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Discussion Starter #1
So my '15 Challenger SRT came with General g-max 255 40r20's all around from the previous owner (not sure why they went with smaller tires). I want to put Nitto nt555 295 40r20's on the rear. Will the O.D. be too much of I keep the g-max up front? Thanks!
 

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So my '15 Challenger SRT came with General g-max 255 40r20's all around from the previous owner (not sure why they went with smaller tires). I want to put Nitto nt555 295 40r20's on the rear. Will the O.D. be too much of I keep the g-max up front? Thanks!
Since the original tire size that came on the car from the factory was 275/40R20's (28.7" dia) and assuming that the speedometer wasn't corrected for the "General g-max 255 40r20's"(28.03" dia), the speedometer was already off and reading about 2.3% HIGHER then actual.

Putting the "nt555 295 40r20's" (29.3" dia) on the back, would change the speedometer to read about 2% LOWER.
So from a speedometer standpoint, no real problem.

Now as far as the difference between the fronts and the back tires and possible impact on the ABS and the electronic stability control. The difference of what you propose, would be about 4.4%. Don't know for sure, and I don't think a lot of people do know for sure, but I have seen a reference to 5% difference without a problem.

One thought would be use a Nitto 295/35/R20. That would closely match the dia of the 255 40r20's.
And give you a touch more torque, as well.:smile:
 

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Discussion Starter #6
Thanks for the thorough response! Turns out I was mistaken and the g-max are actually 255 45r20. So those matched with the 295 40r20 nitto seem to work out fine.
 
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