SRAM GX/NX 12sp install and adjustment tips

[W@nted]

20 minutes ago, DieselnDust said:

initial adjustment should be done with the chain on the 5th, 6th or 7th sprocket.

Micro adjustment should be conducted on the 2nd sprocket and 11th sprocket. 

Once the derailleur is set up in the middle of the cassette do the microadjustments on the 2nd and or 11th

 

if the chain is ticking check the quiklink that both links are fully engaged. 

Ensure that the chain is running correctly on the NW tension pulley wheel (that's the bottom one)

 

To check chain line get a 1m long steel rule and hold it thin edge against the inner side of the chainring. It now cross over the 7th  sprocket on the cassette (counting from the drop out) or thereabouts - there is bit of tolerance involved since this is the bike industry that uses civil engineering tolerances and not mechanical Eng tolerances

 

Thanks! 
 

Some stupid questions from my side:

1. With initial adjustments, do you refer to the b gap settings?

2. Do you count sprockets starting from the 50t or the 10t?

3. Please clarify the derailleur set up in the middle sprockets?

[W@nted]

2 minutes ago, Chadvdw67 said:

The ticking could be burrs on the cassette at those sprockets, my GX cassette did it as well on the same sprocket as yours, I think it is a fairly common problem 

Thanks yes I read about an issue with the gx cassettes on those specific gears. I have not unleashed the dremel on it though…

[DieselnDust]

9 minutes ago, W@nted said:

Thanks! 
 

Some stupid questions from my side:

1. With initial adjustments, do you refer to the b gap settings?

The first setting is the correct indexing followed by upper and lower limits, then the chain length and b-gap. Hereafter micro adjustments may be necessary.

2. Do you count sprockets starting from the 50t or the 10t?

always from the 10t

3. Please clarify the derailleur set up in the middle sprockets?

To get the initial set set up more or less right the chain has to be as straight as possible. So i often first check the chain line using the simple 1m steel rule either on the inside )if there's space or outside of the ring. Once I now what sprocket to work with I move to the next step, setting up the guide pulley to be directly under that sprocket. The idea is to get the upper guide pulley directly below the sprocket that is most aligned to your chainring.  99% of the time getting this right means no further adjustments with an AXS system. Cable derailleurs will require some further tweaking.

Now I can set my limits screws to ensure the derailleur doesn't send the chain into the spokes or drop out. (without the chain fitted)

fit the chain and get the length correct. I first start with the 10t sprocket and make sure the is as long as possible in this gear with the bike in the stand. The pulley cage must have tension on it. If its against its stop it is not tensioning the chain and you will have shifting issues. So thread the chain through find the right length at rest and shorten by one link. Still no tension, reduce length by another length (you can do this with a c shaped wire holding the last roller one end while you adjust it inward on the other end to find the point at which there's tension and you can no remove those excess links. Usually around 5-6 with most 29er XC bikes i.e 119 to 121 links in the remaining chain)

Next check the chain length in the 50/52t sprocket. This has to be checked with the bike sagged and before you set the B-gap. If the derailleur pulley cage still allows for the chain to bend as it travels between the guide pulley wheel and idler tension pulley then the length is ok as a starting point. If the chain bends a lot and the pulley cage is near vertical then the chain is probably too long. BUT FIRST CHECK THIS WITH THE BIKE SAGGED as some bike designs require massive chain growth. After doing this I do an initial set  up of the B-gap.

Once this is done and the shifting is good in the stand I check the chain length again with weight on the bike i.e. go ride it around the block. Often I can take out 1 extra link. I like the pulley cage to be sitting at angle of about 45 degrees from the vertical (measured as a line between the two pulley wheel bolts). This gives a little extra room for suspension movement on rough climbs and descents when a optimally short chain can result in a sometimes harsh ride if the bike is designed with lots of chain tension coupling to reduce suspension bob. If a link is removed I have to check the B-gap again and adjust it correctly. Go ride around the block and cycle the suspension while doing so.

The longer the travel of the bike the more chain growth there is at the sag point and sometimes beyond. It might be a good idea to have the chain one link longer than optimal or set up the chain length with the suspension at the 50% sag or where ever the inflection from chain growth reverses.