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What's with the two calipers on each rear wheel?

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34K views 11 replies 7 participants last post by  MacGeek  
#1 ·
Assuming the second caliper is for the e-brake system, but why? It's a bit confusing to me for a few reasons:

1) why can't it be incorporated like almost every other car?

2) am I the only one that thinks it looks "clunky?"

3) if the engineers are so weight conscious, why add seemingly unnecessary weight where it hurts most (un-sprung weight)?

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Does it just have to do with carbon ceramic brakes? Is it because there is going to be an electronic parking brake? I'm sure other manufacturers have managed to do all of this with one caliper per wheel.

So what gives?
 
#2 ·
yes its the e parking brake caliper. Supercars have always used a two caliper system as do motorcycles with E-parking brakes. Some of the cars we've seen with electronic parking brakes hide the second caliper because they use a drum/disc setup... its also possible we just notice it as often because were not always looking for it...
 
#5 ·
off the top of my head I would imagine that the difference could be that the e-brake is no longer mechanical, therefore isn't compatible with hydraulic brakes. I'm not sure, but my thinking is that the electronic e brake is essentialy brake by wire... the comand is sent to module, which then executes...

Other then that I've got nothing ahaha
 
#7 ·
No...

This has nothing to do with weight saving, nor are we looking at a NEW type of brake. Its a simple rear wheel disc featuring an electronic parking brake. For the most part ANYTHING using a purely electrical parking brake will have a second caliper. just like once upon a time a mechanical cable used to run back there for when you pulled the handle up, now there just needs to be a second caliper for when you press that parking brake button... it cant rely on hydraulic pressure like your car does when you're braking it, nor can it rely on the simple mechanical cable...
 
#11 ·
There must be some benefit worthy of the unsprung weight increase.
 
owns 2020 Alfa Romeo Giulia Ti Sport AWD
#12 ·
It's simply a technical requirement.

If you have a single piston floating caliper, it's easy to integrate the parking brake. You add helical grooves so that when you rotate the piston it also moves axially, and rotate the piston by pulling on a lever with a steel cable, or by integrating an electric motor in the caliper.

If you have a multiple piston fixed caliper, that is no longer feasible. Which means you have to add a separate braking mechanism, either a drum-in-hat or an additional single piston caliper.