Frequent removal/refitting of square taper crank harmful?

[Drago]

You should remove them daily to thwart thieves. No harm will come of it.

 

[scotsbikester]

Thanks for some useful feedback folks. Looks like it's not a good idea, I'll find an alternative way to achieve what I want.

 

[Punkawallah]

Thanks for some useful feedback folks. Looks like it's not a good idea, I'll find an alternative way to achieve what I want.

Tease. What is it that you want? (What you really, really want)

 

[presta]

I can’t see you wanting to remove one on a daily/weekly/monthly basis

To change gear ratios between different types of ride would be my guess.

 

[Punkawallah]

To change gear ratios between different types of ride would be my guess.

It would be a lot simpler just to use a derailleur.

 

[fossyant]

Oh bugger - OP won't tell us why, I suspect he wants different gearing, but the wise person would fit a particular chain set that suits their needs and live with it.

 

[Yellow Saddle]

I'm late to the party here, but since I'm here for a contrarian view, I'll chip in anyway.

No, frequent removal and fitment of a square taper crank will not damage anything. But....there is a proviso or two.

1) You understand the proper torque in the first place and you stick to 40NM religiously.
2) You keep the bolt threads and taper lightly lubricated (with anything) when torquing the crank.
3) You make sure you have a washer between the bolt and crank interface.#
4) You don't forget the washer mentioned above in the crank when pulling it out.


Yes, it is a friction fit, but so what. Each fitment and removal doesn't remove any material, othewise you would have clearly seen the black aluminium rouge on the taper.

God alone knows why you would want to do it, but its your bike, go ahead. I'm opening a beer whilst I mentally savour all the benefits of hollowtech cranks.

 

[fossyant]

I'm late to the party here, but since I'm here for a contrarian view, I'll chip in anyway.

No, frequent removal and fitment of a square taper crank will not damage anything. But....there is a proviso or two.

1) You understand the proper torque in the first place and you stick to 40NM religiously.
2) You keep the bolt threads and taper lightly lubricated (with anything) when torquing the crank.
3) You make sure you have a washer between the bolt and crank interface.#
4) You don't forget the washer mentioned above in the crank when pulling it out.


Yes, it is a friction fit, but so what. Each fitment and removal doesn't remove any material, othewise you would have clearly seen the black aluminium rouge on the taper.

God alone knows why you would want to do it, but its your bike, go ahead. I'm opening a beer whilst I mentally savour all the benefits of hollowtech cranks.

Engineer above (Skolly) said it's not a good idea, as did I. Weekly, why the hell would you do that on any bike, it's introducing the factor of 'ham fisted' home bike mechanics with poor tools. We've seen enough on here, and in-ability to torque parts correctly by hand or using a tool.

Also, who has time to faff like this every week. Just ride.

 

[mickle]

In the olden days, when Stronglight 49D cranks were common, removal of the chainset was a regular event for some riders. If the chain fell off the small ring and found its way betwixt crank and bottom bracket there was no faster way of extracting it.

 

[fossyant]

But it's pointless, and a way of introducing user error. OP was coy about why. I don't remove parts just 'because'....

Track cycling, you'll change chain rings, and sprockets on the wheels, but you don't mess about with chainsets as much.

It would be good if the OP actually explained why...

Some scenarios.... I have two classic early 90's bikes, lovely to ride, but my bottom gear is 39x26. It's not so much fun grinding up really steep stuff on those bikes in my mid 50's, so I have one that has a 34x34. Now if there is an event that is 'old bikes only' and you can get a replica style chainset that is a compact, or sub-compact, then you might be laughing.

Both my classics are a little too new by a year or so for these events - there isn't a replacement chainset unless I buy something very different.

Just interested why we have such a question, TBH...

 

[Yellow Saddle]

Engineer above (Skolly) said it's not a good idea, as did I. Weekly, why the hell would you do that on any bike, it's introducing the factor of 'ham fisted' home bike mechanics with poor tools. We've seen enough on here, and in-ability to torque parts correctly by hand or using a tool.

Also, who has time to faff like this every week. Just ride.

I call appeal to authority.

Engineer above need not display a certificate, just post an explanation. The explantion is invalid, and I explained how.

The questions is not whether or not he/she should do it, just whether it will damage the crank.

Answer remains: no it will not damage the crank if you stick to the provisors.

 

[Drago]

How about the OP remove one-sided every day, leave the other side as the control sample, and report back in sixty years or so?

 

[I like Skol]

Answer remains: no it will not damage the crank if you stick to the provisors.

Stick to the provisors

With the best will in the world, the removal and refitting of a taper chain set is not something that can be repeated infinite times, it just can't, and you know that. Each time introduces a minute deformation of the materials (and let's be honest, the softer aluminium of the chainset is the sacrificial material here, not the hardened steel spindle) until eventually the chainset will 'bottom out' on the taper and not be secured by the retaining nut/bolt. Even under laboratory ideal conditions where the chainset taper interface is scrupulously clean and fitted to the book torque this is not an unlimited process and the described mode of failure will eventually occur. It may be hundreds of cycles down the lifetime of the components, but it will happen, and this time is hastened by frequent unnecessary repetition.

Also, we have to factor in the lack of adherence to the ideal procedure. I work in an industry where machines are serviced by hours and, to pick an example, there are tools that may be serviced at 1000 HR intervals. This involves a fairly intrusive strip down and I can usually tell who did the previous service by how stupidly tight the fasteners are. This is a high-vacuum machine, it pretty much holds itself together once pumped down and the bolts are there just to keep things in place until the vacuum forces take over, but this doesn't stop highly paid and expensively trained 'engineers' from tightening the fittings way beyond any documented values.

Do we think the average bike shop or DIY mechanic can resist exceeding the specified torque for chainset bolts because they 'don't want the cranks to fall off'?

For all intents and purposes, taper chainset removal has limited repeatability. If someone is careful and sticks to best practice this might be hundreds of times. In less ideal conditions, but with some mechanical sympathy it will be double figures. Some ham-fisted feckwits will achieve single figures!

 

[scotsbikester]

Thanks for some useful feedback folks. Looks like it's not a good idea, I'll find an alternative way to achieve what I want.

^^ As I said about half way through this thread.

But thank you all, yet again, for opinions you have offered.

Interestingly, I see a lot more responses if I don't log on. Many of them disappear when I do log on.

But there are some interesting, and varied opinions offered. For those of you who were conjecturing at my competence, no, I am not a "qualified engineer". But as one poster has pointed out, to declare myself as one, or give greater credence to somebody who did declare themselves as such, would be a perfect example of the fallacy of an appeal to authority.

My approach to my work on my own bike (which I did build up from a naked frame, by the way) has been to follow all instructions scrupulously. I have 4 torque wrenches (3 clicker, one beam, for the LH threads). The larger clickers are Teng, which I believe are a fairly well respected brand. And although I haven't had them re-calibrated, I take care to slacken them to their lowest setting, they are stored in a warm house, and the only use they see is occasionally on the bike. I use Zinn as my reference for torque wrench settings. Maybe I am one of the "ham-fisted" idiots that others refer to, but having watched qualified "tradesmen" in all sorts of situations, I suspect I'm no more "ham-fisted" than some people who actually get paid for allegedly skilled work. I even torque things like cable clamps, stems etc. on. Recently, fitting a new rack, I followed Tubus' astonishingly precise torque setting of 4.3 Nm. Friends who make up their own bikes are astonished that I bother, but there you go.

I am also aware that there is, or at least used to be, some discussion around whether square taper spindles should be lubricated or not. As far as I can tell the current opinion is yes, but lightly. Which is what I do, but am careful not to exceed recommended torque settings, as it is so much easier to over tighten if lubricated. I hope I've never overtighted the crank. Yes, I also lubricate the bolt, lightly. I have a variety of lubricants and anti-seize compounds which I try to use appropriately. In the early days I obviously did under tighten a crank. As it became loose soon after making the bike up, I didn't ride it for very long before I found the error. I don't use that bottom bracket any more, or the cranks (I think).

Some of the feedback has been useful. My prediction is that the cranks will probably be on and off a few times, while I try out various options, make adjustments, and so on, and then will stay on either permanently, or change very infrequently, if at all.

As to "why" and my reasons for not disclosing, that is best explained if I give an example of an imaginary discussion on an internet forum, like this one, on any subject:

"Hi folks. I was think of replacing the discomknockerator on my bloggs and smith fuffle valve with a 42mm one. Will that work?"

"Why on earth would you do that. Good old 1.5 inches fuffle valves are fine. They were good enough when I were a lad, these new metric ones are rubbish"

or

"Nobody uses fuffle valves anymore. They are old hat, it's 2025 now grandad, fuffle valves were replaced with bluttering pins years ago"
or any variety of similar responses.

If one has the temerity to say why one wants to use a 42 mm fuffle valve - "so I can fit a durdle-pin" - then there follows a whole barrage of:

"Durdle-pins are only for amateurs, real furtle-wranglers don't use them"

or it's close cousin

"Durdle pins are only for professional furtle-wranglers, don't waste your money"

or a whole slew of why durdle-pins are a really bad idea. Even though fitting a durdle-pin wasn't actually the question.

Cheers

 

[Mike Ayling]

^^ As I said about half way through this thread.

But thank you all, yet again, for opinions you have offered.

Interestingly, I see a lot more responses if I don't log on. Many of them disappear when I do log on.

But there are some interesting, and varied opinions offered. For those of you who were conjecturing at my competence, no, I am not a "qualified engineer". But as one poster has pointed out, to declare myself as one, or give greater credence to somebody who did declare themselves as such, would be a perfect example of the fallacy of an appeal to authority.

My approach to my work on my own bike (which I did build up from a naked frame, by the way) has been to follow all instructions scrupulously. I have 4 torque wrenches (3 clicker, one beam, for the LH threads). The larger clickers are Teng, which I believe are a fairly well respected brand. And although I haven't had them re-calibrated, I take care to slacken them to their lowest setting, they are stored in a warm house, and the only use they see is occasionally on the bike. I use Zinn as my reference for torque wrench settings. Maybe I am one of the "ham-fisted" idiots that others refer to, but having watched qualified "tradesmen" in all sorts of situations, I suspect I'm no more "ham-fisted" than some people who actually get paid for allegedly skilled work. I even torque things like cable clamps, stems etc. on. Recently, fitting a new rack, I followed Tubus' astonishingly precise torque setting of 4.3 Nm. Friends who make up their own bikes are astonished that I bother, but there you go.

I am also aware that there is, or at least used to be, some discussion around whether square taper spindles should be lubricated or not. As far as I can tell the current opinion is yes, but lightly. Which is what I do, but am careful not to exceed recommended torque settings, as it is so much easier to over tighten if lubricated. I hope I've never overtighted the crank. Yes, I also lubricate the bolt, lightly. I have a variety of lubricants and anti-seize compounds which I try to use appropriately. In the early days I obviously did under tighten a crank. As it became loose soon after making the bike up, I didn't ride it for very long before I found the error. I don't use that bottom bracket any more, or the cranks (I think).

Some of the feedback has been useful. My prediction is that the cranks will probably be on and off a few times, while I try out various options, make adjustments, and so on, and then will stay on either permanently, or change very infrequently, if at all.

As to "why" and my reasons for not disclosing, that is best explained if I give an example of an imaginary discussion on an internet forum, like this one, on any subject:

"Hi folks. I was think of replacing the discomknockerator on my bloggs and smith fuffle valve with a 42mm one. Will that work?"

"Why on earth would you do that. Good old 1.5 inches fuffle valves are fine. They were good enough when I were a lad, these new metric ones are rubbish"

or

"Nobody uses fuffle valves anymore. They are old hat, it's 2025 now grandad, fuffle valves were replaced with bluttering pins years ago"
or any variety of similar responses.

If one has the temerity to say why one wants to use a 42 mm fuffle valve - "so I can fit a durdle-pin" - then there follows a whole barrage of:

"Durdle-pins are only for amateurs, real furtle-wranglers don't use them"

or it's close cousin

"Durdle pins are only for professional furtle-wranglers, don't waste your money"

or a whole slew of why durdle-pins are a really bad idea. Even though fitting a durdle-pin wasn't actually the question.

Cheers

Time to stop that or you will go blind!