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MONOBLOCK VERSUS 2-PIECE CALIPERS, answer may surprise you

Brick15 said:
An interesting read, wondering if anyone agrees or disagrees and why


https://centricparts.com/getmedia/3...C_Technical_Whitepaper_D2-MONOBLOC_8-2018.pdf


Taken from here dated August 24, 2018

https://centricparts.com/resources/resource-library?category=Whitepapers
Click to expand...

Carroll Smith died in 2003. The dates listed are likely when Centric just re-hashed the writings on their own letterhead after purchasing StopTech.

I wouldn't say there's really anything to disagree with in the paper. The main assertion - that a bolted two piece caliper will be more rigid than a similarly shaped monobloc - is well grounded in first-principles of structural mechanics and is not a matter of opinion.
 
It's all about designing for a finished system. You can have well-engineered monoblock calipers and 2 piece calipers... or you can have poorly executed versions of both.

At some point, its also worth noting that the difference in caliper stiffness may be negligible if you are not taking into account the mounting stiffness to the spindle.
 
I was wondering the same thing. When i think monoblock i envision holes bored all the way through with screw in plugs or something.
 
Ok, i read the thing. Although it starts by talking about C-shaped (floating) calipers, the whole archaic thing is about the newfangled cnc-manufactured billet 1-piece 4-piston calipers being unnecessary for a firm pedal, compared with 2-piece (when properly designed).
 
Harlard said:
Just to be clear, you are referring to 2-piece calipers as fixed, multi-piston calipers and not sliding/floating ones, correct?
Click to expand...


Yes fixed calipers, not the sliding type.


What I got from the article is that no matter the design of the monoblock, the aluminum itself will always be the weak point, hence the testing numbers.
 
For a given side profile and caliper size, a 2-piece caliper should be stiffer than a monoblock caliper.
Even more so when the caliper is hot, as the stiffness of aluminum (Young’s modulus) varies drastically with temperature. That’s where a 2-piece with a bridge support shines, or a properly designed monoblock :)

As Ben mentioned, caliper mounting is very critical. Just because something is a radial mount, doesn’t mean it’s better. Just because something is a axial mount, doesn’t mean it’s inferior.
 
You know whats even stiffer than everything mentioned in the above article?

Factory 240 Girling calipers. You don't get much stiffer than 2 piece bolted iron.
 
blkaplan said:
You know whats even stiffer than everything mentioned in the above article?

Factory 240 Girling calipers. You don't get much stiffer than 2 piece bolted iron.
Click to expand...

"Opposed piston calipers made from cast iron, in which we have little if any interest here, have
always been two-piece assemblies. The material itself is stiff enough that, always assuming a
basically competent mechanical design, caliper flex is usually not a problem."

It was alluded
 
Quick, someone calculate the total unsprung weight per front corner, with the percentage of change when going from the factory caliper to an RX7, etc. caliper.
 
Why is nobody talking about thermal interface material? IMO the biggest advantage of a monobloc caliper is the unimpeded heat flow through the body of the caliper, allowing better utilisation of the caliper's total thermal mass during a braking event. If you just bolt two pieces of Al together you have a substantial thermal barrier at the joint face...

:roll:
 
DrZiplok said:
Why is nobody talking about thermal interface material? IMO the biggest advantage of a monobloc caliper is the unimpeded heat flow through the body of the caliper, allowing better utilisation of the caliper's total thermal mass during a braking event. If you just bolt two pieces of Al together you have a substantial thermal barrier at the joint face...

:roll:
Click to expand...

The majority of the heat rejection from a standard caliper is through radiation and convection.

While conductive heat transfer is still a part of the picture, it is a smaller part. Think about the conductive heat flow path of a caliper. The conductive heat transfer has to be removed through the bolted interface of the caliper to the adapter. This area is probably 10-25% of the area at the caliper halves. This then goes into the knuckle through another bolted joint of similar area.

Thermal contact resistance of the split halves ads very little to the total picture of heat transfer/cooling of the caliper.
If you really care about the contact resistance, smear a thin layer of heatsink past on all the interfaces...

But that's just my opinion...
 
The xc70/xc90 calipers I have use a split design to enclose the seal and piston in aluminium. Presumably this also helps cooling.
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