| Hi Mototank and a very warm welcome to the forum.
As for your tyres it would depend on what type of vehicle they are for and whether you are aiming for a concourse shiny new car look or a well weathered front wheel on a german WWII half track!!
To tone down your black I would fist mix in a small amount of brown, this will take the edge off the harsh black look of the fresh paint then I would go for a dark brown wash, which will settle in the creases and nooks and crannies and dry to a nice shadow. Finally a dry brushing with a dark or even a medium grey will pick out the tread and highlight details and should simulate the work look of the rubber at the surface.
If you want the heavily weathered variety I would still do the above but then go for slapping on a load of brown earth mixed with talcum powder to clog up the treads with mud.
If I was going for the concourse shiny car model I would still do the above but not as heavily. The wash and the dry brushing will still make the tyre come to life and look a lot more realistic than the single coat of flat black.
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“Dirty British coaster with a salt-caked smoke stack, Butting through the Channel in the mad March days" | 
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