CTS-V Brake Upgrade Spacer Question

[99gst_racer]

We didn't tackle this project with a Wilwwod rotor in mind for basically 2 reasons:
1. They are expensive
2. We would have to start from the beginning, finding a rotor of the correct diameter, thickness, and determine the offset.

The Wilwoods we stock for 2g are too small at only 12.2". These calipers require a rotor around 13" diameter. Also, we already stock the Cobra rotors as we use them in a lot of our other brake upgrade kits and we already have the hubcentric rings for them.

The screenshot I posted above is Wilwood's 94-04 Cobra rotor. 12.9" rotor, with the same offset. The draw to the 2-pc rotor is possibly being able to manipulate the hat to make the rotor fitment more ideal. But you are correct that they aren't cheap at all. $1050 for Wilwood rotors VS ~$150 for a 1-pc drilled/slotted set.

I'd be willing to give the 2-pc a try but Wilwood is out of stock on hats right now. I'm capable or shortening their hat, but I'm not set up to produce my own hats from scratch.

 

[99gst_racer]

I'm just gonna put this out there, but if you are running the car hard enough that you need that much brakes, you shouldn't be running spacers.

Care to elaborate?

third point, if you are going through the trouble of making spacers, it's not much more trouble to just make a rotor hat to use wilwood rotors. Wilwood rotors are not that much money.

People aren't making spacers. They're buying them from CTSV swap.com. As well, you can get a set on eBay for $37 that are very close and just require turning 2mm off on the hub OD. Just mentioning this because most people aren't capable of producing their own hub-centric spacers, let along designing and producing a rotor hat from scratch.

Have you priced out the Wilwood rotor set? Rotor (160-7173-bk) lists for ~$360 and the hat (170-6223) lists for ~$180. You'd have more money tied up in 2 rotors than most people spend on all combined parts to do this swap. Far from inexpensive.

 

[bastarddsm]

Care to elaborate?


People aren't making spacers. They're buying them from CTSV swap.com. As well, you can get a set on eBay for $37 that are very close and just require turning 2mm off on the hub OD. Just mentioning this because most people aren't capable of producing their own hub-centric spacers, let along designing and producing a rotor hat from scratch.

Have you priced out the Wilwood rotor set? Rotor (160-7173-bk) lists for ~$360 and the hat (170-6223) lists for ~$180. You'd have more money tied up in 2 rotors than most people spend on all combined parts to do this swap. Far from inexpensive.

There are several issues, #1, the stock studs are not really long enough for stock wheels #2 longer stud decreases the spring constant of the stud and looses more clamp load under dynamic loading. #3 under reduced clamping you rely on the spacers hub centric design to support the load, which may or may not be sufficient ( remember bolts are not to be loaded in shear) #4 under reduced clamping you rely on the wheel studs to transmit torque which is shear loading fastener, and also gets more ugly with acorn nuts. #5 then there is the increased thermal strain from the extra thickness of material with a high coefficient of expansion, mounted right on a part that gets HOT.

Point is, these are large brakes, and an upgrade such as this would be needed if you are going to be doing fast lapping days, and that's not a situation where you should be questioning your wheel mounting.

I never suggested "people" are making spacers, but someone is. A spacer involves turning and precision drilling, same thing as a hat. That's not a far stretch.

Yeah I know what the wilwood stuff costs, and it comes down to you can have $1500 or whatever in a real set of brakes. Or you can have $500 in a setup with oriellys finest chinesium rotors with spacers on your spacers spacers and wheels that don't fit.

I suppose that's not all bad, your car will look like you are trying to fit in with the camber gang kids, and then the big brakes with no intent to use them will be a perfect blend of modern and classic rice.

Don't you have to slot the mounting ears to use these calipers anyway? These poor cars.

 

[[email protected]]

I'm so confused right now. My research led me to believe this is a bolt on mod for a 1G with the right parts.

It IS bolt on if you're fine with the rotor's centerline running at least 1.1mm offset from true with the caliper. We don't consider that an insignificant amount that could simply be ignored. The reason that all the existing upgrades insist on a 5mm offset is that it's realized that 5mm is the thickest spacer (or reduction from the caliper) anyone could comfortably tolerate and so that magic 5mm number continues to be trotted out as if it were true. It is simply not.

 

[talonesi95t]

Well, ive been collecting my brake swap parts, so far I have new acdelco calipers and rtm hub rings. I was going to shave the 5mm off route but guess ill wait and see whats needed now.

 

[99gst_racer]

Just a heads up that the Wilwood Cobra rotor setup will not work for this swap. The hat diameter is too large and won't clear the CTS-V caliper. It would require a different rotor with at least an inch smaller rotor bolt circle and then a custom machined hat. Bummer - was hoping this would be quicker/easier/cheaper. Just thought I would share.

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[jw4free]

Another option:
Giro disc

Ford SN95 Mustang Front Rotors

We design, manufacture, and sell 2-piece, fully-floating brake rotors for Porsche, BMW, Subaru, and more. Made in the USA from US-sourced materials.

girodisc.com

the hat dimensions may be smaller than the Wilwood.

$950 / set assembly
$650 for two replacement rotors.
So each hat is $150 ???

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[99gst_racer]

Another option:
Giro disc

Ford SN95 Mustang Front Rotors

We design, manufacture, and sell 2-piece, fully-floating brake rotors for Porsche, BMW, Subaru, and more. Made in the USA from US-sourced materials.

girodisc.com

the hat dimensions may be smaller than the Wilwood.

$950 / set assembly
$650 for two replacement rotors.
So each hat is $150 ???

Pricing sounds about right. That's inline with Wilwood. Only issue with that Giro hat is that they use thin ears where the bolts run through. I'd be turning the backside of that down 3-4mm and there likely would not be enough thread engagement afterward. The diameter (rotor bolt pattern) of the Giro looks good though, just wish they would have used the shape/design of the Wilwood hat.

 

[Bedicine]

Just got a notification that cts brake swap has the kits back in stock after a long time

 

[Bedicine]

Says the kit needs the following to bolt up with their spacer

This kit requires-

1. Both front 04-07 CTS-V calipers
2. Front 04-07 CTS-V brake pads
3. Front 04-07 CTS-V Caliper pin kit
4. 03-04 Mustang Cobra 12.99” front brake rotors
5. Evo 8/9 stainless braided brake lines

Probably going to order and report the findings to everyone.

https://cdn.shopify.com/s/files/1/0089/9904/3123/products/CTSV_BRAKE_KIT_2C_Spacers_-_1_1080x.jpg?v=1580329565

 

[koz99eclipse]

I've been struggling through this CTSV swap for the past few weeks and running into spacer/hub assembly issues currently. The hybrid solution mentioned above (milling 3mm off the caliper mounting tabs, and using a 3mm spacer) perfectly centers the rotor in the caliper (using the cobra rotor). However, the issue I'm having now is that with aftermarket hub assemblies (oem replacement steps up from 67.1mm to 69.1mm) the 3mm spacer takes up the majority of space on the 69.1mm "step" on the hub. So the hubcentric ring that centers the rotor on the hub, barely has anything to bite onto and is awkwardly placed between the 67.1mm and 69.1mm steps. Right now the only solution I'm seeing is biting the bullet and dropping $370 on the actual oem hub assemblies (mr455004) that are completely 67.1mm with no step up to 69.1mm. I wanted to just go with the evo x rotor because the center bore is 69mm and it wouldnt require the hubcentic rings, but in order to use them, they need to have their outside diameter machined down from 350mm to 330mm. Either way, kind of a pain.

 

[Rich_Howell]

I'll add some info to this thread (yes I realize it's about 6 months later). I did the CTS-V Brembo / 330mm Cobra rotor swap to the front of my 2G GSX (Dec 1994 build date). First thing's first...this is NOT a bolt-on upgrade like many other threads suggest. I will add that CTS-V calipers have staggered piston sizes and Cadillac mounts them toward the back and not in front of the hub like DSMs and that, to make that work properly, you need to swap them Left to Right, which means you need to put the crossover tubes where the bleeders are and the bleeders go to the previous crossover tube ports.

I took the calipers to a friend of mine that has a Bridgeport mill. I told him I wanted to shave 5mm off of each mounting ear. We ended-up with removing 5.5mm. Ok. This did not center the caliper over the rotor either. I ended up using a 3mm spacer between hub and rotor. I then had to use 1mm shims on the caliper ears to center everything. Nobody makes a 2mm spacer, so that's what I had to do. SO if you're taking a fresh crack at this...shave the ears down 4.5mm and use a 3mm spacer between hub/rotor. I still had enough depth on the hubcentric rotor rings for all of that to work. Yay. Everything was bolted-up and centered.

The next nightmare scenario: wheel fitment. I will preface this by saying the previous owner of my GSX opted for 18" wheels (ADR Vision) with a +48mm offset instead of the more popular +40mm offset for DSMs. I had to use a 15mm hubcentric wheel spacer to get everything to fit. So adding everything up, I was basically at a +30mm offset [48 - (15+3)]. This required extended studs. I also added hubcentric rings to my wheels, so they could utilize the hub centers on the spacers for some peace of mind. So great. Now everything is bolted, centered, aligned, hubcentric, and plenty of stud for the lug nuts to hold everything in place. Mmhmm...

Now with all of this spacing, my spring rate on the front suspension is virtually worthless. Car stops frigging GREAT (also did Evo8 rear Brembos with 300mm rotors and 3g MC + Booster) but what once was a capable suspension for the car now is WAY too soft.

The main culprit in this whole thing? The f***ing Cobra rotors. Why, you ask? The hat depth (rather; lack thereof) forces the whole damn thing further out than a DSM (276mm), Outlander (296mm), or Evo (320mm) rotor would allow. The problem there is that none of those are 330mm. A couple of options exist for this. My Baer Track setup on the front of my GS-T uses 330mm rotors. I made the mistake of thinking they were Cobra 330mm. They are not. They are C4 Corvette rotors (1996?) with the proper 5x114.3mm hole pattern instead of the C4 5x120.Xmm pattern. If you're doing this upgrade on 17" wheels...I recommend trying it with re-drilled C4 330mm rotors. All of the caliper/rotor mounting/spacing data above goes out the window...and you'll have to go from there, but this will save you some wheel fitment/spacing/stud/suspension issues.

Other options:

*Hyundai Genesis 340mm. I got this idea from RTM because I tried to do 2g 3KVR4 calipers on Cobra rotors on my GS-T and ran into the same spacing issues and didn't want to repeat the GSX nightmare. May require a bit of radial spacing (caliper bracket).

*EvoX 350mm. This also has a deeper rotor hat like the Genesis rotors. Will definitely require a caliper bracket that shouldn't be too hard to fab-up. I have recently been told that you CAN fit Brembo calipers and a 350mm EvoX rotor under 17" wheels. I don't believe it, but that's based upon my experience with 3KVR4 calipers, 340mm Hyundai rotors, and the 17" ADR +40mmET wheels on my GS-T...and having to shave the calipers (and remove wheel balancing weights) just to barely fit everything. Brembo calipers MAY allow the extra clearance. IDK.

*Nissan 370Z 355mm. I don't have a lot of info on these, but I can almost guarantee you'll need 18" wheels. If I can fit them, I may go that route when I get back to addressing a re-do of the GSX brake setup for better geometries. The car currently has a blown motor, so it sits for now.

That's it for now. Sorry for the long-winded post, but I wanted to make sure I could contribute as much information as possible. I may update this later when I get around to fixing the GSX. Special thanks to RTM for providing a solution for my GS-T that allows me to reasonably run huge brakes under my 17s with no extended studs or wheel spacers!

 

[99gst_racer]

Worked on this a little more this weekend. I machined up a 6.1mm hubcebtric spacer and then shaved 2.5mm off the rotor hub. The caliper centers perfectly and I think I can live with the wheel and tire sticking out 3.5mm (~.138") more. I am half-way expecting wheel fitment issues and won't be able to confirm for a few weeks when the 1G comes out of winter storage. If there's wheel fitment issues, I'll try again with a Genesis rotor.

EDIT: Figured I might as well order a genesis rotor and see if it can be a better fit for the swap. Hopefully have time to play with that later this week.

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[Bedicine]

Did a mock up tonight for the rtm kit so everyone can see how it looks so far. I’ve read so many different opinions on swapping the rotors to the opposite side since there’s a smaller piston which is staggered? Anyone know about this and the second is about switching the crossover tubes.

All things aside thanks to Paul and Ziggy as this kit is a simple bolt on

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