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GT350 Brakes with 18" Wheels

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So, it's a brake rotor. Find the best price you can on the item you need - 380x34 for those running 1mm titanium shims or 380x36 if you aren't.
 
I’m sure Racing Brakes or Girodisc can make them.
 
I appreciate the info from everyone!

He took 3/8” off the knuckles

No part number he could provide since it was a custom order awhile back, and it looks like the only 15” option they have listed on their website is 31.8mm thick. Might need to call it in, describe what you’re trying to do and see if they’ll do another run. I’ll try and get you a contact at Wilwood to start a conversation.

boardkat - I talked to Wilwood and they don't make custom hats. They try to best match your requirements to hats in already production. Would need two pieces of info. Could you please ask your friend for the offset (rotor surface to hub mounting surface) and the Wilwood rotor ring replacement part number? Also, is he using stock size GT350 pads? Thank you so much!
 
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I appreciate the info from everyone!



boardkat - I talked to Wilwood and they don't make custom hats. They try to best match your requirements to hats in already production. Would need two pieces of info. Could you please ask your friend for the offset (rotor surface to hub mounting surface) and the Wilwood rotor ring replacement part number? Also, is he using stock size GT350 pads? Thank you so much!
Hey Rob - did you ever pursue this further?
 
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Hey Rob - did you ever pursue this further?
FYI - I just installed a pair of RB front calipers on my GT350. They're real racing calipers - top loading, no dust boots, scalloped stainless pistons, anodized finish etc. They have the same caliper mounting offset as OEM (they'll work with OEM rotors if you want) and they bolt directly to the knuckle without any adapters. They were made specifically for the GT350, not just pulled out of a parts bin somewhere and adapted to fit.

Where this gets interesting is that they come in two different heights. The "higher height" version bolts in directly and works with 394mm rotors. Mine, however, are the "lower height" configuration. If you bolt these ones directly to the knuckle, they're the right height to work with 380mm rotors. Mine were delivered with a set of 7mm spacers, so I can use them with either 380mm or 394mm rotors just by swapping the spacers in or out.

These calipers create a surprising array of options for rotors and for pads. Naturally, RB offers both carbon ceramic rotors and iron rotors in both 380 and 394 diameters. Take your pick. It's also extremely likely that rotors from Girodisc will work just as well, provided the rotor offset's the same as GT350 OEM in both sizes.

As for pads, the RB calipers take pads that have the same basic backing plate shape as the GT350 OEM pads. The OEM Ford Brembo pads are a bit of an oddball because they have a "ramp" on the top edge of the backing plate for the anti-rattle spring. The RB calipers take pads the same size but without the "ramp". Pads for Corvettes, Vipers, Enzo's, F488 Challenge cars, McLaren 675LT's and a bunch of other vehicles all fit in this caliper. So long as pad depth is less than the rotor annulus width, you've got a workable combination.

Now, if you combine the different rotor options and the wide range of available pads, you can do pretty much anything you want. It's a whole new world of options for slowing your car down.

Here's a couple of pictures I posted a couple of weeks back in my ceramic brake thread, taken when I was test fitting them:

1644449595845.png

A different view - note the quality machine work and finish on the parts of the caliper that nobody will ever see but you:

1644449564403.png
 
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FYI - I just installed a pair of RB front calipers on my GT350. They're real racing calipers - top loading, no dust boots, scalloped stainless pistons, anodized finish etc. They have the same caliper mounting offset as OEM (they'll work with OEM rotors if you want) and they bolt directly to the knuckle without any adapters. They were made specifically for the GT350, not just pulled out of a parts bin somewhere and adapted to fit.

Where this gets interesting is that they come in two different heights. The "higher height" version bolts in directly and works with 394mm rotors. Mine, however, are the "lower height" configuration. If you bolt these ones directly to the knuckle, they're the right height to work with 380mm rotors. Mine were delivered with a set of 7mm spacers, so I can use them with either 380mm or 394mm rotors just by swapping the spacers in or out.

These calipers create a surprising array of options for rotors and for pads. Naturally, RB offers both carbon ceramic rotors and iron rotors in both 380 and 394 diameters. Take your pick. It's also extremely likely that rotors from Girodisc will work just as well, provided the rotor offset's the same as GT350 OEM in both sizes.

As for pads, the RB calipers take pads that have the same basic backing plate shape as the GT350 OEM pads. The OEM Ford Brembo pads are a bit of an oddball because they have a "ramp" on the top edge of the backing plate for the anti-rattle spring. The RB calipers take pads the same size but without the "ramp". Pads for Corvettes, Vipers, Enzo's, F488 Challenge cars, McLaren 675LT's and a bunch of other vehicles all fit in this caliper. So long as pad depth is less than the rotor annulus width, you've got a workable combination.

Now, if you combine the different rotor options and the wide range of available pads, you can do pretty much anything you want. It's a whole new world of options for slowing your car down.

Here's a couple of pictures I posted a couple of weeks back in my ceramic brake thread, taken when I was test fitting them:

View attachment 72486

A different view - note the quality machine work and finish on the parts of the caliper that nobody will ever see but you:

View attachment 72485
I saw those on your other post. Pretty nice looking unit. Do you happen to have a weight savings per caliper and/or price? They look pretty comparable to the AP Racing kit.

Reason I was curious about the OEM-caliper option was because I fit a set of 18s without the additional $7-8k in the brake upgrade. While that will come later, I'm prioritizing coil overs this year :)
 
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I saw those on your other post. Pretty nice looking unit. Do you happen to have a weight savings per caliper and/or price? They look pretty comparable to the AP Racing kit.

Reason I was curious about the OEM-caliper option was because I fit a set of 18s without the additional $7-8k in the brake upgrade. While that will come later, I'm prioritizing coil overs this year :)
They're lighter than OEM, but I don't know by how much. I got them because I wanted heat resistant top loaders with no dust boots that took a variety of pads. Weight wasn't a factor for my decision (I've already got light weight brakes) so it didn't occur to me to weigh them before I installed them. As for pricing, it's best you to contact RB and chat with Warren.
 
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I saw those on your other post. Pretty nice looking unit. Do you happen to have a weight savings per caliper and/or price? They look pretty comparable to the AP Racing kit.

Reason I was curious about the OEM-caliper option was because I fit a set of 18s without the additional $7-8k in the brake upgrade. While that will come later, I'm prioritizing coil overs this year :)
I checked with RB and here are the weights - both weights include pads but the OEM one is missing one of the retainer pins, and maybe the upper spring as well:

1644528282279.png

OEM GT350 Caliper Weight.png
 
Any updates on any of this? Especially the rotors? I'm thinking about turning my GT350 into an American Iron car and with their 18" wheel and 275 tire size I'm looking for a solution to keep the current brakes. It seems there are zero 18" wheels to fit the GT350 OEM front brakes, but I have a mill and milling down the knuckle and a 380mm rotor may be the most cost effective solution.
 
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Any updates on any of this? Especially the rotors? I'm thinking about turning my GT350 into an American Iron car and with their 18" wheel and 275 tire size I'm looking for a solution to keep the current brakes. It seems there are zero 18" wheels to fit the GT350 OEM front brakes, but I have a mill and milling down the knuckle and a 380mm rotor may be the most cost effective solution.
Here's what Apex says about the situation with their 18" rims on a GT350 (they didn't show any fitments narrower than 11" though):

"Warning! The following wheels require aftermarket race front brakes which provide better clearance for 18" wheels. The only known kits at this time are Essex/AP Racing CP9668/372mm and the Brembo Racing Endurance 380mm kit. These will not fit with the stock front brakes. Factory rear brakes will clear and do not need to be replaced."

The AP Essex 372x34 kit has a 415 mm clearance diameter and the Brembo Racing 380x34 kit mentioned has a 424 mm clearance diameter, while the RB 394x36 kit I have needs 447 mm. I got curious about how much you'd have to mill down the knuckle to lower the RB caliper far enough to fit inside an 18" rim, using the Brembo's 424 mm circle as a guide. I did a CAD sketch and concluded that it's not a practical solution. It's not the caliper height that's the challenge, it's the length. As the barrel inner diameter gets smaller, it's the ends of the calipers that touch it first, long before the top does. To get the 447 mm diameter down to 424, the CAD sketch showed a 19mm (3/4") drop was needed. Taking 1.5" off the 15.5 inch GT350 rotor leaves you running a 14" rotor. It'll fit, but it might not stop more than once or twice. I did a quick measure of the OEM GT350 calipers. They're even longer than the RB calipers so the problem will, at best, be the same.
 
Here's what Apex says about the situation with their 18" rims on a GT350 (they didn't show any fitments narrower than 11" though):

"Warning! The following wheels require aftermarket race front brakes which provide better clearance for 18" wheels. The only known kits at this time are Essex/AP Racing CP9668/372mm and the Brembo Racing Endurance 380mm kit. These will not fit with the stock front brakes. Factory rear brakes will clear and do not need to be replaced."

The AP Essex 372x34 kit has a 415 mm clearance diameter and the Brembo Racing 380x34 kit mentioned has a 424 mm clearance diameter, while the RB 394x36 kit I have needs 447 mm. I got curious about how much you'd have to mill down the knuckle to lower the RB caliper far enough to fit inside an 18" rim, using the Brembo's 424 mm circle as a guide. I did a CAD sketch and concluded that it's not a practical solution. It's not the caliper height that's the challenge, it's the length. As the barrel inner diameter gets smaller, it's the ends of the calipers that touch it first, long before the top does. To get the 447 mm diameter down to 424, the CAD sketch showed a 19mm (3/4") drop was needed. Taking 1.5" off the 15.5 inch GT350 rotor leaves you running a 14" rotor. It'll fit, but it might not stop more than once or twice. I did a quick measure of the OEM GT350 calipers. They're even longer than the RB calipers so the problem will, at best, be the same.
Got ya. Yeah I was taking some rough measurements of my own so everything you wrote makes sense. I scribed a 1/2" line in on the knuckle where the caliper bolts to and you're already into the thick part of the knuckle. On top of that, to move the caliper in that far it seems rotors would then be an issue to find. I'll keep looking for a solution. Just hard to justify spending thousands of dollars to "downgrade" brakes to fit a rule set. Thanks for all the measurements on the other stuff.
 
Could you machine an adapter for a radial mount Wilwood caliper? Wilwood has rotor sizes of 14” , 14.25“ and 15”.
Potentially. But the initial issue I'm having is that the brakes on the car already are great. It doesn't make sense to upgrade to a "big brake kit" that is smaller than whats on the car to meet class rules and hence my wanting to find either a wheel that will work (doesn't seem possible) or to modify something to use my existing calipers but maybe just on a 15" rotor maybe?
 
I saw these rotors when doing my research. You can get just front. There is a typo in the description, “Front rotor is downsized to 380mm to fit 19" wheels.”. Assuming they meant 18”.
Will have to replace front rotors at some point :). This gets you the proper rotor hat to use stock calipers.

“Require to trim front OE caliper legs to fit 380mm rotors.”

https://racingbrake.com/for-irk-06/
 
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I saw these rotors when doing my research. You can get just front. There is a typo in the description, “Front rotor is downsized to 380mm to fit 19" wheels.”. Assuming they meant 18”.
Will have to replace front rotors at some point :). This gets you the proper rotor hat to use stock calipers.

“Require to trim front OE caliper legs to fit 380mm rotors.”

https://racingbrake.com/for-irk-06/
So, your post got me thinking about RB brake parts might solve this problem. Note that I have carbon ceramic brakes and racing calipers from RB on all four corners of my GT350, so I'm pretty familiar with the company and the products. They're excellent. Check out the photos earlier in this thread: https://trackmustangsonline.com/threads/gt350-brakes-with-18-wheels.15664/post-275800. Note that I have the dual-mode calipers - they mount with 7 mm spacers for 394 rotors and no spacers if I want to run 380's.

I had a look at the RB website and I found this: https://racingbrake.com/rccb-gt350-380.380/

That page claims that the 380 rotor and 6-piston caliper set will fit inside 18" rims. The question is "which 18 inch rims?" The page has a drawing showing 380 mm rotor needing a 434 diameter clearance circle. Compared with the 424 clearance circle of the Brembo Racing kit, the caliper only sits 5 mm further out than the Brembo Racing caliper. And, of course, even though the page shows a carbon ceramic rotor, a 380 mm iron rotor will work fine and cost a whole lot less.

Just for a sanity check, I went out and did some measuring on my car, which is equipped with my winter set of 19x9.5 OEM Ford rims left over from my 2014 GT500. They're ET44 on 35mm spacers (so I can put nuts on the long wheel studs) and they clear the 394 rotor and RB 6 piston caliper setup just fine. The tightest point is right where the barrel necks down for the tire mounting relief zone, which starts, on those rims, about 1/2" in from the outer edge of the caliper. There's 5-6 mm of clearance at the tightest point, so if you take 7mm out for the smaller rotor, a carefully selected 18" rim with the relief zone shifted out about 1/2" should clear.

So, that's the RB solution. I have the factory calipers in a drawer here but I'm not in a position to mount them and check whether they'll clear as well as the RB calipers. I know that the 19x9.5 rims that are on the car now will clear them because I used them in winter before I installed the RB calipers. It's entirely possible that the OEM calipers will work just fine, but the only way to find out is to mill down the knuckles and then find an 18" rim with max clearance. I'd look for a light 18x9.5 to fit Ford Mustang with as low an offset as possible so you don't need a whacking great spacer to get the necked down portion of the barrel away from the caliper.
 
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I have a 3D printed hat at the proper offset to just use PP Girodiscs and you should use the PP pad in the GT350 caliper. That way the pad fits better on the rotor so things wear properly. Plenty of clearance with the Apex 18" wheels. We just shorten our Brake Caliper Studs so they screw in to the proper depth.
How can a 3D printed hat possibly be strong enough to handle the roughly 1,500 ft-lbs of torque at nearly 1,000 degrees F that you get from generating 1g+ brake effort with 3800 pounds of car and driver? I've been at the track when a driver's front hat came apart - it's not pretty.

As for needing a custom hat in the first place, are the GT PP brake rotors on a different centerline from the GT350 rotors?
 
How can a 3D printed hat possibly be strong enough to handle the roughly 1,500 ft-lbs of torque at nearly 1,000 degrees F that you get from generating 1g+ brake effort with 3800 pounds of car and driver? I've been at the track when a driver's front hat came apart - it's not pretty.

As for needing a custom hat in the first place, are the GT PP brake rotors on a different centerline from the GT350 rotors?
Ok.
 

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