If you are talking 767 the answer is no. The only approved MLG tyre is H46 size (The "H" denotes lower aspect ratio than some older tyres which may give a flatter appearance?).
On some Airbus types there is a radial/bias option but I believe this is on A320 family only. The radial tyres do give a lower pavement loading.
If your tyres 'look' flat due to low pressure you have a problem - the amount of underinflation to give that sort of effect would be catastophic if rolled!
HTH