LS1GTO Forums banner

1 - 20 of 76 Posts

·
Premium Member
Joined
·
1,185 Posts
Discussion Starter #1 (Edited)
Alright chaps, here's what happened.

I was most certainly hellbent on making a cts-v 4 piston front brembo fit under the stock gto 17" wheel. The problem with the oem gto 17" wheel is that its more like a 16.5 and tapers down to 16" or less by the time it reaches the spokes. GM must have been wanting to win "worst wheel design ever" award by making these wheels , especially with the +48 offset.

Evenso, I have been looking around for standard oem rotors with the oem gto 5x120 bolt patter with 330mm (13") diameters which still retained the oem brembo 32mm grasp thickness. None met all criteria at once. So I had to find one that did without sacrificing essential function components.
Low and behold, the volvo S60r is equipped with essentially the same brembo caliper from the factory, and the car weights just about the same if not more than a gto (3700lbs), therefore this was my most obvious choice to work with. Although the oem volvo s60r sports a 5X108 bolt pattern, it was something that had to be gotten around.

Below are both rotors' oem specs, cts-v on the left, s60r on the right, notice "nominal thickness" is 1.26", which when translated into millimeters (*25.4) = 32mm, and "minimum thickness" 1.18" (*25.4 = 30mm) which is what the volvo s60r rotor thickness is. It is paradigm to use rotors with proper grasp thickness for which the calipers were intended to be used with.



I've allocated a test rotor from Autozone for about 45$, low and behold to my surprise it has both Brembo and Volvo insignias stamped right into.



Not only does the Volvo rotor sport a different bolt pattern but the hub flange circle is smaller too (68mm vs gto 71.4). So, the gto bolt pattern was drilled into the rotor and the hub flange circle opened up to 71.6mm (allowing for some hub clearance). I believe that any machine shop can do this to both rotors, 50$ would be a reasonable starting price. As you can see in the pic the oem volvo rotor has 5 offset rotor mounting holes in the same bolt patter as its lugs. European cars in general do not use wheel studs in their hubs but instead mount the wheels via wheel stud bolts (heavy duty bolts that hold in wheels), so in order for the rotor to not fall off during assembly they secure it to the hub via small screws. This is why you see the small dimples near where the gto studs are sticking out of the buh thru the rotor; I plan to offset the holes to omit these on my second rotor.



Once I had everything measured out, bracket design commenced, looks similar to my 18" bracket design , which can be seen here http://www.ls1gto.com/forums/showthread.php?t=437821&highlight= , but i aside from the hole diameters, is totally different. The final piece basically looks like it hugs the hub mounting casting, it fits so close that any more offset on the holes/bosses and I would have to be grinding down the hub to make it fit, but its fits without compromise and so do the brembos sitting on top. This made me very happy as I knew I was going to be very close based on my calculations.

After the bracket and brembo successfully mounted without compromise, it was time to put the wheel on. The wheel went on and cleared the brembo, but in some parts of the spoke it got hung up, and unless I wanted to grind the tops of the brembos I would have to run a spacer, 5mm minimum for clearance. This was a surprise as the volvo rotor is tall enough to compensate for this compared to my 18" kit, the spacing is built into it, but the 17" wheels just oppressing interior spoke design that it couldn't be helped. Also, if there are any wheel weights inside the rim where the brembo sits, it will be a close fit. Aisde from that, they look pretty mean/nasty behind the stock 17's. Will be going on the car very soon!

I'd imagine something like this might be beneficial for someone whom wants to stick with stock wheels, with little compromise. Or someone whom is running aftermarket 17's in order to keep their tire prices down as the larger the wheel diameter the costlier the tires. Or even someone whom has stock 18's and is a weekend racer and switches out for some slicked out 17's and then throws the 18's back after the event. But that's all speculation.

Cliffs:

-Volvo s60r rotor, drilled with gto bolt pattern & hub circle, bracket bolts in and so do the brembos, need 5mm spacer to clear ridiculous offset oem 17" wheels. Although with these the oem 18's will fit without issue.

I would just like to state, that as with my 18" bracket, I've designed this utilizing cad software from actual bolt spacing measurements (which I did on a CMM, amongst other measuring tools) which I acquired both car's suspension components from, all offsets where made ideally to accommodate spacing, none of this was rigged in any way.






 

·
Registered
Joined
·
10,457 Posts
Sub'd and bank account checked.
 

·
Ecotec tech
Joined
·
2,133 Posts
very happy, but not sure how excited I will be for the smaller rotor :/
 

·
Premium Member
Joined
·
1,185 Posts
Discussion Starter #5
very happy, but not sure how excited I will be for the smaller rotor :/
These brembos came in a variant of cars, with rotors ranging from 12.6-14" (14" being the v), so the smaller rotor is something that they originally were designed to work with, its just gm needed larger rotors to stop the V tank.
 

·
.
Joined
·
18,517 Posts
The CTS-V is not that much heavier than our GTO's, fwiw and the brakes with 14" rotors work excellent stock (on the V)...not sure I'd go any smaller, but the biggest hurdle is the size of the caliper with relation to the back side of the spokes on the wheel, but it looks like they may work with oem 17's, so that's cool.
 

·
Don't drink the Kool-Aid...
Joined
·
2,889 Posts
These brembos came in a variant of cars, with rotors ranging from 12.6-14" (14" being the v), so the smaller rotor is something that they originally were designed to work with, its just gm needed larger rotors to stop the V tank.
Never seen these calipers paired with (from the factory) anything much smaller than 14". If you're thinking WRX, EVO, or 350Z, those are different calipers.

I've only seen this particular caliper used on CTS'Vs, GT500s, and maybe one of the Jeeps; Grand Cherokee SRT8 or something. Not sure about that one though.
 

·
Premium Member
Joined
·
1,185 Posts
Discussion Starter #8
Never seen these calipers paired with (from the factory) anything much smaller than 14". If you're thinking WRX or EVO, those are different calipers.

I've only seen this particular caliper used on CTS'Vs, GT500s, and maybe one of the Jeeps; Grand Cherokee SRT8 or something. Not sure about that one though.
Yes they are, just different hole spacing to mount to the factory hub/spindle. The rear cts-v ones are the ones that are used widely in most other domestic branded vehicles. Ct9a Evo/sti/350z/s60r/g35 all use these up front, piston sizes may vary, pads do not.
 

·
Bear Wrestler
Joined
·
102 Posts
I'm definitely sub'd now. I'd also like to know what the clearance is between the caliper and the face of the wheel. This will hopefully put the kibosh on me having to buy 18's.
 

·
'12-'13 ScrScca SM Champ
Joined
·
7,098 Posts
This setup will fail instantly on the track. No where near enough airflow with it as tight as that.
 

·
Don't drink the Kool-Aid...
Joined
·
2,889 Posts
Yes they are, just different hole spacing to mount to the factory hub/spindle. The rear cts-v ones are the ones that are used widely in most other domestic branded vehicles. Ct9a Evo/sti/350z/s60r/g35 all use these up front, piston sizes may vary, pads do not.
No dude, they're not the same. And no caliper that can comfortably accommodate a 14" or larger rotor will work with a 12.6" rotor...

Do these really look like the same caliper to you?

 

Attachments

·
Ecotec tech
Joined
·
2,133 Posts
No dude, they're not the same. And no caliper that can comfortably accommodate a 14" or larger rotor will work with a 12.6" rotor...

Do these really look like the same caliper to you?
yes actually..?
 

·
Premium Member
Joined
·
1,185 Posts
Discussion Starter #15
No dude, they're not the same. And no caliper that can comfortably accommodate a 14" or larger rotor will work with a 12.6" rotor...

Do these really look like the same caliper to you?

You might have a point, piston buldges look a lil different (possibly due to different piston sizes). I have a spare set (or 2) of front evo8/9 caliper sitting at home, I will check later today.

No need to turn this into a pissing match though.
 

·
Premium Member
Joined
·
1,185 Posts
Discussion Starter #17 (Edited)
first post updated with write/pics!
 

·
o.g.owner since 10/31/2004
Joined
·
584 Posts
i have his 18'' set up and works perfectly fine,nice i wish you would thought of this when i had mine 17 still lol
 

·
Registered
Joined
·
88 Posts
DUDE! You are the f-ing man! Yes!
 
1 - 20 of 76 Posts
Top