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Discussion starter · #41 ·
They also only have 5.2 square inches of piston area, which is significantly less than cast iron D52 or any Wilwood D52 calipers intended for the front. This would throw off any existing front/rear brake balance unless the rear is specifically engineered to match. Especially on these big-ass cars with a lot of rear weight, the rear brakes need to be significantly larger than on something like a 2nd-gen F-body to be effective. Otherwise all you're doing is reducing overall braking force by switching to JL8 front calipers. This isn't a huge deal on drum brake cars, but especially on an Impala SS with a proper proportioning valve, I can see the rear brakes locking up before the fronts. Without ABS, that can be a recipe for disaster.

I'm all for innovative new ideas and options regarding brakes and suspension for these cars, but it's not just a matter of slapping on cool new parts.
 
All true, rear C-locks are problematic for rear disc brakes with continuously wearing out clutch pack posis, but it is possible to long term maintain .010-.015” per side axle end play with an open diff or a true track though.

It’s not so difficult to install aftermarket 45mm press-on bearings and axles too. I’ve done it several times over the last 45 years. I’ve only used Mark Williams parts but pretty sure even Moser has the kit or parts. Those ill conceived cast iron Delco Morraine pieces were the bane of virtually every Vette owner’s existence. Stainless steel repair sleeves, no thanks.

This Rekudo stuff is a retro friendly biased proposition for sure, but in this thread we are still talking about options for upgrading brakes that are similar in goals to the HD12 in spirit.
 
They also only have 5.2 square inches of piston area, which is significantly less than cast iron D52 or any Wilwood D52 calipers intended for the front. This would throw off any existing front/rear brake balance unless the rear is specifically engineered to match. Especially on these big-ass cars with a lot of rear weight, the rear brakes need to be significantly larger than on something like a 2nd-gen F-body to be effective. Otherwise all you're doing is reducing overall braking force by switching to JL8 front calipers. This isn't a huge deal on drum brake cars, but especially on an Impala SS with a proper proportioning valve, I can see the rear brakes locking up before the fronts. Without ABS, that can be a recipe for disaster.

I'm all for innovative new ideas and options regarding brakes and suspension for these cars, but it's not just a matter of slapping on cool new parts.
I’m not trying to sell anyone on this package, but just mentioning it as an interesting 12” rotor option, definitely I wouldn’t do this front swap without matching with a (balanced) rear disc setup.
I’m confident that there will be a benefit if master cylinder bore is properly figured into a balanced front to rear piston area configuration.

Also there are alternate C3 calipers from other suppliers that offer more options for bigger piston diameters including differential bore calipers. C2/C3 disc/disc brake challenges have been addressed in the aftermarket pretty extensively.

So I do see the potential for a worthwhile and reasonably affordable upgrade path, if pursued intelligently.
 
Discussion starter · #44 ·
Yup, it looks like a pretty sweet potential option! Especially for someone looking to really maximize suspension geometry for aggressive handling.
 
Maybe good stuff, but boy, that website... Their marketing guys must be newbies.

Their upper and lower control arm set is quite a bit more expensive than just buying the upper and lower sets separate.
Their 'savings' for the kit is less then 'savings' on individual. You loose $252 in 'savings' on the kit. o_O

Their shocks... they have those magical shocks I've been looking for - the compressed lengths are longer than the extended lengths. (y)

Image


The instructions for setting stiffness, a sketch of turning it this way or that way. No detail on how much rotation they have or how much rotation equals what.

Is it growing pains for the new line? Or just looking to clear out their inventory?
Not promoting well if they are serious on this stuff.


They also only have 5.2 square inches of piston area, which is significantly less than cast iron D52 or any Wilwood D52 calipers intended for the front. This would throw off any existing front/rear brake balance unless the rear is specifically engineered to match.
This is something I could never get straight in my head and never worked out the forces to get it straight. Maybe you can help me understand.

I get you can compare apples to apples on piston sizes whether it be single or dual on a floating caliper and they are on one side of the caliper.

BUT, what is the area/force applied when you have a fixed caliper with pistons on both sides? What's the math? You said 5.2 square inches, which is true of two of their pistons on one side. Why isn't the total area and force applied double that because of 4 pistons, two on each side? Why isn't it 10.4 inches of area?
 
Simple ,
A 5 sqaure inch single piston floating caliper is same as a fixed caliper with a 5 square inch piston on each side .

This because with a single floater the fluid force against the face of the piston pushes one piston and the fluild against the bottom of the bore pushes,
the housing which slides and pushed the other pad.

Fixed caliper
Each side force against pushes a pad but
force against bottom of bore goes nowhere.
In actuality the forces into the bores cancel each other out . If they didnt they would try and bend the rotor or break the caliper mount.
Much the same as when a single floater seizes its sliders
 
Thank you! I never considered the back of the bore as an opposite force. That was the missing piece! So a floating caliper's area is always double the piston area when comparing to fixed.
 
Discussion starter · #49 · (Edited)
Every brake force calculation formula I know of multiplies by 2 somewhere to get the actual brake force applied at the caliper, precisely because of what @95wagon explained: the pressure transferred by the brake fluid from the master cylinder to the caliper is being divided by 2 regardless of whether it's a floating caliper or a fixed one. So it's not really a case of "half of one and all of the other" so much as "we only ever account for half". In the case of the floating caliper, we're ignoring the area of the opposing force, which is essentially the piston that would be on the outside if it existed, and it gets added into the formula by multiplying by 2.
 
Ok, so let us not forget that there are several other critical variables to consider beyond simply calculating caliper piston area in isolation.
Such as:
A) the distance between the pedal pad and fixed brake lever arm top pivot axis,
B) the distance between lever’s pivot and master cylinder pushrod pin, and
C) the master cylinder bore diameters, for both front and rear pistons.

This is all before the introduction of knee-over proportioning valves, adjustable dual master balance bars, ABS interventions and vacuum, electric or hydraulic boost assist, not to mention coefficient of friction vs temperature curves, and the ratio between the clamping center radius on the rotor surface relative to the radius of the rotating tire to the ground, , ,
All of these factors should be considered as changeable (or variable) factors toward achieving the desired optimal total vehicle brake performance.

This is all a bit like f-stop ~ shutter speed ~ ASA film speed for you photography buffs!
 
A) the distance between the pedal pad and fixed brake lever arm top pivot axis,
B) the distance between lever’s pivot and master cylinder pushrod pin, and
C) the master cylinder bore diameters, for both front and rear pistons.

Add in, this era of B body there two different arms resulting in two different pedal ratios.
The info in the replacement market is sketchy and I am willing to bet there are cars running around with mis matched boosters and pedals

Link to the last time


" for both front and rear pistons "

any single master has the same working bore dia, front and rear. If they didnt, the brake warning lamp would come on every time you stepped on the pedal.
 
Discussion starter · #52 ·
None of that is retrofitting, at that point you're engineering a complete new brake system from scratch. Keep in mind, the point of this thread is for a simple retrofit that's easily reversible and works within the existing vehicle's brake system while fitting within stock 15" wheels.
 
None of that is retrofitting, at that point you're engineering a complete new brake system from scratch. Keep in mind, the point of this thread is for a simple retrofit that's easily reversible and works within the existing vehicle's brake system while fitting within stock 15" wheels.
No, not necessarily engineering a whole new system, I only mention any of that because it relates to the Rekudo stuff presenting an option staying within the spirit of HD12 “upgrades” and to fit in 15” wheels.
The caliper piston area discussion addresses only one concern of using those particular pieces, specifically the new forged 7075 JL8 C3 fit calipers.
Also it bears repeating that too many people make one change or another without realizing what real world consequences they have begot. ~ Big diameter tires installed for looks or handling or stance . . . and suddenly they find acceleration and braking have both suffered.
The Rekudo site states that you should be sure to put in a 1.125” bore MC, but that’s for a 70-81 F-body brake lever arm.
This stuff is not rocket science, I just wanted to remind a few possibly uninformed readers that any brake system changes will have to be made thoughtfully. I’ve been modifying these types of things for at least 50 years, and way before store bought stuff was so widely available. I’ve enjoyed the luxury of having worked in machine shops where there were always very talented competent engineering minded “car-guys” to learn from, so every executed “upgrade” really was a substantial upgrade in reality.
I’m pretty sure anyone who wants to keep a 15” wheel would realize an increase in rotor mass heat management benefits with just those spindles, rotors, hubs and calipers. - The front upper and lower control arms, shocks, I believe are optional, and all of it is fully reversible.
No trips to a machine shop with greasy sketches in hand, no rummaging through rusty salvage scrap piles of vanishing obsolete cars, no more inevitable, escalating, frustration of finding out that yet another afternarket supplier has abandoned making a low production count, specialized part.
However, there is a strong high likelihood that brand new and/or reconditioned C3 brake parts will be around virtually forever.
 
Installed with ProTouringF-body bearing spacers, Hawk HPS pads.
 

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Discussion starter · #56 ·
Glad the hats worked out for you, thanks for being the unwitting guinea pig with those cast iron hubs 😁

Those calipers look sweet!
 
used leftover kbs motor coater (brushed) and placed decals. sprayed over them with kbs diamond 1k clear aerosol
 
Discussion starter · #58 ·
If anyone's wondering about the long-term results of installing a bearing spacer for the front wheel bearings, I had the opportunity to inspect mine yesterday while doing a brake pad replacement:


I specifically mention the KORE3 bearing spacer kit in that video, but the results should be the same with the PTFB or other similar kit. For this setup, I torqued the spindle nut to 40 ft-lb then tightened to the next cotter pin slot, even if a slot was already lined up. Both sides are under 0.0015" end play. They both spin the same. The grease inside (Lucas Red & Tacky) still looks new, no maintenance was needed.

Those spacers previously lived 10k miles on my other Roadmaster before I transferred them to this car 2 years ago. I used new bearings during the swap. It's not like there's any kind of wear happening for the spacers themselves, but it's interesting to see how the bearings wear over time when installed with a spacer. Note that I REALLY enjoy high Gs in the turns, and abusing my thick brake rotors 😁
 
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