Chainline help - Light Carbon LCG-071 and Sram Apex axs

[RiegelundGel97]

Hi guys,

I'm planning on building up my first Chinese frame, the LCG-071, with a Sram Apex axs 1x12 WIDE Group. While checking some data, I stumbled over the chainline:

SRAM APEX AXS 1x12 WIDE has a Chainline of 47,5mm

Frame LCG-071 has a chainline for 1by setup: 49mm
LightCarbon website:
"Max Chainring: If use single chainring, max 42T (corresponding chainline=49.7mm ).
If use double chainring, max 54/42T (chainline=43.5mm)， min 46-30T (chainline=47mm)"

is it good that these 2 47,5mm vs 49mm are close together or could it cause problems that they are not the same?

Ty in advance for your help 

[courdacier]

your chainline will be closer to the highest gear by a few mil, so your granny gear might get a bit noisy. if it bothers you too much you can always space the driveside crank arm out a bit and get a chainring w/more offset.

[dsveddy]

Their advice on chainline is pretty unintelligible to me. Having an LCG071 myself on which I run a 43.5mm chainline crankset, I really don't believe that a 54/42T could fit with a 43.5mm chainline. 46-30T just barely fits. Perhaps there's a typo, where:

If use double chainring, max 54/42T (chainline=43.5mm)，min 46-30T (chainline=47mm)

should actually read:

If use double chainring, max 54/42T (chainline=47mm), max 46-30T (chainline=43.5mm)

Similarly, I don't understand why they would recommend a max chainring of 42T for a 49.7mm chainline, which is a wider chainline than the 43.5mm chainline's outer ring (which sits at 46mm), or even that from a 47.5mm chainline. It would make more sense if they were recommending a 42T max chainring for a 43.5mm 1x chainline, which is what you get with a inboard-offset 1x chainring commonly used in 1x conversions.

In any case: I'm betting that with a 47.5mm chainline, you can run 54/42t max.

[RiegelundGel97]

Their advice on chainline is pretty unintelligible to me. Having an LCG071 myself on which I run a 43.5mm chainline crankset, I really don't believe that a 54/42T could fit with a 43.5mm chainline. 46-30T just barely fits. Perhaps there's a typo, where:

should actually read:

Similarly, I don't understand why they would recommend a max chainring of 42T for a 49.7mm chainline, which is a wider chainline than the 43.5mm chainline's outer ring (which sits at 46mm), or even that from a 47.5mm chainline. It would make more sense if they were recommending a 42T max chainring for a 43.5mm 1x chainline, which is what you get with a inboard-offset 1x chainring commonly used in 1x conversions.

TY very much for your answer! helps a lot!

im indecisive which groupset to use.
In any case: I'm betting that with a 47.5mm chainline, you can run 54/42t max.

[dsveddy]

TY very much for your answer! helps a lot!

im indecisive which groupset to use.
In any case: I'm betting that with a 47.5mm chainline, you can run 54/42t max.

What terrain do you plan on riding?

Sram Apex AXS 1x wide is a safe bet if you want 1x, low cost, and gearing that will cover pretty much any situation on-road and off-road as long as you aren't an elite racer or climbing long 30%+ grades off-road. My only reservation is with the dub spindle in the BB86 shell

[RiegelundGel97]

Im riding in extreme flats, Like Netherlands flats! The only Hills are the 5m increase of the bridges over the Highways in the area.
Surface would be Tarmac and a Bit of Gravel, Not through Woods or extreme off-road.
Im Not a Racer or ambitious rider, just Hobby rides After work or weekends.
I don’t Need the lightest groupset or setup, i just don’t See a reason in a Front derailleur and more.

My latest idea is getting a normal Sram Rival 1x setup (But Not WIDE) for the flats, but also to be futureproof if i plan on getting a Front derailleur, then i could add that Later. Maybe with a force crank, because that Supports Single Chain Ring, Rival cranks (Not WIDE) doesnt Support That.

[dsveddy]

My latest idea is getting a normal Sram Rival 1x setup (But Not WIDE) for the flats, but also to be futureproof if i plan on getting a Front derailleur, then i could add that Later. Maybe with a force crank, because that Supports Single Chain Ring, Rival cranks (Not WIDE) doesnt Support That.

I don't see that Sram sells a 1X rival crankset that isn't wide. But the Rival 1x wide crankset comes in up to 46T which should be plenty for your purposes. Probably best to not buy a separate force crank, you'll probably lose out on the discount you get from buying as a groupset. These cranksets are super cheap too. A new set of chainrings costs nearly as much as a crankset so I would just get the 1x groupset and just buy a new crankset when that occasion arrives. Who knows, maybe you'll want to buy a power meter then too. 

[zett]

Maybe I'm misunderstanding, but Lightcarbon's specification doesn't mean you must have a crankset with ~49 mm chainline. It is merely the reference value for determining clearance. If you have a crankset with a smaller chainline value (i.e. more inboard), you probably will run into clearance issues with the specified max of 42T.

The ideal chainline for a 12x142 through axle back wheel is around 46 mm, but cranksets, especially gravel specific ones, sometimes compromise and are a bit more outboard to gain more clearance between chain/crank/front derailleur and tire. Or they might compromise to be more inboard to work better on "classic" 10x130 mm QR where the ideal chainline is 43.5 mm (e.g. 44.5 mm on Shimano road cranks).

Around 49 mm is the ideal chainline with boost (148 mm) axle standards, but those are almost exclusively used on MTBs.

[dsveddy]

Maybe I'm misunderstanding, but Lightcarbon's specification doesn't mean you must have a crankset with ~49 mm chainline. It is merely the reference value for determining clearance. If you have a crankset with a smaller chainline value (i.e. more inboard), you probably will run into clearance issues with the specified max of 42T.

The reason I'm saying the chainline specs are nonsensical is because they are quoting a 42t max chainring size for the furthest outboard chainline, and then quoting a larger 54/42t combo quoted for the further-inboard 43.5 chainline. As you know, that's the opposite of how chainline affects ring clearance.

As an owner of this frame, I know for a fact that the 54/42t max spec for 43.5mm chainline is flat out wrong, I had to shim out my 43.5mm chainline crankset to get a 46/30t set to fit.

[Txapa80]

Hi @RiegelundGel97, I'm sure what you mean about chainline, I guess is how far the chainring sits from the BB.

I have one of this frames and I built it with ultegra cranckset and the chainring fitted where the big chainring of 2x would fit and I used to run a 46T chainring, my rear derailleur is an Sram Rival xplr axs with a 10-45 Shimano cassette.

I don't feel it particularly noisy when I run the lowest gear but it's true that I found the transmission noisier that the standard ultegra that I run on my road bike.

I sent you a picture of the gap with the 40t chainring to show you the gap but as I said I used to run a 46T without any problem even if the gap was quite small

[RiegelundGel97]

Thank you very much!