Removing a stuck chainring bolt

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Brucey
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Re: Removing a stuck chainring bolt

Postby Brucey » 18 Oct 2019, 4:51pm

if you have a new chainset the best thing you can do is to remove the bolts (one at a time) then grease the outer part of the male (bolt) part and the inner part of the female (nut) part. This ensures that there is grease on the entire screw thread (which there won't be if you coat one part only).

If you are giving it the full treatment you make sure that the parts will screw into one another fully before reassembling and retightening on the chainset.

NB it is not necessary (or desirable) to grease anything else; greasing the outside of the 'nut' and/or the interfaces between the chainrings and the spider is 100% counterproductive; it just means the assembly is more likely to fret, creak, and work loose. All those surfaces should be clean, dry, and grease-free.

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Mick F
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Re: Removing a stuck chainring bolt

Postby Mick F » 18 Oct 2019, 5:02pm

Should be?

Sorry, but I've lathered my chainring bolts and mating surfaces as far back as I can remember having them.
Never had the need for a tool to hold the slotted inner bit, and never had any fretting or issues.
All chainrings have been nice and tight, and come off when I wanted them to.

All of them, going back 40years or so.
Mick F. Cornwall

Brucey
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Re: Removing a stuck chainring bolt

Postby Brucey » 18 Oct 2019, 5:15pm

I've seen very many chainrings that worked loose and fretted, and if there is lubricant present it just happens more easily/quickly/quietly. Interfaces that you don't want to move are often better off left dry; they are less likely to move and if they do, they are more likely to make a noise, so won't go unattended.

If you look very closely at used chainring/spider interfaces you will very often see small black marks, covering a small percentage of the interface area. This will be where the surfaces have been contacting one another, and the blackness usually means there has been some rubbing/movement.

Note that if the chainrings are a really good fit on the spider shoulders (some brands not others) then the chances of movement are reduced somewhat.

There are only a few places on bikes where grease is positively harmful; IMHO that is one of them.

cheers
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merseymouth
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Re: Removing a stuck chainring bolt

Postby merseymouth » 18 Oct 2019, 5:49pm

Hi there, I was taught to clean them up to de-grease them, then assemble them with the thread coated in Rubber Solution. Nip up nicely, then they won't seize or vibrate loose. Works for me. TTFN MM

Brucey
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Re: Removing a stuck chainring bolt

Postby Brucey » 18 Oct 2019, 10:45pm

Fretting at the chainring interfaces is so commonplace that I don't recommend threadlock or anything like that on chainring bolts. If the chainring starts to fret and the joint settles, IME the problem never starts with the fastener backing out, even though the bolt appears to be 'loose' it is evident that the threadlock hasn't failed and allowed the joint to come loose; the clearances in the joint have changed. If/when fretting occurs the bolts quickly lose their grip and the chainring is held less well, more fretting occurs, etc etc. Threadlocking agents prevent retorquing of the bolts. You won't lose the bolts but you might end up riding round with chainrings moving around on the spider.

Chainring bolts are very short and this means they don't stretch much when tightened. This means they need to be very tight indeed (to the full torque specified and no less ) else they will probably loosen in service, should the smallest amount of settling occur in the joint.

One of the problems with grease in the spider interfaces is that it doesn't get pushed out immediately. This means the joints settle and the bolts always need to be retightened the next day even if the bike is not ridden. (Aside; The same thing happens if you use copper ease between a car brake disc and the flange it sits on; if you do this and the wheel studs clamp across this interface too (which they do in most cars) a correctly torqued road wheel will be loose the next day. Grease in bolt threads is usually pushed out of the way because the loadings are so much higher and there is shearing which helps to displace the grease too) Regardless of the state of the joint/bolt if you do ride the bike hard and some movement occurs then the joint again settles and the bolts need retightening.

I suspect (but don't know for sure) that in the factory, chainring bolts are routinely tightened to a torque that is in excess of that specified for later service. The reason I think this is that

1) factory bolts are usually incredibly tight; the breakaway torque is usually so high that I am in fear of the 5mm key socket stripping out
2) even though they are dry torqued, factory chainring bolts don't often allow the joint to settle and the bolt to lose tension.
2) when I fit new chainrings (to the recommended torque using greased bolts, on anotherwise dry joint) there is always a chance of the joint settling; I always recommend that the bolts are retorqued after a hundred miles or so
4) when I refit chainrings back in the same place again, the bolts stay tight, presumably because the joint has already settled and doesn't need to settle again.

I can only assume that the clamping load at the recommended torque is less than that obtained when the chainsets are assembled in the factory, and that the load then is high enough that the lumpy bits in the joint plastically deform and settle as the bolt is (over) tightened.

FWIW if you remove a chainring and the interface doesn't just show black high spots, but there is black gunge throughout the joint, this is a pretty good sign that the joint has been fretting away in a persistent fashion. With most chainsets if there is grease in the interface and you are a forceful pedaller, I would describe it as 'extremely unlikely' that there won't be fretting. I'd also describe it is 'extremely likely' that you will have to go back and retighten the bolts on new chainrings, even if the joint is dry, the bolts are greased, and they are torqued correctly; even if they go up another 1/8th of a turn, this means quite a lot of joint settling has occurred.

In bike shops the mechanics know that chainring bolts 'often come loose' and I think that they probably overtighten them too; having customers come back with 'loose bolts' is never good, even if the bolts have not actually backed out. When you are working on your own bike you can keep to the recommended torque level and check the bolts later. They are usually alright for ever after even if they go up another 1/8th of a turn when they are checked after a few hundred miles.

cheers
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Mick F
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Re: Removing a stuck chainring bolt

Postby Mick F » 19 Oct 2019, 7:02am

I'll be carrying on regardless.
I'll be doing as I've always done.
Never ever ever had an issue of fretting, loosening, or inability to undo them when I wanted to.

Much as I respect Brucey's knowledge and experience, it does't wash with me on this subject in my experience.
Mick F. Cornwall

reohn2
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Re: Removing a stuck chainring bolt

Postby reohn2 » 19 Oct 2019, 8:45am

I'm with Mick on this,copperslip on the threads.
I check all bolts and nuts on the bike once every couple of months or so in the time honoured way of going down each side of the bike with a couple of Allen keys and an 8mm spanner which covers all bolts and nuts,it takes about 5 minutes.
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Brucey
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Re: Removing a stuck chainring bolt

Postby Brucey » 19 Oct 2019, 9:28am

I'll be carrying on regardless.
I'll be doing as I've always done.....


do what you like; I can only tell you the best way of doing this, its up to you whether you do it or not. I have seen countless chainrings that moved around on their mountings and there were only ever two reasons for it;

1) the bolts were not tightened enough
and/or
2) there was grease or oil in the interface.

Chainring interfaces are one of those places where you need the higher friction that you get in a dry joint in order for them to be secure when they are assembled (this soon becomes apparent if you do the sums, and if you give a bike with greased-when-assembled chainrings to a strong rider they will wreck it within a week). Dry joint, greased bolt threads; that's the way to do it properly. I doubt very much that you will find anyone competent advising grease in the chainring to spider interface.

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Mick F
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Re: Removing a stuck chainring bolt

Postby Mick F » 19 Oct 2019, 10:31am

Not tight enough then.
Mick F. Cornwall

Brucey
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Re: Removing a stuck chainring bolt

Postby Brucey » 19 Oct 2019, 11:58am

Mick F wrote:Not tight enough then.


No; if you push hard on the pedals the friction coefficient of a well lubricated interface is not sufficient to prevent movement, even if the bolts are tight.

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Mick F
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Re: Removing a stuck chainring bolt

Postby Mick F » 19 Oct 2019, 3:13pm

Ok Brucey.
No complaints from me. You know what you know based on far more experience of these things than me ................ but I can press hard on the pedals and I've never ever ever had a chainwheel bolt come loose.

As I said, I will carry on doing what I do, despite your experiences.
Mick F. Cornwall

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Sweep
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Re: Removing a stuck chainring bolt

Postby Sweep » 19 Oct 2019, 3:30pm

Can I declare peace?
Sweep

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Mick F
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Re: Removing a stuck chainring bolt

Postby Mick F » 19 Oct 2019, 6:22pm

Yes! :D

A completely different subject was raised today with someone we know.
They had one idea, we had another.
Both ideas work.

There's at least two ways of coming at a situation. Neither/none are wrong, just different.
Mick F. Cornwall

Brucey
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Re: Removing a stuck chainring bolt

Postby Brucey » 19 Oct 2019, 11:37pm

if it works for you it works for you. But when you get a creaky chainring the most reliable fix is to clean the interfaces completely, then clean the bolt threads, regrease them and retorque the bolts.

In many rider's use if a bolt comes loose (say) and chain lube has been in the interface, it'll carry on moving if all that is done is the bolt is retightened. A greased interface is just as bad. However if the bolt is tightened onto a clean dry interface, you get enough cold welding that the surfaces are unlikely to move in service unless the bolts come loose, even if chain lube is splashed about afterwards.

Years ago I discovered that you could tighten the bolts up tight (so tight they were in danger of breaking) and a lube/debris -contaminated interface would still allow the chainrings to move about.

FWIW if you take your chainrings off and the interface/grease has turned black, this is a good sign of persistent movement having occurred.

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Mick F
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Re: Removing a stuck chainring bolt

Postby Mick F » 20 Oct 2019, 6:35am

Brucey wrote: .....But when you get a creaky chainring ........
.......... if you get a creaky chainring.
I've never had one.
Mick F. Cornwall