Brake caliper and rotor options

[JohnJL]

Hi,
I need rotors for an autocross car I am building from multiple previous car leftovers. The car will see autocross and track time so no drilled or alu rotors.

My question is focused on selecting the right rotors. I would greatly appreciate if someone could confirm what I have and fitment options on the rear rotors.

Here is a pic of the calipers I have, they are off a RoW 1981 SC and I believe they are known as "narrow A" fronts and "M" rears.







Yes, I painted them way back when...the rears are marked "81" and the fronts "289"


Our host has these slotted fronts:

477-405-083-D-M895


That seems pretty straightforward...fitment shows clearly for my struts which are 1978 SC owers (tops are Hitbits.)

Where I am not sure is the rears. Checking with Anderson's book and looking at my 1985 cab, it looks to me like the rear calipers on the SC and the Carreras were both "M". Yet our host lists a slotted rotor for the Carrera and no slotted rotor for the SC.

Here is the rear slotted rotor our host shows for the Carrera:

911-352-041-08-M895



Perhaps the offsets or something else changed? I would like a slotted rotor in the rear. I am not running an e-brake so if thats the difference then I'd like to know.

Can those above be run in the rear of an SC on M calipers?

Thanks

[Bill Verburg]

Originally Posted by JohnJL

Hi,
I need rotors for an autocross car I am building from multiple previous car leftovers. The car will see autocross and track time so no drilled or alu rotors.

My question is focused on selecting the right rotors. I would greatly appreciate if someone could confirm what I have and fitment options on the rear rotors.

Here is a pic of the calipers I have, they are off a RoW 1981 SC and I believe they are known as "narrow A" fronts and "M" rears.







Yes, I painted them way back when...the rears are marked "81" and the fronts "289"


Our host has these slotted fronts:

477-405-083-D-M895


That seems pretty straightforward...fitment shows clearly for my struts which are 1978 SC owers (tops are Hitbits.)

Where I am not sure is the rears. Checking with Anderson's book and looking at my 1985 cab, it looks to me like the rear calipers on the SC and the Carreras were both "M". Yet our host lists a slotted rotor for the Carrera and no slotted rotor for the SC.

Here is the rear slotted rotor our host shows for the Carrera:

911-352-041-08-M895



Perhaps the offsets or something else changed? I would like a slotted rotor in the rear. I am not running an e-brake so if thats the difference then I'd like to know.

Can those above be run in the rear of an SC on M calipers?

Thanks

The SC's used 20mm rotors and the 3.2 Carrera used 24mm rotors

the fronts have the same pistons

the SCrears and and 3.2 Carrera rears are both M but the 3.2 C has a thicker spacer in the middle and larger 42mm pistons than the SC M 38mm pistons.

the 3.2 C has much more rear bias as a result and so comes oe w/ a 33bar p/v on the rear circuit.

[JohnJL]

Hi Bill,
So glad you answered.

I believe I am OK with the the Host's front rotors, which is what I meant by "narrow A."

Your post mentions a spacer in the back calipers (which the front A "Wides" also have) is that correct? Do you happen to know if a Carrera rear rotor will fit in an SC rear M caliper?

Thanks

[JohnJL]

Also good point about the brake balance. I have a dual-master setup with balance bar so I have some adjustability on the fly and can change out masters to compensate if needed...

[Bill Verburg]

Originally Posted by JohnJL

Hi Bill,
So glad you answered.

I believe I am OK with the the Host's front rotors, which is what I meant by "narrow A."

Your post mentions a spacer in the back calipers (which the front A "Wides" also have) is that correct? Do you happen to know if a Carrera rear rotor will fit in an SC rear M caliper?

Thanks

All of the 3.2 Carrera calipers use a spacer that is 4mm thicker than the spacer in the middle of the SC A & M calipers to accommodate the 4mm thicker rotors.

the calipers are matched to the rotors so though a wide M will bolt to an SC it it must have the matching 24mm rotor and vice versa.

w/ a twin master setup you can dial in what ever bias you want to use.

normally w/ regular A or wide A's in front and M rears you will have great bias.

w A or wide A front and wide A rear you will have lots of rear bias and a softer pedal. twin m/c cures both issues.

[JohnJL]

Thanks Bill. So it looks like i the host has slotted front rotors for the narrow A calipet but only solids or drilled for the rears...

Dave, Wayne or another Pelical on Payroll have a view? Thabks guys.

[unclebilly]

You will be fine with the stock rotors and calipers. Put in a real racing fluid such as Brembo LCF600 or endless (ATE superblue is not racing fluid), and decent race pads such as Pagid yellow or Porterfield sprint pads.

[unclebilly]

Oh and this has been discussed one other time.

Bill V is the resident expert on what fits. I have lots of experience with endurance racing with the stock components.