I have seen alot of dioramas in the past of burnt out tanks with the rubber turned to ash, for example in Hyperscale.com there is a diorama called "Tiger Bait". It is of a IS-2 that was destroy and left as a burnt out hulk. The rubber from the road wheels are just piles of ash due to the intense fire. Some of the authors that tell how they make the ash for the burnt rubber explain that they use actual cigaret ashes, but they do not tell use how they adhere it to the diorama.
Can anyone please give me any insight on how to adhere the ash to the diorama or is there a better way?

hm.... i'd apply some wood glue to the spot where i want the ashes and then just strew the cigarette ash on the still wet glue... that's the way i would do it

I agree with Richard here...
Wood or PVA glue, applied in droplets. The ash could be strewn over the glue droplets, and as I guess (never smoked) the ash would be very brittle, therefore the glue would also give some 'body' to the ash...
Cheers
Brad

I think it would depend how long the wreck had been there, any rain or strong wind would reduce the ashes to just a grey/white mass on the floor. I would be interested to know how you get on with this.
Cheers
Robbo

A little powder mixed with white glue can be placed nicely around the wheel to simulate the burnt rubber. Colour can be made easily with black and white pastels.

I’ve made fine ash by taking fine sawdust from around the sander and carefully burning it with the torch.

Cigarette ash will "disolve" in water based glues- I would go with pastel dust or similar

I would use pastels. In my attached diorama I first made a small mound with putty and then put the white and grey pastels on that using some white glue.

Well, I cant say Ive ever had to make rubber ash, but considering the topic, why not actually burn up some rubber??? Im not trying to be a smart a**, but it would sound logical to do it that way to me. COme to think of it, Im at my shop. I'll try burning up some rubber at lunch time and let you all know the results.