I found some guides online, but not many for road/tt. The two I found were as follows:
1. put the chain on the ring and smallest cog, then see where the chain meets and add 4 links (maybe it was pins). Compared to what I have, that would be removing quite some length.
2. same as above but take the chain through the derailleur and pull it together just a bit, adding tension to the chain. For me that would mean adding some length.

Here is what it looks like now with a 11-32 cassette, which is what I will have on my race wheels. Thoughts?

Smallest cog:

Biggest cog:

Looks fine to me. You might be able to take one link out, but might be too tight then - I'd say leave it.
There are some online calculators based on chainlength and front/rear cog sizes.
BigBoyND wrote:
I found some guides online, but not many for road/tt. The two I found were as follows:

1. put the chain on the ring and smallest cog, then see where the chain meets and add 4 links (maybe it was pins). Compared to what I have, that would be removing quite some length.
2. same as above but take the chain through the derailleur and pull it together just a bit, adding tension to the chain. For me that would mean adding some length.

1. You mean biggest. and it's 2 pins I believe.
From ~5:00

Method 2: (through the derailleur, round the smallest sprocket, pull only enough tension to prevent the derailleur binding) creates the lowest chain tension, which theoretically gives lower friction, but in 1x context maybe increases derailment risk?

Method 1 gives you highest chain tension.
Method 2 gives you more leeway if you want to fit a bigger cassette in future.

Either way, what you have looks fine, just leave it.
Last edited by: MattyK: Apr 17, 19 17:56
blehargh wrote:
Looks fine to me. You might be able to take one link out, but might be too tight then - I'd say leave it.
There are some online calculators based on chainlength and front/rear cog sizes.

MattyK wrote:
BigBoyND wrote:
I found some guides online, but not many for road/tt. The two I found were as follows:

1. put the chain on the ring and smallest cog, then see where the chain meets and add 4 links (maybe it was pins). Compared to what I have, that would be removing quite some length.
2. same as above but take the chain through the derailleur and pull it together just a bit, adding tension to the chain. For me that would mean adding some length.

1. You mean biggest. and it's 2 pins I believe.
From ~5:00

Method 2: (through the derailleur, round the smallest sprocket, pull only enough tension to prevent the derailleur binding) creates the lowest chain tension, which theoretically gives lower friction, but in 1x context maybe increases derailment risk?

Method 1 gives you highest chain tension.
Method 2 gives you more leeway if you want to fit a bigger cassette in future.

Either way, what you have looks fine, just leave it.

You're right, I remembered that incorectly. This is the video by AbsoluteBlack where they add 4 pins. Makes much more sense with the big ring in the back.

Thanks, I'll leave it as is. I didn't think chain tension changes with chain length because I assumed the spring is linear.
Not sure what you are saying there. The shorter the chain the higher the tension.
Springs are either linear or progressive. Linear means their tension is the same throughout usable range. Progressive means tension increases as it is stretched or compressed.

https://www.sciencebuddies.org/...ear-springs-tutorial
A linear spring tension is not CONSTANT. It's tension increases LINEARLY with its stretch.

F = k * d

Where,

F is the applied force
K is the spring constant
d is the displacement

A progressive spring, has a K factor which changes with the displacement or some other factor (rate of displacement, for example).
Last edited by: Tom_hampton: Apr 17, 19 20:21
It looks good. Maybe one link out.

How is it shifting? Is there excessive chain slap? If not, I wouldnâ€™t mess with it.

Oui, mais pas de femme toute de suite (yes, but I am not ready for a woman straight away) -Stephen Roche's reply when asked whether he was okay after collapsing at the finish in the La Plagne stage of the 1987 Tour
You're right! I think I might take out one link then since I'm not running a clutch to keep it a little tighter.
I just put it together and haven't ridden it outside yet, so unsure about chain slap but will keep an eye on that
All drive trains run best with the longest chain possible.
This is why Shimano Di2 locks off the small small combos, it allows a longer chain.
Your setup would be better with an extra link, but seeing as you have already cut it to that length, leave it, it will be fine.

The reason it runs better, is that in the larger cogs, a tight chain pulls the pulleys forward and increases dramatically the angle that the chain comes into the bottom pulley from the front derailleur.
Whenever you put that much angle on the chain coming into the derailleur it will set up a twist in the chain as it moves through the derailleur and can create a small shift in chainline as it goes onto the cassette sprockets.
A short chain also increases chain tension on the non driven side of the chain and increases pulley wear, especially on high priced narrow/wide pulleys.

ALL drivetrains run best with the longest chain that can be fit into the system.
The only valid reason to ever use a shorter chain is if the cassette will be swapped with a smaller cluster regularly that would leave the chain too long.

The best way to size a chain is to have some old quick links to use as you get it sorted.
Start with the chain as long as possible to the point where it almost goes slack in the little cogs.
Run it through all the gear combinations and squeeze a couple of links together to shorten the chain and see if it may be better in every gear. Shorten if needed, but at least you have a safe starting point and it may surprise yo haw long you can run it and how quiet the drivetrain is.
In a one by with a derailleur with a large offset, chain length will decide relative distances of top pulley from cogs in small to large gears.
The best setup has the closest constant pulley clearance.
Very short chains will pull the top pulley away from the cassette in the largest cogs.
BigBoyND wrote:

Biggest cog:

Put a cable crimp on that bad boy before it frays!
i see a chain sizing methods that use the biggest cog, but i never really grasp the thinking. i always place the drive train in the smallest cog total i'm going to use, so, for me, small to second-to-small. then i size the chain so that the chain doesn't rub the upper pulley in this gear. voila. longest possible chain. which is my aim. for both friction, for chain life, for lube life.

Dan Empfield
aka Slowman
Slowman wrote:
i see a chain sizing methods that use the biggest cog, but i never really grasp the thinking. i always place the drive train in the smallest cog total i'm going to use, so, for me, small to second-to-small. then i size the chain so that the chain doesn't rub the upper pulley in this gear. voila. longest possible chain. which is my aim. for both friction, for chain life, for lube life.

Would you aim for longest chain even if you don't have a clutch RD?
BigBoyND wrote:
Slowman wrote:
i see a chain sizing methods that use the biggest cog, but i never really grasp the thinking. i always place the drive train in the smallest cog total i'm going to use, so, for me, small to second-to-small. then i size the chain so that the chain doesn't rub the upper pulley in this gear. voila. longest possible chain. which is my aim. for both friction, for chain life, for lube life.

Would you aim for longest chain even if you don't have a clutch RD?

i've been aiming for the longest chain over my entire cycling life, so, from the 1970s.

Dan Empfield
aka Slowman