ZDan

I think you'd be better off with +40 or +45. Then you should easily be able to run 245/35 fronts and 265 or 275/35-18 rears.


Counterpoint to lOOkatme's comments:
Personally, I hate the stretch look, but of course looks are subjective...
Running minimum tire width on a wheel does make the rims more vulnerable to curbs

I've got 245/40-17 on 17x8.5" up front and 275/35-18 on 18x9.5" in back, and to me, they already look the tiniest bit stretched. But then I'm used to running 225/50-15s on 15x7s on the 240Z...

Regarding handling, 245/35-18 on a 9.5" wide rim might (*might*) give "better" handling than the same tire on 8.5" width. But I would put money on 275s on the 9.5" generating more lateral grip than 245s on the same wheel...

lOOkatme

iTrader: (19)

I am not into the hellaflush crap or anything like that. I did a lot of research on handling and wheel width.

My research and even experience in the past with cars shows that running a wider wheel with a tread width equal to or less than the wheel width is much more confidence inspiring and I can drive much better at the limit with a slight stretch on the wheel then one that does not have a stretch.

Anyway, here are a couple of links to think about.

urge designs.
URGE designs

Michelin pilot sport for porsche cup car (slide 34 and on)

http://www.cb-racing.com/PilotCup_Presentation.PPT


Urge engineers

"Match your tires with a slight stretch

Another thing to consider is tire width. Many people believe that wider tires improve grip. However, this is not true. You need to fit your tires to your wheels so they have a slight stretch. Fitting the widest tires possible on specific wheel sizes will deaden response and cause the car to roll due to unsupported sidewalls. Additionally this will decrease the performance and function of your dampers as you introduce a major damping mechanism into your system. Extra tire width is not used as the tire is pinched; creating a muffin top close to the wheel lip that is not in consistent contact with the ground. It’s important to note that none of the racing series above use tires that are wider than the wheels. Every team has their tire widths matched to the wheel width. On TV you will noticed a slight stretch of the tire as the wheel is slightly wider than the tire."


Michelin engineers/drivers

"Bigger isn’t always better, both in terms of ease of driving and in terms of lap times.
Frequently, the tire looks “stretched out” on the application wheel, forming what looks to be a “trapezoidal” cross-section, with the tread width close to or less than the width of the tire’s beads. This is because of the simple fact that a “high-tension” tire shape is more efficient, in most cases, than a fat, “low-tension” shape."

"We have found the smaller-tire + wide-rim combination, with its accompanying “high-tension” inflated shape, can be more efficient:
More direct yaw response Decreased “phase lag” between steering wheel input and vehicle turn-in
Less “overshoot” at corner exit Less of a tendency to “wiggle” at corner exit (thus upsetting the car) when you roll back into the throttle
Can result in decreased negative camber requirements, thus increasing braking and accelerating efficiency
Can improve vehicle response to air pressure tuning"

Bad wheel fitment on left, good on right.

ZDan

I know, what you've recommended isn't a stretch beyond manufacturers recommendations, should be totally fine. Just saying that, to *my* eye, running the minimum width tire on a given wheel does begin to *look* a little stretched, and of course it does make the rim more vulnerable to curbage.

And my experience is that running 225/245 on my S2000's 6.5"/7.5" wheels is faster than running 205/225s on them, with the driveability/tossability largely unaffected (stock suspension, though, so not exactly track-optimized...).

Running the minimum width tire for a given rim size is a sure-fire recipe for slower lap times.

I'm certainly not advocating for running pooched tires, though.


Not *always* true, I'd say.

Is this what is considered a "slight stretch"?


Because that's about the amount of "stretch" I have with 245s on 8.5" and 275 on 9.5"


The tire is a spring/damper. Running less stretch will give some lateral compliance and damping which *may* be beneficial. For sure there is a sweet spot, which will be highly dependent on the car and setup. A bigger/heavier car will want more stretch, a smaller/lighter-weight car may want a bit less.

Depends on setup, but I've never had any problems utilizing the ENTIRE tread surface running the maximum width tire on the AP1's wheels. Again, that's a stock suspension with minimal camber, so not an ideal track setup. But most people won't have an ideal track setup for their street car anyway.

Major point: What is best for the track isn't necessarily what is best for the street.

Anyway, all I'm suggesting is that running the minimum width tire on a given wheel might not be what *everybody* really wants.

And on 8.5"/9.5" wheels, my money is on 245/275s being faster than 215/245s.

lOOkatme

iTrader: (19)

slight stretch is a wheel width of 10" and the tread width of 9.6" and a section width of 10.7" on a 11" (10" wheel) is a slight stretch for me.

I ran a 17x7.5 wheel with 215/40/17 tire on my old prelude which had a tread width of 7.2" and a section width of 8.4. slight stretch.

Picture attached.

ZDan

Are you saying the tire section width should be a bit wider than the overall wheel width? I agree with that. That's why I wouldn't run a 9.6" section width 245 on a 9.5" (10.5" total width) wheel, even if it falls within the recommended range. The rim is totally exposed, it will hit the curb first, before the tire.

To *me*, 245/35-18 on 18x9.5 would be a bit too stretched, even though the rim width is within the recommended range for the tire. I'd sooner go with 18x8.5" for that tire size.

lOOkatme

iTrader: (19)

I wouldn't be so stuck on the width of 245/35/18...I would be more interested in the tread width published by the tire manufacturer.

A kumho XS in 245/35/18 has a tread width of 9.2". I would run that on a 9.5" wheel no doubt. On the other hand a falken fk452 tire has a tread width of 8.8" I would run a 9" wheel for that. If I had a 9.5" wheel and I wanted to run a FK452 tire, I would go to a 255/35/18 which has a tread width of 9.1".

So the tread width of the Kumho XS at 9.2" in 245/35/18 is wider than a 255/35/18 FK452.

If you check out the widths of a AD08, they are wide as hell, the 265/35/18 AD08 has the same tread width as a Hankook TD 285/30/18. (10.3")

ZDan

I wouldn't get too hung up on "tread width", either. For one thing, it's a bit of an arbitrary measurement. A very square-sidewalled tire will have a wider tread width, while a more rounded profile could have a much smaller "tread width" depending on how that dimension is defined. Even if they're both designed to run on the same wheel widths.

In any case, tire manufacturers take into account their own tires' dimensions and construction when giving wheel width ranges (which can differ between tire models for the same tire size).

For aesthetic and rim-protection and maximum-grip-for-given-wheel-size reasons, I like to run tire sizes that agree with the "measuring rim" size.

And I'd run the 265/35-18 or 275/35-18 on the same 9.5" wheel.
Section width of the 245/35-18 is 9.7". 18x9.5" wheel is 10.5" wide. The rim is outboard of the tire by nearly 1/2".

I don't see a need to second-guess the manufacturers' rim width recommendations based on "tread widths". They know more about what wheel widths are appropriate for their tires than we do.

Hell, there are super-wide cantilever slicks specifically designed to work on very narrow wheels for classes where stock wheel sizes are required. 9.5" section width, 9.2" tread width, designed for a max rim width of 7"!

Just stay within tire manufacturers' recommendations for rim width for the specific tire and you're fine. Personally, I prefer to run the measuring rim width, which is generally more on the "poochy" end of the range.

infinit1

What is the Max size 18" STREET tire you can fit in the front on a rolled or cut fender. Preferably something like a Michelin PS2. Not a road race tire that is streetable.
I would like to put a 295/35/18 but I am sure that is too tall. As my 245/40/18 already rubs a bit.
If I have to I will get some aftermarket fenders(burnout or mazdaspeed) to fit something but I would rather not.

I will be getting HRE Custom wheels so size and offset would be nice.

For the rear I want to run a 335/30/18. I will be doing a slight body flare in the rear to fit the excess outer width. I have aftermarket trailing arms and Tein HA coil overs for inner clearance issues.

imitek

hey guys i have searched and this post is the best i have found
i have re-super g kit on my car with stock wheels on i am wanting rpf1 in 18"
i want 10" rear and 9.5" front but tight against arch
im just worried about the offset of wheels, both front and rear arches are wider than stock fenders
i am asking for advice on offset for front and rear please
buy my ester-mate rear arch is 1" wider than stock front about 1.5"
any help would be appreciated

thewird

iTrader: (8)

Anyone know what offset I would need to fit 17x12" rim with a 335/35 hoosier r6 tire on the back?

thewird

jkstill

iTrader: (11)

Just learned of a new tool at Summit Racing that may be of interest in this thread:

Percy's WheelRite

BLUE TII

iTrader: (9)

I just test fit my 18x11 +45 wheels on my FD with no tires yet.

Front wheel inner lip does contact the rear of the lower arm slightly at full lock turning.

Rear wheel inner lip is less than 1/8" from coilover body at full droop (gains clearance as suspension compresses).

Rear wheel inner lip is less than 1/4" from stock trailing arm at full droop/compression (has the most clearance with the lower transverse arm level to the ground ie at rest).

I will update with pics once I get the 295/30-18 Ventus TD mounted. Stock body with just front fender lip rolled under and auto-x alignment.

Rockford_vzla

Hi i'm n00b on this and only hace a little question:

I got a friend that is swaping his '93 FD with a LS engine.... and he's asking me what size of wheels and tires are good for drag race, i was looking for this wheels:
http://www.ebay.com/itm/Weld-Racing-71MB-510A55A-RT-S-Series-Wheel-/111059846742?pt=Motors_Car_Truck_Parts_Accessories&hash=item19dbaec656&vxp=mtr
and some MT 325/50r15 tyres ET

now the doubt is... what offset i need for the wheel????



thanks

BLUE TII

iTrader: (9)

and some MT 325/50r15 tyres ET

now the doubt is... what offset i need for the wheel????


Because of the tall and wide sidewall on the 325/50-15 drag tire interfering with the trailing arm he would have to run a +15 offset and the tire will stick out of stock fenders about 1.75 inches.

Basically, it would need a large 50mm widebody flare and cutting the stock body under it.

Flyweight

iTrader: (1)

As all of you know it is difficult to find a high offset wide wheel. Well, we have a new option!
Outsource Performance has created what I think to be the best size and offset for the rear of an RX7 which is an Enkei PF01 18x10.5 +47. It took them well over a year to convince Enkei to produce the wheel but it is finally here! Outsource primarily supports the Mustang aftermarket and so they had Enkei build this wheel so that Mustang guys can fit 315s front. If you are looking to fit a 295/30 18 or if you are ambitious and want to fit a 315/30 18 with a strong fender roll and trailing arms this is your fitment.

Weight is approximately 22 lbs as the 18x10.5 +38 is listed at 22 lbs and these should be lighter given a higher offset and therefore a thinner mounting pad. Very light for a strong wheel!
PF01 have HUGE brake caliper clearance. Probably the biggest I have ever seen. Big brake kits should be no problem here.

These wheels are MAT cast and are more rigid than the already rigid RPF1 according to Enkei.
The PF01 comes in 18x9.5 +45 as well for a perfectly paired front set of wheels. You could, as I am going to do, have the 18x9.5 +45 wheels widened by .5 inches for the holy grail of wide tire front fitment in an FD of 18x10 +52 front wheel.

I immediately snapped up a set of these wheels and I have two extra if someone is interested (shameless plug)

https://www.rx7club.com/wheels-tires...nyone-1037098/

BLUE TII

iTrader: (9)

Not bad!

It took me 4 months to get my 18x11 +45 @ 22.5Lbs Forgestars made to replace my 18x10.5 +38 Enkei PF01, so maybe its faster to convince Enkei to produce custom offsets.

The new enkei PF01 18x10.5 +47 will be perfect front and rear on FD BTW.

Flyweight

iTrader: (1)

I would definitely not run the PF01 18x10.5 +47 on the front of a stock rolled fender FD. An 18x10 +52 is very very close as it is. But for the rear...I think the 18x10.5 +47 is perfect.

BLUE TII

iTrader: (9)

It is close and but will fit with stock front fender lips rolled under and camber.

18x10.5 +47 is 1.4mm closer to the suspension than 18x10 +52 and the wheel will still clear the lower arm at full steering lock.

The +47 more favorable offset (compared to +52) pushes the tire out away from the suspension, so that is less of an issue. Yet it will still tuck in the fender with a 285/295 and -2.4 deg camber.

Flyweight

iTrader: (1)

That is a lot of camber especially for an 18 inch tire. Usually people running 18s run 1.5 degrees or less on track. I would expect there to be adverse performance effects running so much camber on the track.

BLUE TII

iTrader: (9)

I see.

I auto-x and the competitive people with FDs find ways to add more than the around -2.4 deg front camber available with stock components.

BLUE TII

iTrader: (9)

Been talking it up a while- finally some pics.

18x11 +45 295/30-18 Hankook Ventus TD Z221 in front and rear.

I retested the front wheel/tire one side at a time to see about rub.

The rim doesn't actually rub the lower arm at full lock when it was torqued down. I had just a couple nuts hand tight before and the hub centric ring is really tight on these, must have been cocked to a side.

The tire DOES rub on the arms of my Tripoint front swaybar at full lock. I will take the tube in and have it cut down/re-splined at one end so it is shorter. My class does now allow steering limiters if I have to go that route.

I had to roll the lip under on my rear fenders as well as the front I had done already.

Rxmfn7

iTrader: (4)

^ Absolutely love it! I wanted to do something similar but I was very nervous about going that wide in the front with no PS. So I limited myself to 265F and 285R since I didnt want to have too much of a stagger. Perhaps after I play with it for a while if its not too bad I may have to copy your setup

BLUE TII

iTrader: (9)

I was very nervous about going that wide in the front with no PS

Yes, that sounds insane to me. I did my last weekend of auto-x on my old 18x10.5 +38 with narrower 265 Ventus TDs and I was working my *** off keeping up with the car on steering inputs WITH my PS.

Finally I found the limits of the tires and was able to drive it with the pedals on the last runs of Sunday.

Now I have to start over.

BLUE TII

iTrader: (9)

Local machine shop can't broach new splines on the bar.

Have a 34" torsion tube coming for the Tripoint bar to replace the standard 35" one.

Mark @ Tripoint is getting it made and to me within a week- what a boss!

Flyweight

iTrader: (1)

Blue TII, I picked up a set of R888 and was wondering what you thought about the TDs vs the R888. The price was too good to pass up. 285/30 front and 295/30 rear.