The Shiny New AM831 Group Buy (A) Thread!

[Snacks]

I tried the line on the back of the derailleur as well and it doesn't matter if the line is above, below, or right at the teeth tips, the line isn't perpendicular and one side angles away, like the angle is wrong. I cut the chain at front and biggest rear plus 5 and a quick link. Something seems off and not finding what and the shifting isn't great and isn't spinning very smooth.

I've gone over Shimanos installation documents a bunch and keep double checking and expecting to find something off but it hasn't happened yet...

This is how mine lines up now. It was a bit off when the chain was short but sound like you sized yours correctly. My only other thoughts are limit screw not allowing the derailleur to line up with the big cog or maybe hanger is bent?

[JJJ]

Has anyone that's gone with Shimano 12 speed been able to get the derailleur set up right? It seems like when the B screw adjustment is correct the derailleur isn't at the right angle. I'm still playing with it but shifting isn't very good so far.

I'm also going to try to find Shimanos specs on derailleur placement in relation to the axle. I'm new to 12 speed but was a bike mechanic for quite a few years and something seems "off".

I successfully installed an XTR with an E13 Helix-R cassette, and Hyperglide chain. What model derailleur and cassette are you using? Make sure you place the guide between the screw and the hanger. Post a picture.

[FlaMtnBkr]

I'm using an SLX 10-51 cassette, SLX m7100 derailleur and chain, SLX crank and 32t ring, and an XT Shifter.

I got a spare hanger so it's pretty easy to measure, and found the Sram frame fit specs and the hanger definitely isn't within current specs for the rear derailleur. I didn't find one for Shimano but I imagine it's about the same. There is also a push for a universal hanger which falls on one end of Sram's specs: www.UniversalDerailleurHanger.com

The hanger that came with the frame puts the derailleur 2mm higher and about 5mm further back. Not a lot, but well out of the range specified. Since a couple mm of the B screw adjustment can make a big difference I would think it can have a fairly big impact.

Here is a link to the Sram specs and I'll post a picture. Everything else I've found shows the line much more perpendicular with the tips and haven't found a pic of one that isn't except the one above which looks like it might be a little better than mine. I also added 2 links, an inner and outer, to the chain and the derailleur looked a lot better when setting B screw, but too much slack in the 10 cog so I removed it.

https://www.sram.com/globalassets/document-hierarchy/frame-fit-specifications/mtb/2021-mtb-frame-fit-specifications.pdf

[JJJ]

The hanger that came with the frame puts the derailleur 2mm higher and about 5mm further back. Not a lot, but well out of the range specified. Since a couple mm of the B screw adjustment can make a big difference I would think it can have a fairly big impact.

Looks like your hanger is wrong, indeed. I'd say loosen the B-screw so that the guide line falls at the valleys of the teeth instead of the tips. Post a pic of the hanger.

[FlaMtnBkr]

Well I actually got 2 extra and all 3 are the same and looks like the CAD drawing on the geo charts. I'm betting it's the same hanger everyone else has. It's pretty easy to take a ruler and eyeball the dimensions given in that Sram document, and tell if it's out of spec. Micrometer will get you closer to the exact numbers. If you measure the diameter of a hole and then measure to the far side of the hole and subtract half the diameter, it's a lot easier than trying to measure to the center. If anyone is so inclined...

I'll get a picture tomorrow. I also tried raising the line close to the teeth valleys all the way to about the same distance under and the line never straightens out perpendicular. I should be getting some parts tomorrow so planned on some stand time and try a wide range of adjustments to see if anything gets things to smooth out some.

But at this point I would say going with a 1x11 setup would be a safer bet than 12 speed. Not sure what I will do if I can't get things quite a bit better than they currently are but I'm not tracking down and buying a different drivetrain in the hopes it will work better with this hanger.

Hope others are having better luck and have good, silent, crisp shifting. Though I can't imagine it's as good as it could be if we all have the same hanger.

Someone asked and I forgot to mention, but the hanger is straight as that's the first thing I check when installing a drivetrain, even when brand new.

[JJJ]

FlaMtnBkr, I have X = 15 and L = 28, which is 5 mm further back and 2 mm shorter than the specs, the same as you. Yet my XTR works fine, even when backpedaling, and the teeth are perpendicular to the guide line (with the guide line in the valleys, as per recommended by E13 with the Helix-R cassette, that has 50 teeth).

[emu26]

are you both measuring the "L" as 90 degrees to the line between centre rear axle and centre bb or 90 to a horizontal line through the rear axle?  The SRAM doc says axle to bb.

[JJJ]

are you both measuring the "L" as 90 degrees to the line between centre rear axle and centre bb or 90 to a horizontal line through the rear axle?  The SRAM doc says axle to bb.

[FlaMtnBkr]

Axle to BB, though the angle doesn't change "L", just "X"

I will try to go thru a wide range of adjustments and see if I can find a combo that smooths things out. Hopefully will get to it before my daughter's softball game this afternoon. I'm glad others are getting along with it!

[SVChucko]

@FlaMtnBkr, your photo looks like my similar setup with a Shimano XT 12-speed derailleur and Deore 11-speed 11-51t cassette... when I had a chain that was 2 links shorter than recommended.

[FlaMtnBkr]

When I was first messing with it, a longer chain looked like the only way to get the line at teeth tips and perpendicular, so I cut an inner link and used a second quick link to add 2 links and the line looked the way it's supposed to. However, in the 10 T cog the chain was obviously too long so I removed it.

Thanks for the suggestion! But I think it's going to be a compromise and getting things as good as possible, at least with 12 speed. I think 11 or 10 speed will work better, though it's probably possible to get shifting good with 12, just not as good as it could be. At least with the setup I have...

[emu26]

Axle to BB, though the angle doesn't change "L", just "X"

Good point.  That's the problem with late night posts.

Hope you sort it out.

[JJJ]

When I was first messing with it, a longer chain looked like the only way to get the line at teeth tips and perpendicular, so I cut an inner link and used a second quick link to add 2 links and the line looked the way it's supposed to. However, in the 10 T cog the chain was obviously too long so I removed it.

I've installed an e13 Helix-R cassette, with a 9-tooth cog, and there is no chain slack on that cog with the prescribed number of links. Sounds like your cage length is too short! Is your derailleur the 7100-SGS or 7120-SGS model? The 7120 is for a 2x12 drivetrain and goes only up to a 45T cog.

[Thrill21]

Gentlemen,

Anyone completed the build with the crown spacer to prevent the front fork from hitting the downtube?  I'm quite confused on what we should use;  +0.5° crown spacer?  My fork hit the downtube (Frame Size S).  The rated head tube angle is 65.5° -  This would make 65° with the crown spacer?  I assumed the headset uses 45 degree bearing race. 

https://reverse-components-usa.com/products/reverse-angle-spacer

Thank you for your input & sharing with us.

I used the one that someone suggested and put a link in, further back to one of the first builds and, yes it does change angle, but I've been riding a stumpy eco prior to this so it doesn't bother me. I'd rather that then frame damage

[darius72]

Bike finished; lighter than expected at 12.3 Kg, where the tyres alone are 2 Kg! I will make a build thread later on if I will have time, for now main components list:
Fork manitou mezzer, rear shock DT swiss 531, rims carbonality carbon asymmetric with dt swiss hubs, tyres maxis DHF ant  + rekon post, saddle,post,pedals aliexpress, handlebar OG evkin, groupset and brakes shimano XT.
Test drive:  I climbed steep asphalt road (average 18%) and the position is ok, no front wheel lifting despite the 4 cm spacers under stem, also I appreciated the lock on rear shock and the mezzer with all dials at maximun is stable too; the bike isn't very fast on flat road, it's hard to mantain 30 km/h, probably due to the draggy tyres, but uphill doesn't feel worse than my 9 Kg XC bike; downhill as expected is a all trails  eater, very fast on flow sections, I really enjoyed the ride; of course it needs more suspension tuning.