First time chain replacement

[BikerBob38]

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.

I am going to follow that last sentence of your post. I put the new chain on here is a photo of it on the bike on the large/large.

Here is a photo of the small/small.

One of the responders to this post linked me to a site showing the derailleur arm ideally pointing at or below 4 o'clock when in the large/large. Mine looks close to 6 o'clock. The same article showed the small/small setup with the derailleur arm looking more like the next photo where I am holding in what I suspect may be the correct position.

IF, big if, I am correct, even though the new chain runs through the gears just fine and even though I would never ride with the chain in the small/small configuration it seems that removing one link would pull the arm up closer to the 4 o'clock position and pull the arm a little further down in the small/small config.

What to you think?

 

[Dogtrousers]

it seems that removing one link would pull the arm up closer to the 4 o'clock position and pull the arm a little further down in the small/small config.

What to you think?

The aesthetics of what happens in small-small would not be my primary concern. Is the chain long enough to engage big-big? If you cut it too short that this is a safety issue.

I think you are massively over-thinking this. Count the links in the old chain. Cut the new to that number of links. Test ride. See if there's any problem.

If you are really super concerned about length then use the "big-big without derailleur plus a bit" method to double check.

If, after doing all that, you still have slack in the system in small-small small that's more likely to be a function of your derailleur having insufficient capacity than your chain being too long.

 

[Ajax Bay]

The chain above is the correct length. "4 o'clock" is the absolute minimum (120 degrees) for safety.
Suspect your 50-34t compact and the cassette ? 11-36t is a combo out of spec for the RD you have, btw, though it's clearly a long cage (make/model?). This is safe, but the noise when in inner- small sprockets will soon tell you to shift up at the front.

I think you are massively over-thinking this. Count the links in the old chain. Cut the new to that number of links. Test ride. See if there's any problem.

This ^^
The chain below is a (one inch) link too long.

 

[N0bodyOfTheGoat]

I've used link below for a while now, ~10 years. It started giving a warnings about not being a secure website ~5+ years ago.

http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html

Good timing to see this thread and type reply, been on verge of ordering a new chain for my ebike for the first time, turns out the chainstay/big ring/big sprocket combo as supplied recommends 57 links (what KMC call 114 links, a standard length chain they supply)... But I'm toying with the idea of swapping out the 11-34 cassette for an 11-36, which the equation says is 57.36 links and so gets rounded up to 58 links (KMC 116), so I either need to buy a bigger length new chain or add an extra pair of quick links to a 114 box.

 

[BikerBob38]

Just a wrap-up posting to note that since the old chain ran smoothly and passed the large/large and small/small test, what I finally did was to lay the new and old chains beside one another, link by link. This led me to remove only one link from the new chain and after putting it back on the bike, it works just fine and the position of the derailleur in both configurations looks perfect to me.

Thanks for your patience and for all the great tips and links to relevant sites.