ok let me start off with the car.
2003 g35 coupe 6 speed. (car stock ran 13.8@101)
mods technosquare reflash, 7100 rev limiter 350z intake, K&N filter, crawford plenum, crawford high flow cats, gruppe s y pipe and ud pully. I WILL NOT BE DOING ANY MORE MODS TO ENGINE IE NITROUS OR BLOWER, OR TURBO.


with stock tires tranny ratios on the 6 speed are
1 - 3.79 7100 rpm= 42 mph
2 - 2.32 7100 rpm= 69
3 - 1.62 7100 rpm= 99
4 - 1.27 7100 rpm= 126
5 - 1.00 7100 rpm= 161
6 - 0.79 7100 rpm= 206
THIS IS WITH THE STOCK 245 45 18 26.7 tall tire

now im looking to drop the tire to about a 24.5x8 slick. This will bring up my gear ratio so that the speed at 7100 rpm will look like this.
1- 6700 rpm= 38
2- 6700 rpm= 62
3- 6700 rpm= 89
4- 6700 rpm= 113
5- 6700 rpm= 144
6- 6700 rpm= 182

now let say ok im going to go with 3.91 gears with stock tires see how she does then ill look like this
1- 6700 rpm= 38
2- 6700 rpm= 62
3- 6700 rpm= 89
4- 6700 rpm= 113
5- 6700 rpm= 144
6- 6700 rpm= 182

and lets say last but not least if i do go with 3.91 gears with a 26 inch tall slick we will look like this
1- 6700 rpm= 37
2- 6700 rpm= 61
3- 6700 rpm= 87
4- 6700 rpm= 111
5- 6700 rpm= 140
6- 6700 rpm= 178

SO OVERALL QUESTION what would you guys do.

now i know you dont want to get into 5th cause 5th doest pull as good with 1.00 ratio. can anyone help me out here.

 

I think your numbers on the configuration with stock 18" wheels is a bit off. That is unless there is something different in the G. My Z is the track model with the same sized 18's and I don't get anywhere near those speeds, even past the stock redline.

It could be that I am not going all the way to 7100, but i am coming pretty close and even hitting that at times.

 

im sorry all those are in 7100 rpms not 6700

 

I would go with the shorter tire. I dropped .1 seconds in the 1/4 mile and increased my trap around 1 mph by going from stocks tires to the 245/40-18 BFGoodrich KD tires. When I switched tires it felt like the car was accelerating harder but I thought it was my imagination. Then I took it out to the drag strip and it was consistently running 1 mph faster in trap speed.

 

so stx, you're running 245/40/18 front and rear? how's the wheel gap in the back?

 

The gap wasn't that bad before the coilovers. I will see if I have some pics and I will post them.

 

Here is some pics of the wheel gaps with and without coilovers.

With coilovers with a 1/2" drop in front and a 1" drop in the rear.



This is with stock suspension

 

I just went to a 245/40/18 myself and hope to see a difference at the track. I just hope wheel hop didn't get worse with the lower profile. Not to mention that I was running out of 4th gear at the end of the track as it was. Hopefully I didn't add another shift with this change.