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Nice video, although as an engineer who’s spent the past 7 years designing and testing performance brake calipers I would add a small caveat to your assumption that monoblock calipers are always stiffer than 2-piece bolted brake calipers. At room temperature this may be true, but the tensile modulus of aluminium decreases by 10-20% at 150 degrees C whereas a high tensile steel bolt has negligible change in tensile modulus at 150 C. Calipers on race cars run between 150-200C, but since the bridge region of the brake caliper runs just a mere couple millimetres away from the brake disc, which itself might be 800C+, the spot temp measured at the caliper bridge is much higher than the average body temperature for the caliper of a whole, meaning bridge temps can see 200C+. Furthermore, it’s the bridge region of the caliper that’s always ‘lit up’ on FEA models thus indicating regions of highest stress. Combine all this together and the idea of a 2-piece caliper, with a couple high tensile bolts to reinforce the bridge region, starts to become the favourable route. As the saying goes, “steel is strong”. A designer for a brake caliper faces a cacophony of compromises. The worst one being when customers wish to run large diameter discs in small diameter wheels. Inevitably this means the thickness of the caliper bridge gets reduced below what would be considered optimal. At which point, employing a few high tensile bolts with a roll-thread becomes the only way to prevent excessive flex of this region of the caliper. So, whilst it’s true that a monoblock caliper CAN be designed to have a better stiffness-to-weight ratio than a 2-piece bolted caliper, the issue really is whether the clearance envelope will allow for a very chunky aluminium bridge region. Often for fast-road applications or club-racing, packaging in the wheel is very tight hence the more compact nature of a 2-piece caliper makes it more suitable, otherwise a monoblock caliper with a thin bridge (say less than 15mm cross section) would simply flex too much. Interestingly enough, there’s actually a patent out there for a monoblock caliper but that employs multiple steel rods threaded through the bridge section… Why go to the hassle of drilling, threading and inserting steel bars into a monoblock caliper if it didn’t strengthen the bridge region? And this is before we consider the effects of cyclic thermal aging of the aluminium bridge.

Good general overview. Alcon, Stoptech, AP racing, Willwood racing all use 2 piece calipers. Even in their Motorsports calipers. Bespoke brake cooling ducts and deflectors can make even mediocre brakes somewhat adequate. Cooling is everything for effective brakes.

Where was this 25 years ago when I did my first 4 wheel disk conversion 😉 It's crazy how much easier it is now to find 4 & 6 piston callipers in the wreckers now.

Such a great video… I’ve now signed up at HPA!

To calculate the force from the pistons, you would only add the area of the pistons on one side of the caliper. Opposing pistons on the caliper is just a reaction force of the pistons on the other side.

Thanks

nice video. I'd like to understand what happens to the brake pedal travel when you go up with both the disk diameter (say 30mm extra) and also the piston area (even though only slightly). Would you have to push more on the brake pedal with a biting point closer to the car floor (which I wouldn't like, would make heel and toe more complicated) or less? My understanding is that bigger disk diameter equal to more brake force given the same pressure on the pedal while bigger piston area would imply that the biting point of the brake pedal would be lower (closer to the floor of the car); is this what longer pedal travel (more brake fluid to be displaced) mean? Would these two factor (disk diameter and slightly bigger piston area) kinda compensate each other?

Could you talk about smaller lines vs. Larger lines and how the master and caliper piston size matter, however line size doesnt effect pedal?

👏👏👏

Any insight or information as to the mounting of calipers in front of or behind the hub? That's always something I've wondered if it makes any difference or is only a packaging/cooling decision

Cool vid and nicely explained. I have to say I’ve never heard anyone use the term retard though for slowing a car 🤣 I totally get it’s base meaning but that’s a very different I will say. More so as I’d normally associate that with a tuning terminology.

Hey HPA. I would like to ask. I've upgraded my brake calipers at the front. From a 1 piston to 4 pot brembo on upgraded discs same size. The brakes are way sharper at low speed. But I think there worse at high speed. I thing the abs is causing the problem. Am I right?

Great video! I see the bleed nipples are on the side of the trailing pistons. If I understood your explanation correctly, shouldn't they be on the side of the leading pistons?

why are there no protective anthers on sports calipers?

Can I upgrade my calipers and break pads and leave the same factory disc?

Why do manufacturers use multiple round pistons rather than one oblong piston? You could get the same piston surface area in a smaller caliper body. Seem like it should be lighter as well right?

What will happen if you keep the same caliper but change the master cylinder to one with a bigger piston diameter?

Those Endless brakes are just pure porn

Please correct the information you provide. Clamping force is not equal to the total area of all pistons! Only one side area*pressure will give you the clamping force. The other side is just opposing this same force to prevent bending of the rotor with solid mounted calipers. A floating caliper with same area of pistons on one side and no pistons on the other will have SAME clamping force. Also similar volume will be needed as if its simetric caliper with twice the area..

Man with that middle part remove you won't even feel the dam difference .