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Replacement securing bolts for chain ring

Posted: 28 Jun 2018, 10:11am
by Laowai_1
The photo shows the securing bolts and 'collars' that I have removed from the chainring (Deore LX M550) on my Raleigh Dynatech MTB. AS you can see some of them are corroded, some are a little damaged by the clumsy use of an Allen key. Are these bolts still available as a set?

When putting them back should I be using thread lock?

Re: Replacement securing bolts for chain ring

Posted: 28 Jun 2018, 10:22am
by Brucey
'no' to threadlock! Just grease the threads on both parts of the bolt, leave the rest of the bolt (and the chainring interface) clean and dry, and tighten normally. It is a good idea to run the bolts in and out of the sleeves to be sure that the threads are in good order, before you install them.

Bolts are readily available, and can be had in stainless steel too.

https://www.sjscycles.co.uk/chainsets-spares/?page=2

cheers

Re: Replacement securing bolts for chain ring

Posted: 28 Jun 2018, 11:26am
by Laowai_1
I have to say this forum is the most pleasurable to use, out of all the forums I access, irrespective of topic. Like a dummy, I ask daft questions and get helpful answers, quickly. That's 2 characteristics that differentiate this forum from others.

Could I now be so bold as to ask a supplementary?

Before becoming really old intellectually challenged I remember taking the triple chain ring off the bike (it was then 15 years old and worn) to replace it. I seem to remember there were spacers between the rings. But having disassembled it again I find no spacers. Should there be any? It is the old Deore LX M550 Biopace design.

Re: Replacement securing bolts for chain ring

Posted: 28 Jun 2018, 11:43am
by hamster
Shimano did occasionally put in thin spacers behind rings. They weren't on the exploded views of official documentation. I reckon it was a rework process for out-of true spiders - they machined them flat and added the spacer if necessary.

Frankly they never seemed to make a difference.

Re: Replacement securing bolts for chain ring

Posted: 28 Jun 2018, 6:23pm
by Brucey
some chainrings had spacers as mentioned above. However if you tried to use the chainset without them, IME it doesn't work too well; the chain catches on the big ring when running middle-small for example.

I think the spacers were or were not required depending on how the middle ring was made; if the ring has spacers it is made from thin gauge aluminium (or steel) throughout, whereas if the chainring was made from thicker gauge aluminium it would not need the spacers where it was mounted, but it would be more expensive to make the chainring because it would have to be machined thinner where the teeth are.

If you fit a non-shimano replacement ring, chances are that the spacers are not required. The spider arms are a conventional width and have not been machined, in the cranks I have seen where spacers are used.

You can clearly see the spacers (part of item #2 here)

http://si.shimano.com/pdfs/ev/EV-FC-M550-1101A.pdf

in those chainsets that had them.

cheers