Right now I have the stock tire size 245-45-17 on a stock rim for a 2004 gt can I go to a 255 or 275 tire on the same rim. I like the rims that came with the car. just want wider tires in the rear for more traction.
I bought the car with 275's and am still running them..no problems.
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1999 GT-ACT Stage 2 Clutch, BBK Cold Air Intake, BBK Strut Tower Brace, Steeda Tri-Ax, Straight Pipes from cats back 1999 Ford Explorer XLT-K&N Cold Air Intake, Flowmaster 50 Series SUV Muffler
My friend has a 2000 stang and has 275s on his stock wheels. He says they fit fine but bulge a little which he thinks it causes his car to float a little in the rear if that makes sense. He doesn't seem to get good traction because of that. He had more traction with his 245s.
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92 Lx 5 speed. BBK cold air, flowmaster mufflers, ac delete, timing at 14*. Future install 390s
check some tire places on the internet such as tire rack. They can tell you what tires will work with a given wheel size.
They will say that a 255/45 is the best fit for a 17x8 wheel. But a 275/40 is the biggest you can put on an 8in wheel. I went from 245 to 275 and didn't notice any "floating" or loss of control. If anything, I gained a bit of traction.
I ran 275/35 on my 17x8 bullit wheels and they looked and worked great. Now I have a 295/45 on 18x10 on the back of my car with the 275 on 17s on the front. works good for me. Although the back is a little to tall for me on my car. I have a 96 gt.
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rear tire size - 
