Author Topic: Replacement triple chain ring bolts  (Read 504 times)

Replacement triple chain ring bolts
« on: January 10, 2020, 03:26:29 pm »
Whilst on turbo earlier the bolts sheared on the middle chain ring of my triple. It’s a Shimano XTR triple. Are all chain ring bolts equal or are there specific ones I need to order?
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Kim

  • Timelord
Re: Replacement triple chain ring bolts
« Reply #1 on: January 10, 2020, 04:03:03 pm »
I don't know about your chainset, but if you can find them, Truvativ chainring bolts are the ones that use a different-sized allen key for the back side, rather than that shitty tool that slips and causes you to get bitten by the chainrings.  I think they're a MTB thing and mostly come in 4s.
Careful, Kim. Your sarcasm's showing...

Re: Replacement triple chain ring bolts
« Reply #2 on: January 10, 2020, 04:31:46 pm »
Just checked and spare chain ring is 4 bolt. So assuming the truvativ fit they sound ideal for fitting with Allen keys.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Replacement triple chain ring bolts
« Reply #3 on: January 10, 2020, 05:44:40 pm »
chainring bolts are often dimensionally common between lots of different chainsets. The main variable is the length of the sleeve part of the bolt; this should match the old ones.

Materials used include

- plated steel
- Titanium
- Stainless steel
- Aluminium

IIRC some XTR chainsets were fitted with aluminium bolts. If you spray these with salty water (sweat) they will often just break, so it kind of makes sense on a turbo that this happened. Normally the centre part of an aluminium bolt will fail first.

Some folk like the kinds of chainring bolts which use two allen keys to tighten them, but I don't. 'Meh' at best.  They usually have;

- shallow sockets for the allen keys (easily rounded)
- fewer threads engaged on the bolt itself
- a nasty crevice internally that water can pool in
- slightly higher weight than many other bolts
- a reduced selection of lengths
- less scope for adjusting the length of any given bolt
- highly indifferent plating quality (they go rusty)

Yes the two pronged tool on standard bolts is annoying, but the only time you need to use it is if you have not kept your bolts clean/well greased.  If you keep them clean and well greased (NB on the screw threads only), there is no need to hold the sleeve part of the bolt as you tighten them; simple friction does this for you.

My suggestion is that you buy some stainless steel ones (most I have seen are of standard design) and use those.

cheers

Re: Replacement triple chain ring bolts
« Reply #4 on: January 10, 2020, 05:50:55 pm »

IIRC some XTR chainsets were fitted with aluminium bolts. If you spray these with salty water (sweat) they will often just break, so it kind of makes sense on a turbo that this

It’s on a recumbent so sweat gets nowhere near them on turbo. But it’s off an old mtn bike so plenty of opportunity when they were used off road in that capacity.

Thanks for the other info
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Replacement triple chain ring bolts
« Reply #5 on: January 11, 2020, 12:59:58 pm »
Hmm, found chain ring bolts on patio this morning. Don’t look damaged and just look as though they’ve come undone.  Fine to reuse assuming no other issues with chain ring?
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

zigzag

  • unfuckwithable
Re: Replacement triple chain ring bolts
« Reply #6 on: January 11, 2020, 02:13:14 pm »
have they all come undone simultaneously without you realising that the chainring is getting wobbly? it's one of the strangest mechanicals i've heard so far! (could anyone sabotage your bike? :) )

Re: Replacement triple chain ring bolts
« Reply #7 on: January 11, 2020, 02:40:24 pm »
if they are undamaged, they should be OK to re-use.  FWIW new chainrings often 'settle' in the first period of use. Shimano and other manufacturers often overtighten the bolts in new chainsets so that they are not so likely to back out and loosen etc but IME if you grease the threads and use the correct torque on a new chainring, it isn't unusual for the joint to settle in use and for the bolt to need retightening.

 Once a chainring has settled, it doesn't seem to be likely to settle a second time, not on the same spider.  I think the settling stems from there being microscopic burrs on the parts, and that overtightening the bolts in the factory helps to squash them. However this (and that they seem to use no grease on them) does nothing for your chances of getting the bolts undone months or years later.  Thus my habit is undo new chainring bolts on new chainsets (with difficulty, they are usually v. tight), to grease them (on the threads only, both halves, the rest of the part should be scrupulously clean) and then reassemble.

 Presumably because such an assembly has been overtightened once already, the joints seem less likely to settle and need retightening.  Needless to say it is an excellent idea to check them after a hundred miles or so anyway.

I find that if you use decent grease as specified, bolts so treated come apart again quite easily even years later, no peg spanner required.

cheers

Re: Replacement triple chain ring bolts
« Reply #8 on: January 11, 2020, 06:19:25 pm »
have they all come undone simultaneously without you realising that the chainring is getting wobbly? it's one of the strangest mechanicals i've heard so far! (could anyone sabotage your bike? :) )

Didn’t get chance to get recumbent out today and take a close look. So I don’t know. But I have noticed middle ring possibly moving a bit, but put it down to some bent teeth or something.  The long chain run of the recumbent means it clearly didn’t caught a problem till it did.  I also run the derailleur on a friction bar end so any rubbing I just moved the derailleur slightly when it might have indicated bolts coming lose.

Anyway will be taking a look tomorrow to see if I can rebolt or need to wait for the replacement bolts I’ve ordered anyway.

Edit - Just had a look and no they didn’t all come out at once. I have picked up less bolts than are missing. So some must have come out at some earlier Unknown date

If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Kim

  • Timelord
Re: Replacement triple chain ring bolts
« Reply #9 on: January 11, 2020, 07:24:48 pm »
Thus my habit is undo new chainring bolts on new chainsets (with difficulty, they are usually v. tight), to grease them (on the threads only, both halves, the rest of the part should be scrupulously clean) and then reassemble.

I've had exactly zero chainring bolt issues since I started greasing the threads.  (Having said that, I expect they'll explode next week or something.)
Careful, Kim. Your sarcasm's showing...