Chainring bolt question

What is with the chainring bolts that have the slots on the nut as opposed to a hex? I’ve always had chainring bolts that have hex on both parts. Just replaced my because they were getting rusty and it was a good thing I happened to have the tool on a chain checker. They were definitely harder to install than what I’ve always though is the standard. Is there some advantage I’m not seeing?

They’re horrible - you need a special tool for them, and it’s hard to get good purchase using the tool round the back of the chainring while you try and crank the male part down like 8+ NM

Always get stainless with hex. Truvativ (SRAM) are usually the easiest to find. Alloy / Aluminium bolts always deform and you have to drill 1 in 20 out.

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Praxis bolts use two hex keys of different size. The practicality is that this then becomes a slight fiddle in terms of one hex being a narrow size and going all the way through the bolt. I imagine the reason for the original design (for which there is a Shimano tool) is that there can be a greater overlap of threads, as the bolt can go all the way through. The Praxis design means the bolt needs to be shorter for the larger hex key to have sufficient grip.

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I think it’s so you can remove chainrings whilst keeping the cranks on. Removing cranks on old square BBs is a massive pita.

But yep, I always get hex ones.

That seems to be the original design. At least my campy nuovo record chainring bolts were like that 40 years ago.