I have a 2004 6MT and planning on doing TT early next year. Question for the experts out there regarding final gear to use with forced induction... Stock is 3.5 and there is 3.9 available. Can a 3.9 be used with FI? Is there a 3.7 available and who makes it? Or using a final gear other than the stock 3.5 overkill?

 

many drop to the 3.3 AT final gear to address traction issues and to keep you in each lower gear longer...

 

it all depends on what power you're running and what tires and LSD, etc you have.

you can use whatever final drive you want, but traction will dictate if it's a good choice or not.

performance nissan has a 3.7 final drive that works for the Z/G

ideally, you want the most aggressive gearing that you can make use of with the power you're running. You need to find a balance between gearing, power, and traction

 

That is my worry with the 3.9 FD - tire spin. I still plan to run 285/35R19 rear tires but going to switch to a sticker tire like Advan Sport, Michelin PS2, or Pirelli PZero Rosso. I want to build a 400rwhp to 450rwhp G-ride. Maybe a 3.7 FD would be better to use. I could always swap back in the 3.5 FD if 3.7 is still too much.

 

well i'd try getting to 400-450whp first and see how traction is first, then try messing with the final drive

285 in those tire sizes might do ok with traction, but probably won't hook in first gear. If you're thinking of a turbo, then those tires in that size probably won't hook in 1st or 2nd gear going WOT. The mid range torque is too strong for typical street tires. You might end up having to step up into competition tires or something like a 305 or 315 to get full traction at WOT

 

Great advice. I will follow your suggestion on final drive gear. As far as tires... to hook on 1st gear the only tires I can think of that are street legal are Nitto NT-01 315/30/18 (have go down to 18-inch wheels and about 1-inch shorter overall tire diameter) or 295/30/19 Pirelli P-Zero Corsa System.

 

look into the michelin pilot sport cups

 

there's lots of competition tires here's a bunch
http://www.europeancarweb.com/tech/0...e_r_compounds/

 

Thanks man. My issue with competition tires is that most are only available up to 18-inches. The only one that comes to mind in 19-inch is the Pirelli P-Zero Corsa. I like the look of 19-inch wheels so I'm aware that I am limiting myself to a few tire brands.

 

the michelin pilot sport cups take a bit to heat up more than a lot of other tires. I know some people that really like them, but don't really recommend them so much for the street when there's other competition tires that heat up sooner

 

sentry65 - how do you like the Pirelli Corsas? How many miles can one expect out of them before replacement?

 

i'm expecting 8000 miles out of the rears if that

they work really well and are lightweight and have been able to hold the power in 1st gear with my vortech setup at my power level and 3.9 final drive and light flywheel/wheels/crank pulley etc

 

8,000 miles? not bad at all. i can live with that.

 

Many want to drop the FD instead of raising it to 3.9... Kinda causes alot of grip issues