Maximum Wheel and Tire Width Fitment Guide for the FD
 

Every week I see a new thread being made asking whether or not a wide wheel and tire package will fit an FD. This thread will hopefully compile all the knowledge of the forum's wheel and tire experts into one thread and provide a guide for FD owners trying to fit the widest wheel and tire package possibe on a stock fendered or a slightly rolled fendered FD.

This thread is an overview of the wheel options people trying to fit the largest possible tires on a stock or slightly rolled fender FD. The fitments discussed assume that the FD has stiffer than stock suspension. This is not a hella flush thread. This is not a widebody thread.

For years track and performance FDs have struggled to find wide wheels with the high offsets that the FD requires. It is possible to fit a 10 in wide wheel in the front of an FD, however, it requires a +50 to +52 offset. Off the shelf wheels do not carry the high offsets required to fit a 10 in wide wheel.

FD owners either purchased a custom offset wheel such as CCWs (which now go for over $2000 for the set) or settled for a narrower wheel. I will discuss four options for wide wheel and tire fitment on an FD.

A few things to consider before purchasing wide wheels to fit wide tires…
1. How much money do you want to spend?
2. What tires do you want to run (is this a street car or a race car)?
3. Do you want to be able to rotate tires front to rear?

NEW Option 1: 949 Racing’s new 6ULR
 

NEW Option 1: 949 Racing’s new 6ULR
949racing.com
$280 per wheel

949 racing has just released a 17x10 +52 wheel that is designed to fit the front of the S2000. This is the perfect size for the front of an FD. Not only this, but the wheel is designed to fit large brake kits for the S2000 so I bet that the wheel would fit a Stoptech equipped FD. The problem with this wheel is that it is currently only available in 17 in format. Please refer to the 17 vs. 18 in tire section towards the bottom of the post.

The 6ULR is 19 lbs.
The 6ULR is $280.

This is a very nice alternative to more expensive CCWs or narrower front wheels.

There is a problem with this wheel being 17 inches though. The FD needs a 25 in overall diameter tire in the front in order to not rub the fenders. Howard Colman has gone over the benefits of running a 25 in ride high from the ground to the highest point on the fender and you will need a 25 in overall diameter tire to do this safely.

There are not many WIDE (over a 255 width) 25 in overall diameter 17 inch tires. Here are a few options:

1. Run a 6ULR 17x10 + 52 front with any 255/40 17. There are MANY options here.

2. Run a 295/35 17. This is a VERY rare tire size. For an autox car you can run the Hoosier A6. For a track car you can run a Hoosier R6. For a street car you can run the Kumho XS (I am so glad these are being made!). If you decide to run a 295/35 17 be wary of your fenders. This is a very wide tire for the front of your car. For example the Kumho XS is 11.9 inches wide in 295/35 17 form. The Kumho XS in 255/40 17 is 10.2 in wide.

3. Run a staggered tire package with 255/40 front and 275/40 rear (this rear tire diameter will change your gearing significantly).

Option 2: Enkei RPF1
 

Option 2: Enkei RPF1
enkei.com
~$300 per wheel

Enkei RPF1s are extremely light and inexpensive. If you are even thinking of purchasing RPF1s you should contact AutoRND (Rishie) from this forum. Expect to pay around 300 per wheel. The downside of the RPF1 is that you can not fit a 10in wide RPF1 in the front of an FD unlike the other options. You will also need to consider if you want to run Stoptech brakes with your wheels or not as some of the fitments will not fit Stoptechs.

RPF1 fitments that work without destroying your fenders with tire recommendations:

Conservative 17 in set up that will fit Stoptech brakes:
17x8.5 + 40 Front (Will fit Stoptech brakes if you are thinking about them in the future)
17x9.5 + 38 Rear

Allows you to run a 255/40 17 in front
Allows you to run a 275/40 17 in rear (note the change in gearing that a 25.7 in overall diameter wheel causes)

Aggressive 17 in set up that will NOT fit Stoptech brakes.
17x9 +45 Front
17x10 + 38 Rear

Allows you to run a 255/40 17 in front
Allows you to run a 275/40 17 (note the change in gearing that a 25.7 in wheel causes) or 295/35 17 (will probably require a fender roll)


Conservative 18 in set up (I would assume that this would fit Stoptech brakes but I don't know)

18x8.5 +40 Front
18x9.5 +38 Rear

Allows you to run a 255/35 18 front
A allows you to run a 285/30 (less acceleration grip due to less side wall but more lateral grip) or 275/35 (more acceleration grip but less lateral grip) (note the change in gearing that a 25.7 in wheel causes) in the rear.

Aggressive 18 in set that will fit Stoptech brakes:

18x9.5 +45 in Front
18x10 +38 in Rear

Allows you to run a 255/35 18 or a 285/30 18 (not recommended by tire manufactures but many people have been running a 285/30 on a 9.5 in wheel without problems) front.
A allows you to run a 285/30 or 295/30 (less acceleration grip due to less side wall but more lateral grip) or 275/35 (more acceleration grip but less lateral grip) (note the change in gearing that a 25.7 in wheel causes) in the rear.

Fitments that allow you to rotate wheels from front to rear:
18x9.5 +45 Front and Rear (Will clear Stoptech brakes)

Allows you to run a 255/35 18, a 265/35 (taller than 25 in overall diameter…be wary), and a 285/30 (not recommended by tire manufactures but many people have been running a 285/30 on a 9.5 in wheel without problems)

17x9 +45 (Will not clear stoptech brakes)

Allows you to run a 255/40 17.

Option 3: Custom Offet CCWs
 

Option 3: Custom Offet CCWs
ccwheel.com
~$550 - $700 per wheel

CCW has been producing custom offset wheels for FDs for quite some time. They can produce a 18x10 +52 wheel for the front of your FD that allow you to run a 285/30. CCWs do clear Stoptech brakes.

This will allow you to run a 285/30 18.

285/30 18 in wheels have a very short side wall. This is nice for the front of your car but is not as desirable for acceleration grip.

Many people have run 18x10 +52 front and rear with 285/30 18 tires. This fitment allows you to rotate your tires and is a proven setup.

Because CCWs allow for custom offsets some people have run an 18x11 +48 in the rear of their FD.

An example of this rear fitment was recently discussed on v8rx7forum.com.

http://www.v8rx7forum.com/showthread...-stock-body-FD

A few of the problems that the owner who ran a 315/30 ran into were:
1. Rubbing the inner subframe
2. Rubbing the trailing arms
3. Fender clearance

If fitting a 315 in the rear is your goal I would look into a 10.5 +48 wheel. This will give you a bit more (less than 6mm per side because of tire bulge) clearance and may allow for an easier fitment. That said no one to my knowledge has attempted this fitment.

I do not know if you will run into trailing arm clearance problems with the 18x10.5 +48. There has been some interest in creating a slightly bent trailing arm for the rear of the FD to provide more clearance for a 315 rear tire on v8rx7forum.com. Here is the link to the thread:

http://www.v8rx7forum.com/showthread...est&highlight=

Kevin T. Wyum fit a 315/35 17 back in the day with modified trailing arms (if I remember correctly). People seem to have less trailing arm problems fitting 18 inch wheels.

Below is a quote about his fitment:

“With 275/40 17s in the front and 315/35 17's in the rear I had to cut the rear fender lips and get a workout with a BFH in the rear fender lining and it still rubs under some conditions. I might be off on the specific sidewall height. It's been awhile since I've looked at the tires.”

Kevin T. Wyum


I think that fitting a 315/30 18 is possible but it will require a very precise fitment and will more than likely depend on the 315 tire used.

Option 4: Create your own Wide Wheel Wide Tire fitment:
 

Option 4: Create your own Wide Wheel Wide Tire fitment:

Because the number of wheels available in the aftermarket is endless, it is not reasonable to cover each option. This section will provide a general guide for FD width and offset for WWWT front and rear fitment.

I believe that the offset chart that is displayed in the FAQ for the FD is too conservative for people trying to fit the widest wheels and tires possible. Many FD owners have been able to successfully run wider and lower offset wheels than what is specified in the FAQ. That said I believe that the FAQ is an EXCELLENT guide for standard (read not maximum tire and wheel width) fitment. I have created a new chart of what I believe to be a more accurate representation of proper FD wheel sizing for the purpose of fitting the widest tires possible inside stock or rolled stock fenders. The lower the offset the more fender rolling will be required.

A conservative fitment is one that is in-between the offset ranges. A 9.5 +29 will work in the rear insofar as it will stick just as far out towards the fender as an 11 in +48 wheel. That said, there is no reason to run a 9.5 +29 wheel as you can easily find a better offset that does not have all the problems of fender rolling associated with it. I have included what I believe to be the ideal offset for the listed wheel width. The ideal will not require a fender roll to fit the wheel provided you have a 25 in overall diameter tire in the front and have stiffer than stock suspension. The exceptions to this rule are the 10.5 and 11 in wide rear wheel which will both require a fender roll.

FRONT
Wheel Width Offset range Ideal
10 +50 to +52 +52
9.5 +44 to +56 +48
9 +37 to +63 +45

REAR Offset range Ideal
11 +48 +48 (will require fender roll)
10.5 +42 to +54 +48 (will require fender roll depending on tire size)
10 +35 to +61 +44
9.5 +29 to more than+60 +40

On the whether to run a 17 or 18 inch wheel…
 

On the whether to run a 17 or 18 inch wheel…

Advantages to running 17 inch tires:
1. Tires are cheaper new.

2. 17s that are 25 inches in overall diameter have more sidewall and will generally ride better than 18s.

3. 17s allow for a larger sidewall for the tire. This generally aids traction during hard acceleration in lower gears. 275/40 17 and 295/35 17s are excellent at putting big power to the ground.

4. A 255/40 wheel and tire package is generally lighter than a 255/35 18 or 285/30 18 wheel and tire package.

Disadvantages of running 17 inch tires:

1. There are a limited number of available tires that are wider than 255 and are 25 inches in overall diameter. KumhoXS (an excellent autox/street tire) comes in a 295/35 17. Hoosier makes 295/35 17 autox (A6) and road race (R6) tires. The FD is limited to running either a 255/40 or a 295/35 17 in the front to maintain the required 25 in overall diameter. That said many people have successfully run a 275/40 17 in the rear of the FD. This tire size measures 25.7 inches in overall diameter.

2. The 275/40 17 tire size will change the overall gearing significantly. Many people have opted to run a different than stock final drive ratio to compensate for this change.

3. The 275/40 17 and the 295/35 17 create a wheel and tire package that is generally heavier than a 285/30 18 or 295/30 wheel and tire package.

Advantages of running 18 inch tires:
1. While wide 17 inch tires are cheaper new, wide 18 inch tires are more readily available used. Because of this it is possible to purchase wide 18 inch tires for cheaper than new 17s. If you are in the market for a set of 18 inch wide tires you may want to check out EVO, STI, RX8, NASA, SCCA and Z classified forums.

2. 18 inch tires have shorter sidewall which makes them more responsive than their larger sidewall 17 inch counterparts.

3. There are a few companies that produce a 285/30 tire which is actually shorter than the ideal 25 inch overall diameter. This allows for the FD to swallow a wide front tire.

4. The 285/30 wheel and tire combo is generally lighter than a 275/40 17 or 295/35 17 wheel and tire combo.

Disadvantages of running 18 inch tires:
1. Tires are more expensive when purchased new.

2. 18 inch tires generally have less traction in lower gear acceleration than 17s due to 18s having less sidewall.



I hope all of this helps...

-Andrew

Good luck with that. People that post asking are usually Newbies that are too lazy to search or others that just plain too lazy to read the existing threads on the topic.

From the suspension archives:
https://www.rx7club.com/forumdisplay...c&daysprune=-1
https://www.rx7club.com/suspension-wheels-tires-brakes-archive-112/fd-wheel-tire-sizing-475828/
https://www.rx7club.com/suspension-wheels-tires-brakes-archive-112/max-front-wheel-tire-fd-rx7-fitments-111964/

And stickied right here in this forum:
https://www.rx7club.com/suspension-wheels-tires-brakes-20/fd-wheel-tire-sizing-416251/

Another thread on 17" vs 18":
https://www.rx7club.com/suspension-wheels-tires-brakes-archive-112/17-vs-18-racing-mind-narrow-vs-wide-tires-292194/

More:
https://www.rx7club.com/suspension-wheels-tires-brakes-archive-112/need-suggestions-wheel-gurus-330780/

The list goes on and on...


And don't get me started on the "what coilover threads should I get?" threads... :facepalm2::uh:

Great thread :beer:

yes definitely respect the time and thoughtfulness of this. I am positive i'll still get asked the same questions all the time but hey, that's my job. Sometimes people need to go through a physical Q&A session with a professional. A lot of times they have all the data but still can't assess their needs.

I can't wait for someone to bite the bullet and get a set of the 949 Racings 6ULRs. I think that this with the 295/35 17 Kumho XS is an AMAZING street/track/autox package...all for less than $2000.

Would you think 18X9.5 +38 would fit up front of an FD? 255/35/18 tire

not without fender mods. +45 is pushing it.

rishie

can a FD fit a 275/35/18 on a 9" with +43 off set on the front ?
will that look silly ?

275/35/18 is not an option for the FD UP FRONT. It is too tall a tire for the fender arch UP FRONT.

DO YOUR RESEARCH GUYS. THERE IS A SHITLOAD OF THIS INFORMATION ON THE BOARD. I PERSONALLY KNOW I'VE STATED THESE FITMENTS A MILLION TIMES OVER THE PAST 10 YEARS.

Thanks,
Rishie

i know i know i should search. thanks ARD T2 for responding. i want to go wider on my rears so i was planning to put the 275 on 9s in the front and going with 2 new tires 295 or 305s on 10s for rears. i have seen a fd wearing 295s on rears has a very nice stance.

for the 9" you can do 255/35 or 265/35 as a max tire diameter, minor fender tab mods might be required. What is the offset for the rear? All I can say is that your tire width is going to be dependent on the width/offset of wheel you run.

Also keep in mind that the wider that rear tire gets the worst the car might handle. Keep front and rear near to size. Optimally 10" front and rear with 285/30/18. this is max width and good tire diameter.

my rear off set is a +44. a 275 toyo t1r on a 10" tire looks a little strechted, i like the more meaty look more tire on the side. i heard some nittos run smaller, on the other hand iv seen
pics of a nitto 285 drag radial on a 10" tire and it looks way wider then a 275 t1r street tire on the 10" by far.

I assume the drag radial you are talking about is the NT555r. This radial only comes in a 285/35 18 which is 25.91 in overall diameter...way too big.

The g-Force T/A Drag Radial does come in a 275/35 17 which would fit in the rear...it will change your gearing significantly. This is the only 18 inch DOT drag radial that I know of that will fit an FD.

As I am sure you know a drag radial is quite a bit different than your current mild Toyo T1Rs.

what fender mods you have to go through to fit a 315/35/17 dr with a 17x10 w/38 offset on a fd?? how much pull would you need? or a 305/35-30

awesome thread!!

if i want to run 18x10 +48 front
18x10.5 + 44 rear

how much rim lip will i get? and i'm going to roll, cut, my fender .
or do you suggest a better option .

thank you

It is difficult to tell someone "How much to roll a fender." There are no standard units to use when explaining this. It depends on how much the fender liner is rolled...How large the tire is...ect.

That said I will say a couple things about your fitment. I do not know which drag radial you are planning on running, however, a 315/35 17 does not fit well on a 10 inch wheel. The BFGoodrich g-Force T/A Drag Radial 2 recommends at least an 11 inch wheel.

A 17x10 +38 wheel is pushing it in terms of fender clearance for someone not wanting to stretch their tires. You are trying to fit not only an EXTREMELY wide tire on a comparatively skinny wheel but the overall diameter of the tire is also very large at ~25,6 inches. This will not work.

My recommendation is to one of three solutions:

1. Run a 275/40 17 drag radial. You can fit this on your 17x10 +38 inch wheel with a decent sized fender roll. The benefits to this are that you can run an Enkei wheel (cheap and light) and there are many drag radial options in this tire size.

2. Go the custom wheel rout. Here you are in relatively unmarked territory. Some people have been able to fit a 315/30 18 in the rear of an RX. You will have fender issues...You will need aftermarket rear trailing arms...You will need ~18x10.5 +48 or a ~18x11 +48 wheel. I do not know if you can use a 17 inch wheel. Again this is relatively uncharted territory. Read my posts above for further reference.

3. If you are looking to simply go drag racing...don't use a drag radial...use a pure drag tire on your stock 16s and buy a set of street wheels.

It is very difficult to answer your questions without knowing which wheels and which tires you have in mind.

18x10 +48 is a VERY difficult wheel size to find without going to custom offset wheels. If you are going the custom offset wheel rout I would recommend going with a +50 up front provided you do not want to stretch your tires. 18x10 +48 is too low of an offset to run a 285/30 tire without a decent amount of fender work.

18x10.5 is again a very difficult wheel size to find. If you are going with custom offset wheels I would recommend going with 18x10.5 +48.

Wheel lip is dependent on the specific wheel you have in mind.

If you are fixated on a wheel with the offsets you mentioned I would run a 255/35 up front and a 295/30 in the rear.

Good luck and let us know your results.

You can run 275/40/17's up front, particularly on the track. That used to be the set-up before 18" got more popular.

You will have to run the car a little higher, but that's not necessarily a bad thing. There are many people who will tell you not to run the car any lower than a height that will keep the lower suspension arms parallel to the ground for roll-center reasons. 25" is definitely lower than that, so it's a compromise. Fritz runs the size (as have I), and he gets around just fine.

I'd run that before I stuffed a 295 on a 9.5" or 10" wheel.

While I wouldn't run a 295/35 17 or a 295/30 18 on a 9.5 in wheel I would run them on a 10 inch wheel. A 295 width tire on a 10 inch wheel is within the tire manufactures wheel width recommendations.

Some people have run a 270/40 17 or a 275/35 up front before. This does require raising the front of the car beyond the optimal (according to Howard Colman) 25 inch ground to top of fender ride hight. I would rather run something shorter up front but there are many ways to skin a cat.

18x9 +15 front 18x10 +23 rear????
 

Awesome info Flyweight. I swear I have read through this thread 20 times at least. I have also search and searched trying to find some info on a set of rims that I have to see if they would fit and if so what size tires I would/should get with them. I have a set of Volk GT-S that I would love to put on my FD.
They are 18x9 +15 offset for the front and 18x10 +23 offset for the rear. I know that is an extremely small offset for the FD but is there any possibility that I can get these to fit on my car? If I have to roll my fenders I am willing to do so but if I am able to get them to fit, what size tires would look and function the best, and most importantly would fit? I have a stock setup as far as brakes and suspension goes if that helps at all. I really appreciate any information. I will keep searching but have spent about the last 2 weeks trying to find anything close to my setup and haven't had any luck so I figured I would go to one of the masters. Thanks for any help.

Flyweight,

Base on the following quotes, would you please indicate whether 275/40/17 on an Enkei 17X10 +38 offset requires fender rolling or not?

"Aggressive 17 in set up that will NOT fit Stoptech brakes.
17x9 +45 Front
17x10 + 38 Rear

Allows you to run a 255/40 17 in front
Allows you to run a 275/40 17 (note the change in gearing that a 25.7 in wheel causes) or 295/35 17 (will probably require a fender roll)"


"1. Run a 275/40 17 drag radial. You can fit this on your 17x10 +38 inch wheel with a decent sized fender roll. "

Hello there,

The wheels and tires you purchased will not fit unless you pull the crap out of your fenders and run rubber bands for tires...or run a widebody kit. The purpose of this thread is to provide information for people trying to run the largest tires possible under a stock fd body.

If you want to run the sizes that you mentioned you will need either...

1. Consult someone who knows more about "Hella Flush" fitments i.e. extreme rolled fenders, and extreme streached tires. This "Hella Flush" movement is more about the look of the car and does detrimentally affect the dynamics and functionality of the car.

OR

2. Look into installing a wide body kit for your FD. This is very expensive as you will need to purchase the kit, paint the kit and fit the kit to your car. I personally love the look of a stock bodied FD and would never consider running a widebody kit. I think they are ugly and you can easily fit a 18x9 front and an 18x10 rear on a stock bodied FD. Which leads me to your 3rd and in my opinion best option...

OR

3. Sell the wheels! Silvia or Z car folk would be interested in the size and offset of the Volk wheels that you have. You can then use the money that you recouped to purchase a set of wheels that actually fit and FD. Do your research and don't spend any money until you know exactly what you want.

Good luck!

Whether or not your car needs a fender roll is dependent not only on the wheel and tire but also on your ride hight and the stiffness of the suspension that you are running. That said a 275/40 17 is a large tire and with the relatively low offset of +38 on a 10 inch wheel I will assume that you will need a fender roll to fit the tire properly. How much of a roll will again depend on your ride height and how stiff your suspension is.

Good luck and post pictures of the results!

thanks.

This may be a silly question, but i havent seen it mentioned at all. What would be the problem with runnin somethin like an 18X9.5 on the back and a 17X8.5 or 9 on the front? A guy could have the size and footprint on the back where theres room, and still have a pretty good sized tire on the front without havin to roll the fenders. Any problem with that?

Ok, time for a new set of summer tires for my front!

These tires came with the wheels when I bought it and were purchased at 2 different times by the previous owner so the front ones are needing to go.

Front: 235/45/R17 - Bridgestone Potenza RE050 Mounted on 17x8 et35
Rear: 255/40/R17 - Dunlop Le Mans LM702 Mounted on 17x9 et35

The wheels are BBS LM's

I'm thinking about going with a 235/40/17, I would like the same stretch as the rear which is pretty nice. But I'm afraid it won't be enough or any at all? What do you guys recommend?

235/40-17 is only 24.5 inch overall diameter, so shorter than stock. I've seen guys use it, but you'll most likely have issue with the front lip scraping in certain instances.

If I were you, I'd consider 225/45 and 255/40---- 25 inch overall diameter evenly matched front to rear. those are also the standard width tires for those width wheels.

Check these out, good pricing and amazing tires for the street: http://www.tirerack.com/tires/tires....t+Z1+Star+Spec

Thanks for the advice goodfella, what will the width be like? will it be an even stretch compared to the rear? The front is currently taller than the rear, which I don't like

what about a 17x10 et 38 front with an agresive fender roll can that be done?

Pretty sure I already answered these questions in my last post...... it should be perfectly even wrt to overall height and also the relation of tire width to wheel width.

on the rear you can run that without a roll at all with 265s. On the front you'd need skinny tires to have a chance at it.

The benefit of running 18s is that you can run a shorter sidewall which improves turn-in/response. 18s are better in the front.

The benefit of running 17s is that a bigger sidewall tire generally has more grip on launch/acceleration. 17s are better in the rear.

That said a 18 front 17 rear car would look rather dumb. A couple of supra track and autox guys run a CCW set up with 18s front and 17s rear for the exact reasons I mention above. Check out: http://www.tunerzine.com/view-article/just-fine

That said t is very easy to find a 17x9.5 wheel that will fit the rear of an RX7.

I am going to have to disagree with Goodfella here on this one.

An excellent option for you would be to run a 265/40 17 rear and a 245/40 front. Unfortunately, these sizes are rather rare. That said, the Dunlop Direzza Sport Z1 Star Spec does come in these sizes and is an EXCELLENT street/autox tire. This would give you much more meat for tires. If I were you this is the setup I would run.

You could also run a 275/40 rear. This would give you many more tire options. Read my posts on the first page about running a 275/40 rear...summary: worse gearing...better traction...more difficult to fit...heavier.

I would not run a 225/45 17 front as Goodfella recommends. The tire is too narrow. If you are checking out this thread you are interested in fitting the largest tires under a stock body RX7. Check out a 245/40. They are slightly shorter than but much wider than a 225.

Good luck!

This is my recommended range for fitting the largest size tires on a stock bodied RX7. Going with an offset lower than what is recommended will require smaller tires...not the purpose of this thread...that said you MIGHT be able to squeez a 255/40 or a 240/40 on a 17x10 +45...maybe...depending on fender roll, ride height, suspension ect.

FRONT
Wheel Width Offset range Ideal
10 +50 to +52 +52
9.5 +44 to +56 +48
9 +37 to +63 +45

REAR Offset range Ideal
11 +48 +48 (will require fender roll)
10.5 +42 to +54 +48 (will require fender roll depending on tire size)
10 +35 to +61 +44
9.5 +29 to more than+60 +40

If the wheel you are thinking about is an Enkei RP-F1 you should look at my recommended RP-F1 fitments on the first page. You will not be happy with a 17x10 +38 in the front if you want a large tire up front.

this is the reason for my autox setup:

Front: 18x10 - 285/30/18
285 is the widest "short" tire, allowing the car to be as low as possible wih no fender issues (i might try 295's if i can find em cheap enough)

Rear: 17x10.5 - 315/35/18
315's are $100 cheaper per tire in 17 vs 315/30/18, and a bit cushier for laying down power out of corners.

i dont care if it looks dumb, it works

That's all good info, however it's not what I asked... My original question was the reverse of what you told me. I would like to run 17s in the front and 18s in the back. I'm not lookin for the perfect setup for racin, I want it to look right. A 1" difference from front to back would look fine with the smaller on the front wouldn't it? It may not be perfect for performance, but it would allow a bigger tire on the back and a fairly big tire on the front without havin to worry about rolin fenders. This car isn't gonna be a track car, it's gonna be a Sunday driver and show car. With that said, any problem with my theory?

Your idea of running a 17in front wheel and an 18 inch rear wheel has been done many times especially by the 240 crowd. In terms of performance...this is not ideal. In terms of style...well that is up to you and not the purpose of this thread.

It is not the wheel diameter that requires a fender roll it is the width, offset, suspension, and overall diameter of the tire that determines whether or not you need a fender roll. You need 25 in tire front. A 255/40 17 is a 25 inch overall diameter tire. A 255/35 18 is a 25 inch overall diameter tire.

That's a much better answer, thank you. 17s were covered at the beginning of the thread and that will work perfect for me and what I'm wanting. You put it in very good terms for me to understand. I've been haven a hard time gettin my head wrapped around rollin fenders but it makes much more sense now.
Thanks again

I provided a link to the Star Specs earlier in the thread, so we're on the same page there.

Wrt to tire sizing on a given rim width, it's my opinion that the sizes you're recommending are certainly an option, but I'm not sure it's a good one.

Why fit an overly large tire onto a relatively narrow rim? You'll get better grip for braking and acceleration, but the car's cornering abilities can/will suffer.

Mustang guys run 275s on 9 inch rears, but i've never recommended it for FDs that will see auto-x, road race, or canyon-run type driving.

Different strokes for different folks, I suppose :)

There are a few differing thoughts on fitting wide tires on relatively small wheels. Fitting a 275/40 on a 9 inch wheel may not be as ideal as fitting that tire on a 10 inch wheel. The tire sidewall will flex more and you will lose some responsiveness. However, I will refer to autocrossers here. All competitive autocrossers run the largest size tires that they can possibly fit even in classes that do not limit wheel width...and they run faster because of it despite the reduction in responsiveness.

The larger the sidewall the smaller wheel you can run. For example a 275/40 17 generally have a wheel range of 9-11 inches whereas a 285/30 18 generally has a wheel range of 10-11 inches.

I would rather have a 275/40 on a 10 inch wheel but if I have a 9 inch wheel and I am looking for performance I would still take a 275/40 over a 255/40 provided I do not mind the change in gearing/weight.

Is there any reason why a 16x10 offset 50 wheel wouldnt work? I plan on measuring on the car this weekend to double check.
Widening the factory wheels or getting a custom set made are the only options that I know of here. Widening that Ive looked into would cost ~240 per wheel and custom steel wheels im still waiting on prices and weights.

Kumho and Hoosier both make an attractive size 16" tire 265/45/16 25.2" tall and 275/45/16 25.6" tall, that in the real world are probably closer to a 285 in width.

Also keep in mind that running less sidewall generally results in less traction on bumpy surfaces. You do get "better" steering feel b/c of less sidewall but you also get less conformance to pavement irregularities.

Grassroots Motorsports just did a test on a NC Miata testing 17" and 18" wheels on an autox course. The 17" wheels won out for the reason I mentioned above.

Also in their test, running a 245 instead of a 255 on the 17 x 9 wheel resulted in quicker times. IIRC, They felt that was b/c there was less squirm from the 245 on a 9" wheel compared to the 255/40/17.

A 16x10 +50 would work just fine. I have read that Westcraft does a good job widening aluminum wheels. The domestic market (Mustang, Camero, Corvette crowd) seems to have had success with them. http://www.weldcraftwheels.com/index-1.html. That said, the stock FD wheels that are scalloped have been prone to cracking. I do not know how they would do with being widened...Also you will need to very accurately measure where you want your wheel widener to cut and add two inches of wheel to get your +50 offset. This will require a lot of measuring and remeasuring.

Ordering a set of 16x10 steel wheels might be a good option as well...maybe even cheaper. Of course you could go completely custom and nab a set of Kodiak 16x10s...although for a lot more money. Just a few options if you are interested in running 16s.

I would personally run the 265 as opposed to the 275 because of the height of the tire.

Good luck and post your results,

Andrew

Weldcraft is where I got my price from, there are a few shops locally that may be setup to do it but I havent looked in that much detail yet. All the width gets added to the backside of the rim, so adding 2 inches would turn the offset to 75.4 and would need a 1inch spacer to bring it back to 50mm. I was thinking a bolt on 1" hubcentric spacer would likely do the job and still be safe.

The FD rims that crack are I believe 2lbs lighter than the ones that dont. Truthfully I am worried about cracking and flexing the stock wheel with an extra 2" built into it, but its one of those things you wont know untill you try. And 710's are also my first tire choice.

Heard back about the steel wheels, Diamond Racing Wheels. 16x10 back spaced as requested. $169each 25lbs each. Very good pricing, but too heavy for me.

Widening the stock FD wheels sounds like a great project and one I think a lot of autoxers would be interested in. If Weldcraft is not willing to add the extra width anywhere but the outer edge I would try another company.

Kevin Doe widened his Enkeis to 18x11. He added his extra band in the middle of the wheel and has been autoxing on them. This would allow you to run without the spacer...less weight, more safety. Do you have the light verson of the FD wheel or the heavier version?

I am excited to see your results.

-Andrew

Attachment 711550

well open this up agian im going ccw i like to run 255 35 18 up frount on a 18-10 wheel + 48 basiclly i want fit ment like Enkei RPF1 18-9.5 +45 i guess my ? is what offset to run.

for the back i want to run a 285-295 30 18 so a 10.5 or 11 rim again i want it to fit like the Enkei RPF1 18-10 +38 so a 10.5 should be a +44 ?? and 11 +44 ??

thanks
Martin R