scarified

Hey road racers,

Quick introduction, I am building an FD RX-7 to be an amazing weekend track warrior, but still maintain enough streetability. I am NOT into the whole "stance" thing or crazy stretched tires, I AM into function first and form second.

Side note, I have probably spent ~2 months researching wheel size, offset, fitment, tire selection, etc. on this forum especially, among others.

I have narrowed my choices down to only square fitments:
18x9.5 +45 -- 255/35/18 square
17x9.5 +38/45 -- 255/40/17 square
17x9 +35/45 -- 255/40/17 square

Lastly I submit,
17x10 +45 -- 255/40/17 square (or maybe 275/35/17)

Now in my research everyone seems to suggest 18x10 +50, with 285/30/18 is the ultimate track setup. My idea was to drop to a 17" to shave weight/increase accel., lower offset by 5 to avoid aftermarket trailing arms, and run a 255/40 tire to match the width of the wheel. I plan on having CCW to build the wheel exactly how I want it (7.5" backspacing?). Ultimately, this should result in lighter weight all around, still provide an aesthetic, meaty performance-oriented look, offer amazing performance on the track, and as a bonus look great with a satin black finish and gloss black (or polished) lip on my '94 white FD (I'll also take suggestions on alternate colors here ). I think the added sidewall with the 255/40 will also make it easier to street versus the 18" options.

Additional information: I will be running Ohlins coilovers (11kg/11kg rates) and a 25" ride height is a MUST have. I am also going to roll my fenders to avoid any fender catching and to help run the slightly lower offset (+45) in the front.

My concerns: even with fender rolling it'll still rub in places when I'm on the track and cornering hard or big bumps, I'll still end up needing trailing arms, and it'll rub the inside and wear away wiring in the wheel well. I'm also afraid I'm not going to be happy with the looks or the way it drives on the street/track.

I have tried desperately to find pictures of what this might look like, but it seems that no one has ran this setup???...

Any and all help would be greatly appreciated, thanks!!!

scarified

Since I can't seem to find a way to edit my post, I also wanted to add one more question.

If I were to run 18x10 +45 instead of the 17, what (if any) difference would that make? Assume I'd want to run 285/30/18 tires.

Thanks.

lOOkatme

iTrader: (19)

you want to run the tires with a slight stretch.

optimal would be 285/30/18 on a 10.5" or 11" wide wheel depending on tire selection.

optimal offset is +45mm and an 18x11" wheel, someone on this forum has already done it.

so I would go with a 285 30 18 18x11 +45mm offset if you can do it. I know the forgestar wheels (F14) has this size and offset. BlueTII runs this on his car with stock fenders (rolled flat). Might need some negative camber up front, -2 degrees, which is good for handling anyway.

If you go with 17's, a 255/40/17 tire runs great on a 10" wheel width and get a +38 to +50 offset.

gracer7-rx7

iTrader: (16)

18x10 +50 is a good setup but really depends on how much power you are putting down and your overall driving level. 45 offset is the wrong direction for that wide of a wheel. It puts the wheel and tire closer to the fender so higher chance of rubbing. If you are in the Advanced group and putting down fast laps, you can make the most of a 285 tire in that setup. If you are a beginner or intermediate driver, 255, 265 work just as well.

25" is not a MUST. It's a recommendation. Generally 25-25.5" work for track cars that are street driven. You can go lower but then you may lose suspension travel (probably not w/ Ohlins) or scrape on driveways and such. If you have coilovers and are seriously hardcore about track days, you'll want to corner balance the car. That is the purpose of coilovers - adjusting corner weights - not necessarily stance.... If you aren't that hardcore, you can set your ride height so that it is visually even at around 25 1/4 - 1/2 so you don't scrape as much or hit bump stops in the rear on big dips. Note that you'll probably want to set the ride height with your weight in the car. That ride height works for me on my 17x9 +45 w/ 255 setup.

Be aware that the FD chassis is very well balanced / corner weighted as is. I was able to get an almost perfect 51/49 cross weight and 49f/51r % just by setting ride height evenly at 25 1/4 front and 25 1/2 rear with my weight in the car.

Even with my relatively conservative setup, my front wheels occasionally rub the front fenders.

scarified

I've had a few track events in a 370z and C6 Z06. My car isn't making much more than stock power (down pipe and catback for now). My short term power goal is roughly ~325rwhp on the stock twins and plan on switching to a single turbo setup after a few years. I was afraid that 18x10 +50 285/30/18 might be a little too much for the car, which is why I was thinking the 17x10 w/ 255/40/17.

The +45 is to clear the trailing arms, but now you have me worried about rubbing on the outside -- should I just say screw it and go with 17x10 +50, 255/40/17 all around?

Randall.K

iTrader: (6)

Not sure if this helps you or not as my setup remains untested for now, but I do expect minimal rubbing. 18x9.5 +40 on all four corners with a 275/35 tire. The tread width is only ~.25" wider than the distance between the mounting flanges. I did need to pull the front fenders just a little bit and rolled the lips in the rear for good measure. I measure 25.25" floor to fender. Hopefully you can do something with this info.

ArmenMAxx

iTrader: (21)

Not sure if there is an advantage performance wise between 17in and 18in rims on our Rx7's. What I can tell you is that the difference in tire prices is decent. Also, with 17inch tires your car can have a more aggressive stance and sit a bit lower without rubbing due to its smaller diameter of a 275/35/17 vs 275/35/18.

I run 18x9.5 +45 up front with 265/35/18 tires. Pulled fenders and I only rub the fender liner occasionally on bumps or hard turns.

FASTMETABOLISM

i loveeeeee nt03!!!
sooo sexy

Natey

iTrader: (19)

17x10 + 48, CCW Classics wrapped in 265/40 Falkens. No rub, even lowered on coilovers with stock(ish) fenders bombing down the Rainey Curve. Hopefully this kinda sorta gives you an idea.

Natey

iTrader: (19)

Too late to edit, but this has to be said.
One thing to think about is tire availability. There are a ton more choices for 265+ wide tires for 18" rims than 17".

Yoloswag13b

^what he said. I'm currently doing someresearch on track setups. A quick search on google or tire rack will tell you 265/35r17 is basically non existent. And 265/40r17, I only see street tires. I know I want to run r888's or something similar. Also bearing into mind what Fritz Flynn has said in other threads about power output and skill level. There's a lot of factors that determine if you really need to use, or even can use those extra few MM of rubber. From what I've been told the less rotational mass the better, and if you're going lightweight pricier wheels, you can still argue 17's are still the lightest option. I have also been told that if 17's can clear my brakes, go 17's.
I'd be going with the sakebomb kit FD3S: AP Competition Brake System - SakeBomb Garage LLC and it says you need 17's to run it. If you want to run wide rubber and go 17 your only option would be the 275/40, and i think if youre going to have a tire that large you might as well do 285/30. smaller diameter overall. maybe someone can chime in if I'm right about the brakes idea. I'm no engineer this is just what I was told.

lOOkatme

iTrader: (19)

Here is my input. If it were me, I would go with a tire diameter of 25" or 24.7" or so. If you decide to drop the front of the car to 25" you will want 25" or less because you will rub the hell out of the fender liner and possibly other components.

so tire choices are basically 285/30/18, 255/35/18, 245/35/18, 245/40/17, 255/40/17.

Those are the sizes I would run. The wheel widths I would run below.

285 = 11 or 11.5" depending on tire manufacturer.
255 = 10"
245 = 9.5"

I would run a +45mm +42mm on the 11-11.5" wheel width.
run a +38 to +50 on the 10" wheel width
run a +35 to +50 9.5" wheel.

These recommendations will need a fender roll. stick to a slight stretch on the tires as they handle infinitely better.

I run the 99 spec brakes, I think they are good and maintain the stock brake bias and use the stock brake pads and have pretty large rotors.

When you start venturing away from the stock stuff, brake bias might not be the same or it might not work well if you continually trying to figure out what the bias should be.

Just MO.

Yoloswag13b

Well with 255 in the and 17 being two recommendations, what would you say is more important, the wheel size or sidewall height. Cause autocross/track days are very controversial among us enthusiasts.
I've been told thicker side walls help with cornering and bigger wheels give you sharper steering response.
I do see a **** load of japanese tuners run the 255 size on the 17s so that's why I was leaning on that as well. If Fujita wins all those races on 255's then who's to say I'm a better driver and can use more rubber
edit: also side not, a lot of those cars are over 400hp some are even 500 and they all run 255.

lOOkatme

iTrader: (19)

Typically the wider the tire, as long as you can heat them (which shouldn't be tough), the wider the better as long as you stretch the tires on the wheels. When I say stretch, it means the tire beads on the tire are wider than the tread width. it creates the most efficient tire shape for supporting the tire treads on the ground. It also has the flatest tread on the ground as well using the entire tread. It also has many other steering benefits, more traction, less disruptions of the car when entering and exiting corners, etc.


Most of those tuner videos are old, and they didn't have many options back in the day for tires, etc. It was common to see many high WHP cars running 265/35/18 or 255/40/17 tires. All of the world time attack cars run as wide as they can on the widest wheels available.

The newer cars keep coming out with wider and wider wheels because lap times drop when you run super wide front wheels. I am running 11.5" all around in 18's on 285/30/18 tires (11" tread width). They barely fit +41MM effective offset.

255/40/17 is a good size on a 17x10 rpf1 +38mm offset. Or get a volk ce28n 17x10 +45mm.

18's have the best stiffness to grip ratio. the smaller sidewall flexes less and maintains the best grip for the tire due to the sidewall height.

just to see some race cars stretching them tires.




cyberevo's old 17" set up


Cyberevo's went to 18" and went to 11" wide wheels, times dropped a lot. stretched as well.

Yoloswag13b

guess it's time to invest in some FEED fenders. 285's will line up perfectly with a 10" so for a stretch I would have to go 275 at least correct? If I didn't want to go with a wider wheel

lOOkatme

iTrader: (19)

I am not sure which tires you are talking about, but on a 10" wide wheel I would run a 255/35/18 extreme sport tire. The tread width on most of these tires is 9.5" to 10" wide for this size. they would be perfect for a 10" wide wheel.


a 285/30/18 extreme sports tire has a width of 10.8 to 11" tread. These would be better suited on an 11" wide wheel and possibly a 11.5" wide wheel.

You can easily fit a 255/35/18 tire on the front of our cars with stock rolled fenders. If you go with a feed wide body fender, then I would push an 11.5 or 12" wide wheel and a 295/30/18 AD08 (tread width of 11.5") on a +40MM or so offset wheel. Obviously need to make a custom wheel or widen a previous set of wheels and run a little spacer or something.

Yoloswag13b

I just thought 10" is usually run with 285 without a stretch. Didn't think the tire was actually wider.
I want a slight stretch for the advantages, just want to make sure 255 isn't that stance HELLA stretch look these people are into now a days

Mahjik

iTrader: (1)

You have to look at each tire's overall width. Given the same tread width (285), each manufacturer may have an overall width that is different. For instance, in the racing tires, Hoosiers are almost a full inch wider in the same size of their competitors (Hankook, Kumho, etc).

lOOkatme

iTrader: (19)

Go with a set below in a 255/35/18 on a 10" wide wheel.

Hankook R-S3
Bridgestone RE-11
Yokohama AD08R
Toyo R1R
Dunlop Z2


These are all super wide, have a ton of grip, do wear quickly, but handle like a beast. These would all fit great on a 10" wide wheel. most of these tread widths are between 9.5-10" wide.

Yoloswag13b

yea this is actually what I decided on. Thanks for all the input. Seen the toyo r888 overall diameter for the 255s are 10" so its going to be 18x10 all the way around.

Yoloswag13b

I'll probably do FEED fenders up front to be safe and keep the rear stock

Natey

iTrader: (19)

My car's on 17x10 wheels and 255's. No stretch.

10" = 254mm.

lOOkatme

iTrader: (19)

Let us know how it turns out. turn in should be crisp, the breakaway should be clean and predictable, and the grip should be good.