Going 18x11" Square with 305 tires and rotatable! It can be done!

Surfergeek

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It's been a months long process to get this figured out, but thanks to many of the members across multiple forums along with some of our own measurements we have come up with the formula for wheels to get as much tire as possible under the car without a wide body kit or extensive modifications. Shout out and thanks to James Jeffers with Pinnacle Performance Motorsports as well.

But what I really wanted was a set of 18x11" wheels that I could run as a square setup and rotate front to rear, to get as much life out of my track rubber as possible without having to deal with taking the tires off the rims to rotate tires. We found the formula to an 18x11" rim that you can run square and rotate because they are all the same offset if you are willing to do some minor mods and run a hub centric spacer up front.

Album on Flickr with all the pictures: https://www.flickr.com/photos/surfergeek/albums/72157660194695686

What's Required:

Hub centric spacers
Extended Length Racing Studs (ARP/Ford Racing)
Negative Camber up front

We test fit on 2 configurations:

1. Cortex Racing Extreme Grip Coilovers w/ 14" Brembo, Maximum Motorsports Camber plates, Ford Racing Hubs / Extended Length Studs

2. Koni Struts, Lowering Springs, 15" 6 Piston Brembo brakes, Maximum Motorsports Camber Plates, Ford Racing Hubs / Extended Length Studs

The wheels

Forgestar CF5, custom ordered from Auto RnD (http://www.autornd.com) Rishie is the owner there and I have worked with him for 15 years, extremely knowledgeable.

After reading and researching, talking to people, and taking our own measurements we finally settled in on an offset to use. I went with the Forgestar CF5 for their relative affordability, strength (don't read about a lot of failures on these), competitive pricing, the fact that the clear 15" 6 piston brakes for future upgrades and ability to order in any offset we wanted.

After seeing them on my car, I am ready to get a second set and make them my daily driver wheel as well as my track wheel, clearing the path for me to go 6 piston brakes in the future if I wanted to. Bonus, the factory Forgestar center caps fit!

We settled in on an 18"x11" CF5 wheel with a +52MM offset.

Wheel Test Fit Day by Jared Elson, on Flickr

We wrapped these wheels in NT01 Tires with a 305/35R18 tire (Pictured compared to RS3 285/35R18 tire on 18x10 wheel)

Wheel Test Fit Day by Jared Elson, on Flickr

The Fitment I am Going With:

My car is on the Cortex Setup. The full flickr album has more photos with descriptions for each one, but this is what I am ultimately going with.

Using an 8MM hub centric spacer in the front. The wheels fit with no spacer, but clearance from the offset strut, was unacceptable. A 5MM spacer left plenty of clearance, but we opted for a little more spacer to get some scrub radius back and give me more room for turning with my brake cooling ducts. It doesn't look like steering stops will be required, but I'll be installing them as a precaution.

With my ARP extended length studs, there is still plenty of stud to support this spacer.

I am running about -1.8 - -1.9 degrees of camber in the front.

There are no other clearance issues in the front or the rear. It looks great in both spots, and looks like fender rolling won't even be required in the front.

Some photos with the 8MM spacers:

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Additional Test Fit For Vehicle 2:

We had a 2010 GT with Konis / Springs most importantly 6 piston brembo 15" calipers. This let us check clearance on a strut strut / spring set-up and with the big brakes.

The CF5 has no problems clearing the 15" 6 piston Brembo. Plenty of space even in the 18" wheel size.

It takes more spacer to get the front rims to fit (as expected), but it's not completely unreasonable to do. With our +52MM offset, we tried no spacer (no go, 5MM spacer, no go, 10MM spacer damn close to going, and 15MM spacer, going with a decent amount of clearance. If you aren't going to go coilovers and are going to stick with struts/springs you may want to consider as others have, a +55MM offset and you can run a little less spacer (most likely an 8MM or 10MM). If you are okay with a 15MM spacer, the +52 offset worked for us in our test fit.

Here are the pictures from the second car, note the pictures of the wheel/tire/strut didn't come out great in this case, but there was plenty of room in there.

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

Paint Transfer is from testing 5MM spacer and no spacer:

Wheel Test Fit Day by Jared Elson, on Flickr

Wheel Test Fit Day by Jared Elson, on Flickr

I hope this and the full album of Flickr images is helpful!

First day at the track on the new wheels and tires will be in November and I can't wait to give them a go.
 

Norm Peterson

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Using an 8MM hub centric spacer in the front. The wheels fit with no spacer, but clearance from the offset strut, was unacceptable. A 5MM spacer left plenty of clearance, but we opted for a little more spacer
Leaving out the matters of scrub radius and brake ducts for a moment, just how much clearance do you need in order to consider it 'acceptable'? Serious question.


Here are the pictures from the second car, note the pictures of the wheel/tire/strut didn't come out great in this case, but there was plenty of room in there.

Wheel
Is that tire actually inflated in that picture or do those tires run that narrow? It looks like I'm seeing way too much flange here, all the way onto the inside face.


FWIW, that's a ton of room compared to my own fully streetable track day setup (18x11 F14's with 285/35 PSS, Koni yellows, no spacer, just not rotatable front to rear).


Norm
 
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irishpwr46

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this is awesome info. wasnt vorshlag running a setup like this that they were keeping the specs on very hush hush?
 

Surfergeek

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Leaving out the matters of scrub radius and brake ducts for a moment, just how much clearance do you need in order to consider it 'acceptable'? Serious question.


Is that tire actually inflated in that picture or do those tires run that narrow? It looks like I'm seeing way too much flange here, all the way onto the inside face.


FWIW, that's a ton of room compared to my own fully streetable track day setup (18x11 F14's with 285/35 PSS, Koni yellows, no spacer, just not rotatable front to rear).


Norm


3MM or so of space would be acceptable for me. I know it can be very close. We had more than that with the 5MM spacer but lock to lock resulted in clearance issues with brake cooling ducts.

The tire is fully inflated. NT01 tires don't have a rim protector on them. Which is why they look the way they do. In the pictures it makes it look like there is extra flange on the rim but there isn't. No rim protector means no extra rubber to go over the flange of the rim.


Sent from my iPhone using Tapatalk
 

Surfergeek

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this is awesome info. wasnt vorshlag running a setup like this that they were keeping the specs on very hush hush?


Vorshlag has 18x11 wheels but they have different offsets front and rear. The specs are hush hush, I don't know what they are. They felt that to offer something square with same offsets would have required too much spacer in the front. I don't know what they consider too much.

Keep in mind this setup requires ARP extended length studs and negative camber though nothing too extreme and Vorshlag would like for their solution to be as universal as possible. The Cortex Offset struts go a long way in minimizing the amount of spacer I have to run. You are looking at a pretty good sized spacer with these specs on the front with a stock style suspension.

I think Vorshlag does a lot of great things for the community and love that they brought 18x11 wheels to the table but I really wanted to be able to rotate them.


Sent from my iPhone using Tapatalk
 

irishpwr46

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Vorshlag has 18x11 wheels but they have different offsets front and rear. The specs are hush hush, I don't know what they are. They felt that to offer something square with same offsets would have required too much spacer in the front. I don't know what they consider too much.

Keep in mind this setup requires ARP extended length studs and negative camber though nothing too extreme and Vorshlag would like for their solution to be as universal as possible. The Cortex Offset struts go a long way in minimizing the amount of spacer I have to run. You are looking at a pretty good sized spacer with these specs on the front with a stock style suspension.

I think Vorshlag does a lot of great things for the community and love that they brought 18x11 wheels to the table but I really wanted to be able to rotate them.


Sent from my iPhone using Tapatalk


the rotation is key, i figured they were running different offsets front and rear, were they running a square tire setup making rotation possible but more difficult?
 

Surfergeek

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the rotation is key, i figured they were running different offsets front and rear, were they running a square tire setup making rotation possible but more difficult?


They let you run square tires, yes. But it can't be rotated front and rear because of the difference in offsets between front and rear wheels.


Sent from my iPhone using Tapatalk
 

Norm Peterson

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You can still swap side to side, assuming that you aren't running directional tires. Asymmetric tires such as Michelin's PSS will swap L to R without any problems.

Given that most road courses beat up the tires turning in one direction more than when turning in the other, simple side to side swaps between consecutive events where the same side takes the brunt of the abuse does help.


There is probably a range of offsets where you're getting too thick for a plain spacer (and longer lugs) but not thick enough to use an adapter-style spacer. Never mind that there are different limits on the available offsets for each of the different variations of Forgestar wheel that carry the same basic style (i.e. F14, CF5).


Norm
 

2Fass240us

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Using an 8MM hub centric spacer in the front. The wheels fit with no spacer, but clearance from the offset strut, was unacceptable. A 5MM spacer left plenty of clearance, but we opted for a little more spacer to get some scrub radius back and give me more room for turning with my brake cooling ducts. It doesn't look like steering stops will be required, but I'll be installing them as a precaution.
What diameter ducts are you running, and do you have any pictures of how they're routed? The latter is less important as there aren't many choices for where to put them. But in the case of fitment/rubbing, every mm counts.
 

Surfergeek

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I can't take any additional pictures at the moment, but it's pretty standard routing for the brake cooling ducts.

The brake cooling ducts are the Ford Racing / Boss 302 ducts. We did remove the windshield washer fluid bottle to make more room and lose some weight off the front of the car, but the pictures in this thread were taken before that washer bottle was removed.

Ford racing kits are 3" ducts.

Instructions have pretty good pictures: https://fordperformanceracingparts.com/download/instructionsheets/FordInstShtM-2004-MBA.pdf
 

cbass

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I need to borrow an 8mm spacer from somebody. My rears are 20x11 with 305 nittos and a +51mm offset. If I could run a set that allowed rotation, I would be in hog heaven.
 

2013MustangGT

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Vorshlag did that with the F14 wheels (still a secret). The CF5 wheels have more room. Terry showed the difference in the wheels when he did the write up for the fitting of 18x11 on the 2015 Mustangs.
 

Surfergeek

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A proper hub centric spacer is acceptable to use, as long as you make the mods to accommodate it, like long studs. Everyone will be comfortable with a different amount of spacer. You don't want too much spacer of course, but if you want to run even more spacer, you'll want to get something like Rehagen offers with Studs built into the spacer.
 

El_Tortuga

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...


Additional Test Fit For Vehicle 2:

We had a 2010 GT with Konis / Springs most importantly 6 piston brembo 15" calipers.
...
It takes more spacer to get the front rims to fit (as expected), but it's not completely unreasonable to do. With our +52MM offset, we tried no spacer (no go, 5MM spacer, no go, 10MM spacer damn close to going, and 15MM spacer, going with a decent amount of clearance. If you aren't going to go coilovers and are going to stick with struts/springs you may want to consider as others have, a +55MM offset and you can run a little less spacer (most likely an 8MM or 10MM). If you are okay with a 15MM spacer, the +52 offset worked for us in our test fit.

Here are the pictures from the second car, note the pictures of the wheel/tire/strut didn't come out great in this case, but there was plenty of room in there.

.

I'm not following. Wouldn't bigger offset (+55) need bigger spacer (+15) to clear strut?
 

Mark Aubele

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A proper hub centric spacer is acceptable to use, as long as you make the mods to accommodate it, like long studs. Everyone will be comfortable with a different amount of spacer. You don't want too much spacer of course, but if you want to run even more spacer, you'll want to get something like Rehagen offers with Studs built into the spacer.

I run a 3/4" spacer up front to make a square 18x10.5 setup work on my car. No issues. Obviously ARP studs. Could run less spacer but that's what I had laying around.
 

Need4SpeedMotors

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This is an amazing thread, thank you sir for the awesome info to the community! Ive had my fair share of what most consider " aggressive" fitments, this is a great functional fitment and the wheel choice is spot on as well.
 

2Fass240us

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To clarify, the Cortex offset strut gives you 8-10mm additional Clarence?
 

Boone

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I'm seriously considering this when I spring for track wheels and tires. The only tires I can find to fit this setup is the Nitto NT-01 as mentioned earlier and a Toyo Proxes R888. Both are 100TW.

Does any manufacturer make a 200TW tire that will fit the 18x11? I don't want to drop below a 26" diameter tire, though. I prefer 26.5" diameter. A 19" rim will provide more options with a 305/30/19. I believe that's what the new GT350 is running.
 

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