Changing chain rings 1x - need to change chain?

Howdy All,

Hoping for some wisdom. Newbie to having a 1x on a gravel bike. Bike came with the 10-44 xplr cassette and 40t chain ring which I will use for big climbs in racing. Most of local training riding though I plan on using a 44t chain ring to get more top end and still maintain a 1:1 bailout.

Question - with a 4t difference do I need to have two chains for each set up or is this where the B-screw adjustment comes into play?

Or would you try to size for a 42 chain ring to split the difference between the two perhaps?

Appreciate the wisom of those fellow wrenchers.

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You will need another chain. Especially going up 4 teeth.

I swap chainrings on two bikes from 34 to 46 chainrings and have found 36&38 uses same chain length, 40&42 have same chain length.

Big assumption here, did you get a Lauf Seigla? Race Witeless? Make sure you get a 12speed flattop chain for the XPLR group set.

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Appreciate the wisdom @SirDAN appreciate the perspective. I do wonder if I sized a new chain for a 42T if it would work for both the 40 and 44 given it’s only two teeth either way.

The shop set it up with the 44t with the same chain as the 40t, it works but is a bit noisy in the 10T and next two.

All good, I have the flattop chain and will keep one chain for racing and the other for the bulk of my training.

It should be looser when in the 40t if they set it up with the 44t, be wary of excessive chainslap. I found 40t&42t used the same chain, it was too much of a stretch (pun intended) for the 44t. At second worst, you will likely break a chain and have non-optimal changing of gears.

It is very easy to check. I always use the following video.

6:45 - 7:10 is your reference point (pun intended if you watch the video)

Thank you @SirDAN, I’ll have a look at the video. The bike’s chain was sized to the 40t as that was the chain installed from the manufacturer, they put on the 44t and somehow managed to keep it working but as I said it is a bit noisy and suspect that it’s probably not quite optimal.

Was the chain you sized on your 40t&42t bike sized originally for the 40 or the 42? Just curious.

from the 42t originally

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You can calculate the chain length, think I found an equation on the park tool website. It depends not only on the gears front and back, but also on the length of the chainstays. The longer the chainstays, the less important the gears.

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Thanks @splash, I’ll have a look for that formula. Kind of makes sense that the gears plus the over all length of the chain would have an impact (as would the B-screw adjustment)