I wanted to get in on the fun. I don't think I run a spall liner on any tank. They only reason I can see for running a spall liner is the 50% crew protection boost, and then only in tanks like the Tortoise that have a weak spot that always kills a crew member. Spall liner against HE isn't that effective. It doesn't reduce damage by 50% or 25% or whatever is the listed amount. It boosts the amount of damage your armor absorbs from the splash by the stated amount. A tank with 200 mm of armor would get boosted by 50% in the calculation so it would get 300 mm of armor to absorb the splash. A tank with 20 mm of armor would get boosted to 30 mm of armor. It's just not worth it to run a spall liner on tanks that have no armor, and it's questionable to run it on tanks that do have it.
I've gone back and found a nice post from way back when about this topic from Matthew J35U5. The thread is here : http://forum-console.worldoftanks.com/index.php?/topic/16681-the-spall-liner%E2%80%94a-questionable-choice/
Here is Matthew's post from Jan. 11th 2014:
The Spall liner item description reads: +x% (20, 25, 30, or 50%) to armour protection from ramming and explosions. The most common usage of this equipment is (the fun of ramming not-withstanding) to protect yourself against HE shells, most commonly the large HE shells fired by artillery. However, there are arguments against this choice. First of all, the spall liners do not protect you against penetrating hits by HE shells. This means that the "one-hit kills" that artillery get by landing penetrating hits will still happen just as often. One-hit kills by artillery aren't all that common though, so lets examine the effect that spall liners have in protecting you from splash damage. The formula for calculating the damage caused by non-penetrating HE shells is this:
actual damage=0.5*nominal damage*(1-impact distance/splash radius)-1.1*nominal armour thickness*spall coefficient
Let us then imagine one of the large artillery, a GW Tiger with its 21 cm gun. The nominal average damage by the GW Tiger's gun is 2000, but the penetration of the HE rounds are only 105 mm. If the GW Tiger is shooting at a comparable tier heavy tank such as the E-75, you will see that there are no locations on the E-75 where the GW Tiger is likely to penetrate with its HE rounds. So, taking the E-75 as an example, let us see how much damage the GW Tiger will do with a non-penetrating direct hit.
To avoid the messiness of tracks absorbing HE damage, let us assume that the GW Tiger lands a hit on the side of the E-75's turret. The side of the upgraded turret has 160 mm of armour, making the nominal armour thickness 160. Plugging into our formula, we get:
actual damage= 0.5*(2000)*(1-0/x*)-1.1*160*1**
*I didn't bother to find out what the splash radius on the GW Tiger was, and it doesn't matter for this example. 0/x=0
**Without a spall liner equipped, the spall coefficient is 1.
That's a lot of damage to take in an E-75, how much can you reduce it with a spall liner equipped?
Wow. That's really exciting. Now instead of losing 43% of your health from an artillery shell you only lose 38% of your health. Maybe this isn't the best example though, the tier 8 artillery all have extremely high damage and your saving grace is more avoiding getting hit than hoping you can tank the damage.
Instead, lets look at a lower tier tank like the T14. I actually use a spall liner on my T14, because I find that a lot of lower tier tanks switch to HE when they find they can't penetrate my armour, and I thought that it would help to mount a spall liner. What does it do against artillery? The tier 5 german artillery, the Grille has an alpha damage of 680 with its top gun, and 75 mm of penetration with its HE shells. The hull armour on the T14 is better than the 50 mm of thickness would suggest because of the way that it is sloped. So while the T14 only has 50 mm of nominal armour thickness, I wouldn't expect a Grille to penetrate my armour with its HE shells all that often. But, because of how thin my armour actually is, I wouldn't be surprised if splash damage still was very dangerous to me. So:
actual damage= 285
***I am not positive that the nominal armour thickness does use the raw thickness of your armour, but the result I got isn't all that surprising to me.
285 is pretty bad, its about 41% of your starting health. What will mounting a spall liner do? (+30% spall liner is available on the T14)
actual damage= 269
With the spall liner equipped, you'll only lose 39% of your health, what an improvement!
From these 2 calculations, you can see that the spall liners really don't do a lot against artillery. In general, if you find yourself to be an artillery magnet and you're thinking a spall liner will help you out, look at how much damage artillery is usually hitting you for. If you're in an E-75 and you keep getting hit for 700-800 damage, consider that a spall liner isn't likely to help you mitigate more than 100 damage from that hit. And think, do you really want to spend up to 750,000 credits on an item that will make it so that artillery "only" hits you for 700 damage instead of 800? To me, that's not worth the money.
Conclusion: If you're looking at a spall liner as a way to increase your survivability against artillery, don't bother. As you can see from the formula, increasing the distance between you and where the artillery shell hits will reduce the damage you take by far more than mounting a spall liner. (For example, if you are half the splash radius away from the artillery shell, the nominal damage will be halved twice so that your armour is mitigating 1/4 of the nominal damage rather than 1/2 of it. So if you don't want to get killed by artillery, keep moving and hope that the RNG is on your side.
Edited by TocFanKe4, 20 March 2017 - 08:01 PM.