Chain ring PIN lost from large ring-what is it`s function?

I have read two different opinions regarding the purpose/function of the Pin .

One was that it stops the chain getting jammed if it came off the ring. Another was that it helps the chain move across to the next chain ring when changing.
 

I like Skol

Hold my beer and watch this....
Depends which pin you are referring to. Two different pins, two different functions.
 

ColinJ

It's a puzzle ...
If it's the pin between the crank and the ring, then it's to prevent it getting jammed.
I was out on a ride with someone once and noticed that the pin was in the wrong place so I told him that he had fitted the ring in the wrong orientation.

He told me that it didn't matter so I explained that... "The pin is supposed to block the gap between the ring and the crank to stop the chain wedging in there if it falls off"

Literally a few seconds later his chain fell off and DID get wedged between the ring and the crank... "like THAT!" :laugh:
 

I like Skol

Hold my beer and watch this....
It was the pin attached to the large chainring and facing in towards the small chainring. Can replacement pins be obtained and fitted?
This is to help the chain ride up from the smaller chainring to the larger one. There should be others around the chainring maybe in 3 or 4 places? I don't think you can get pins separately. Is the changing being noticeably hindered by the absence of this 1 pin? If not, ignore it and carry on :okay:
 
Skol, everything was working ok when I tried/road the 8 month old bike prior to purchase as far as I recall. The bike was very clean frame wise, but I needed to remove the rings to clean the areas that I could not access. I`m still unsure what happened, but after I put the rings back on, the chain would not go round properly. I then found that as long as it was on the small chainring it worked perfect in every gear. However, everytime I tried to change on to the large chainring the chain would come off and jam behid the small ring. It kept doing this , and I kept freeing it. All of the above was in the house-I was not riding it at the time.

At some point between the chain jamming and me freeing it I felt somerthing under my foot and it was the pin from the large chainring. There are no other pins on the chainring.
 

I like Skol

Hold my beer and watch this....
Have you fitted the chain rings on the right way round. That large pin was to face outwards to the crank, not inwards, hence your issues.
I was about to say the same.
 
I`ve just turned the large chainring round but the chain is still not going on to the large ring. It was as you said Fossy, the wrong way round. I`m not sure what to do now because I have not touched any of the adjustment screws anywhere.
 
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I have looked at the small ring and it appears to be the same on both sides of it, other than numbers & letters stamped on to one side. It does not appear shaped differntly on each side like the large ring is.
 
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