Removing a stuck chainring bolt

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Sweep
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Re: Removing a stuck chainring bolt

Postby Sweep » 20 Oct 2019, 10:16am

Go for a ride mick :)

On a related point, while brucey is here, is there a recommended way to tighten the bolts?
Am I right in assuming that you work on opposing pairs (or pairsish with 5 bolt spiders) , tightening gradually gradually, to keep everything balanced?
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Mick F
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Re: Removing a stuck chainring bolt

Postby Mick F » 20 Oct 2019, 10:51am

Can't today, and it'll be Wednesday before I have chance.
Up in Llandindrod Wells Monday and Tuesday handing over the fabled RSW16. I could ride it the couple of hundred yards to the museum!
Better still, let Mrs Mick F ride it! :D

Yes, that's the way I do the bolts up. Loose at first, then finger-tight and make sure all the things seat properly. Then I go opposites ....... and then round counting one two three four five to check 'em.
Mick F. Cornwall

Brucey
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Re: Removing a stuck chainring bolt

Postby Brucey » 20 Oct 2019, 11:02am

Sweep wrote:Go for a ride mick :)

On a related point, while brucey is here, is there a recommended way to tighten the bolts?
Am I right in assuming that you work on opposing pairs (or pairsish with 5 bolt spiders) , tightening gradually , to keep everything balanced?


what you describe is like the usual method for tightening multiple bolts between two (fairly rigid) parts. If there are five bolts (say) then you would usually be advised to tighten them in stages, in a sequence such as 1,3,5,2,4. The reason for this is that if the bolts are tightened fully, in one go, in any sequence, from full slack, then

a) the part may distort when the first bolt is fully tightened
b) the part may move when the first bolt is fully tightened
c) the part may not be seated correctly as soon as the first bolt is fully tightened

It is not a bad idea to tighten chainring bolts using a similar method, because some of the same things can happen. However if the seating for the chainring is distorted (eg one bent or twisted spider arm) then the chainring will distort regardless; chainrings are almost invariably far less stiff than the spider they are connected to. Plenty of chainrings are made badly enough that if you install and tighten just one bolt, you probably won't even be able to fit some of the remaining bolts.

Thus (IMHO) the best method is to

a) fit all the bolts loosely, and then
b) just nip them up (eg twirling the shaft of the allen key in your fingers).
c) double-check that the chainring is seated and also that the sleeve parts of the bolts are fully seated. Then
d) go round the bolt pattern and half tighten them all
e) repeat using full torque.

The main purpose of this is to use low enough torque in b) that even if there is some issue with the chainring or bolt seating, no damage is caused through premature bolt tightening. If fitting new (or different) chainrings, in a) it is a really good idea to check that the sleeve part of the bolt starts through the big ring, yet doesn't poke out beyond the depth of the counterbore; if it does then you need shorter bolts. If the sleeve is so short it doesn't start through the big ring, this is also unsatisfactory. Either situation can arise because chainrings vary in exact thickness and counterbore depth.

If you need to shorten bolts it is easy enough to shorten the sleeve parts, but there is a catch; the upper part of the sleeve is usually relieved, i.e. it may have no threads in it for ~1mm. This is often done because the male part of the bolt also has no threads on it near the head. Thus a matching pair of bolt halves will pull up until the head touches the top pf the sleeve, but a badly made or shortened sleeve may not permit this without the threads binding.

Because used bolts are often dirty, and/or the parts may not fit one another perfectly in various ways, I recommend that having cleaned and greased the bolt threads, it isn't a bad idea to run the male part into the sleeve fully and make sure that there is no binding and that the head will pull up far enough (preferably so that it contacts the top of the sleeve). If the bolt halves won't run into one another smoothly, then this can cause problems when tightening the bolts; you shouldn't need a spanner to hold the sleeve part of the bolt; if you do, it normally means there is something that is not quite right.

cheers
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Re: Removing a stuck chainring bolt

Postby Sweep » 20 Oct 2019, 11:07am

Thanks brucey.
Sweep

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Re: Removing a stuck chainring bolt

Postby Brucey » 20 Oct 2019, 11:20am

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


does the grease (that shouldn't be there IMHO) in the interface between the chainrings and spider change colour so that it comes out black and horrible after a few thousand miles? If it does then there has probably been persistent movement.

With greased interfaces this would be a very likely outcome for lots of riders, e.g. many racers (extremely high loads during sprints and hill climbs) and mountain bikers (small BCD = high loadings).

As I mentioned previously if the chainring is a really good fit on the shoulders of the spider, this may limit the amount of movement that occurs and the assembly may appear to be satisfactory, even though movement is occurring.

cheers
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Re: Removing a stuck chainring bolt

Postby Mick F » 20 Oct 2019, 2:33pm

The bolts get dirty.
Dirty from chain muck and the chain lube, just like the other parts of the transmission.
No fretting or creaking.

I've had fretting and creaking on a bike, but grease has stopped it.
Saddle rails and clamps for instance, and quill stems into steerers as well.
Mick F. Cornwall

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Re: Removing a stuck chainring bolt

Postby Brucey » 20 Oct 2019, 4:52pm

Mick F wrote:The bolts get dirty...


but does the grease (that shouldn't be there) between the chainrings and the spider turn black?

A long time ago I experimented with this and my grease turned as black as hades after a few (fair weather) rides; compelling evidence that the parts were on the move. When they move like that they (eventually, if you pedal hard) come loose and/or start creaking. Parts of better tolerance go for longer before this happens.

The other places where you have put grease to 'stop creaks' are ones where the parts are very flexy and/or the clamping forces are not high enough to (ever) prevent movement. Nor do they see the full load from pedalling with every pedal stroke.

A lot of this discussion is a bit like the 'do you grease crank tapers or not?' discussion. Some folk lubricate their tapers with all kinds of weird stuff and say 'it works for me' but others know full well that if they were daft enough to do likewise they would have a set of wrecked cranks on their hands after one or two rides. The difference is often in how the bike is ridden.

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Re: Removing a stuck chainring bolt

Postby Sweep » 20 Oct 2019, 5:01pm

New point alert.
So your opinion brucey is that you definitely should NOT grease the taper interface?
Honest question, honestly interested in your opinion.
Must admit i do grease but as i have several bikes may have been saved.
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Re: Removing a stuck chainring bolt

Postby Mick F » 20 Oct 2019, 5:47pm

Brucey wrote:
Mick F wrote:The bolts get dirty...

but does the grease (that shouldn't be there) between the chainrings and the spider turn black?

No, never.

The grease SHOULD be there in my experience.
Any grease is fine. Copper grease is better.

I think that both my bikes have a mixture of copper and general purpose. Go back years, and it was always general purpose grease.

Make sure the bolts are tight.
Mick F. Cornwall

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Re: Removing a stuck chainring bolt

Postby Brucey » 20 Oct 2019, 5:57pm

Re greasing tapers; the clue is when you take apart a crankset where the cranks have been in situ, not moving around or coming off, despite being given merry hell for ages. What you will usually find is that there has been aluminium transferred from the crank to a square taper spindle, and that the coefficient of friction between the two parts is very high (because there has been some cold welding). The disassembled interfaces will be dry, not slobbered in grease.

However the trick is in how to get from 'here' to 'there', and the best method varies with the parts.

Campag say not to grease.

Shimano say to grease and to use a higher torque on the bolt. Only shimano grease is like dishwater (relatively speaking; it doesn't appear to have any solid lubricants or EP additives in it, and it certainly isn't waterproof) so if you put a little bit in the joint it probaby won't last long anyway.

My opinion is that the shimano recommendation to use grease and a high torque is because their parts are not exactly dimensioned precisely and that when you (over) tighten the bolt the parts deform and 'size' to one another. Thus new parts that don't fit exactly are made to when fitted together under very high force. After a short while grease is squeezed out/washed away (just like it is in hub bearings, ahem) and the parts mate for life.

Lubrication is not required in campag parts because they are made to better fit one another from the word 'go'. Nor is it required when you refit shimano cranks onto the same BB spindle in the same position.

If new shimano (and other) cranks are tightened to about 50% torque and then removed, you will be able to see where the tapered joint has made contact and where it hasn't. The contact area is 'disappointingly small' in most cases, and only becomes adequate once the full torque is used on an interface that has some lubrication rather than none.

This can all go horribly wrong if

a) the cranks are subject to really high service loads before the lube has had a chance to get negated/squeezed out fully/washed away.
b) the bolt isn't rechecked after a period of use
c) a better grease (more persistent, containing solid lubricants and EP additives) is used.

Note that the pressure inside the tapered joint is huge; about x100 more than in a simpler bolted joint (like a chainring interface) so anything that is fluid will soon get squeezed out of the joint, but solids, thickeners etc may be left behind. Note also that many riders simply don't pedal hard enough to challenge the joint, so may get away with setups which are substandard.

Note that if there is a little movement within the joint, it will occur under very high pressure, and under those extreme conditions the local transient temperatures are very high; this may mean that the remaining grease/oil can react (eg burn) and no longer persist as a useful (harmful) lubricant per se.

cheers
Last edited by Brucey on 20 Oct 2019, 6:10pm, edited 1 time in total.
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Re: Removing a stuck chainring bolt

Postby Brucey » 20 Oct 2019, 6:02pm

Mick F wrote:
Brucey wrote:
Mick F wrote:The bolts get dirty...

but does the grease (that shouldn't be there) between the chainrings and the spider turn black?

No, never.

in which case your conditions of use are different from mine (and a lot of other people's)

The grease SHOULD be there in my experience.
Any grease is fine...


Please try and find a competent recommendation that says that you should put grease in that interface. My guess is that you won't find one. Greases vary enormously; if it were really doing you any good it would matter which one it was for sure.

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Re: Removing a stuck chainring bolt

Postby Mick F » 20 Oct 2019, 6:10pm

Have it your way Brucey. Recommend what you want.
Bored with this now.

I'll carry on regardless and recommend that people grease their chainring bolts as I have always done.

You pays your money, and you takes your chance. Do as you please.
Mick F. Cornwall

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Re: Removing a stuck chainring bolt

Postby Brucey » 20 Oct 2019, 6:17pm

Mick F wrote:I'll carry on regardless and recommend that people grease their chainring bolts as I have always done.
.


except that you are not recommending that you grease the bolts, you are recommending that you grease the interfaces that the chainring sit on as well. Greasing bolts is something that is widely recommended because it is a Very Good Idea. Greasing the chainring interfaces isn't, because it, er, isn't.

Do what you like (I'm sure you will... :wink: ), but recommending that other people follow your example when isn't recommended (by anyone, as far as I can tell) and it definitely doesn't work for many other riders doesn't make sense.

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Re: Removing a stuck chainring bolt

Postby Sweep » 20 Oct 2019, 7:19pm

Thanks for the square taper reply brucey.
All mine shimano.
I tighten the bolts good and tight and always check for tightness after i have ridden for a bit post- fitting.
Sweep

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Re: Removing a stuck chainring bolt

Postby Mick F » 21 Oct 2019, 8:22am

Yes.
Check after a ride.
I don't grease the ST Campag BBs, and didn't with the Stronglight 651 either.

Square tapers need a good clean mating surface to work. Any taper joint is the same and you shouldn't grease.
Not sure what Mr Shimano says on the subject but as I'm unlikely to ever use one, I've never paid much attention to the subject from that side of the house.
Mick F. Cornwall