Bugs & Issues – Le Mans Ultimate (LMU)
This page collects known and suspected bugs when using RaceLab with Le Mans Ultimate (LMU) – overlays not appearing, stutters, freezes, or strange behaviour in sessions. It helps you decide whether you are seeing a core LMU bug, a RaceLab bug, or a PC / network / plugin issue.
Before you call it a “bug”
- Confirm LMU is updated to the latest patch / hotfix.
- Confirm you are on the latest RaceLab version.
- Restart LMU, RaceLab, and (if needed) your PC to clear “stuck” plugins.
- Test in a simple offline session (single car, no AI or only a few AI).
- Temporarily disable other plugins / overlays to rule out conflicts.
Common symptom categories in LMU
- No overlays / no data – RaceLab layout started, but nothing appears on screen.
- Wrong driver / car data – overlays look like they are following another car. [3]
- Performance & FPS issues – stutters, freezes or heavy drops when overlays or plugins are active. [2]
- Triple-screen / multi-monitor quirks – micro-stutters or UI issues when using certain setups.
- UI / HUD conflicts – LMU’s own HUD clashing with plugin overlays or broadcast tools. [1]
What to collect for a report
- LMU version / build and whether you are on RaceControl official online or offline practice.
- Your PC specs (CPU, GPU, RAM), monitor setup (single / triple / ultra-wide), and wheel base.
- RaceLab version and which overlay layout you were using.
- Any plugins or extra overlays you run alongside RaceLab.
- Screenshots or a short video clearly showing the problem and the overlays.
Where to report
For core LMU bugs (crashes, RaceControl issues, severe stuttering, triple-screen problems), use the official Le Mans Ultimate support channels, known-issues lists, and community forums. [1] For problems that only occur when RaceLab is active – especially overlays and data – use the RaceLab Discord bug-report channels or the RaceLab roadmap / tracker. [4]
Quick triage – is this an LMU bug, a RaceLab bug, or something else?
Use this panel as a fast checklist before you post a bug report. It helps you send your issue to the right place and include the details the devs actually need.
1. Does LMU misbehave without RaceLab?
- Close RaceLab and any other overlays / plugins completely.
- Restart LMU and join the same type of session (offline / RaceControl).
- If the stutters, freezes, or HUD problems still happen, treat it as a core LMU issue. [1]
- If the problem only appears when RaceLab is active, continue below.
2. Is it linked to overlays / data connection?
- In RaceLab, confirm LMU is selected as the active sim and a layout is chosen.
- Load into the car in LMU, then press Start layout in RaceLab.
- Use borderless or windowed mode rather than exclusive fullscreen for overlays.
- Check that no other app is using the same overlay / telemetry port.
- If symptoms follow a specific layout or overlay, log it as a RaceLab overlay / LMU integration bug. [3]
3. Could it be performance, triples or VR?
- Test with plugins and overlays disabled to see if stutters disappear. [2]
- Lower graphics settings and test with fewer AI, especially on triple screens or VR.
- Try borderless window instead of exclusive fullscreen on multi-monitor setups.
- Monitor CPU/GPU usage and VRAM to see if you are hitting a performance limit.
- If performance issues improve when plugins / overlays are removed, treat it as a performance / configuration issue rather than a pure LMU or RaceLab bug.
Before posting your report
- Write a short, clear title – e.g. “LMU – RaceLab overlays cause stutter after 5–10 laps”.
- Include your PC specs (CPU, GPU, RAM), monitor layout (single / triple / VR), and wheel base.
- State whether the session was offline, RaceControl daily race, or custom server.
- Mention the exact LMU build and RaceLab version you are running. [4]
- Attach at least one screenshot or a short clip showing the overlays and the issue.
- List what you have already tried (restarts, different tracks, disabling plugins, changing graphics, etc.).
Sources & References
- Official Le Mans Ultimate known-issues lists, support articles and forum “Known Issues” threads for current LMU bugs. ↩ back
- Le Mans Ultimate performance guidance and community reports where plugins and overlays affect FPS and stability. ↩ back
- RaceLab LMU integration notes and community bug reports about overlays not showing or tracking the wrong driver. ↩ back
- LMU and RaceLab release notes (version numbers, recent changes and temporary compatibility issues). ↩ back