Any ideas on breaks ?

[CBODY67]

Disc brakes by their nature have a lot of drag at rest. The pistons don't retract. When going down the road the few thou of end play in the wheel bearings allow the rotor and hub to move enough to push them back and make clearance.

Kevin

The disc brake pistons do retract when pressure is released. If they didn't, they wouldn't release. What they do is not retract all of the way, on the earlier generations of disc brakes, always with a light drag against the rotor. This helps initial brake response and helps keep the rotors dry in damp weather. From about '81 on (on some models), the pistons would retract more for less drag against the rotor, but quicker apply functions.

Funny that we went from the earlier 4-piston calipers (same number as on the Corvettes for many years), to the simpler single-piston calipers, and now we're back to 4-6 piston calipers for better braking performance. The Corvette guys started to sleeve the piston bores so the durability issues of pitted piston bores were decreased. Progress?

CBODY67

 

[bajajoaquin]

...funny that we went from the earlier 4-piston calipers (same number as on the Corvettes for many years), to the simpler single-piston calipers, and now we're back to 4-6 piston calipers for better braking performance.

Two separate things here. The first is single-piston calipers versus 2+ pistons. In a single-piston caliper, the caliper slides as the single-side piston pushes the pad against the rotor. It's cheaper, but the sliding mechanism has friction, and they don't work as well. Having a piston on each side of the rotor has less friction, greater power and better modulation.

Bigger disks work by having both more mass to absorb heat and more leverage against the rotating wheel. The leverage is figured as the radius from the center of the hub to the center of the brake pad. Since pad swept area is generally set by master cylinder and slave cylinder area ratios, you can't just increase the swept area easily by changing the pads. However, you can take the same pad area, make it thinner but longer by using 4 or 6 pistons. This makes the radius to the center of the pad greater by half the measurement of the pad reduction.

If you want to maximize braking within a restriction of wheel size, one way to do it then is to add long, skinny brake pads pushed by lots of small pistons. There are trade-offs with caliper weight and rigidity, but that's a different discussion.

Just in case anyone was wondering why the move to different caliper types

 

[CBODY67]

Before the discussion of "clamping force" and such were operative, the issues with the 4-piston calipers was pitting of the caliper piston bores. A durability issue and an expensive one for Corvette customers (before the stainless steel sleeves for the piston bores were devised). The Corvette issues also seemed to fuel the advocacy of synthetic brake fluid, by observation.

The single-piston calipers were obviously a simpler way to apply force to the brake pads, in a time when braking demands were obviously less than they later came to be. One large piston in one large caliper bore. The key thing was that the later single-piston cars probably saw greater use and any accumulated moisture in the brake fluid was decreased. Plus the possible increased use of brake fluids that didn't as aggressively absorb moisture?

Granted, with the latest developments of skinnier brake pads and the need for efficient clamping force, the multi-piston caliper is the best way to do that.

The later SRT Challengers have something relating to "decreased kick-back of the caliper" in higher-performance use.

There are probably several different "conversations" about how brake caliper design has progressed since the first Corvette 4-wheel disc design of the middle 1960s or the 1966 Chrysler power disc brakes, OR the first automotive disc brakes Chrysler used in the middle 1950s.

Happy New Year!
CBODY67

 

[commando1]

Payton, you still with us?...

 

[68PK21 440.6bbl]

I love sea clams!

 

[Carmine]

 

[Ripinator]

Yes it pressed em back with a c clam

 

[70bigblockdodge]

I usually scrap them when they breaks in half.

 

[saylor]

kurtis blow - well played sir

 

[jct]

Payton, you still with us?...

did we run him off?!

 

[commando1]

Freshman hazing can be a *****.

 

[1978 NYB]

He'll be back.....