Mud texture on truck wheels

First off I apologise as I've definitely seen this thread before but I couldn't find it via searching.

I'm not a modder myself but I enjoy editing textures, xmls etc (for personal use obviously). Recently I've edited a BFG wheel texture for the rightside wheel to counteract the mirroring bug thing; I just mirrored the sidewall graphics in the texture so they get mirrored back in-game. Everything is great except the wheel doesn't get dirty anymore when driving through the mud, something which is a fairly common error I've noticed a lot across ST/MR.

Is this something I could fix? I'm fair with and GIMP but my model knowledge doesn't really extend beyond using MeshConvert.

Just go into and set the transparency of your diffuse map (this filename should end with __d_a) image file to 128. It needs the semi-transparency to overlay dirt/water. The underscore 'a' suffix indicates the image has an alpha channel (transparency).

Make sure your texture has an alpha channel. The brightness of the alpha dictates the intensity of the mud.

@zirrow @Mexican_420 Thanks guys 🙂 I suspected it may have something to do with alpha channels but I don't really have a full understanding of how they work, I am now a little bit closer so thanks again!