Brembo 345mm front brakes - new option - Pontiac G8 Forum: G8 Forums - G8Board.com
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post #1 of 76 (permalink) Old 05-03-2018, 09:04 PM Thread Starter
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Brembo 345mm front brakes - new option

This topic actually came up in a Regional Forum - posting here for better exposure.

Thread: https://www.g8board.com/forums/42-ca...ml#post3629506

Pertinent posts from the thread above:
#7 https://www.g8board.com/forums/3624953-post7.html
#10 https://www.g8board.com/forums/3625585-post10.html
#16 https://www.g8board.com/forums/3626129-post16.html
#18 https://www.g8board.com/forums/3629506-post18.html (with photos)

To recap, standard G8 GT uses 321mm front rotors with a twin-piston floating aluminum caliper. A popular mod has been to use the Brembo 4-piston fixed caliper and 355x32 rotor found on Gen5 Camaro SS, SS sedan, etc. Different wheels than production G8 18x8 or 19x8 are typically required to work with this brake setup.

The Caprice PPV, with the same Zeta sedan suspension as G8 & SS sedan, is fitted with a 345x30 rotor, and a single-piston floating caliper that is common with Gen5 Camaro V6. As addressed in the thread/posts above, there is now the possibility of a "hybrid" combination of Zeta & Alpha brake components to add 345mm rotors & Brembo calipers to any G8 with "small" front brakes, and continue to use the stock 18" or 19" (non-GXP) wheels.

While not offering the same effect as going to the 355mm or even 370mm/6-piston front setup, the change to the 345mm rotor ultimately provides at least 90% of the improvement of the larger brake options, and will quite effectively out-perform the stock 321mm brakes.

All components bolt-on:
(L/R)Calipers - Cadillac J56 for 2014-2016 CTS - specifically PN 84089036 & 84133555 (new from GM Parts Direct at $148 each, no core charge)
(2)Rotors - 2011-2017 Caprice PPV 345mm - many sources/styles available
(1)Pads - FMSI D1474 or D1001 (addressed in thread/posts above)
(2)Pin kit - GM 22813180 (or equivalent)
(4)Bolts for mounting calipers - M14x2.0 - GM 11570092 (must drill mounting bolt holes for spindles - now 12mm)
(A/R)Hoses - stock hose may work, or custom hose

Bill Harper
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post #2 of 76 (permalink) Old 05-04-2018, 07:21 AM
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but they are smaller rotor then ss and cts v
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post #3 of 76 (permalink) Old 05-04-2018, 07:32 AM Thread Starter
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Quote:
Originally Posted by inov8rPPV View Post
While not offering the same effect as going to the 355mm or even 370mm/6-piston front setup, the change to the 345mm rotor ultimately provides at least 90% of the improvement of the larger brake options, and will quite effectively out-perform the stock 321mm brakes.
I clearly acknowledged that fact up front--still, it's a significant improvement over the production G8 GT's brake package, and it allows use of production G8 wheels. For someone wanting to stay with OE wheels and enjoy improved braking performance, this is an option that wasn't presented previously, to my knowledge.

Am I missing some further point in your response?
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post #4 of 76 (permalink) Old 05-04-2018, 09:06 AM
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this was posted be before its not new option ATS AND CTS CALIPERS WERE KNOWN TO FIT THE G8. But you did a detailed write up
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post #5 of 76 (permalink) Old 05-04-2018, 10:20 AM Thread Starter
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Originally Posted by gmpontiacguy View Post
this was posted be before its not new option ATS AND CTS CALIPERS WERE KNOWN TO FIT THE G8. But you did a detailed write up
I was not entirely aware, but the base ATS/CTS happens to use a 321mm front rotor, which does not backfit to G8, so unless the 345mm option was also mentioned, I don't know if that's already been covered. As a PPV owner, I'm not familiar with anyone talking about using the Camaro/Alpha Brembos for the larger rotors.

Got a link?

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post #6 of 76 (permalink) Old 05-04-2018, 10:27 AM
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Interesting read.
I like the fact that in this case you your can still run OE rims.
Keeps expenses down since you don't have to buy aftermarket rims/tires plus I've never been a big fan of the wheel spacer option.
Would my Base OE 18" rims clear this application or only the GT OE 18" or 19" rims clear.
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post #7 of 76 (permalink) Old 05-04-2018, 10:56 AM
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yes the base 18 wheels would cleat
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post #8 of 76 (permalink) Old 05-05-2018, 10:34 AM
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Thank you.
I picked up a set of 18" GT rims too so I can switch back and forth between Base and GT rims....why I would want to do this....haven't got a clue....
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post #9 of 76 (permalink) Old 05-05-2018, 12:22 PM
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Quote:
Originally Posted by inov8rPPV View Post
While not offering the same effect as going to the 355mm or even 370mm/6-piston front setup, the change to the 345mm rotor ultimately provides at least 90% of the improvement of the larger brake options
This statement is not accurate.
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post #10 of 76 (permalink) Old 05-05-2018, 01:14 PM Thread Starter
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We're talking about the difference in the performance characteristics of the G8 GT 321mm front brakes vs 345mm/Brembo brakes vs 355mm/Brembo brakes--both Brembo options using the same pads.

Should I retract the statement, or is there a better way of addressing the impact of the change? Would you be more in agreement if the number was 75%, 50%, or....???

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post #11 of 76 (permalink) Old 05-07-2018, 10:14 AM
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Quote:
Originally Posted by MGMGXP View Post
This statement is not accurate.
Why, and what would be more accurate?

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post #12 of 76 (permalink) Old 05-07-2018, 03:36 PM
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Why, and what would be more accurate?

Thanks,

JAM
Because how could you possibly slap a % increase number to anything automotive unless it is easily measured, like horsepower or weight or something like that? Sounds like a guess or a hunch to me.
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post #13 of 76 (permalink) Old 05-07-2018, 04:49 PM
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Quote:
Originally Posted by inov8rPPV View Post

To recap, standard G8 GT uses 321mm front rotors with a twin-piston floating aluminum caliper. A popular mod has been to use the Brembo 4-piston fixed caliper and 355x32 rotor found on Gen5 Camaro SS, SS sedan, etc. Different wheels than production G8 18x8 or 19x8 are typically required to work with this brake setup.

The Caprice PPV, with the same Zeta sedan suspension as G8 & SS sedan, is fitted with a 345x30 rotor, and a single-piston floating caliper that is common with Gen5 Camaro V6. As addressed in the thread/posts above, there is now the possibility of a "hybrid" combination of Zeta & Alpha brake components to add 345mm rotors & Brembo calipers to any G8 with "small" front brakes, and continue to use the stock 18" or 19" (non-GXP) wheels.

While not offering the same effect as going to the 355mm or even 370mm/6-piston front setup, the change to the 345mm rotor ultimately provides at least 90% of the improvement of the larger brake options, and will quite effectively out-perform the stock 321mm brakes.
I think he's just trying to illustrate that the the DELTA difference from going from a 321mm dia rotor to a 345 mm one (24 mm increase 7.4%) is ALMOST as good as going up to a 355mm dia rotor (34 mm increase 10.5%) 3% less increase in brake dia. but the ability to still run stock 18 wheels. Is that 3% loss worth it to be able to use the stock oem wheels?

Question though. Dia is okay but is the spoke spacing still enough to clear the additional width? I assume these are a little wider

Last edited by Jeff92se; 05-08-2018 at 01:56 PM.
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post #14 of 76 (permalink) Old 05-07-2018, 06:31 PM Thread Starter
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When it comes to rotors, there are 2 major considerations - we are trying to make an apples-to-apples comparison, so all rotors mentioned here are vented, OE or equivalent.

The 2 main things to look at are weight and diameter. You'll see an interesting twist in the assumptions we might make from this information.

The data below is from the manufacturer, in this case, Centric, which openly publishes it's rotor weight information. The actual data is taken from Rock Auto listings. There could be deviations in weight/mass from the same application(s) for OEM or other sourced rotors, but this is all I can provide for this discussion.

Other obvious differences are diameter, and rotor thickness--which means the 355mm rotor could be assumed to be the best at dissipating heat, since the air passages are probably slightly larger (32mm vs 30mm for the 321 & 345 rotors). I've not confirmed this--the rotor cheeks COULD be thicker, but the weight differences between 345 & 355 rotors may put this in question. In other words, the air passages could be the same between 345 & 355 rotors, but considering the revelation that the mass of the 345mm rotor is actually greater than the 355 rotor, I'm inclined to think the 345 rotor may actually have thicker cheeks, thus a narrower air path.

I've left the 370mm/6-piston combination out of this discussion, as it absolutely requires a larger wheel with greater lateral/outboard clearance than the 4-piston combinations.

When I stated that the 345mm rotor/Brembo caliper would offer "at least" 90% of the 355mm rotor/Brembo caliper performance, I had not actually looked up the data below. The one thing I am NOT sure of is the size of the pistons on the Brembo caliper used with the 345 rotor, but that would have a minor influence, if any, on actual braking force/power...if there is any difference in piston sizes compared to the 355mm Brembo caliper.

Centric G8 rotor - 321mm - 20.2#

Centric PPV rotor - 345mm - 25.6#

Centric GXP/Camaro SS/SS sedan rotor - 355mm - 25.15#

A little "math":

Rotor mass comparison
321mm vs 355mm - 24.5% increase
321mm vs 345mm - 26.7% increase
345mm vs 355mm - 1.8% decrease - favoring the 345mm rotor

MASS = thermal capacity - for a given amount of work (brake friction > heat energy > rotor temp change), greater mass slows rotor temp rate of change, reduces thermal range of pad/rotor interface, and/or allows more aggressive pad/friction coefficient vs smaller/lower mass rotor while operating at same max temp due to improved ability to transfer & shed heat

Rotor diameter comparison
321mm vs 355mm - 34mm difference = 10.6% increase
321mm vs 345mm - 24mm difference = 7.5% increase
345mm vs 355mm - 10mm difference = 2.9% increase

The other thing we don't know precisely includes what the clamping radius of the caliper-to-pad is, however, as already stated, both 345 & 355 brake packages use the same Brembo pad specs, so a figure of 5mm radially as the difference in the "lever" that will produce brake torque can be assumed. Certainly this matters in one respect, which is to calculate maximum torque potential, not always or often used in average street-tired braking events.

To be clear, I'm not a mechanical engineer, so it may be easy to blow up my statements. There are certainly other considerations to be made in a true comparison of the 345 & 355 brake combinations presented. Zero-out as many of the variables as possible - same wheels, same tires, same pads, same ambient conditions - and with the data presented, someone needs to convince me that the 345mm/Brembo package will not achieve 90% or more of the performance of the 355mm/Brembo package, with justifications.

As previously stated, I continue to believe there is clear evidence that both the 345 & 355 brake combinations will substantially improve braking performance over the G8 GT's 321mm brake package.

Quote:
Originally Posted by Jeff92se View Post
I think he's just trying to illustrate that the the DELTA difference from going from a 321mm dia rotor to a 345 mm one (24 mm increase 7.4%) is ALMOST as good as going up to a 355mm dia rotor (34 mm increase 10.5%) 3% less increase in brake dia. but the ability to still run stock 18 wheels. Is that 3% loss worth it to be able to use the stock oem wheels?

Question though. Dia is okay but is the spoke spacing still enough to clear the additional width? I assume these are a little wider
Correct.

Second part of your comments--I have no actual data. The 345 caliper is a more compact design, so I am optimistic that it will work with G8 18" wheels, though I'm not aware of anyone that can confirm it.

So far, I know of one PPV with the 345/Brembo combination, in Elk River, Minnesota, running steel PPV wheels, which are already known to clear the 355/Brembo package--there may be others--so the objective would be to see if he or another PPV or G8 owner that has done the 345's can answer this, or would agree/offer to meet with a stock 18" wheel G8 owner for a test fit.
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post #15 of 76 (permalink) Old 05-07-2018, 09:44 PM Thread Starter
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need a G8 owner to help with a fit-check on 345/Brembo brakes

G8 owners in Minneapolis area still running production 18" wheels (or having in their possession) - looking for someone who would be willing to make a run to Elk River to do a wheel-fit validation of the 345/Brembo front brakes.

Consider it a service to the G8 community.

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post #16 of 76 (permalink) Old 05-09-2018, 07:33 PM Thread Starter
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18" fit confirmed

PPV owner with the 345/Brembo conversion in Minnesota followed up and confirmed fit with G8 GT 8" wheel (5-spoke).

There has been no test fit of the V6 split-spoke 18x8 or optional GT 19" 5-spoke wheels, but my confidence level is high that there will be no issues, as long as pad selection is correct.

One caveat, as mentioned previously - using the D1001-spec pad is necessary for clearance.

The later D1474-spec pad, fitted with dampers that extend beyond the outer (radial) surface of the caliper DO interfere with wheel fit.

The D1001 pad is the same as was used on G8 GXP (specific 19" wheel) and 1stGen CTS-V (18" wheel).

The D1474 pad is from 5thGen Camaro SS and Chevy SS sedan, which used wheels sized to provide clearance for the dampers. The dampers are for vibration control to help reduce brake noise. It will be a non-issue using this pad with the GT 19" option wheel.

Thanks goes to Scott Abramson, in Elk River MN. He's a racer and NHRA tech inspector at the Brainerd track, and runs a speed shop. He's on Facebook, and can reach out to him if you feel the need to have further assurances on fitting this combination on a G8 GT or G8 V6.

Bill Harper
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post #17 of 76 (permalink) Old 05-09-2018, 08:12 PM
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Good information. Thanks for heading it up and providing all the details. I may just look into it some day. Did you take any pics of the test fitment?

2009 G8 GT, White Hot, Cortex, Camaro Trans Pan, VCM Intake, GXP Mufflers
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post #18 of 76 (permalink) Old 05-09-2018, 11:50 PM Thread Starter
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Did you take any pics of the test fitment?
The install & test was done in Minnesota--I'm in Georgia. Installer made a few photos, but none with the G8 18" wheel.

There are photos of the car with a PPV stock steel wheel--also 18x8--installed with no clearance issues.

Photos of the rotor & caliper installed
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post #19 of 76 (permalink) Old 05-10-2018, 07:39 AM
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Good stuff. Worst case scenario you can probably cut the dampers off the pads if you have a set already.

Matt Jones
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post #20 of 76 (permalink) Old 05-10-2018, 11:19 AM
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Awesome work. Glad I kept my oem 18s.

I was actually going to put snows on my 18s as I got some Camaro 20s. But ended up getting a great deal on snows and wheels but they are 17s. If I go this route, I'll definately sell the 17s and use the 18s for winter.
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