Below is a X-Post that I thought might be informative (performed on a Large Yelli Screamy).
Just got my Wolf Tooth Red 42T GC in last Thursday. Sram specific GC went on a Sram 1050 cassette (11-36) on a Canfield Yelli Screamy. I am running a regular Shimano 64BCD 28t "granny" chainring on the front. I have run this chainring, cassette, KMC X10SL chain, and a Sram X9 type II mid-cage derailleur for more than a year without a single dropped chain. The 28t "granny" does not have the ramps/teeth of a shifting middle or large ring, and the teeth are actually longer, so it pretty much works like a SS ring. The chainline on the Yelli is PERFECT with this ring in the 64 BCD position on a 2X (XT M785) crankset with one bottom bracket spacer on the drive side (as Shimano instructions say should be done). Perfect 1X10 shifting and no dropped chains in over a year (riding in AZ chunk).
I was nervous about the GC with the Yelli's chainstays being so short. I mounted it per directions, but I left out the 15t cog, as I always use the 17t and 19t. I ordered a new KMC X10SL chain, as I new I would need a longer chain and these cannot be lengthened as they have mushroomed pins, and the pin mushroom is destroyed when you push a pin out. I could have used another quick-link, but I did not want two on a chain.
I measured the chain using the large chainring (my only chainring, 28T), around the GC, bypass the derailler, and added two links. Cut (pushed pin) the chain to my measured length and installed it in the derailler. Adjusted "B" screw so that there was no rubbing between 36T and GC. I did not need the longer screw included with the GC. In fact, I still had 3mm of screw showing with the correct adjustment. I went for a driveway test and adjusted trim on the derailler. Shifting was marginal (at best). I was quite dissapointed, so I started the typical break-down of potential problems.
I started with the derailler hanger allignment. Made a small tweek using the 5mm allen key in the derailler mounting hole on the hanger and eyeballed the derailler allignment. Looked good.
I then looked at chain tension. My derailler was almost at full tension with the 28T X 42T (GC) combo. The way the Sram (maybe Shimano too) deraillers are set-up, the upper cage pulley is offset, so that the farther the cage is pulled (larger cogs), the further it is pulled away from the cog. Although it seemed to me that I would want the shortest chain possible to take advantage of this design (cage pulled towards the crankset as far as possible) I re-visited proper chain length. I went the opposite way this time. I put the derailler in the 11T position and added links using two quick-links until the chain still had tension on the smallest cog (11T) and did not rub on itself where it wrapped through the cage. I made sure the chain below the bottom pulley heading to the chainring did not rub on chain below the top pulley, as the two pulleys are nearly horizontal to each other in the highest (smallest) cog. I then shifted to the 42T GC. The derailler was less into it's total swing, as I added three links. I did the driveway test and surprisingly shifting was better, but not where it was before the GC installation. More frustration.
I then decided that with a new chain maybe I had wear in my drivetrain and the new chain wasn't matching up with old cassette. I did not want to buy a new cassette unless completely necessary. I then decided that I would try to install some new jockey pulleys on the derailler. I picked up some $15 alloy pulleys from the LBS, installed, and ......PERFECT SHIFTING!!!
I ordered a new KMC X10SL chain as I did not want a chain with two quick links in it. Installed yesterday and I cannot say that I now notice any shifting difference between stock Sram 11-36 and now Sram/Wolf Tooth 11-42. Here are the key points I found:
1) Install a new chain (as most 10spd chains have mushroomed pins and cannot be lengthened by putting a pin back through them). Make sure that it is as long a possible in the highest gear (smallest cog), but that it will still have tension and does not rub on itself.
2) Adjust "B" screw tension so that there is no rubbing in shifts between 36T and 42T. Turn screw out until there is just a little rubbing from 36T to 42T, and then screw it in (more tension) half a turn.
3) I removed the 15T and shifting is perfect up and down across all cogs, even the 13T to 17T.
4) The key to my final shifting issue was the derailler jockey pulleys. Once I installed new allow pulleys (these) everything is PERFECT.
5) NOTE: Adding B screw tension lengthens the drivetrain, effectively shortening your chain. Make sure you account for this in measuring your chain before shortening!!!
Hope this helps...
Another general drivetrain
Chain on 11T
Chain gap on 11T
Chain on 11T
Chain on GC 42T
Chain on GC 42T backside
Derailler position on GC 42T
Alloy jockey pulley
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