Turboimpreza07

iTrader: (4)

Hey guys,

I'm going to autocrossing my 350Z Enthusiast this spring and I need to know your opinion on the best wheel size. 18" or 19"? I currently have 20's that I really hate, but will live with for now. Also, what type of tires do you recommend. I'm leaning toward a staggered fit of rims by Stern ST-7. They are 8.5" (+32mm) in the front and 9.5" (+35mm)in the rear. I just need to know if I should run 18 or 19? I currently have no other suspension upgrades done to the car yet as this is going to be my first time doing something like this, but I know I can't use the wheels I have on there now. So this is my first step. Then suspension. Any help is appreciated. Thanks, Doug
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ev0k1ll3r

most say 18s

davidv

iTrader: (2)

Autocross with the car as is for a season. Then you will be familiar with club rules concerning wheels and tires. You will also see what other racers are running. Then you will be able to make an informed decision.

first350

iTrader: (24)

^ +1 ...the class you run in may dictate the size of wheels you're allowed to run. (i.e. stock class = OE size rims with +/- 5mm offset, a street prepared class = anything you want).

FWIW, 17" tires cost less...and if you'll be doing autoX, you'll tend to burn through rubber. (some reasons to go to a 18" is for break clearance, or if you can't find the right wheel width you want).

Turboimpreza07

iTrader: (4)

I've been checking out the rules and regs for the season autocross and I'm gonna go with the 18's. Now what tires do you recommend with them? 18x8.5" front and 18x9.5" rear. I'm not sure if I'll need to roll my fenders, but I don't think I will with the offset, +32mm front and +35mm rear. Do you think I'll need to roll them? Thanks for all your help in advance.

davidv

iTrader: (2)

Are these street or competition tires?

first350

iTrader: (24)

front: 18X8.5 +32 --> max tire 275. (a 285 could be fit, but you'd probably have to run at least a 5mm spacer...but then you're starting to really push tire mounting - depending on the tire type, a 285 could be extremely hard to mount).

Rear: 18X9.5 +35 --> max tire 295 (you'll have plenty of room on the outside, but the insider will be getting close to the strut...I have JIC coilovers and their struts are bigger than OE struts, so it may also depend on what you have).

Are you planning to have this a dedicated AutoX set of wheels? R-comps? Street tire? (most autoX clubs have classes split up for both R-compound and street tires).

Falken 615's are one of the best street autoX tires.
Hoosier A6 or Kumho V710 are the 2 best for R-comp autoX. (Hoosier's tend to wear out more quickly, but they can be flipped while the V710 cannot...)


***I just mounted my 18X10 enkei RPF1's, Front 285, Rear 295s...I'm planning to go for Front 295 and Rear 305/315 for my 2nd set this summer. So I've been playing w/ getting the max tire and needed offset down to a few mm's

Turboimpreza07

iTrader: (4)

They'll be street tires, but mainly used on the weekend. What's the difference between the tire sizes you mentioned above and the one's I was told by my local tire shop...
Front 245/40/18
Rear 275/35/18
I just checked out the Falken RT615's on discounttiredirect.com and this is what I came up with.

front= 275/35/18
rear= 295/40/18
Does my rear tire need to be taller than the front? why?

Because with these tires, the rears are 4.65in. tall off the bead of the rim and the fronts are 3.79in. tall.
http://auto.howstuffworks.com/tire2.htm

Will I be able to use my OEM tpms system?
I know I sound like a newbie and I'm asking alot of questions, but I just want to understand how to select my tire size especially in the near future. I don't really want to roll any fenders and I only have OEM suspension..for now ;-) Thanks.

first350

iTrader: (24)

1) which tires did your shop tell you to get?

2) Larger overall diameter in the rear vs. Front is to keep the TCS happy...it's b/c the OE tire set-up like this - so the ideal is to match the same ratio of front to back as OE (assuming you car about maintaining your TCS...I turn mine off every time I get in )

3)TPMS sensors - you can transfer them from your OE wheels to your new wheels...how they mount will depend on the type of wheel you're getting.

4) Are you stock? (intake, exhaust,..??) If so, and you're trying to get into AutoX, you may really want to wait on these...staying in a stock class is great for beginning at autoX.

z-u-later

iTrader: (43)

Yeah, I'd like to see that . . . OP has 20" rims.

Go to the Autocross Section and do some research . . .

Turboimpreza07

iTrader: (4)

First350,

What do you think about these tires and size? I don't have a track dedicated set of wheels yet, so I need something that handles well in all weather conditions,except for snow of course. I'm thinking about running
BF Goodrich g-Force KDW NT's with these sizes...
F=275/35/18
R=295/35/18

What do you think? Are the sizes ok? The rear is still a little bit taller than the front, but not like the falkens at 295/40's. Will it still be ok to make the TCS happy? ;-) Thanks for your opinion in advance...

davidv

iTrader: (2)

Wheel size is fine but there are better tire choices. 295 mm of rubber on the road is a lot of rubber. But I would just as soon run 245 mm of “better” rubber on the OEM wheels.

first350

iTrader: (24)

Assuming you can get the right offsets, those would work well. I had those same tires (different sizes) and would use them for some practice autoXs...they performed well (didn't overheat or get greasy too easily, and could still do okay in the cold). In general I was about 2 seconds slower vs. my R-comps on a 40s course.

+1 to being fairly wide for the street...gas mileage will probably go down - but I'd probably run something similar if I was in the same position.

*road noise may also go up w/ running a 35 series...but that's the price you pay - The KDW's I ran were also 35 series and I really liked that the sidewall didn't come into play much for quick transitions (I've been in cars were you can feel an extra bit of spring due to higher sidewalls)

terrasmak

iTrader: (8)

Nothing wrong with 17's and square setups either. Falken 275/35-18's front and back on 9 or 9.5's would be great. The other popular setup is 275/40-17's front and rear on 9's to 10's.

first350

iTrader: (24)

+1...but I think he still wants to preserve TCS.

baileyrx

iTrader: (16)

if they're going to be dedicated auto-cross tires go with:
17in: 275/40 r17 all the way around
18in: 275/40 r18 all the way around

Turboimpreza07

iTrader: (4)

I only use it mainly in wet weather driving, but I usually turn it off because of the 20" wheel size on the car now. When I'm doing 70, and I accelerate to 75, the TCS (slip light) starts blinking. All I did was accelerate on a straight road and the engine power was gone. The dealer told me it's fine and the reason was because of the oversize rims on the car. But I do like the TCS option. I have a hard time keeping the tires from sliding, just because I like to drive fast and I really like to slide. So, I leave TCS on when I'm in the city so I don't get pulled over too much. C'mon, you guys know how fun these cars are, and when they're sliding sideways, it's even more fun!!!! ;-)

So how wide do you recommend I go to still keep the gas mileage in a good spot? front's =255's and rear's 275's or 285's? I still want to keep alot of tire on the ground for traction purposes when I autocross and just on the street in general.

Turboimpreza07

iTrader: (4)

I've bee trying to pair a set of sizes and it goes like this...
Maybe I should start a poll on which size would be good for traction, gas mileage, and autocross...

Front's= 235/35, 245/35, 255/35, 255/35, 265/35, 275/35
Rear's= 255/35, 265/35, 275/35, 285/40, 285/40, 295/35

The front size is the match for the rear size in that same position of the row. If that makes any sense. How do I start a poll to see which one is best.

first350

iTrader: (24)

assuming the same tire, the max tires you can fit will likely be the best for autoX and the worst for gas mileage. I don't care much for gas mileage b/c I have a little civic pulling 40+MPG...so I'm not really sure how much of a difference it makes.

Turboimpreza07

iTrader: (4)

I see your point. How bad will my mileage be affected anyway? Not more than 2-3mpg, right? With the way prices are now for gas, does it really matter, we're all getting it in the place where the sun doesn't shine anyway! Another quick question, Should I fill my tires with nitrogen? I've been reading alot about it and it seems like a good idea. I know that there is 78% nitrogen in the air we breathe anyway, but I know that alot of racers use 100% nitrogen. What's your opinion? Thanks