chainring bolts

[silva]

Question:
The Stronglight Track 2000 chainset has mounting bolts whose female (the part at the side of the frame, the "nut") part is not entirely cilindric, first a kind of ring, slightly larger diameter with grip ridges that fret themselves in the alu of the spider of the crankset, then a conical part, then the cilindric part.
Purpose is to eliminate the need for a tool at the frame side, when tightening.
I find this handy when replacing a chainring, would it be an option to use these Stronglight bolts (I carefully hammered these female parts out of the spider) on a new crankset now mounted?

The slightly larger diameter of the ring is also present in the Stronglight (a scrap one) spider, and not in the new spider. Not sure if Stronglight drilled it out that single (or so) mm, or if it was the tightening that deformed the aluminium along those grip ridges in the steel "nut".

Second question, what are the pros and cons of stainless versus usual steel grade for chainring bolts?
Stainless is less chance on rust, but stainless can fret out aluminium due to galvanic corrosion, I have had this problem on my bikes stand, and also one can see it at nearly any inner tube valve, white powder on the stainless of the valve meaning the hole in the rim got bigger.
Also, stainless 3xx grade is like half the strength of steel.
So maybe the less chance on rust / no rust comes at a price (in terms of drawback) that is too big.
Opinions?

 

[silva]

What I forgot to add: the female part has also a conical part. Maybe as one of the means necessary to fix it so that a tool on the frame side becomes unnecessary.

 

[Stompier]

Depends how often you are fitting/removing them. The more you work on them, the more important it is to have bolts which can withstand the additional application of tools on them.

In terms of strength, the bolts themselves don't actually have to do very much, assuming the chainring is a good fit on the spider.

 

[midlife]

Mine are chrome plated, mind you they are from the 70's

 

[silva]

Mine are chrome plated, mind you they are from the 70's

Good 'ol 70's when things were made to last unlike now when things are made to NOT last so that ppl have to pay replacement bills. What they name "chrome plated" now has like a fraction of the thickness of then.
I was recommended the stainless bolts but knowing what I know now, I'd gone for nonstainless steel.
Sometimes things are chosen with good intentions / to do the best, stainless costs way more, but it has drawbacks, especially in combination with aluminium of bikes. I've seen white alu powder around nearly any stainless steel bicycle bolt present.

This morning (well, it took me nearly the entire am) I've put enough grease on the ss bolts to make it spill out when tightening. To prevent the corrosion since it needs electrical conduction and the grease may increase the resistence and thus prevent or make it less worse/fast.
Before, I didn't need a tool at the frame side, now I did, and I didn't have one. In the end, I found a piece of sharp-edged profiled steel with the required thickness (a piece I got from demolishing shoes, the steel that fixes the sole-heel slope/height difference).
I made a test ride and when back I could tension one bolt a little further. Over some minutes I'll make a longer test ride.

But I don't trust those stainless steel bolts. They are as short as the steel ones before, and knowing that the strength of stainless is only halve steels, the thread connection is too.

Makes me think about that stainless steel chain (Z1X INOX) that KMC ceased to produce. I have used it for many years, until a few disasters along the road due to road salt fretting away the riveted end of non stainless steel pins (KMC finally admitted in a mail that these weren't stainless). The chain links plates had twice the thickness of common steel chains links (alike the KMC Z1RB). I thought the chain was stronger, but it clearly was to compensate for the strength loss due to stainless.

The thing is that I had the idea to swap to bigger chainring after a chain worn abit longer and thus frame clearance increased. But these bolts make that now abit harder and problematic (faster bolt head damage).
I think I'll order common steel ones and replace asap.

 

[Stompier]

Good 'ol 70's when things were made to last unlike now when things are made to NOT last so that ppl have to pay replacement bills. What they name "chrome plated" now has like a fraction of the thickness of then.

Chrome is a plating, not an indication of 'strength'. You can chrome-plate plastic, but it's still plastic underneath.

 

[silva]

Chrome is a plating, not an indication of 'strength'. You can chrome-plate plastic, but it's still plastic underneath.

I didn't reference plating in a strength context, but in a context of lasting, being that the thicker the plating, the more/longer the underlying steel is protected against rust. Look at todays plating of clothes racks etc. Racks of decades old, don't show a single spot rust, while for the later ones a couple months in a same humid environment suffices to make them develop spots all over the tubes' surface.
Simply because the plating is alot thinner, and very likely also less different layers ("ancient" plating had several different kinds of layers on top of each other, each with a specific purpose on their location).

About my thoughts on stainless: I had a Surly stainless steel (grade 304-most common/cheapest) chainring on the bike like it was delivered. It took like just a month riding to have sharkfin teeth and requiring replacement, while the aluminium 7075T6 that replaced it, lasted 18 months, with 12 of them under precisely the same working environment as the Surly SS.
Stainless is not crap or so, it has its (big) benefits, but from a mechanical strength viewpoint, it's plain rubbish. With the possible exception of some special 10 times more expensive versions.

 

[silva]

Depends how often you are fitting/removing them. The more you work on them, the more important it is to have bolts which can withstand the additional application of tools on them.

In terms of strength, the bolts themselves don't actually have to do very much, assuming the chainring is a good fit on the spider.

Can you explain your last statement?
From what I understand, the bolts have to withstand the pedaling force straight-on. The spider notches serve only for centering - they don't absorb (part of) the force - how would they - they are parallel not perpendicular to the direction of the force.
This isn't a case alike for ex a wheel mount in the frame. There the bolt or nut only has to withstand the tension force needed to clamp the frame on the wheel - the mount doesn't sit in the path that the pedaling force follows (cog > axle > hub > spokes > rim). The chainring bolts do sit in the path (pedal > crank arm > spider > chainring > chain).


.

 

[Stompier]

Can you explain your last statement?
From what I understand, the bolts have to withstand the pedaling force straight-on. The spider notches serve only for centering - they don't absorb (part of) the force - how would they - they are parallel not perpendicular to the direction of the force.

The load is rarely borne by a single bolt, anywhere in the rotation, is what I meant. You hear stories of people losing two or more bolts on a ride with no particular ill effects.

 

[silva]

The load is rarely borne by a single bolt, anywhere in the rotation, is what I meant. You hear stories of people losing two or more bolts on a ride with no particular ill effects.

Yes due to the force origin being human legs unlike a motor which has (at this frequency) nearly a constant torque.
The latter is likely due to a designed reserve. Consequences of a lost reserve don't have to manifest themselves immediately. People can lose 2+ bolts on a ride and get back home. But the lost reserve (of the entire mount) may stress the remaining bolts enough to cause sudden failure (aka breaking). A typical series of failures is 1 lost, some time later 2 breaks, some shorter time later 3 breaks, to then suddenly a chainring completely coming off. Because load is divided, and the fewer left the more load the remaining have to withstand.
If todays mounted stainless steel bolts have half the strength of previous steel bolts, then that reserve will be reduced the same rate, so that in this case a single loose or broken bolt may arrive to that last story end in alot shorter time.

I'm now thinking of something "totally different". My application is fixed gear. Meaning that there is alot free room / clearance. Maybe I could just mount the chainring with standard bolts and nuts, what is the bolt hole diameter of a chainring? 10 mm? Maybe I can just take M10 bolts with hexagon head and length enough to give a common nut and eventual washers a place?
Or did I overlook something here?

 

[Stompier]

I've never really thought that much about it, to be honest.

 

[raleighnut]

Yes due to the force origin being human legs unlike a motor which has (at this frequency) nearly a constant torque.
The latter is likely due to a designed reserve. Consequences of a lost reserve don't have to manifest themselves immediately. People can lose 2+ bolts on a ride and get back home. But the lost reserve (of the entire mount) may stress the remaining bolts enough to cause sudden failure (aka breaking). A typical series of failures is 1 lost, some time later 2 breaks, some shorter time later 3 breaks, to then suddenly a chainring completely coming off. Because load is divided, and the fewer left the more load the remaining have to withstand.
If todays mounted stainless steel bolts have half the strength of previous steel bolts, then that reserve will be reduced the same rate, so that in this case a single loose or broken bolt may arrive to that last story end in alot shorter time.

I'm now thinking of something "totally different". My application is fixed gear. Meaning that there is alot free room / clearance. Maybe I could just mount the chainring with standard bolts and nuts, what is the bolt hole diameter of a chainring? 10 mm? Maybe I can just take M10 bolts with hexagon head and length enough to give a common nut and eventual washers a place?
Or did I overlook something here?

The 'bolts' don't bear any load they simply stop the internally threaded dowel pins from falling out.

Oh and BTW Grease won't prevent corrosion, far better to use Petroleum Jelly (Vaseline) in that application.

 

[silva]

Simple mounts executed with common tools allowing quick DIY instead of having to rely on dealers (I've received numerous bad jobs in the past) makes biking life easier so that I then have more time avail to do what I DO like.
Hence my "alot" thinking about it.
Ex yesterday, if I haven't had thought about buying spare set of bolts, I would have sit stuck now with the bike, due to a dealer delivering too long chainring bolts despite having removed the old (and not mount compatible anymore) chainring himself, knowing that a same would be placed just with a different bcd.
Yesterday I noticed that the stainless steel bolts clearly were easier to damage (the frame side) than the steel ones before, and I recognized that in my single chainring case there is no need for sunk bolts at all - there is plenty room for a common bolt+nut and thus common tool.

To illustrate the current situation I arrived at, thinking this way, the little bag around my middle contains a tiny bag with a zipper, containing a few allen keys. That's (now was) all I need to tension my chain, to replace a cog, and until yesterday to replace a chainring. I'm not happy with the latter - the dealer didn't tell me at all I had to discover it "the hard way".
As an interim solution, I used a smallish profile steel plate as a second tool to mount the chainring, and added that to the tiny bags keys. But I want to go back to the allen-key-only of before.

In meantime a specific question.
The Stronglight Track 2000 crankset that was mounted by the dealer of the bike, had 'special' bolt holes - the side of the frame has a 2mm deep bigger diameter drilled recess, followed by the normal diameter but the inner side of that normal diameter range covered with a same regular ridge pattern (very similar to the ridges on the side of monetary coins) as on the nuts.
All together likely to give grip so that a tool isn't needed at that side to hold the nut when tensioning.
So both spider holes and nuts have special adjustments.
I managed to recover the set bolts+nuts from the broken Stronglight cranksets spider, by screwing in a bolt in the nut and ticking them out one by one. But I cannot reuse them on the spider of the new crankset because those bolt holes don't have the mentioned adjustments.
I just searched alike half an hour on the web to find these chainring bolts, and despite having quite some experience in looking up / selecting keywords, I couldn't find these anywhere.
It looks like the Stronglight Track 2000 chainset spiders (at least mine) underwent special / nonstandard / undocumented? modifications (larger diameter recess) to allow chainring mounting without tool on one side only. And special (ridges/conical part) nuts produced.
Likely, the ridges on the inside of the holes were pressed in the aluminium during the tightening of the special (a ring of ridges at their beginning) steel nuts. So actually "damaging" the cranksets chainring mount holes, making it more awkward with every subsequent chainring replacement - even in the case of steel this is awkward, let alone aluminium.
Could be compared with a square taper axle, eventual, after enough refittings it may bottom out causing inability to tension the cranks. But such axle is steel, and much more material than a tiny mount of a chainring.
So unless I missed something, the Stronglight Track 2000 chainset, crank thread already stripped by one removal, both cranks broke at their pedal mounts, and a chainring mount method that is like a throwaway one time only, looks like garbage.

Anyone seen this kind of chainring bolts/mount before / elsewhere?
In short, a chainring bolt set with its nuts having a ring of reeds on their circumference and no tool provisions just flat on their exposed (frame) side.

 

[silva]

The 'bolts' don't bear any load they simply stop the internally threaded dowel pins from falling out.

If your interest is semantics then feel free to replace 'bolt' with your 'internally threaded dowel pin'.
User Stompier clearly chosed 'bolt' as a reference for the mount / being a pair (2) components. Clear enough for me since the context was too.

Oh and BTW Grease won't prevent corrosion, far better to use Petroleum Jelly (Vaseline) in that application.

https://www.w8ji.com/dielectric_grease_vs_conductive_grease.htm

Both dielectric grease and "conductive" greases (anti-seize) are insulators. The primary difference between dielectric greases and "conductive" greases is that "conductive" greases and anti-seize greases include some amount of finely-powdered metal. The finely powdered metal is suspended by insulating grease, so it does not conduct. The suspended metal powder does lower the voltage breakdown of any arc paths through the grease.

Galvanic corrosion (as in this case stainless steel on aluminium) requires an electrical current, which an electrical insulator decreases (alot). The galvanic voltage over these (and any) different metals is (way) too low for ionisation.
This is the GREASE I used:
https://www.nyco-group.com/site/content/uploads/TGN46-4E4a.pdf
cheap @ 3 euro per kilo, purchased 5 years ago in a metalware shop, never have had galvanic (and any) corrosion wherever I used it.
For what it matters, no electrically conducting content.
https://www.sciencedirect.com/topics/materials-science/galvanic-corrosion

3.5.2 Presence of an electrolyte
The contact area must be wetted by an aqueous liquid in order to ensure ionic conduction. Otherwise there will be no possibility of galvanic corrosion. This is the case of the tank of an electrical transformer, in which possible junctions between aluminium conductors and copper conductors, immersed in the oil bath of the transformer, are not a source of galvanic corrosion of aluminium.

 

[midlife]

Buy a new / used Stronglight 2000 crankset?