Back when I put new 8:75x16.5 Cooper 6 ply bias ply snow tires on my '72 K5,it would just about shake the body off its mounts on cold mornings for 10+ miles,felt like they were square until the finally warmed up...they were nylon cord,which was likely why..you could run curbs over at speed and dent the rims and never hurt those tires,but they were super stiff..
I had other bias ply tires on it rated 4 ply that were not that way at all--but once I drove it with radial tires,I never put another bias ply on anything I drove after that..it was night & day difference..rode much smoother,no wobbling,steering wheel jitters,etc..better traction too..
I had a '67 Impala that had bias ply tires on 14" stock steel rims and the thing always pulled to the ditch side on certain roads,or would zig and zag if you hit a patch of new tar--I figured it needed an alignment or ball joints,etc,but everything checked out ok...
I bought for 15" steel rims with LR-78-15 radials off a 70's Monte Carlo from a salvage yard ,after I put those on it I was amazed,it rode and handled like a Coupe DeVille compared to before!..no more pulling,darting around,and it went over bumps like it had new springs & shocks..its amazing how much different tires can make,and brand to brand can act differently too..
That was the first car I had that didn't have any "mismatched" tires ,previously every car I had,had at least one tire that was a different brand,or ply rating,different belt construction,size (like 70 series,and the other 3 were 78 series),etc...putting a set of 4 new matched tires on can make a new vehicle out of it!..
Some of my trucks though,don't seem to care what tires I run,my '82 GMC has 4 different ones on it now--a BF Goodrich 8 ply TA up front,the other front tire is a Cooper 255/70-16,and the two rear ones came off salvage yard trucks,the spares that never touched the ground,one is a 4 ply and the other is a 6 ply..truck doesn't seem any different than when I had 4 tires all matching sizes,plys and brands on it..I think the heavier the vehicle the less it seems to show up somehow..
