27mm master cylinders with SSVR Brembo brakes

[RevNev]

Master cylinder size has been discussed several times with Holden fitting 27mm master cylinders with Brembo brakes. My Aug '17 SSVR Ute has a 25mm master cylinder I believe is absolutely a factory fitment perhaps incorrect fitment or maybe not. The question whether or not a 4-piston brake upgrade needs the bigger 27mm master cylinder, here's a photo of an MY15 R8 Maloo Ute 25mm factory master cylinder fitment with the HSV 4 piston AP brakes. I'm not sure if the GTS 6-piston calipers had the 27mm master cylinder but the HSV 4 pistons certainly don't.

 

[kleanphil]

I put a 27mm on mine when i put the 6 pot cts-v Brembo's on , i bought it from Salvage Auto's and believe it was attached to a GTS booster , was definitely from some sort of HSV

 

[RevNev]

I put a 27mm on mine when i put the 6 pot cts-v Brembo's on , i bought it from Salvage Auto's and believe it was attached to a GTS booster , was definitely from some sort of HSV

GTS with the 6 pots is likely to have the 27mm as it displaces more fluid. The 3 Clubsport sedans I've looked at, one a GenF2 LSA and this Maloo with the 4 pots have all had the stock 25mm master cylinder.

 

[NJD-1992]

Paging Ron Burgundy in 3…2….1….

 

[Ron Burgundy]

My 2016 SS which came with police spec heavy duty brakes on the front from the factory also has 27mm BMC. Sounds like Holden run out of them and did not bother In all likelihood probably not really needed either....

 

[Thorby]

I put a 27mm on mine when i put the 6 pot cts-v Brembo's on , i bought it from Salvage Auto's and believe it was attached to a GTS booster , was definitely from some sort of HSV

Bought mine from Dean at Salvage as well same deal with the 27mm on a GTS booster.

 

[panhead]

My Aug '17 SSVR Ute has a 25mm master cylinder

View attachment 259106

Gee, that looks so small





.

 

[Pazzu]

I have done the calculations based on the info I can get when I was upgrading the brakes. AP info was a bit hard to get so it may not be the accurate figures. But the and brembo,pbr & mando caliper specs i'm confident.
Bottom line is that I have ran the brembo 6/4 pot combo on a 25 MC and it was signed off by the engineered
So I would say don't worry unless you plan to upgrading to a bigger kit being the AP 6 pot kit which would require more volume

 

[NJD-1992]

Certainly seems its a bloke thing to be worried over 2mm

Genuine question, wouldn't tires have a far greater influence overall on real world brake performance, such as stopping distance? (Ignoring things like brake fade, pedal travel etc) Still boggles my mind the amount of SSVR's and LSA HSV's I see rolling round that have the cheapest bargin basement tyres on them

 

[RevNev]

Bottom line is that I have ran the brembo 6/4 pot combo on a 25 MC and it was signed off by the engineered
So I would say don't worry unless you plan to upgrading to a bigger kit being the AP 6 pot kit which would require more volume

Harrop did the calculation for their 6-spot front and 4-spot rear kits and also determined the 25mm master cylinder was plenty big enough. It's almost like Holden assumed the 25mm master cylinder was on the cusp with the stock brake system where in fact, a 23mm master cylinder was probably big enough for the stock system.