993 brake upgrade for Carrera - questions

[polizei]

I need to replace my existing rotors/pads on my 911, and I have been considering turbocharging in a couple of years. In anticipation of turbocharging (light boost in the .5 bar range - nothing crazy), I would like to get some more powerful brakes on my car. Does anyone think the 993 TT brakes would provide a material advantage over the 993 brakes? I drive predominantly on the street, but I plan on some occassional track time.

I know the standard advice from you brake geeks is that the Carrera brakes are more than enough for the average user, but in turbocharging the car, I presume more braking capability is advised. Please set me straight if i'm misled! Thanks!

[polizei]

Noah, even though the 930 came with upgraded brakes you don't think I would need an upgrade if I turbocharged my Carrera?

[IROC]

Like Noah says, it all depends on the usage. You're still going to be stopping the same car (weight, etc) with the same tires. After all, if you can lock up the tires now, your brakes are "powerful" enough - then it just comes down to heat capacity. Carrera brakes work really well, in actuality. Unless you're going to making repeated hard stops from high speed, I bet the stock brakes are fine.

I use Carrera brakes on my '76 with a 250 hp 3.2 and they work fine - even on the track...

[polizei]

Fair enough - thanks for the advice!

[Fishey]

I just want to say I really have a problem of people looking for advice on the internet for things like this without giving all important details.

1. What Brakes you running now? and what are the details? Calipers (front and Rear)? Bias setup? Booster? Master cylinder? ABS or NO? What controller? Pad compound? Rotor type?
2. What do you want to switch too? just saying 993TT brakes really doesn't give any information.
3. Whats done to the car? What tire setup?
4. What is the general use of the car?

Without this information not a single person can give good information to you. Just like every other part of the car you should have a good understanding and plan for your cars next upgrades or changes. Otherwise you will end up like 90% of the porsches I get to see (aka, Botched)

P.S. To add what noah said the larger brakes can have advantages and disadvantages (even on the track) so its important to understand what you are doing. Just an example of this is that larger rotors also act like a longer wrench where less force is needed to move (on in this case) stop the center hub. This also can be a drawback as unsprung weight is increased as well as this distance increase means any deflection of the hub is increased as go further from the hub center and can result in a pad knock back situation.

[Lukesportsman]

Wow, Fishey, you must feel strong about this. Your 3rd post in nearly 5 years. Have you been gone for most this time or have you been lurking quietly all these years?

Just the same, good recommendations in that there aren't generic silver bullet mod's.

[Fishey]

No, I just make my rounds from community to community of car forums. I just happened to be browsing on pelican today as I was looking into some very interesting information for my own knowledge. I usually post on rennlist but even now I rarely post there.

[Bill Verburg]

Originally posted by polizei
Does anyone think the 993 TT brakes would provide a material advantage over the 993 brakes? I drive predominantly on the street, but I plan on some occassional track time.

Yes, they certainly do provide a signnificant advantage. The question is do you need them and what else needs to be changed to take full advantage.

You stock brakes are fine on the street, but inadequate for track use. This is because while brake torque is adequate thermal performance is not.

I usually urge '78-89 930 size rotors w/ what ever calipers you can get at a reasonable cost. '78-89 930, 964, 965 and 993 are usually available. These setups will be fine for any use street or track that 99% of all users will ever need. You do want to upgrade wheels and tires to take full advantage of them.

The 993tt is almost as much an improvement over 993 as 930 are over regular 911. They are way overkill for a 911 but do provide much greater brake torque and rotor temperature reduction at a small cost in weight. Some of the faster 930s can take full advantage of them but everyone benfits from reduced maintainance costs due to lower operating temps.

[Bill Verburg]

Originally posted by Fishey
I just want to say I really have a problem of people looking for advice on the internet for things like this without giving all important details.

1. What Brakes you running now? and what are the details? Calipers (front and Rear)? Bias setup? Booster? Master cylinder? ABS or NO? What controller? Pad compound? Rotor type?
2. What do you want to switch too? just saying 993TT brakes really doesn't give any information.
3. Whats done to the car? What tire setup?
4. What is the general use of the car?

Without this information not a single person can give good information to you. Just like every other part of the car you should have a good understanding and plan for your cars next upgrades or changes. Otherwise you will end up like 90% of the porsches I get to see (aka, Botched)

While I generally agree w/ what you are saying, I disagree in this particular case, it is clear that polizei has an '87 Carrera w/ stock brakes, the properties of which are well defined. He clearly stated his plans for the car and asked a specific question as to the comparison of 2 other well defined brake systems used on these cars.

[Fishey]

If thats the case then its a botch job without a doubt.

Here is why.
see
1. The 993 TT brakes are too big for his master cylinder due to increased volume consumtion this means pedal threshold is effected.
2. The 993 TT brakes fluid requirements also require a change in bias. Since its volume isn't similar to the factory fronts (its alot more) what happens is that you get less pad movement vs pedal throw. This bias is somewhat offset by the increased "bite" of the pad. However, The difference is to great and your back brakes will end up taking over more brake duty in normal driving conditions. On the flip side of that when you do "slam the pedal" in an emergency stop or under hard track braking your fronts while lagging behind the rears still pre-maturely lockup. This is because they do when pushed have far more bite.
3. The ABS system will suffer as the stock ABS pump is again not made to handle that volume of fluid. This means your ABS performance is degraded.
4. The design of the 1987 hub wasn't designed for use with a 13" rotor and 17" wheels. This can cause pre-mature wheel bearing failure as well as knockback
5. There are better solutions for 1/10th the cost.

[Bill Verburg]

Originally posted by Fishey
If thats the case then its a botch job without a doubt.

Here is why.
see
1. The 993 TT brakes are too big for his master cylinder due to increased volume consumtion this means pedal threshold is effected.
2. The 993 TT brakes fluid requirements also require a change in bias. Since its volume isn't similar to the factory fronts (its alot more) what happens is that you get less pad movement vs pedal throw. This bias is somewhat offset by the increased "bite" of the pad. However, The difference is to great and your back brakes will end up taking over more brake duty in normal driving conditions. On the flip side of that when you do "slam the pedal" in an emergency stop or under hard track braking your fronts while lagging behind the rears still pre-maturely lockup. This is because they do when pushed have far more bite.
3. The ABS system will suffer as the stock ABS pump is again not made to handle that volume of fluid. This means your ABS performance is degraded.
4. The design of the 1987 hub wasn't designed for use with a 13" rotor and 17" wheels. This can cause pre-mature wheel bearing failure as well as knockback
5. There are better solutions for 1/10th the cost.

1. )true, a 23.8mm m/c is needed for either 993 or 993tt or 993RS, I have no idea what you mean by "pedal threshold ", but the ratio of slave to master ratios is important for the feel of the pedal. The lower this # is the higher, harder w/ less travel a pedal has, this is good up to the point that the drivers leg can no longer supply the necessary input force. 23.8 to 25.4 mm is the correct size for 993 or 993tt or 993RS brakes

2.)Not true at all, the fluid requirements of the 993 tt fronts are exactly the same as 993 because they have exactly the same pistons. The fluid requirements of the 993tt in the back are less than for 993 because the 993tt pistons in the back are smaller than 993. 993RS rears are bigger but that still doesn't change the m/c requirements for either from 23.8 -25.4mm

3.) wrong again, an '87 Carrera doesn't have ABS, on a 993 the exact same brain and ABS pump are used for all 2wd w/ ABD a different brain is used for AWD versions

4.)not that I or a 1000 other users have seen or experienced

5.) name one?

[Fishey]

Originally posted by Bill Verburg
1. )true, a 23.8mm m/c is needed for either 993 or 993tt or 993RS, I have no idea what you mean by "pedal threshold ", but the ratio of slave to master ratios is important for the feel of the pedal. The lower this # is the higher, harder w/ less travel a pedal has, this is good up to the point that the drivers leg can no longer supply the necessary input force. 23.8 to 25.4 mm is the correct size for 993 or 993tt or 993RS brakes

2.)Not true at all, the fluid requirements of the 993 tt fronts are exactly the same as 993 because they have exactly the same pistons. The fluid requirements of the 993tt in the back are less than for 993 because the 993tt pistons in the back are smaller than 993. 993RS rears are bigger but that still doesn't change the m/c requirements for either from 23.8 -25.4mm

3.) wrong again, an '87 Carrera doesn't have ABS, on a 993 the exact same brain and ABS pump are used for all 2wd w/ ABD a different brain is used for AWD versions

4.)not that I or a 1000 other users have seen or experienced

5.) name one?

1. So The ratio of the master to the slave huh?

So you think changing the volume of the "Slave" would be pretty important in that equation? I mean say I have (made up numbers) 80 cc volume and spit it between 4 "slaves" of the same volume say 10cc. I get 1 full movement in each slave for ever 1/2 movement of the Master cylinder. So now lets change the "slaves" Now I have that same 80cc of volume and split it between two 20mm slaves and two 10mm slaves. So now we must use more then that same 40cc (since the total is now 60cc) aka we get a lower pedal under full braking. (continued below)

2. It is true as 1987 calipers are not anywhere near the same fluid requirements as any 993 brake.

(continuation from before)
So, now that we have learned that we have changed "slaves" we get a different volume total (60cc vs 40cc) or 1.5x the volume. However, since there is no bias change and everything still works off the same open system giving 1/4 flow to each of the 4 cylinders we quickly learn that that same 1/2 movement of the master nets the same 1 full movement in the 10cc chambers and now 1/2 movement in the 20cc chambers. (FANTASTIC)

3. Funny, I always forget the 911 was very late to add ABS (1987 was standard ABS on the 944)

4. Most people think there brakes are "fading" and have no idea what is going on. So I say your point is not valid..

5. Hah... I don't give away my info.

[polizei]

Originally posted by Bill Verburg
Yes, they certainly do provide a signnificant advantage. The question is do you need them and what else needs to be changed to take full advantage.

You stock brakes are fine on the street, but inadequate for track use. This is because while brake torque is adequate thermal performance is not.

I usually urge '78-89 930 size rotors w/ what ever calipers you can get at a reasonable cost. '78-89 930, 964, 965 and 993 are usually available. These setups will be fine for any use street or track that 99% of all users will ever need. You do want to upgrade wheels and tires to take full advantage of them.

The 993tt is almost as much an improvement over 993 as 930 are over regular 911. They are way overkill for a 911 but do provide much greater brake torque and rotor temperature reduction at a small cost in weight. Some of the faster 930s can take full advantage of them but everyone benfits from reduced maintainance costs due to lower operating temps.

Thanks for the helpful reply Bill. I do have 17" cup wheels (7.5's in the front and 9's in the rear) to handle the bigger brake setups, but from what I'm gathering from you and other advisers, if I'm not tracking it but 1 or 2 times a year, the stock brakes are fine (regardless of turbocharging). I've got to decide on a street pad now... Thanks!

[efhughes3]

Originally posted by Fishey
1. So The ratio of the master to the slave huh?

So you think changing the volume of the "Slave" would be pretty important in that equation? I mean say I have (made up numbers) 80 cc volume and spit it between 4 "slaves" of the same volume say 10cc. I get 1 full movement in each slave for ever 1/2 movement of the Master cylinder. So now lets change the "slaves" Now I have that same 80cc of volume and split it between two 20mm slaves and two 10mm slaves. So now we must use more then that same 40cc (since the total is now 60cc) aka we get a lower pedal under full braking. (continued below)

2. It is true as 1987 calipers are not anywhere near the same fluid requirements as any 993 brake.

(continuation from before)
So, now that we have learned that we have changed "slaves" we get a different volume total (60cc vs 40cc) or 1.5x the volume. However, since there is no bias change and everything still works off the same open system we quickly learn that that same 1/2 movement of the master nets us 2/3 movement in the 10cc chambers and 1/3 movement in the 20cc chambers. (FANTASTIC)

3. Funny, I always forget the 911 was very late to add ABS (1987 was standard ABS on the 944)

4. Most people think there brakes are "fading" and have no idea what is going on. So I say your point is not valid..

5. Hah... I don't give away my info.

Dude, you picked the wrong forum and the wrong person (Bill V)to pick a fight with about 911 brakes.

FWIW, the change to 4 piston calipers is a pretty popular one on pre-89 911's and with the exception of having to adapt the calipers to the old mounts, fabricating new hard lines and the update to the 23.8mm M/C (and removal of PV), it's a no brainer for those of us who track regularly. As Bill said, he and many, many others (myself included) have made the change with no ill effects.

The 911 i(nor any P-car) s not a marginally built car, but with its power and handling, allows a good driver to work the stock brakes pretty damn hard. Having this upgrade makes for a more enjoyable track weekend without worrying about "cooked" brake fluid and the resultant problems.

[Fishey]

Originally posted by efhughes3
Dude, you picked the wrong forum and the wrong person (Bill V)to pick a fight with about 911 brakes.

FWIW, the change to 4 piston calipers is a pretty popular one on pre-89 911's and with the exception of having to adapt the calipers to the old mounts, fabricating new hard lines and the update to the 23.8mm M/C (and removal of PV), it's a no brainer for those of us who track regularly. As Bill said, he and many, many others (myself included) have made the change with no ill effects.

The 911 i(nor any P-car) s not a marginally built car, but with its power and handling, allows a good driver to work the stock brakes pretty damn hard. Having this upgrade makes for a more enjoyable track weekend without worrying about "cooked" brake fluid and the resultant problems.

My math was off before for some reason I wasn't thinking strait and edited my post about the volume. Also, just because something is "popular" doesn't mean its right or in any way correct.

[Wil Ferch]

Fishey:

As others here have said..do your homework as to who ( and what topic) you wish to pick bones about. Bill V has a wealth of experience and sound judgment backing up is replies. You're not dealing with a rookie...at least not as far as brakes or wheels are concerned. If you study the history of various people's responses, you'll soon find out some of us have carved out some unique and specific niches. Bills "thing" is brakes and tires/wheels ( among a few other things).

Bill V = brakes.....with enough empirial evidence to prove him right almost all the time.

Best,
- Wil

[JeremyD]

Originally posted by Fishey
My math was off before for some reason I wasn't thinking strait and edited my post about the volume. Also, just because something is "popular" doesn't mean its right or in any way correct.

No - you are right - but it can mean that others have paved the way - and issues along the way have been documented, troubleshot, and resolved.

BTW - Where I spent the most time and money in the brake dept was when I didn't take Bill's advice.

[Fishey]

I just want to know are we talking full 993 setup or just the front brakes? If its the full setup I agree with Bill but if its just front brakes then I don't agree with him. Again like I said in my original post more information would be helpful.

-Fishey

[efhughes3]

Originally posted by Fishey
I just want to know are we talking full 993 setup or just the front brakes? If its the full setup I agree with Bill but if its just front brakes then I don't agree with him. Again like I said in my original post more information would be helpful.

-Fishey

I know of nobody that has done just the fronts.....the 993 or 930 caliper conversion is a 4 caliper deal. This is pretty much implied when having the discussion on brake upgrades on our 911's.