LG C6 165 Hz G-SYNC Hitches: Isolate 120, 144 and 165 Hz

Quick Answer

If an LG C6 feels smooth at 120 or 144 Hz but repeatedly hitches at 165 Hz with G-SYNC, keep 144 Hz as the safe fallback and isolate the render path before blaming the panel. Confirm a stable fixed-refresh baseline, measure game frame times, then add G-SYNC, an FPS limit, HDR and 165 Hz one at a time. A 2026 LG product page advertises 4K 165 Hz and G-SYNC Compatible support, but that capability claim does not establish that every cable, GPU driver, game and firmware combination will behave identically.

Evidence is limited. The ledger links an early Reddit report from one 48-inch C6/RTX 4090 owner who described 165 Hz hitches while 120 and 144 Hz were smooth. The same discussion contains different outcomes and unsuccessful cable substitutions. That proves a report exists; it does not prove a C6-wide defect, prevalence, cause or remedy.

Symptom Checklist

Windows offers 120, 144 and 165 Hz for the exact C6 input.

The issue is repeatable in a named game or frame-time test, not only by eye on a menu.

Fixed 165 Hz, G-SYNC 165 Hz and G-SYNC 144 Hz have been compared separately.

The GPU is connected directly to the TV during diagnosis.

Resolution, HDR state, output format, color depth, driver version and TV firmware are recorded.

A stable frame-rate cap is used so the game is not continually hitting the refresh ceiling.

A hitch is a delayed frame, not tearing, an HDMI retrain, near-black VRR flicker or low-frame-rate video judder.

Likely Causes, Ordered by Probability

1. Game or render-queue frame pacing

An average of 165 fps does not mean 165 evenly spaced frames. Shader compilation, asset streaming, CPU spikes and an uncapped queue can create visible pauses that become easier to notice on a fast OLED. Reproduce the event with an on-screen frame-time graph or NVIDIA FrameView rather than relying only on an FPS average.

2. Refresh-ceiling and synchronization interaction

When output repeatedly reaches or crosses the active ceiling, V-SYNC, G-SYNC and the game's limiter can interact. NVIDIA documents G-SYNC setup and a driver maximum-frame-rate control. Test one limiter at a time and cap slightly below the selected ceiling; do not assume a copied universal cap is optimal for every engine.

3. The 165 Hz HDMI link state

165 Hz is a more demanding transport state than 120 or 144 Hz. Cable length, connector quality, GPU output, receiver, adapter or marginal negotiation can matter. However, a cable label alone does not diagnose frame pacing, and the cited early owner reported that several cable changes did not resolve the symptom. A direct short certified cable is a controlled test; success still depends on the rest of the signal chain.

4. NVIDIA driver or TV firmware interaction

A driver can alter VRR, display identification and presentation behavior; TV firmware can alter high-refresh handling. Record versions before updating. Use normal NVIDIA and LG channels, restart both endpoints, and retest the same baseline. Do not install unofficial firmware, cross-region packages or an EDID override as an early step.

5. Hardware fault

Hardware becomes more plausible if conservative modes also fail, the link drops across independent GPUs and cables, artifacts appear outside games, or the port behaves abnormally at 4K/60. Hitches confined to one mode or title are weaker hardware evidence.

Step-by-Step Safe Diagnosis

Step 1: Build a known-good 120 Hz baseline

Connect the NVIDIA GPU directly to the C6. Select native 4K, 120 Hz and SDR. Disable G-SYNC temporarily and use a game or repeatable test with a stable frame-time trace. Confirm that the TV's Game Optimizer information matches the Windows refresh rate. Leave service menus and OLED protection untouched.

Step 2: Separate fixed refresh from VRR

At 120 Hz, compare fixed refresh and G-SYNC using the same scene and graphics settings. Enable G-SYNC in NVIDIA Control Panel for the intended display mode and make the C6 the active gaming display. If only VRR fails already at 120 Hz, 165 Hz is not the first variable to investigate.

Step 3: Compare 144 Hz before 165 Hz

Move to 144 Hz without changing resolution, HDR, color format or the game preset. Repeat fixed-refresh and G-SYNC runs. Log frame-time spikes, not just subjective smoothness. A clean 144 Hz result creates a practical fallback and narrows the transition to the maximum mode.

Step 4: Test 165 Hz in layers

Select 165 Hz with G-SYNC off first. If fixed 165 Hz hitches, inspect the game frame-time trace and link stability. If fixed 165 Hz is clean, enable G-SYNC and apply a deliberate FPS cap below the ceiling. Then test HDR separately. A failure introduced only after HDR may involve bandwidth, output format or game HDR behavior rather than G-SYNC alone.

Step 5: Reduce the physical chain

Remove receivers, capture cards, switches and adapters. Try another GPU HDMI output where available and one known certified Ultra High Speed cable of practical length. Reseat both ends with devices powered down. Do not repeatedly hot-plug during firmware installation.

Step 6: Cross-check software

Test another game with different engine behavior and a simple synchronized workload. Clear only game shader caches through supported methods when relevant. Update one component at a time, retain version notes and preserve the last stable 144 Hz configuration. A factory reset of TV and PC together destroys useful contrast and is not an early diagnostic.

Fixes That Match the Evidence

Use stable 120 or 144 Hz; maximum refresh is not mandatory. Keep G-SYNC only where it reduces tearing without repeatable instability. Use a controlled limiter and direct link rather than unrelated picture changes.

If a specific NVIDIA release introduced the issue, report it with GPU, driver, game, cable route, TV firmware and reproducible steps. Roll back only through NVIDIA-supported installation methods when appropriate. If a TV update coincides with the change, report the same evidence to LG rather than forcing unofficial downgrade files.

Model, Size and Firmware Differences

LG's UK C6 page advertises up to 4K 165 Hz with G-SYNC Compatible and FreeSync Premium. Regional suffixes, sizes and software releases can differ, so verify the exact product page and on-TV guide. Consoles do not test this PC-only ceiling because PlayStation 5 and Xbox output no more than 120 Hz.

Reporting is too sparse to estimate frequency. One setup cannot establish a systemic fault, while another owner's success does not invalidate a reproducible local problem.

When to Contact Service

Contact LG when fixed 4K/120 or 4K/60 also fails across two known-good cables and another source, when multiple HDMI ports show artifacts, when TV menus corrupt, or when the set resets or overheats. For a 165-Hz-only hitch, first provide LG and NVIDIA a video, frame-time capture, exact model suffix, driver, firmware and the 120/144/165 comparison. Do not disable protection, enter the service menu, repeatedly pixel-clean, or flash unofficial software for a synchronization symptom.