How to loosen chain ring bolts

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mercalia
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How to loosen chain ring bolts

Postby mercalia » 23 Jan 2015, 11:36pm

How to loosen chain ring bolts. I have managed to loose those that hold the outer and middle ring to the arms ( the bolts gointo nut inserts) but I can not loosen the bolts that hold the small outer ring to the aluminium base of the cranks. The have never been undone before and been installed for 14+ years, I dont want to damage the cranks, I dont really want to remove the inner ring but have to to change the middle ring ( I can not remove the nut inserts as they are fouled by the outer ring teeth), Any ideas?

Brucey
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Re: How to loosen chain ring bolts

Postby Brucey » 23 Jan 2015, 11:50pm

a good start is to spray penetrant in through the holes in the bolts. If they are very stubborn it make take the combined persuasive abilities of a miniature blowtorch and a torx bit hammered into the bolts (once you have failed with a 5mm key) to shift them.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Valbrona
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Re: How to loosen chain ring bolts

Postby Valbrona » 24 Jan 2015, 1:13am

T or P handle hex wrench.
I should coco.

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Mick F
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Re: How to loosen chain ring bolts

Postby Mick F » 24 Jan 2015, 7:25am

It's a bit late for you, but what you should have done was release them periodically, and dab a bit of copper grease on the threads. Fourteen years is way too long for leaving anything untouched.

If I were in your position, I'd do as Brucey suggests and use some penetrating oil for a time - few days maybe. Possibly warm up the crank gently in a warm oven - not HOT! - just warm. After the penetrating oil has done its stuff, and you've warmed it up, it could shift.

Keep us informed please.
Mick F. Cornwall

pete75
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Re: How to loosen chain ring bolts

Postby pete75 » 24 Jan 2015, 8:14am

If you're using releasing fluid you may find plus gas works best.

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Mick F
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Re: How to loosen chain ring bolts

Postby Mick F » 24 Jan 2015, 9:03am

+1
Far better than WD40 or thin oil.
Mick F. Cornwall

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gentlegreen
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Re: How to loosen chain ring bolts

Postby gentlegreen » 24 Jan 2015, 9:48am

how did you make chainrings last 14 years ? !!

mercalia
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Re: How to loosen chain ring bolts

Postby mercalia » 24 Jan 2015, 11:16am

gentlegreen wrote:how did you make chainrings last 14 years ? !!


This Dawes 1-Down was my spare bike that I didnt use much until my other tourer was trashed a few years ago, so has been in storage really, thats why the frame particularly is almost mint. The middle chain ring has a bit of wear compare to the new one I also have ,is still ok I think just thinking of the future as this will be my final bike so want to keep it going for a very long time.

Brucey
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Re: How to loosen chain ring bolts

Postby Brucey » 24 Jan 2015, 12:49pm

chainrings can last a long time if you choose them carefully and keep on top of your chain wear and cleanliness. Plenty of riders have stuck 30-40000 miles into quality chainrings eg steel or 7000 series (campag, or 'zicral' etc) ones. If you use tiny chainrings with half-height teeth, made of cheap rubbish and then let your chain stretch too much, they won't last a tenth of that time.

BTW the recommendation of using a micro-blowtorch is based on having freed off many such bolts. If you apply an oil with a high flashpoint (such as ATF) you will be able to get the bolt (NB the bolt alone, not the crank) to about 250C for a few minutes without charring the oil too badly. At those temperatures the oil is probably thinner than plus gas is at room temperature. Repeated heating and dousing in oil will drive out the oxide hydration (you will see steam bubbling out through the oil) and the water will be replaced with oil. After a few cycles the bolt will come free and can often be re-used if necessary; this time refitted with copper ease.

The reason this works is that oxides normally hydrate and when hydrated, they swell up and this is what jams the bolt. Heat cycles remove the water, reduce the swelling, and the oxide structure is also physically broken down by the thermal stresses.

The micro-blowtorch avoids gross heating of the crank that could damage it (by altering the heat treatment condition of the aluminium, or by simply damaging the finish).

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

mercalia
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Re: How to loosen chain ring bolts

Postby mercalia » 24 Jan 2015, 3:24pm

well in the end didnt need to just used a much longer lever so all ok

pete75
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Re: How to loosen chain ring bolts

Postby pete75 » 24 Jan 2015, 5:02pm

Brucey wrote:
BTW the recommendation of using a micro-blowtorch is based on having freed off many such bolts.

The micro-blowtorch avoids gross heating of the crank that could damage it (by altering the heat treatment condition of the aluminium, or by simply damaging the finish).

cheers



Believe me using one of those can get you into a lot of trouble. I thought it would be a good idea to use one for something similar and found a very nice one in the kitchen cupboard. All seemed to be going well until my wife caught me using it......... :(

grani
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Re: How to loosen chain ring bolts

Postby grani » 24 Jan 2015, 5:38pm

pete75 wrote:
Brucey wrote:
BTW the recommendation of using a micro-blowtorch is based on having freed off many such bolts.

The micro-blowtorch avoids gross heating of the crank that could damage it (by altering the heat treatment condition of the aluminium, or by simply damaging the finish).

cheers



Believe me using one of those can get you into a lot of trouble. I thought it would be a good idea to use one for something similar and found a very nice one in the kitchen cupboard. All seemed to be going well until my wife caught me using it......... :(


Mine has migrated from the kitchen to its new home on the workbench. Not enough Crème brulees and too many old bike bits:-)