even with a flange too small to grasp with Vise-Grips (mole grips).

If these methods don't do the job, give a shout and I'll dive a little deeper into my bag of tricks. I had to go the whole nine yards on an in-tank fuel pump replacement last winter.  A whole tank of fuel (and the weight of it), and the line fittings had seized completely.  What a mess.  Got it loose with no damage, but it took a careful mix of thought, force, and patience.

Truly, best of luck Andre.  Let us know how you come out...

Dan.
« Last Edit: January 22, 2012, 07:04:24 AM by Danneaux »

Andre Jute

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Re: Aargh! Chainring nut stuck.
« Reply #4 on: January 21, 2012, 07:15:57 PM »
Thanks, all, gentlemen. The ring bolt and nut combo was cross threaded for sure. There was no sign of corrosion. I tried WD40 and had no joy. Then I tried the easy out, which Dan reminded me I have a kit of, and that just stopped my 550W drill dead in its tracks. I tried putting a spanner on the easy out but it just ripped out pieces of metal. So I drilled the nut out as i should have done in the first instance.

The chainrings are saved, but that doesn't matter to me as I have a Surly stainless steel chainring on order and presumably on its way to me, so the chainrings that came with the crankset are surplus to requirements (they're in any event pinned, which is irrelevant to me since I use a single chainring to drive a hub gearbox, and pins interfere with my Hebie Chainglider.