Chainring slotted female nuts ?

[dragonrider]

I really do hesitate to argue with Brucey’s depth of knowledge but my problems were usually on taking it apart and when I had previously no involvement with the assembly e.g a secondhand bike repair.

I don’t think we would be discussing it at all if there was a small nib on the chain ring and a corresponding slot on the female nut so preventing it turning. Perhaps there is a reason it is not done - it just seems so obvious.

[Mick F]

As I said before, the Stronglight Triple on my Moulton has Allen heads on both sides.
Easy peasy, and I can't for the life of me work out why ALL chainsets aren't like that.

[Brucey]

I have had similar problems too of course; with other people's bikes. But there are any number of parts on a bike that will seize up and be difficult to remove if they are not assembled correctly, of which chainring bolts are far from the most troublesome.

IMHO anytime you encounter seized chainring bolts you can rest assured that there will be other parts on the same bike that have been poorly assembled and maintained. You could change the design but it so often turns out that an increase of pennies in manufacturing cost turns into pounds of retail price increase.

In addition I would be wary of the law of unintended consequences; for example attempts to make things more idiot proof so often prompt the creation of a new, improved, idiot.....

cheers

[Brucey]

As I said before, the Stronglight Triple on my Moulton has Allen heads on both sides.
Easy peasy, and I can't for the life of me work out why ALL chainsets aren't like that.

Because

a) it is not necessary and
b) the bolts are noticeably inferior as, er, bolts.

Whether the latter is inherent to the arrangement is not clear, but I think it is and I have noticed that

- the allen key sockets are shallower, so that there is an increased chance of rounding out
- the thread engagement of the bolts is reduced
- the plating on such bolts is inferior, so that they are more likely to corrode
- there is a worse (much worse) crevice in the assembled bolt, that will trap water and cause corrosion.

in other words they are more likely to seize and more likely to fail when you try to undo them. Because there is less thread engagement, at least they are easier to drill out....

cheers

[Tigerbiten]

As I said before, the Stronglight Triple on my Moulton has Allen heads on both sides.
Easy peasy, and I can't for the life of me work out why ALL chainsets aren't like that.

Probably because the double allen key setup will only work within a narrow range of chainring-spider-chainring thicknesses.
Outside that range you won't get the second allen key to work in the screw head because the bolt body will block it.
You don't get this problem with the slotted screwdriver.

[Mick F]

I don't agree with either Brucey or Tigerbiten.

Corrosion is a subject regarding materials. Maybe the Stronglight offering could corrode, but the design is fine.
The distance issue is easily surmountable. Maybe the stronglight offering could be redesigned.

Whatever .......... the Allen back and front is good IMHO.


Tell you what, I'll be doing some bike maintenance later this morning. I'll swap a Stronglight from Moulton and see if it fits on Chorus Triple Mercian. If not, I'll see why.

[Mick F]

Both Campag and Stronglight fit in each other's chainsets perfectly.

Top is Stronglight Allen/Allen
Bottom is Campag Allen/Slot
Note the inferior Campag .......... corrosion ........... though it is ten years old or more. Stronglight only two years old.
Also note that the Campag has a longer thread ......... stronger? Does it need to be?
I know which I prefer.

[Brucey]

when assembled, the bolt you like has a really bad crevice on the inside, and it will corrode like fury because water will be able to pool within it. In several respects (mostly as described previously, but there are others....) it is a daft design.

For example in engineering texts you will find equations that describe that three threads are enough to withstand 90-something percent of the rated load of a nut and bolt. I'm sure this is the case, but any spanner wielding chimp will tell you that if you retighten such an arrangement a few times then the chances of the thread stripping are very high indeed. More threads engaged is better!

Both Campag and Stronglight fit in each other's chainsets perfectly

...some of the time....

They are obviously different to one another and often these small differences are important.

cheers

[Mick F]

You and I disagree here.

It doesn't matter. They fit well. One is easier than the other.
They are only chainrings.

[Brucey]

'only chainrings'...? -chainring bolts need to be tight in order to prevent creaks and fretting. I doubt very much that repeated tightening of a bolt with so few threads engaged will be a happy arrangement. In fact your photograph appears to show bits of swarf lurking in the threads of the stronglight bolt, which is exactly what I'd expect to happen as it fails.

cheers

[Mick F]

I've never ever had a problem with fretting or anything with any chainring bolts.
Never ever used a torque wrench. I tighten them by hand and I don't worry about them ............ and never have and won't in the future either.

I suspect you have a pessimistic outlook on this due to having to fix bikes.

[Gattonero]

Why are they designed thus?

Has anyone tried to use the

https://www.parktool.com/product/chainr ... %20Bracket

spanner?

Is it the worst ever hand tool?

AFAIK, the slotted design goes back many decades, and it worked without need to go mad.
One cannot blame a design when lets the bike go rusty, otherwise a 8mm drill bit would remove the stuck bolt.

Like pretty much all the tools, "power is nothing without control" which means that if you can hold the spanner properly in the slots, it's unlikely will fail, unless there are other conditions. Chainring bolts are usually meant to be tightened to 5-7Nm max, if needs more than there is slack or imperfection in the chainrings/spider interface.

[Gattonero]

I've never ever had a problem with fretting or anything with any chainring bolts.
Never ever used a torque wrench. I tighten them by hand and I don't worry about them ............ and never have and won't in the future either.

I suspect you have a pessimistic outlook on this due to having to fix bikes.

You have experience for your bikes and your type of riding an maintenance, but other will wildly differ.

[Samuel D]

Chainring bolts are usually meant to be tightened to 5-7Nm max, if needs more than there is slack or imperfection in the chainrings/spider interface.

Shimano seems to specify about double that in most cases.

The other day I took possession of a friend’s bicycle with all five chainring bolts loose enough to rattle. No idea how it got to that state without at least one of them falling onto the road.

[Gattonero]

Shimano can make silly statements, i.e. they specify to torque the encasso nuts on forks up to 10Nm, doesn't matter what the forks are made of!