Carrera brake rotor advice, please...

[Joe Bob]

I am up grading my SC to Boxster brake calipers and the larger Carrera rotors.

I have been a Zimmermann cross drilled rotor user for many years. But I see a new rotor made by Sebro listed on the Pelican site. I don't know anyone that has used them.

Are the Sebro worth the extra money?

My current and future use is an occasional DE or AX and spirited weekend driving.....

[Bill Verburg]

Originally Posted by Joe Bob

I am up grading my SC to Boxster brake calipers and the larger Carrera rotors.

I have been a Zimmermann cross drilled rotor user for many years. But I see a new rotor made by Sebro listed on the Pelican site. I don't know anyone that has used them.

Are the Sebro worth the extra money?

My current and future use is an occasional DE or AX and spirited weekend driving.....

The only part that's an upgrade is the 24mm front rotors, either Zimmerman or Sebro are going to be fine, I'd avoid drilled ones for any track use.

as for changing the calipers you are opening a can of worms by just doing the fronts and in addition adding to front heat issues while at the same time degrading bias

[trond]

just did the 'upgrade', including going to carrera rear calipers and larger turbo master cylinder that just happened to be on my shelf. So far after 1000 miles I can say I like it for the street and will not go back to stock anytime soon. May not be an improvement as the stock setup was more than capable of locking up wheels and also lighter, but I still like the Boxter setup better. With the right pads I had as good or even better brakes with stock SC setup but I gave up finding pads after I used up the ones I really liked. Could be I had other issued but very happy with current setup. Car will not be tracked so no heat issues now or before. If you have the parts then why not except added weight

[Bill Verburg]

Originally Posted by trond

just did the 'upgrade', including going to carrera rear calipers and larger turbo master cylinder that just happened to be on my shelf. So far after 1000 miles I can say I like it for the street and will not go back to stock anytime soon. May not be an improvement as the stock setup was more than capable of locking up wheels and also lighter, but I still like the Boxter setup better. With the right pads I had as good or even better brakes with stock SC setup but I gave up finding pads after I used up the ones I really liked. Could be I had other issued but very happy with current setup. Car will not be tracked so no heat issues now or before. If you have the parts then why not except added weight

At least you did the back and m/c so it's not totally messed up

you have increased front bias, it's not terrible, especially for street use, but also not as good as oe SC

The best thing is the improved pedal you now have

[911tracker85]

I had done the boxster front calipers on my 85 911 when using it for DE.

but the pedal travel was too muck so I also did the turbo MC. I also replaced the stock rear bias valve with an adjustable and added cooling ducts to the front.

after some track time found I could completely open the rear bias valve and not get rear lockup. felt pretty balanced to me. I ran pagid yellow for track, and they have decent bite for the street. running them on my 951 DE car. retired the 911 from the track and reverted to the carerra front calipers and original MC.

this setup worked well for me. especially after I learned proper braking technique for the track.

PS. I am pretty sure I have a couple sets of partially used pads for this setup. just laying on the shelf so PM me if interested and I'll let you know what I have.

[911tracker85]

and as noted, used slotted rotors for track, I will not use drilled for track.

[juanbenae]

easiest to simply go with the front Carrera caliper and wider 24mm rotors and stock SC rears. I had this set up with front cooling on my spec racer and now on my 75S and never have had any brake issues. I guess the boxster calipers look cool, but as mr verburg suggests they are a can of worms for very little gain.

[Bill Verburg]

Originally Posted by juanbenae

easiest to simply go with the front Carrera caliper and wider 24mm rotors and stock SC rears. I had this set up with front cooling on my spec racer and now on my 75S and never have had any brake issues. I guess the boxster calipers look cool, but as mr verburg suggests they are a can of worms for very little gain.

Exactly!!

[Bill Verburg]

Originally Posted by 911tracker85

I had done the boxster front calipers on my 85 911 when using it for DE.

but the pedal travel was too muck so I also did the turbo MC. I also replaced the stock rear bias valve with an adjustable and added cooling ducts to the front.

after some track time found I could completely open the rear bias valve and not get rear lockup. felt pretty balanced to me. I ran pagid yellow for track, and they have decent bite for the street. running them on my 951 DE car. retired the 911 from the track and reverted to the carerra front calipers and original MC.

this setup worked well for me. especially after I learned proper braking technique for the track.

PS. I am pretty sure I have a couple sets of partially used pads for this setup. just laying on the shelf so PM me if interested and I'll let you know what I have.

Don't confuse working w/ OK, w/ best

The issues, in no particular order
Bias
Stock brake torque bias on a 911 through 1983 @1.491 is very good for both street and track use, you do tend to replace fronts more often than rears in street use, not so much for track use. Bias goes to 1.220/2.26 in 1984 thru 1989 and a p/v was added to alleviate too much rear bias at high line pressures. Change the front to Boxster and leave the rear alone(but do remove the p/v) bias goes back to a more normal and useable 1.554. This 1.554, while ok, still leaves a lot on the table compared to 1.491(even this leaves some performance on the table compared to an optimised system), Do the same on an SC w/o changing the rears and you get 1.889(too much front). Brake bias affects where heat goes(later for that) and also stopping rate. The more that grip can be spread the faster the car will stop. Again there are limits, ~1.426 is close to the limit for most 911s, there are things that can be done to use more rear but they are all track oriented and make for a less desirable street car. Late Porsche RSR run driver adjustable bias in the range from 1.875 to 1.260

Pedal
Boosted SC brakes have a reasonably stiff pedal w/o too much bias. The pedal ratio is 35.328. I lower # is desirable for track and performance use down to ~29+/- and a higher # for less vigorous drivers or less boost. Thru '76 the ratio was 41.3. Too high(~45+/-) and the brakes turn to mush because the m/c can no longer service the slaves wt volume. When adding calipers w/ larger pistons the pedal ratio goes up, possibly too far up depending on exactly what calipers are used. A 23.8mm 930 m/c is desirable and usually necessary when using calipers w/ bigger pistons.

Heat
The only real weak spot wrt to SC and earlier brakes is that w/ track use more heat can be put into them than they can efficiently process and reject. The result is excessive rotor/pad/fluid temperatures, particularly in front. This is why more usable rear bias is desirable. Some heat is now processed by the understressed rears rather than the over stressed fronts.

It is also why any increase in front brake torque adds to the front heat issue.

Things that alleviate the heat issue
reduce weight
add brake cooling
use track pads
use higher temp brake fluid
use bigger rotors
use effective aero

[gtc]

I've used zimmerman, sebro, and ate rotors on my Carrera. I haven't noticed any functional difference between them.

[Sboxin]

Originally Posted by Joe Bob

I am up grading my SC to Boxster brake calipers and the larger Carrera rotors.

I have been a Zimmermann cross drilled rotor user for many years. But I see a new rotor made by Sebro listed on the Pelican site. I don't know anyone that has used them.

Are the Sebro worth the extra money?

My current and future use is an occasional DE or AX and spirited weekend driving.....

Yes, we have Sebro slotted rotors on the rear of the 911 race car and they work
fine . . . and we use Pagid Black pads on the rear with stock SC calipers . . . fronts are
also slotted rotors from Stop Tech and Raybestos race pads in stock calipers . . . 78
911SC power brakes and huge Hoosier tires stops just fine and need to be a little
careful when tires are cold to not lock up the brakes . . . 10 years racing and
car/driver-son does very well with this brake set up . . . its the pads that make all
the difference . . . and the driver technique also . . .


Regards,

[911tracker85]

Don't confuse working w/ OK, w/ best

I did not mean doing this is a big improvement or the 'the best'.

just sharing my experience, back when I believed the snake-oil adds.

I have learned much since then.

doing proper 930 calipers on my 930 conversion.

rebuilt the calipers on my 951, use pagid yellow, and motul. along with 3" cooling ducts. what really helped braking at threshold on the track was a complete suspension upgrade. the old stock suspension allowed for way to much forward weight transfer. now I can brake hard with more confidence. and having learned proper braking technique for the track this is working very well for me. but understand you do not want to do this on the street or you'll get rear-ended in short order.

speaking of overkill, one guy is putting 996tt brakes all around on a SWB 912 based project. why? because they are 'cool'.....

good luck.

[Bill Verburg]

Originally Posted by 911tracker85

I did not mean doing this is a big improvement or the 'the best'.

just sharing my experience, back when I believed the snake-oil adds.

I have learned much since then.

doing proper 930 calipers on my 930 conversion.

rebuilt the calipers on my 951, use pagid yellow, and motul. along with 3" cooling ducts. what really helped braking at threshold on the track was a complete suspension upgrade. the old stock suspension allowed for way to much forward weight transfer. now I can brake hard with more confidence. and having learned proper braking technique for the track this is working very well for me. but understand you do not want to do this on the street or you'll get rear-ended in short order.

speaking of overkill, one guy is putting 996tt brakes all around on a SWB 912 based project. why? because they are 'cool'.....

good luck.

996tt is among the worst possible brake setups that could be put on a 911
they are heavy using 350x34mm rotors front and 330x28mm rotors rear
they have way too much front torque bias @2.072

993tt is another poor choice for similar reasons

[Bob Kontak]

Originally Posted by Joe Bob

I am up grading my SC to Boxster brake calipers and the larger Carrera rotors.

I did mine a long time ago. Bill V said exactly the same to me then that he is saying now. He's consistent.

Only thing I will add is I bought them as an upgrade "kit". The kit came with factory calipers but they were plumbed for a Boxster. If you don't flip the plumbing and orient them with the bleeder up the pistons are backwards on your rotors. The little piston is the lead piston and the pads will squeal.

Make sure the fat piston leads and little trails. (EDIT: See below - little leads and big trails for the 911)

[Bill Verburg]

Originally Posted by Bob Kontak

....
Make sure the fat piston leads and little trails.

Absolutely wrong

[Bob Kontak]

Originally Posted by Bill Verburg

Absolutely wrong

Reverse? Hey, I am getting old.

Since I opened my mouth, I'll pull them to see. Cripes. Maybe I have them on backwards? It sure did stop the squealing.

[juanbenae]

Originally Posted by bill verburg

absolutely wrong

lol!

[Bob Kontak]

Originally Posted by juanbenae

lol!

Verburg does not waste words.

[Bob Kontak]

Ahem. I am slow but at least age is catching up with me.



Thanks Bill.

[trond]

i'll check mine tmrw. Did not even notice different sizes !