Trying to decide on a wheel/tire combo and have some questions.

ppw350Zunit runs this setup but hasn't been online for a few days to answer my questions and I'm trying to make a decision today. Anyone else run this setup on a Z?

 

well, i'm running 255/40/18 (f) and 295/35/18 (r) with no rubbing

 

I think that that setup will mess with the VDC. The front diameter is 25.71 while the back is 25.57. You need the back tires to be just a little bit taller than the fronts (don't know exactly how much but someone else can chime in that knows) Why not just run a 275/40 in the rear like most people do.

 

Mostly aesthetics, I have a mild drop on Hotchkis like ppw350Zunit and using the lower profile in the rear seems to minimize the wheel gap. I'm trying to figure out why as it seems counterintuitive to most of the logic I read on this board which is taller profile to fill wheel gap.

Maybe more weight is shifted rearward since the car is lower in the rear by about an inch compared to a 275/40?


Their is also some performance gains to be had with a decreased sidewall; less flex and better gearing. But I want to know at what cost. I don't have VDC, but will I have to keep TCS off all the time? More importantly, will ABS be negatively effected?

 

What really peaked my interest is this issue of Hyper Rev magazine I got when I visited New York earlier this year. In it, many Japanese tuners run this exact setup.

 

If you think about what you just said its completely wrong. Think of it this way. If you measure from the center of your wheel to the top of the fenderwell you get 14 inches, now if you have a tire that is a 275/35 the diameter is 25.57 half of this is 12.78 leaving you a gap of 1.22 inches. Now if you take a 275/40 tire the diameter is 26.66 and half of this number is 13.33. With this setup you are looking at a .67 wheel well gap. But also keep in mind that the 275/40 setup is also going to raise your car by about a half inch, but you will still have less gap up top. The only reasoning i can think of for the setup the tuners run is to keep the sidewall height the same, thus having the same amount of sidewall flex at all four corners of the car.

Sorry i sounded like an *** in the first sentence, i don't know about the weight shifting to the rear of the car

 

I understand, the math doesn't add up. That's why I'm wondering if there are other things we're not taking into consideration:

Does 1" lower in the rear transfer enough weight to the rear to affect spring compression? Some track ***** with corner weight experience might be able to answer this. =)

Also, the effects of the tire stretch. if the 245/40 is mounted to the same width rim as the 265/35 does it's diameter shrink, evening out the otherwise reverse stagger?

I know the Japanese tuner cars are probably all running ride-height adjustable coil-overs but in this comparison we are looking at two near identical setups. Both are on Hotchkis springs with 18x9.5 wheels (+22 offsets for the white, +30 for the black). White car is 265/35, Black is 275/40 a difference of 34.5mm. By your calculations that should yield a 17.25mm larger gap for the white car. Look how much lower to the ground the side sill is on the white car...I would venture to say 34.5mm lower. Maybe the suspension compensates for the decreased wheel diameter?

 

I agree that the white car looks lower. This is probably due to the decresed tire size. To me the black car has less wheel well gap than the white car.

 

The black Z also has less gap in front and behind the tire as well. The white Z tire just looks small, like it came off of a 240SX.

If you really leave VDC/TCS off all the time, than stagger does not really matter.

On a side note, I think some tuners do things simply because they are different, "the whole taller tire in the back is so "done" by everybody else, especially the factory, how can we stand out?" There are lots of tuner parts out there that don't do much of anything but look pretty.

Chris

 

That's an excellent point...the front and rear gap proportionally increases in relation to the top gap as you lower a car so this may all just be a trick of the eye I'm experiencing.

Really? Not even to ABS?

 

The white car looks so much better. I know we're not talking about looks here, but even with more gap, the lower profile just looks so much sleeker on the car. Now I know what size wheel to get. Black car looks 4x4ish in comparison.

 

Agreed. That's one of the reasons I wanted to run a smaller sidewall in the back...from what I'm reading in the autox/road section it will hurt ABS performance though.

 

I posted this in another thread too...

http://mp-racing.net/Gallery/TE37

18x10.5 +22...295/35...slight rolling required
18x9.5 +22...265/35....no rubbing

 

Forgot you were running the 265 up front! Thanks!
Do you get an tramlining or does the steering feel heavy in daily driving with the 265 up front?

 

Hi guys,

I'm also very keen to get feedback on the setup mentioned by 350zeno. Have to make a decision very soon b4 tire guy goes to Japan to place orders.

Looking to upsize to 18" on volks gtv. (F 18x8 R 18x9) Tire guy suggested 235/40/18 (Front Tires) and 265/35/18 (rear tires).

What's with the different heights? A quick check on tire calculator seems ok, under the 3% rule of thumb but concern with TCS issues etc. It feels 'weird' to have different tire heights no?

Pls advise.

Cheers,
B

 

I am salivating...the perfect wheels bar none. Performance and looks, what more could you ask for!

 

That is another popular combo I've seen from the Japanese tuners, but again falls into the front being a few mm taller than the rear.

245/40F, 264/40R would be a good "safe" setup.

 

Hi 350zeno,

Thanks for the feedback.

Will look into your suggestion.

Cheers

 

i just pm'd you...been out of the country for a month...just got back from japan.