TL;DR: a handful of vehicles are most likely using a separate set of hidden, server-side mobility stats. There’s a new formula for effective top speed on different terrain types, which is now live on tanks.gg. There are a handful of minor but unusual bugs with the movement mechanics.
I’ve been working with WGNA and they’ve forwarded all of this information to their global team. Hopefully, that means these issues will be fixed soon™.
Part of an in-depth series on game mechanics:
Mobility Mechanics: Recap
In last week’s episode, I posted about how hidden stats can change a vehicle’s engine power, top speed, and rolling friction.
For some vehicles, the hidden stats don’t match the stated ones, and all testing indicates the hidden stats are used. However, as we will see shortly, there are several scenarios where the hidden stats don’t explain everything.
Also, a quick primer: movement is calculated server-side. You say “I’m holding W” and the server determines the result. The client can visually move things to make the game appear smoother, but your actual vehicle position is decided by the server.
Server-Side Mobility Stats
I’ve typed up a clear, data-driven explanation for this, but it was too long to put here so I moved it to a comment below.
What does this mean? At least in regards to mobility stats, your garage is wrong and the game files are wrong. Even tanks.gg is wrong. The only way to know your vehicle’s mobility is to test it in-game.
I’ve tested around 60 vehicles, and these are the errors I’ve found so far:
T-22 medium – The real base hull traverse is 54 deg/s, not 40 FV217 Badger – Base hull traverse is 24 deg/s, not 22 Grille 15 – Base hull traverse is 26 deg/s, not 24; terrain resistance while turning is 1.6 / 2.0 / 3.9, not 1 / 1.2 / 3.5 Primo Victoria – Base hull traverse is 42 deg/s, not 36 Strv S1 – Base hull traverse is 35 deg/s, not 26
The following have large prediction errors, but not large enough to be certain:
STB-1 – Base hull traverse might be 54 deg/s instead of 52 E 75 TS – Base hull traverse might be 25 deg/s instead of 26 Lansen C – Base hull traverse might be 38 deg/s instead of 40 WZ-120-1G FT – Base hull traverse might be 44 deg/s instead of 42
Effective Top Speed
Some vehicles struggle to reach their rated top speed on some or all terrain types. Why is this, and what factors affect it?
First, what is an “effective” top speed (ETS)? My definition is the vehicle’s top speed on perfectly level terrain. If you drive for long enough, you will (eventually) reach this speed. You can of course exceed this speed, especially when going downhill or over uneven terrain, but more on that later.
The lower the effective top speed, the harder it is to exceed it. If a tank is rated for 15 km/h, like a superheavy on soft terrain, that’s a pretty hard cap. By the time you reach a 50 km/h ETS, it’s more of a suggestion – it’s still accurate, but it takes so long to reach this value that you’ll never see it during normal gameplay. For example, the IS-7’s hard terrain ETS is 51.52 km/h, but in practice the acceleration drops off once you hit 49-50 km/h.
The formula is surprisingly simple:
Effective Top Speed (ETS) = 3.649 * powerToWeightRatio / terrainResistance
It took a lot of AMX 40s and 105 Octane to obtain this formula, which is accurate to within 0.01 km/h.
While testing, I found two bugs, one noticeable and one very obscure.
The more noticeable bug is that driving over slightly hilly terrain is faster than perfectly flat terrain. You know the little wooden walkways and random curbs that litter the railyard on Himmelsdorf? You gain speed by driving over these bumps. However, it’s not just because you gain more speed going down than you lose going up – under certain circumstances, you gain speed when going up the curb. Yes, really. Tanks like the IS-7 can gain several km/h of speed by going over a handful of bumps. (This gives a whole new meaning to the word “speedbump”.)
The very obscure bug affects turning in soft terrain. Tanks normally turn 15% slower while moving (as opposed to being still), but not always:
Tanks up to 130 tons turn faster when reversing to the right (holding S+D) than reversing to the left (S+A) or turning while going forward (W+A/D) Tanks below 45 tons turn faster when reversing to the right (S+D) than while stationary
Tl;dr: If you need to turn left on soft terrain and weigh less than 45 tons, instead of holding A, hold S+D – you’ll turn faster.
Turbo vs Grousers? Grousers reduce rolling friction, and typically improve a vehicle’s effective top speed more than a turbo. However, a turbo also benefits acceleration. I’m a ways away from getting acceleration curves, but in general, if you want to get from point A to point B faster, a turbo is much more useful.
Vehicles with hydro suspension turn slightly faster when the vehicle is fully elevated or depressed. Not by a very large amount, though: the STB-1 turns about 0.5% faster, while the Strv S1 turns 2.1% faster.
Swedish TDs turn slower when in siege mode, and I haven’t quite figured out why.
Damaged tracks do not affect mobility in any way. Destroyed ones do.