I'll jump on the band wagon too, bear in mind your tyres contact the ground in only four small areas not much bigger than the palm of your hand.
Those four contact patches have to handle steering,braking and acceleration,not to mention supporting a few tons of iron.

Here in Blighty,cracked tyres simply wouldn't pass our yearly inspection,and even if they did 'slip through the net' the Cops would throw the book at you.
In extreme cases you can be fined up to £2500 per tyre!

We do have some pretty tough laws regarding tyre tread and condition here.
Personally I would start saving for some new shoes for your ride.JMO

Last edited by jockbolter50; 06/16/2011 7:14 AM.
1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.