Le Mans Ultimate has always been known for close online racing. Then V1.4 changed the network protocol, and for a few weeks in August and September a lot of people got hit by cars that were nowhere near them. This is what changed, what was rolled back, and what fixed it.
Everything here is from Studio 397's own release notes and community updates on Steam, from V1.4 on 28 July 2026 to V1.4.3 on 6 October 2026.
What "netcode" means here
Netcode is how the game tells every car in a lobby where the other cars are. Your PC only knows where an opponent was a few milliseconds ago, so it predicts where they are now. When the prediction is wrong, you see contact that didn't really happen, or miss contact that did.
In a 60 car race at Le Mans with drivers all over the world, that is the hard part of any sim. It is also why two people can describe the same incident completely differently after the race.
V1.4: the switch to Reliable UDP
The V1.4 release notes of 28 July say Studio 397 "replaced TCP game connections with Reliable UDP for more reliable network connectivity". The same update also:
- Fixed clients who couldn't see other cars because of latency, which caused collisions for other people.
- Allowed a flexible port range, to make connections more robust.
- Restored a car's damage state correctly when you rejoin a race after a disconnect.
Hotfixes on 30 and 31 July added more networking threads and RUDP optimisations for stability.
The rollback in August
It didn't work for everyone. In the August community update, Studio 397 wrote that some users "with particular connection types" still had problems, and V1.4.1.3 on 19 August reverted some of the network protocol to the version used since launch.
They also said RUDP is not being abandoned. They still believe it helps with disconnects, but it "clearly needs more time to mature", so they set up a way to run RUDP test sessions in the public game while other servers use the older protocol.
The real fix: V1.4.1.5
The September community update is the interesting one. Studio 397 said a single line of code, "unrelated to the network protocol itself", was likely behind the phantom collisions, even with RUDP.
V1.4.1.5 on 15 September shipped it:
- Fixed false collisions present since the V1.4 update.
- Added an option to select which version of netcode a server runs.
- Added optional extended network logging for clients and servers.
- Fixed some connection issues under the new netcode.
So the protocol change got the blame, and the protocol did have problems for some connections, but the collisions most people noticed came from somewhere else.
Since then
- V1.4.2, 22 September: fixed unintended collisions while cars are moved into place during pit stops.
- V1.4.2.1, 24 September: fixed long synchronisation times loading into a team based event.
- V1.4.3, 6 October: fixed damage not being restored after disconnecting from an event.
Studio 397 also ran public open beta network tests in September, starting with a 6 hour race at Silverstone and a 12 hour Le Mans test with 62 cars, ahead of their 24 Hours of Le Mans event in October.
What to do if online still feels wrong
- Update the game. Every fix above only works on the current build.
- Check the server. Hosts can now pick the netcode version, so two servers can behave differently.
- Leave room on the first lap. This is true in every sim, but especially in a big multi class field. Plenty of incidents blamed on netcode are just two cars trying to use the same piece of track at the same time.
- Protest only when you are sure. V1.4 gave each player 3 protests per month, returned when a protest is successful.
Your safety rating is what decides who you race with, so a clean race is still worth more than a fast one. And if you race endurance events with teammates, my driver swaps guide covers the part of online racing where a disconnect costs the most.
What comes next for the game is on my Le Mans Ultimate 1.5 update page.
FAQ
Does Le Mans Ultimate have good netcode?
It has a reputation for close racing, and Studio 397 calls it one of the reasons players love the game. V1.4 caused problems, and the false collisions were fixed on 15 September 2026.
What is RUDP in Le Mans Ultimate?
Reliable UDP. V1.4 used it to replace TCP game connections. Part of the change was reverted in August, and RUDP is now tested in public sessions while other servers use the older protocol.
Why did I get phantom collisions in Le Mans Ultimate?
Studio 397 traced them to one line of code unrelated to the network protocol. V1.4.1.5 on 15 September 2026 fixed false collisions present since V1.4.
Can server hosts choose the netcode version?
Yes. Since V1.4.1.5, a server can be set to run a chosen version of the netcode.
How many protests do you get in Le Mans Ultimate?
Three per month since V1.4, and a protest is returned when it is successful.