So I got my rims in 275/30/20 in the back.

Anyhow the guy at the tire shop tells me when I'm doing 68 miles/hour I am actually doing bout 67.4 miles/hour or something. He says this really is no big deal, which I agree. Do you think its worth recalibrating?

And one more newb question, you don't need to get alignment unless you lower the car correct? Going from 17 to 20, you don't need anything else?

Thanks.

 

That's not even 1%. Well almost. I wouldn't worry about it that much?

 

I don't think we can get our speedo's recalibrated anyway?? where would one even go??.... certainly not the dealer right? .....

 

It's not worth recalibrating. Not even sure if it's possible. If it really bugs you, just go with 285-30-20 which will be virtually identical to stock.

Alignment won't be affected when going from 17" to 20" rims/tires. As for "anything else", I would strongly suggest lowering the car as 20" rims on a stock height G35 just doesn't look good. Of course, once you lower it, you'll have to get alignment and a rear camber kit wouldn't hurt either if you want to maximize the tread life for your rear tires.

 

on my stock tires, my speedo is off my ~3-5 mph ALL the time. I don't know why, but i pass these radar things that tell you your speed all the time, and in my tahoe, and my brother's honda accord its exactly showing the right speed. on my car it always shows about 3 or more mph less than what my speedo says...

 

the roadside speed check signs aren't always accurate. the further away it is from being directly in front of your car, the more it will underestimate your speed.