# Chainring bolt length.



## Dave88LX (Aug 29, 2007)

I'm beating my head against the desk because I'm sure I am overanalyzing this. I need new chainring bolts to replace the old rusted garbage ones I have.

Spider thickness is .15" (3.8mm) and the chainring I'm buying is 3mm (.125") thick. Total thickness of ~6.8mm to 7mm.

How much engagement of the threads is required, and how deep of a 'nut' is required?


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## tigris99 (Aug 26, 2012)

Definitely over analyzing.

U can't readily find sizes that specific. Most come in single,double etc. Some have sizes iirc the smallest is 8mm (maybe its 6mm) You just need to buy bolt/nut sets for ur application. Single ring set.
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## Saul Lumikko (Oct 23, 2012)

Just buy short ones and it'll be fine.

The nut is deep enough when it goes through the spider and a little bit into the chainring holes to help alignment. If you use the same bolt as supplied with the nut and the nut comes almost all the way through, thread engagement will be sufficient.


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## Dave88LX (Aug 29, 2007)

Oh yeah, I know I way over-analyze! I'm just thinking that with a 4mm bolt, 7mm thick area to hold together, there's going to be maybe 1mm of thread engagement -- not nearly enough I don't think.

The "long" bolts are 8mm, but I don't know if the thread will come out the back a little (open thread) or if they're closed thread. Haven't seen enough up close yet.


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## tigris99 (Aug 26, 2012)

Chainring nuts r like any nut, their hollow, so open. But bolt won't actually really stick out. Figure there is 1-1.5mm head on the nut side so then u end up at 8mm.

Simply get "single" chainring bolts set and everything will be perfect.
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## Dave88LX (Aug 29, 2007)

Yeah I have a set of "standard" 4mm ones right now and they just seem too short. I'll have to do some digging I guess.


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## tigris99 (Aug 26, 2012)

If the nuts go through the ring and into the spider just slightly (half way give or take). 

Like I said ur way over thinking this lol. Chainring bolts are a standard, one size spec for granny rings, no nuts, the single, double (or u can get longer bolts for single with bashgaurd or double with bash guard).

So 4mm nuts and bolts to go with them is proper size. Single nuts are short, u go any longer u can't properly tighten. Nuts must be shorter than actual total thickness. Just buy a set of single rung chainring bolts/nuts install and ride.
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