Rigged with heavy explosives, the spiked balls are set to go off when they lose all their spikes.
~ BTD5 Official Description
Spiked Mines is the final upgrade for path 1 of the Spike Factory in Bloons Tower Defense 5. Each spiked ball can pop up to 16 bloons before exploding. It cost $11900 on Easy, $14000 on Medium, $15120 on Hard, $16800 on Impoppable. There is a skull on top of the spiked mine production chute, and a skull on top of the mines it produces. This upgrade rigs the spike balls with heavy explosives, causing them to go off when they lose all their spikes. The explosion gives bloons a napalm effect, similar to the Mortar Tower's Burny Stuff upgrade. The napalm pops bloons every 2 seconds for 6 seconds. The explosions pop 4 layers.
Spiked Mines in action with path 2 upgrades
Beating round 101 with only Spiked Mines
Spiked Mines as seen in Legendary Spike Factory Card
Three of these upgraded 4/0 can easily destroy a M.O.A.B.
This upgrade causes deployment speed of the Spiked Mines to double.
The Even Faster Production upgrade will enable the tower to produce spiked balls hypersonically and can destroy a whole bunch of incoming Ceramic Bloons, or any Bloons for that matter, at once.
Spiked Mines with Even Faster Production upgrade, Spikes R Us tier 2, and Tack Awesomizer can destroy an entire ZOMG, provided the spike factory is located far enough from the start of the track and the mines are sufficiently concentrated.
To see the max amount a 4-2 spike factory can pop, see
If Spiked Mines is near a Monkey Village with Jungle Drums upgrade, with Even Faster Production, Spiked Mines will shoot Spiked Balls as fast as a Turbo Charge Boomer with the Ability activated.
If the Spiked Mines are not used, they will explode after a while in the same way normal spikes or Spiked Balls disappear after a certain amount of time.
If a Spiked Mine Factory is put into the Socket of Power in "The Crucible", it will produce so fast that it appears that the hatch is not moving. This only happens on fast forward, however.
The Tier 4 upgrades for the Spike Factory are the last to be unlocked, the second last are the Dartling Gun Tier 4 upgrades, and the third last are the Mortar Tower Tier 4 upgrades, however, it is the third last in BTD5D, followed by the Monkey Engineer and Bloonchipper, respectively.
But after the Monkey sub update, it is the third last to be unlocked, as the Monkey Sub's Tier 4 upgrades are the last (on BTD5 Mobile, of course).
4/2 Spiked Mines work twice as fast as x/4 Spike Storm factories.
It takes 4 4/2 Spiked Mines to pop a Z.O.M.G..
It takes however two to pop a ZOMG fully on long, easy, 'one end' track.
It takes one only to pop a ZOMG fully in BMC, a long track and only one ending, like the flower grass terrain track, without any support. As seen, the spiked mines upgrade is really useful in capturing tiles in BMC.