First time chain replacement

[Bristolian]

I have run into a problem.
when I use the online calculator it returned I needed a chain with 114 links.
I found the formula for making the calculation and had Copilot.AI and Perplexity.AI each run the formula using the same inputs as the chain-link-calculator and they both returned 112 links.
Any thoughts on this discrepancy??

Here was the Perplexity.ai calculation:
View attachment 800960

Yes, AI isn't intelligent - it doesn't fact check itself.

 

[roubaixtuesday]

Yes, AI isn't intelligent - it doesn't fact check itself.

This is a very typical use of AI:

1) the answer is already obvious
2) AI gets it wrong but sounds convincing
3) More time is spent correcting the AI than it would have taken to get a simple answer in the first place.

Meanwhile, the environment burns and the stock market bubbles.

 

[BikerBob38]

Thoughts? That you have too many. You're over thinking it to a quite alarming extent.

Just replace it with one the same length.

What! Me overthinking something!!?? You would not be the first person to so accuse me. 😎

I live by this/these maxims:
The important things are always simple.
The simple things are always hard.
The easy way always mined.

[Former USMC sergeant]

 

[BikerBob38]

The chain and link breaker have been ordered and are due later this week.
Promise to report back on how it goes and, again, what a wonderfully generous bunch you folks are with all your advice.

 

[Ming the Merciless]

I have run into a problem.
when I use the online calculator it returned I needed a chain with 114 links.
I found the formula for making the calculation and had Copilot.AI and Perplexity.AI each run the formula using the same inputs as the chain-link-calculator and they both returned 112 links.
Any thoughts on this discrepancy??

Here was the Perplexity.ai calculation:
View attachment 800960

Those AIs do not do any calculation. That is the problem you are seeing.

 

[Dogtrousers]

I hesitate to add another confusing method to the mix, when there is already a reliable solution (count the links in the old one) BUT, as well as multiple online calculators that don't agree, and AI that says anything that looks vaguely plausible, there's also a practical method.

Wrap the chain round the bigger chainring and biggest sprocket, and ... I won't bother describing it, it's described in detail here https://bettershifting.com/installation-guide/installing-a-new-chain-length-and-direction/

 

[mickle]

I'm keeping out of this.

 

[BikerBob38]

No need to assume. Before removing old chain shove it in large-large and if the chain is the correct length the RD cage will point 'below' 4 o'clock. If it points after 6 o'clock, the chain is probably too long.

Chain arrived today and I re-read all the suggestions before tackling the job and this one I had glossed over too quickly. Having done more reading, it makes more sense to me, so here is a photo of my chain in the large-large position and it would appear that the chain it came with from the factory is maybe a link or two too long? Would you agree or disagree?
This would fit with what I learned when I went to a chain link

Watch this...

Er, I didn't say anything about side plates stretching!

But you are still wrong; not just slightly wrong - comprehensively wrong!!

If you had ever placed a worn chain next to a new one it would have been very obvious how much longer the worn one was for a given number of links.

Chain wear tools work by showing that the prongs can squeeze in where they shouldn't be able to, because the chain rivets and/or rollers are worn.

Watch this...

I watched that video and after removing the chain I laid it out as straight as possible and here are photos of my measurements.
Rather than show the entire chain I took photos of each of the chain laid against a steel ruler.

And here is the end of the old and new chain laid side by side.

 

[Dogtrousers]

here is a photo of my chain in the large-large position and it would appear that the chain it came with from the factory is maybe a link or two too long? Would you agree or disagree?

I'd disagree.

Specifically, I'd disagree with your method rather than your conclusion. I don't think that photo necessarily supports your conclusion. If you really want to figure out the required length then use the new chain, and put it round big-big without feeding it through the derailleur. Then follow the rather fiddly calculations for adding a couple of links or so as outlined in the link I posted above.

Do you have any other reason for believing the chain to be too long? For instance are you getting chain-slap and paint damage on your chain stays?

Be careful as a slightly too long chain isn't necessarily much of a problem. But a too short chain can be downright dangerous as you won't be able to get it into big-big without breaking something.

Another less drastic problem that I once had that I suspect was due to having the chain slightly short (I may be wrong on this) was that it would engage big big ok but wouldn't change out of it unless I dropped down to the small ring.

I've read (in Nicole Cooke's autobiography) that pro mountain bikers sometimes knowingly run short chains, but they have to trust themselves to avoid inadvertently selecting extreme gear combos.

What I'd do would be to fit the same size as the existing one. If that proves to be wrong, it's easy to take a link out. It's harder to add one back in.

 

[Ajax Bay]

here is a photo of my chain in the large-large position and it would appear that the chain it came with from the factory is maybe a link or two too long? Would you agree or disagree?

The chain as shown is exactly the right length (imho). Trying to take a (one inch) link out could make it too short. Having said that your large sprocket is 'massive' (?36t) so how about an image with the chain on inner (?34t) - small?

here is the end of the old and new chain laid side by side.

First, the old chain in that image is one (inch) link shorter than the new one: doesn't change my opinion that the new chain is the correct length.
So by my measurement the old chain has elongated 6mm which is 0.4%, however.
Accurate measurement of chain length has to be done when the chain (each chain) is under gentle tension (and lying on the fibreboard, these two are not). But fuss not, looks like the new chain on your old cassette should be OK. As said, don't throw away the old one until sure.

 

[Shearwater Missile]

Perhaps I am old school in thinking. If the original chain gave no problem, then a simple link count whilst on the bike would suffice. I count, count and then count again, in case I miscounted !

 

[BikerBob38]

I wonder why my results are so different from those shown on the Park Tool videos?

Here is a still showing the sizing of a new chain. The chain is over the largest cassette and largest chainring, but does not go through the derailleur. Note the amount of chain sag.

Below it my old chain strung exactly the same. Look at the difference in sag between the two. If I followed the PT instructions, my chain would be, I think, far too short. But, PT knows what they are talking about so I must be wrong and would welcome pointing out where I went wrong/what I don't understand.

 

[Dogtrousers]

Sheldon also has an article on sizing chains. https://www.sheldonbrown.com/derailer-adjustment.html#chain

 

[Erasmus]

See pictures (I think I took these from another part of PT website, but could be elsewhere. Taking out the 2 links gives the right amount of 'sag' to allow for threading through the RD.

 

[Ming the Merciless]

Go for a ride. Change through all your gear options on both chain rings. You will soon see if there is a problem. If not, leave be.