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...

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.

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"?
http://assets.speedtv.com/images/ad_...3477/13477.jpg

Because that's about the amount of "stretch" I have with 245s on 8.5" and 275 on 9.5"
http://sphotos-a.xx.fbcdn.net/hphoto...71214357_n.jpg

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.

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.

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.

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")

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.

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.

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

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

thewird

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

Percy's WheelRite

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.

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

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.

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/

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. :lol:

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

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.

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.

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.

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.

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.

https://www.rx7club.com/attachments/...ont-fender-jpg
https://www.rx7club.com/attachments/...-side-rear-jpg
https://www.rx7club.com/attachments/...tire-close-jpg
https://www.rx7club.com/attachments/...el-n-brake-jpg

^ 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 :D

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 ass 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.

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!

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.

Sorry, I haven't raced/driven with R888 on my FD- just friends cars.

But what I feel based on my experience with NT01 and RA1 (same compound as R888 I believe) is that the R888 will have less ultimate grip and take a bit longer to warm up than the Z221 C70 compound, but last longer and have more consistent grip/warm up time over its life (ie not hear cycle out so badly).

I think the Z221 C50 and R888 would be a closer comparison and based on what I know I would take the R888 for its known consistency, lower price ($240) and the fact that I am not thrilled over Z221 lazy sidewall/carcass feel.

Got my shortened Tripoint swaybar torsion tube today.

4 work days delivered for a custom spec part made to order from a subcontractor.

Mark at Tripoint is the man! He obviously has a great team working with him at Tripoint and chose his subcontractors well too.

thread very usefull thanks everyone!

Slightly over -2 in my case.

With offset bushings it is now -3.3

And contrary to what some may say, more camber can be quite good on an FD, especially for autox.

The extra camber does sacrifice some braking and acceleration for cornering speed, which is just fine for autox, and possibly tracks with short straights.

Looks pretty good. :icon_tup:

In that first pic it appears that the steering wheel flips up.

Is that the case?

Yes, that is a Works Bell Rapfix GTC Hybrid steering wheel boss.

It makes it easier to get into race seats in the FD with short fat legs.

Thanks for the pointer - I also thought this was a great idea for a tool so ordered it.

Turns out it is made of plastic pieces that flex enough (or are mold-warped enough) that I wouldn't trust it's accuracy to more than +/- 5mm clearance. It's too bad, since a well-made metal piece would have some utility.

And you need to know the profile of the tire you want to run sufficiently well to be able to bend a piece of wire to match its shape. Using a wire isn't a bad solution, but be aware that simulating tire profile is just hard to do without the tire.

And it won't help much with trailing rod interference, since that depends on the mfg-specific internal dimensions of the wheel.

All in all, since most of these questions come down to millimeters, far more accurate information is available on this forum, from the experience of others.

Too bad that tool turned out to be less than useful.

Sounds like it would have been more useful if stouter material were used to build it.

Thanks for the report.

Hello)
I've recently bought a set of Volk GT-C face2 18" from JDM RX 7.
Tire width is 9",front offset +11, rear +6.
Front tyres 245/40, rear 275/35.

Now it's winter in our region, so I haven't installed them yet.

Will they fit to stock archs? Or I need to roll it?
Thanks

You wont fit that properly without over fenders.

Only rear?
Where can I buy over fenders?

so just to be sure
front: 18x9.5 with 255/30/18 +45
rear: 18x10 with 285/30/18 +38
these will clear without rub or fender roll/pull?

The fronts should fit with a roll.
The rears will cut it fairly close but should fit, might require a little pull.

I don't think your front will fit either to be honest. Not even with rubber band tires.
Those specs are waaaay to aggressive for stock body.
Shine Auto sells good ones in various styles. Check the 3rd gen classifieds I seen a set for sale there too.

I would run a 18x10 front and rear with 255/35/18 tires. OR front 18x10 255/35/18, rear 18x10.5 +38 to +30 with a 285/30/18.

You will need to roll the fender lips, and possibly a slight pull depending on the car and offset you choose.

Aggressive: if you want, you can run -2 degrees camber and run 18x10 front and rear with 285/30/18 tires and an aggressive roll of the fenders. if you use +38 offset. I am getting mine to work with a 18x10.5 +30mm offset and 285/30/18 tires with not too much of an aggressive drop. fender height is 25" front and 25.5" rear. +38mm would be the better offset to do it with. I am currently running 18x10 +38mm front and rear with 265/35/18 tires and -2 degrees camber front and -1.3 rear. The camber is what is good for handling and also fitting tires. you could do a 285/30/18 18x10.5 +38MM enkei PF01.

so just to be sure
front: 18x9.5 with 255/30/18 +45
rear: 18x10 with 285/30/18 +38
these will clear without rub or fender roll/pull?

Front will fit fine, but will require at least 1.4 degrees negative camber up front if the stock fender front lip is not rolled under (with a little variance depending on tire manufacturer.)
I ran 17x8.5 +30 with 255 from my TII on the front of my FD with around 2 deg negative camber and it *barely* caught the unrolled fender edge when a really good driver auto-x'ed it. I wasn't able to load it enough to get it to rub.

It is only tire width and offset that matter. Rim width only comes into play when you gonzo on it and start running into the suspension on the inboard side.

Rear will fit fine with a 265/35-18 and anything over about 1.3 deg negative camber on unrolled fenders. The 265 is a better fit for a 10" wide wheel anyways, especially if you are "stretching" a 255 on a 9.5 up front.
I ran 18x10.5 +38 and 265/35-18 on unrolled rear with 1.2 deg neg camber and it barely barely rubbed just the letters on the sidewall.

But really do yourself a favor and run a square (10" wide) set up front and rear so you can rotate the tires and not have so much understeer. Keep the offset as close to +45 as you can in order to fit the max tire width.

Those specs are waaaay to aggressive for stock body.

Well, this thread is for max width and those are actually quite conservative, but I do understand he said stipulated unrolled fenders and one can assume he doesn't want much camber either.

Basically, wrong thread for this poster.

I'm looking at getting a set of Advan TCIII.
ADVAN Wheels - ADVAN Racing TCIII

I can get a deal on 18x9.5 +45 for the rears, but only two. I was planning on running those in the rear as I think they will be too much for the fronts. What size should I get for the fronts? I was thinking of doing a 18x9.0 +40. What do you think?

Those sizes and offsets will definitely work.

If it were me, hell I would run a rolled fender lips with 18x10 +35mm front and rear 255/35/18 tires.

If wanted to go widebody I would use 18x11 +30mm with 295/30/18 tires.

I don't plan on going widebody, but I will roll the fenders. I can get two of the 18x10 +35, but I don't think the 18x9.5 +45 will fit on the fronts.

I can get two of the 18x10 +35, but I don't think the 18x9.5 +45 will fit on the fronts.

Why not?

As far as I am concerned, +45 is the perfect offset front and rear to center the tire between the stock (rolled) fender arch and the suspension.

I run 18x11 +45 w/ 295 front and rear with rolled fenders and -2.4 front camber and coilovers.

If you went down to -1.4 camber in front you could still run a 265 with that +45 offset and rolled fenders.

If you went down to -.4 camber up front you could still run a 255 or 245 with that +45 offset, which would be best on a 9.5" wide wheel anyways.

Don't stagger front to rear by half an inch. If you are going to stagger you might as well do it a meaningful amount- not just enough to nix rotating tires without any noticeable performance or visual difference.

I know, I did this on my first wheels on my RX-7 TII.

None of this should be in this thread though.

Think of the people who do search, now they have to wade through all this conservative fitment talk to find some specs for "maximum wheel and tire width fitment guide for the FD" which is the title of the thread.

Thanks for the feedback and knowledge. I have the 18x9.5 on the way. Luckily I'll be able to see what they look like and go from there on the other two. I think you're right about not staggering.

I could have posted in a better thread. I was searching through the forum, and had 10 tabs open on my screen.

I just read all of this, started off lost and finished more lost than I started. Help for a newb rotard?

I want to order these but unsure if they will fit:

Wedssport SA-60M, with 18 x 10 x +36 offset for rear and 18 x 9 x +35 offset for the front.

I don't mind rolling the fenders...

yes they will fit.

F: 225/40-18
R: 255/35-18

Or

F: 235/40-18
R: 275/35-18

I would go with a 18x10 +36mm front and rear with 255/35/18 tires front and rear. roll front and rear fenders.

I'm having a tough time spec'ing new front tires.

My wheels are
Front: 18-8.5 offset 35 - 255/35/18 or 245/35/18
Rear: 18-9.5 offset 38 - 265/35/18

Fenders are NOT rolled

Currently I'm running 225/40 front and 265/35 rear and everything is fine but I was hoping to get wider fronts. I was told 255 would work but I looked into it again and it looks like there will be some rubbing but I'm not 100% on this.

Based on the wheel sizing excel sheet
Front wheel offset (35mm)
Tire clearance, outside (0.12in.)
Tire clearance, inside (1.38in.)

It's making me start to think that 245 would even rub due to the low outside tire clearance. What do you guys think?