It's been a months long process to get this figured out, but thanks to many of the members (Cloud9, Neema, cp85gt, Wingrider, VooDooBoss and I am sure others I have missed) here 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.

Set-up looks good. I've run my set-up for 2 track days, 13 sessions for about 4-1/2 hours, and the 20mm spacer combo worked well. After the first couple of sessions the combo held torque at 90 ft/lbs for the rest of the time, so I assume it was just new wheels. It looks like there is a lot of clearance with the 15" 6 pot brake set-up on the blue mustang. Is there more than 1/4" clearance between the caliper and the barrel of the wheel? It looks like all the measurements you got are the same as mine. I think with an NTO1 (no curb protector) the +52 18 x 11 wheel looks better in the rear than a +55. I might try a small spacer so the rear looks similar to my front. Its too bad that Forgestar doesn't make wheels in 1/2" increments because you have a lot of clearance to the fender with you're Cortex off-set-struts up in the front with the small spacer. Enough I think that an 11.5" wide rotatable square set-up could be figured out.

Looks great. Impressive brake clearance on those CF5s. I'm wondering if I should get a set of those now...

I believe the CF5 is a bit heavier than the F14 but lots of brake clearance with them. I like the looks too. Thanks for posting.

cp85gt said:

Set-up looks good. I've run my set-up for 2 track days, 13 sessions for about 4-1/2 hours, and the 20mm spacer combo worked well. After the first couple of sessions the combo held torque at 90 ft/lbs for the rest of the time, so I assume it was just new wheels. It looks like there is a lot of clearance with the 15" 6 pot brake set-up on the blue mustang. Is there more than 1/4" clearance between the caliper and the barrel of the wheel? It looks like all the measurements you got are the same as mine. I think with an NTO1 (no curb protector) the +52 18 x 11 wheel looks better in the rear than a +55. I might try a small spacer so the rear looks similar to my front. Its too bad that Forgestar doesn't make wheels in 1/2" increments because you have a lot of clearance to the fender with you're Cortex off-set-struts up in the front with the small spacer. Enough I think that an 11.5" wide rotatable square set-up could be figured out.

Click to expand...

I didn't grab a measurement of the caliper to barrel clearance on the 6 Piston brakes, but from eyeball perspective I would say it's 1/4" or a little more. It certainly fills the rim, but there is still plenty of room. I can see if we can get that measurement and update here when we get it.

VooDooBOSS said:

I believe the CF5 is a bit heavier than the F14 but lots of brake clearance with them. I like the looks too. Thanks for posting.

Click to expand...

The CF5 is about about 1lb. heavier than F14, still a very lightweight wheel though. With more brake clearance and a design that quite frankly seems to be bit sturdier it's worth the tradeoff in my eyes.

After seeing these on my car side by side with the F14, I am sold on the CF5 look for all the time, not just track wheels.

nice write up, I'm glad to see that I'm not the only one that writes all over their suspension parts..lol

Awesome infos. Thank you very much.

From your measurement is there enough space to fit a 12" square?

Swiss Boss said:

Awesome infos. Thank you very much.

From your measurement is there enough space to fit a 12" square?

Click to expand...

12" Square was never a consideration though I think it would take more modifications to the fenders, wide body kit or something of similar nature. Offset strut coil overs like these from cortex would be a requirement.

11.5" with the cortex offset struts and the right offsets maybe. But I am not sure it would gain us that much in performance. I have read a lot and talked with a lot of folks that have gone 315 square and went back to 305 because beyond the 305 you start to sacrifice more of your turn in and have a tough time keeping the scrub radius right.

Nice write up! I went through very similar trial ans error and gave been running the same setup all season. Feels great on track, and I used steering stops from cortex to prevent rubbing. I did have to upgrade from single adjustable jri shocks to double adjustable in order to clear the 11s in the rear!

Surfergeek said:

12" Square was never a consideration though I think it would take more modifications to the fenders, wide body kit or something of similar nature. Offset strut coil overs like these from cortex would be a requirement.

11.5" with the cortex offset struts and the right offsets maybe. But I am not sure it would gain us that much in performance. I have read a lot and talked with a lot of folks that have gone 315 square and went back to 305 because beyond the 305 you start to sacrifice more of your turn in and have a tough time keeping the scrub radius right.

Click to expand...

Re: Going 18x11" Square with 305 Tires and Rotatable. It Can Be Done!




Sent from my iPad using Tapatalk

LTNYC said:

Nice write up! I went through very similar trial ans error and gave been running the same setup all season. Feels great on track, and I used steering stops from cortex to prevent rubbing. I did have to upgrade from single adjustable jri shocks to double adjustable in order to clear the 11s in the rear!

Click to expand...

What wheels did you go with?

Re: Going 18x11" Square with 305 Tires and Rotatable. It Can Be Done!

Ccw


Sent from my iPad using Tapatalk

Surfergeek said:

12" Square was never a consideration though I think it would take more modifications to the fenders, wide body kit or something of similar nature. Offset strut coil overs like these from cortex would be a requirement.

11.5" with the cortex offset struts and the right offsets maybe. But I am not sure it would gain us that much in performance. I have read a lot and talked with a lot of folks that have gone 315 square and went back to 305 because beyond the 305 you start to sacrifice more of your turn in and have a tough time keeping the scrub radius right.

Click to expand...

Ok thanks.That's good to know.

So how did this setup work on track?

Re: Going 18x11" Square with 305 Tires and Rotatable. It Can Be Done!

It was great. Have run it a couple of times. Once at Laguna Seca and that was great. And a second time at Thunderhill. Though it was a rainy day so I couldn't really open it up all the way. My first track day in the rain a good learning experience with lots of seat time.


Sent from my iPhone using Tapatalk

our T1 car runs 315s with 11 inch wheels but we run different shocks, it's tight, but can be done

blacksheep-1 said:

our T1 car runs 315s with 11 inch wheels but we run different shocks, it's tight, but can be done

Click to expand...

Thats what I am hoping to do in the future (no Hoosier in 305's) ... Do you run with the same offset front and rear?

Re: Going 18x11" Square with 305 Tires and Rotatable. It Can Be Done!

Swiss Boss said:

Awesome infos. Thank you very much.

From your measurement is there enough space to fit a 12" square?

Click to expand...

12s are possible but you need: 1. Cortex offset struts, 2. a 20mm spacer up front if square offset desired, 3. camber. The fronts will be aggressive; camber is a must.

I ordered mine in et38 front/et58 rear. Still haven't gotten around to mounting them up.

18 X 11 CF5 with 52 off set on stock struts with -2.8 degrees of camber along with a 15 mm spacer and I have 3/16 " clearance between the wheel and strut. Now to get the 305 NT 01's mounted.