Self-extracting crank bolt problem

[jessand]

Carrying out my usual post winter service today and was removing the cranks. I fitted self-extracting crank bolts when I fitted the chainset as I thought it a good idea. I removed the non-drive side easily enough but had to use a lot of force (8mm hex key) and it suddenly came loose. The aluminium part of the bolt (the part that has the pin spanner holes in) had sheared off leaving half of it inside. Fortunately, I was able to get enough of a crank extractor tool in and by putting a nut inside the crank was able to pull the crank off. I should say it took me quite a while to work out how to do it!

I previously had an Ultegra chainset with self-extracting bolts and it worked faultlessly for over 10 years. I always use plenty of anti-seize so I am surprised to have had the problem. Anyone else had this problem?

I also had a job to remove the drive side pedal (turning it the right way) although it succumbed to penetrating fluid and a hex key in the vice. They are A600s which have no flats for a pedal spanner. I'm sure I read a while ago I read that Brucey was suggesting using grease on pedal threads rather than anti-seize (I use Coppaslip). A search didn't find it though, perhaps someone could enlighten me - Brucey??

[Brucey]

octalink and ISIS should be greased where they engage whereas square taper cranks (IMHO) need not be greased at all (or only when they are first fitted if the fit is poor and the crank needs to 'size itself' to the BB spindle). Using an anti-seize compound on any of these interfaces is not recommended; if you pedal at all hard then the interface will probably move and wear, whereas it is meant to (essentially) cold-weld itself in the case of ST and not move in service. Regarding Isis and octalink if the cranks go on and off a few times the fit can become poor and then it is a good idea to use a little Loctite on the interface rather than a little grease, and to prepare yourself for a fight whenever the cranks come off.

Problems with self-extracting crankbolts are not uncommon. Plenty of people find that if the cranks are on well enough not to move around and cause problems in service, then self-extracting crankbolts won't be reliable either.

Regarding pedal threads, I think that lots of grease is the best way when you are fitting a set of pedals (with full shoulders on the spindles) into any given set of cranks for the first time. The reason is that the joint may settle slightly and the pedal ought to be able to precess in order to self-tighten and anti-seize compounds might allow movement but not precession. When refitting the same pedals anti-seize is OK (the joint will already have settled) and if the pedals have not got a full shoulder then precession is inhibited in any case; tightening more than normal is probably the only way of being reasonably sure that the pedal isn't going to move around in service.

cheers

[Airsporter1st]

I believe copper-based anti-seize can cause its own problems of electrolysis where dissimilar metals are involved. I used this stuff http://agaus.com.au/product/weicon-anti-seize-high-tech/ industrially, and also on my bikes.

[jessand]

Many thanks both.

Brucey

The bb is square taper with nothing applied it was the s-e crank bolts where I'd used Copaslip, but I take your point. My pedals had been on and off a few times so they should have been OK with anti-seize. Isn't it strange that these things crop up after many years of riding all year and using the same products and servicing routine with no problems at all!

Airsporter

Thanks for the link, I'll investigate that.

[Brucey]

FWIW if you run the joint at some fantastic temperature you do need to worry about what is in your anti-seize. But otherwise you don't, not really. For example the Royal Naval approval for Rocol copper grease says that it can be used on any combination of materials.

cheers

[Gattonero]

Carrying out my usual post winter service today and was removing the cranks. I fitted self-extracting crank bolts when I fitted the chainset as I thought it a good idea. I removed the non-drive side easily enough but had to use a lot of force (8mm hex key) and it suddenly came loose. The aluminium part of the bolt (the part that has the pin spanner holes in) had sheared off leaving half of it inside. Fortunately, I was able to get enough of a crank extractor tool in and by putting a nut inside the crank was able to pull the crank off. I should say it took me quite a while to work out how to do it!...

That sounds like there was friction in between the crank bolt and the self-extracting cover. There should be a thin plain washer in between, and best to grease the interface in between those two.
Sometimes you get those self-extracting covers not manufactured correctly and their fit is a tad loose, this makes them to unscrew when the pressure of the crank bolt been removed pushes onto. In fact, is better to fit those rings with a bit of threadlock on their threads (not on the crank threads) to prevent them from moving.

[andrew_s]

Yes, some aftermarket self-extracting bolts aren't as good as they might be.

I stripped the threads of a Middleburn self-extractor cap one time (fully home, torque no more than normal).
Fortunately the (square taper) crank threads were undamaged, so it was just a case of spending some time picking the crank threads clean and using a normal crank extractor.

Since then, I've treated self-extracting bolts as something to use out on the road, and removed the self-extractors beforehand for home maintenance.

[Marcus Aurelius]

The last self extractor bolt I had stick on me was a nightmare. I had to use a dremel multi tool to cut it off. I hate them. I use these now.

https://www.tredz.co.uk/.Wheels-Manufac ... gJ4gvD_BwE

[tatanab]

I've been using self extractors for 20 years now on 5 machines. These are after market ones I bought when I lived in the USA. Some have titanium screws, some steel. All have aluminium caps. I liberally smeared copper grease when I assembled them. I take my cranks off probably every year as a part of cleaning muck from the chainrings, and I use the bolts to tighten the cranks in place as well. So the bolts are used regularly and I have yet to have a problem. Maybe I've just been lucky, or maybe the ones I have happen to be exceptionally good.

[Gattonero]

I've been using self extractors for 20 years now on 5 machines. These are after market ones I bought when I lived in the USA. Some have titanium screws, some steel. All have aluminium caps. I liberally smeared copper grease when I assembled them. I take my cranks off probably every year as a part of cleaning muck from the chainrings, and I use the bolts to tighten the cranks in place as well. So the bolts are used regularly and I have yet to have a problem. Maybe I've just been lucky, or maybe the ones I have happen to be exceptionally good.

Threads work by slight elongation in them, this creates friction in their flanks and keeps them in place. When the self-extracting collar is made of alluminium, this is a material that does not like elongation, also if the threads are simply "cut" this creates a fracture point in a thin section.
This is the reason why self-extracting bolts have a head that is slightly smaller in the OD of their flange, to leave more room for a thicker collar.
Is also important the amount of thread available for the extractor, some cranks offer a very shallow thread that may not give full engagement.

[Airsporter1st]

FWIW if you run the joint at some fantastic temperature you do need to worry about what is in your anti-seize. But otherwise you don't, not really. For example the Royal Naval approval for Rocol copper grease says that it can be used on any combination of materials.

cheers

I’m not doubting that what you say is true, but I find it very strange because I have a marine background where copper based anti-seize was a complete no-no due to the risk of electrolysis that it engendered. However I now wonder if I’ve got that right, because the conductivity of the grease would actually keep everything at the same potential. I will look into this a bit more.

[jessand]

That sounds like there was friction in between the crank bolt and the self-extracting cover. There should be a thin plain washer in between, and best to grease the interface in between those two.
Sometimes you get those self-extracting covers not manufactured correctly and their fit is a tad loose, this makes them to unscrew when the pressure of the crank bolt been removed pushes onto. In fact, is better to fit those rings with a bit of threadlock on their threads (not on the crank threads) to prevent them from moving.

Yes I think you're right. I've decided to go back to standard bolts, the idea of being able to remove the cranks with an Allen seemed attractive at the time but as I've only ever removed cranks at home it's not a huge benefit. I'll let you know when I've broken down miles away and could have fixed if I'd had SE crank bolts!

I assume my old Ultegra cranks worked so well because the SE bolts were factory fitted (they did work smoothly) - or perhaps they work better with Octalink than my current square taper?

Thanks for all the replies.

[slowster]

I'll let you know when I've broken down miles away and could have fixed if I'd had SE crank bolts!

Ison Distribution still have some of the old 'Cool Tool' crank extractor tools if you want to take a very small light(ish) (42g) crank removal tool instead of using self-extracting crank bolts.

Disclaimer: I don't know how good they are, since although I bought one when I originally bought a Cool Tool, I have never used it or felt the need to take it out with me, and it ended up just sat in my toolbox. It requires either an 8mm hex key or 14mm spanner (both the hex socket and the spanner flats are a bit shallow for my liking).

Whereas the two part design of the typical crank extractor allows the tool to be fully screwed into the crank before the bolt part is turned to press against the axle and pull the crank off it, for the Cool Tool crank extractor it is the actual screwing in of the tool into the crank threads that presses the tip of the tool against the axle. I imagine that it would work OK providing the depth of the crank thread was sufficient for the tool to be well engaged before it started to press against the axle, although I would not use it if I had my workshop tool available (especially if it was someone else's bike with cranks that had possibly been over-torqued and/or never removed for many years).

http://www.ison-distribution.com/englis ... rt=2CLTLCE

[Brucey]

I assume my old Ultegra cranks worked so well because the SE bolts were factory fitted (they did work smoothly) - or perhaps they work better with Octalink than my current square taper?.

Octalink bolts use a much larger screw thread (which will withstand larger loads quite easily), have stronger steel collars (IIRC) and have a fairly well-defined extraction force (because the fit is not on a taper). All these things are not the case with square taper, so yes, octalink is likely to work better with SE bolts.

Consider that there is a wide spectrum of crank extraction loads required, and occasionally ST cranks are so well set on the spindle that a workshop tool or the crank is wrecked when it is employed. ST SE bolts are a small fraction of the strength of a workshop tool; IME there is a range of extraction loads that ST SE bolts just won't manage.

cheers

[jessand]

Thanks Brucey, that explains the different experience with the Octalink. I've just fiitted the replacement Spa cranks which arrived today - using standard bolts.