[firebirdcrazy1959]

I run that size on the back and do 255/60/15's on the front.right now I have a brand new set of 275/60/15's on the rear and a new set of 255/60/15's not mounted yet..I want to use the 255/60/15's on my 79 Bonneville cause the tires are old and a little hard,and i'm driving it to Florida in January so i don't need any flats on the way.And i'm gonna buy 2 more tires for it anyway.So will 275/60/15's be fine on the T/A fronts?

[amcmike]

I think they're going to be too tall. Swap your front and rear tires, put some cardboard between the tire and cement, load an extra pair of cylinder heads way up front, and then turn the wheels full lock checking both side.

[Torquewar]

255 are the biggest u can go. Issue is turning geometry and suspension travel , as mentioned too tall.

[Half-Inch Stud]

Will understeer if you pursue fitting them in.

[amcmike]

Originally Posted by Half-Inch Stud

Will understeer if you pursue fitting them in.

That's not a definite. The taller sidewall may flex more, possibly causing e more understeer, but the wider contact patch of tread increases in the direction oversteer and probably have a greater effect than the tidewall stiffness.

And these only move it towards more of one or the other. Whether it actually oversteers or understeers will depend on the static alignment settings, shock settings (if adjustable), camber gain (if modified), front/rear springs, rake, antirollbar stiffness, tire pressures, and weight bias.

The second generation T/As were setup pretty neutral from the factory with all 4 tires the same size, so if he's kept the suspension close to stock then it will probably remain so.