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Rear two piece rotors - Just for the weight saving?
Originally posted on Hellcat forum:For one piece rotor, the disc and hat are "casted" together with the same material (Cast Iron) after machined it's a finished product - like OEM so no concern on the rear drum brake because it has the same material as the disc.
A typical REAR one piece rotor with a DRUM brake. (Ford F150/Raptor)
However when it comes to making a "two piece rotor" for the rear like for Jeep SRT8 with a drum brake it's more challenging and tricky due to the hat must be made with a harder metal (Iron or Steel) in order to withstand the abrasiveness of the brake shoe like for one piece rotor, otherwise when a parking brake is applied, if you ever forget to release it before wheel is rolling, the brake shoe will "score" the aluminum drum hat and damage/ wear & enlarge the drum diameter then the brake shoe must be adjusted to fit the larger drum or the pedal travel distance will increase.
After a few more times the rotor hat wall material gets thinner eventually you rear rotor hat will be destroyed and you would lose the parking brake, not mention if you have to use it for emergency braking when driving!
This is why OE offers very few applications on rear for iron and for CCB rear stainless steel is used for for the rotor hats (eg. ZR1/Z28, PCCB). For aftermarket BBK (Brembo, AP, Stoptech) usually offers only front and very few on rear, or disclosing to "delete" the rear emergency/parking brake for installing their rear BBK. See the installation note on AP/Essex rear BBK for Supra MK5
RB developed a composite hat (aluminum shell + iron sleeve) and was first introduced in early 2000 for Camaro SS. The inner hat has an Iron liner - A true rear two piece rotor; light weight yet still retaining the functionality of OE emergency brake which is also a popular replacement to OE's stainless steel hat (can save 4 lbs/ea) for ZR1/Z28 OE CCM rear rotors.
If you don't disagree that safety is of the prime concern you should inquire the supplier if their rear two piece rotors are made for parking/emergency brake "functionality", not just to fit the brake shoe, before you buy and what they have sold you, otherwise you are better off to stay with OE or aftermarket one piece rotor.
What's your current rotor size and the oversize you are looking for.
My current rotor sizes are 317 mm front and 298 mm rear. In terms of oversizing, I guess it depends on what your offerings are. I'm not looking for too much oversizing as I'm mainly interested in weight saving. If I have to put a number on it, I'd say 325 mm front and rear.
I have Girodisc rotors front and rear rotors on my base 997.1 C2. They bump the front diameter from 317mm to 340mm, and rear from 298mm to 325mm. 0 pad overhang, 0 issues. However, since these increased in diameter I did not save weight. The fronts were within half a pound each, the rears were about a pound heavier each. They seem to pop up on the marketplace from time to time for a good discount (that's where I got mine). Interesting thoughts on aluminum hats vs cast iron.
02-11-2021, 11:44 AM
Rear two piece rotors - Just for the weight saving?
