Sorry it didn't work, hoped it would. what size tires are you using? might be heavy. have you run it hard and got it real hot accidentally? What you are describing seems like a weakening magnet

Tires are the stocker MGT tires, roughly 6.25 inches diameter.

I really thought the 1518 would never get hot no matter what I did to it. So this is odd to me.

I haven't ever seen it over 163 degrees. I'm not the only owner though, so there is a slight variable.

14-15lb? I think we just solved that issue then...

I would still like to think it shouldn't be running quite that warm, but as long as you keep an eye on it it seems like it'll be fine as is.

How much does a Flux or a LST conversion weigh? They have to be equally heavy vehicles right, and those mostly run the 2200 k/v motors without too many heat issues outside of people really pushing them hard.

my savage flux has the stock 1515 2200kv motor in it. here's my setup:

1offrc xl conversion kit
18t pinion
40 series mashers on axial beadlocks (HEAVY!)
2x2s 30c 5200mah lipo
other small uprades here and there
geared for about 40mph with a little tire ballooning.
weights about 14-15lbs, maybe more

the motor temps consistently between 130-150F after a good run with 100F ambient temp

im having the same heat with d8t and 1520 6s, tried all kind of different gearing.
So just drive and if you think its to hot just take a break to let i cool itself down.

Also have two savage flux, one old where the motor is super cool and one new one where the motor is running alot hotter, im not worrying to much about it.
it isn't that hot that it will ruin the motor, but im frequently stopping to take an temp readings..

i also noticed that the old one have an shorter shaft than the new one.

If you stay below 80c (176f) i think you are safe. 90-100c not so much.