The mother of all IB brake upgrades?

[Peter Bull]

I don't trust my brakes. Well there I said it. The brake pedal feels spongy. The car once had firm pedal, but it was lost many years ago. I've tried steel braided brake lines, and I've tried several different racing brake pads. No luck so far. When going into a 90 degree bend at 180 km/h I would prefer to trust my brakes blindly.

 

A couple of years back I bought almost all the parts necessary to run 993 RS and 964 turbo 2 calipers front and rear respectively. But I wimped out when I discovered how much of the front hubs I had to remove on the lathe for the discs to fit. I sold the parts to a friend and continued searching for the firm brake pedal.

 

Then one day I discovered that Instant-G had a kit for fitting 996 turbo brakes. Please bear in mind that I'm an engineer within the field of lightweight structures. I react to the combination of monoblock and calipers the same way Jeremy Clarkson's German engineer alter ego reacts to the combination of silicone and carbide. After drooling and shaking wildly for a while I forced myself to see that it was way over the top. But, I also found out that a kit for fitting 996 Carrera calipers was available. The shaking and drooling started again, and I just had to get that kit.

 

The kit consisted of front hubs with new wheel bearings, front and rear caliper adapters, and mounting hardware. A set of four reasonably worn 996 Carrera calipers was sourced from eBay, new discs from Type 911, an AP Racing adjustable proportioning valve from Raceparts and a set of Performance Friction PFC 01 from their Swedish agent.

 

I haven't called the kit a bolt on because it wasn't. Bolt on-ish, maybe. I'll try to describe what I had to do to make the parts fit. Dealing with Instant-G was pleasant enough, but it took a lot of time. A couple of deliveries were wrong, and getting the right parts took even more time.

 

Front axle

 

 

1. The front hubs came with studs, but they couldn't be used because they were too short.
   
2. When I first mounted the discs they didn't seat properly on the hubs; some flash left from the machining had to be removed with careful use of a file.
   
3. The offset on the adapters was wrong. I had to add 1 mm thick washers between the adapter and the strut in order for the calipers to center on the discs.
   
4. The dust caps on the new hubs had a larger diameter than the stock dust caps. Since I'm using spacers I had to do some creative machining of the spacers in order for them to fit over the new dust caps. The old dust caps didn't fit the new hubs, so using the old ones wasn't an option.
   
5. The 996 has trailing calipers, which means they had to be turned upside down to fit on my car. Swapping the cross over tube and bleed screws was quite simple.
   
6. New brake lines were required.
   

 

Rear axle

 

 

1. The caliper mounts on the banana arms had to be trimmed in order for the calipers to seat on the adapters.
   
2. The rear adapters didn't fit; a little bit of filing was required for them to fit onto the mounts. This hurt a little bit because they were nicely anodized.
   
3. Then trying to fit the brake pads I discovered that the adapters had the wrong offset. One millimeter had to be machined away from the adapter in order for the caliper to center on the brake discs.
   
4. The 996 has a different way of adjusting the hand brake; the hole in the discs required to reach the adjustment screw wasn't there. That was, however, easily solved by drilling an extra hole in the disc bells.
   
5. New brake lines were required.
   

 

So, was it the mother of all IB brake upgrades? It's too much snow here at the moment so its a little difficult to answer that question. The brakes do look the part, and considering the car they were meant for; they should work quite nicely.

 

/Peter

Edited September 21, 2010 by Peter Bull

[sladey]

Wow Peter - looks impressive - be interested to hear your thoughts on using them in anger

[Von Twinzig]

Nice job Peter. I think this set-up may rearrange your internal organs when you hit the stop pedal now. Will these fit behind a 17" rim?

[Phill]

Nice work. Makes the Boxster conversion look like a walk in the park.

[Al_W]

I wish I had the mechanical skills to do this sort of thing.

I look forward to hearing the test results too

[Peter Bull]

Will these fit behind a 17" rim?

 

Yes:

 

 

/Peter

[Richard Bernau]

So what are the sizes? Disc diameter and thickness? Caliper piston diameters? My guess is that theses are very close to 964 size brakes. I am also curious about your bias now. With ABS Porsche moved the bias frontwards - not a bad thing but you don't have ABS...

 

It does look like a lovely upgrade but the engineer in you will appreciate the quest for facts.

[Peter Bull]

You've got a point about the forward brake bias. What I did when I when I started to think about this upgrade was to analyze the standard brake bias and the brake bias with 996 brakes. Below is a slip diagram for both brake setups. According to this the rear brakes will lock up before the front brakes when braking at more than 0.7g with standard brakes. On the 996 setup the rear brakes will lock up first when braking at more than 1.2g.

 

 

The new front bias is larger than standard, but still worth investigating. A 997 Carrera S can brake at an average acceleration of 1.2g on Michelin Pilot Sport 2, so believing that I can reach similar values on warm Michelin Pilot Sport Cup is quite realistic. And I've had problems with the rears locking up on the stock setup, which has got a proportioning valve.

 

These are the vital statistics of the calipers, rotors, and pads:

 

Front caliper piston size 40 mm, 36 mm

Rear caliper piston size 30 mm, 28 mm

 

Rotor size front: 318 x 28 mm

Rotor size rear: 299 x 24 mm

 

Front pad radial height: 60 mm

Rear pad radial height: 48 mm

 

/Peter

Edited March 10, 2010 by Peter Bull

[Richard Bernau]

So this is almost exactly like the 964 brakes - small front Brembo calipers are 40/36 and rear calipers 30/28. Your front 996 rotor is 18mm bigger in diameter, so a little more torque on the front axle and hence moving the bias a little forward. Also a little more thermal mass in the bigger front rotor. I suspect the monoblock calipers are a touch lighter, maybe stiffer and certainly newer and maybe they don't have the aluminium vs steel slider corrosion problem that plagues all the little black and big red calipers.

 

I don't think you are showing the effect of the proportioning valve in your graph?

 

For reference there is a lot of info here - http://forums.pelicanparts.com/porsche-911...-questions.html

[Fred]

I understand this post as much as that thing below:

[puyney pete]

Silly question but have you uprated the tyres?

 

Could you lock the wheels when braking before the mods?

 

The problem with uprating the brakes is that all that extra ability just ends up locking the wheels with less sensitivity than your right foot can provide in my experience just changing to a higher spec brake pad makes more than enough difference unless full on racing is to be undertaken and the heat dissipation of a larger disc is welcome.

 

But what do I know

Edited March 31, 2010 by puyney pete

[GaryH]

The problem with uprating the brakes is that all that extra ability just ends up locking the wheels with less sensitivity than your left foot can provide in my experience just changing to a higher spec brake pad makes more than enough difference unless full on racing is to be undertaken and the heat dissipation of a larger disc is welcome.

 

But what do I know

Trackday usage is arguably a harsher heat dissipation test than racing, as most trackday sessions are 25/30 mins, much longer than most actual races. Combined with the fact that even on a sessioned or OPL trackday you may do 5 or six sessions as opposed to the few qualifying laps and couple of races on a typical race meeting.

 

The bigger Turbo MC can give more sensitivity when upgrading the brakes in this way.

[Richard Bernau]

Your average trackday car is usually heavier than a race car an often has a heavy passenger on board. With sticky tyres and a few suspension mods plu alignment a trackday car is not much slower than a race car and less expert braking creates greater thermal loads. As Gary says, heat management is the biggest problem not retardation. The other benefit not to be underestimated is that with better heat management and bigger pads, you double or even triple your pad life. Those of us using the 964 calipers now have a very widely used pad - its the "930" pad that is used in 930s, 964s, some 944Ts, 944S2s, 928s and 968s - which is relatively cheap and widely available.

 

Peter - what is pad availability and pricing like for 996 size pads?

[puyney pete]

The bigger Turbo MC can give more sensitivity when upgrading the brakes in this way.

 

Not sure about this, since "better" brakes will use less pedal force to elicit the same braking effect. Therefore you have less sensitivity. What you are saying is the brakes are more sensitive, which is a whole different kettle of fish.

Edited March 31, 2010 by puyney pete

[Richard Bernau]

Not sure about this, since "better" brakes will use less pedal force to elicit the same braking effect. Therefore you have less sensitivity. What you are saying is the brakes are more sensitive, which is a whole different kettle of fish.

 

Not that simple - an appropriate size MC is required to move sufficient fluid and up to a point bigger will give you a firmer, higher pedal with better ability to modulate and hence brake sensitively.

[GaryH]

Not that simple - an appropriate size MC is required to move sufficient fluid and up to a point bigger will give you a firmer, higher pedal with better ability to modulate and hence brake sensitively.

That was my understanding (probably gleaned from RB in the first place ) but I was waiting for this post to confirm my recollection.

[Peter Bull]

... they don't have the aluminium vs steel slider corrosion problem that plagues all the little black and big red calipers.

 

I don't think you are showing the effect of the proportioning valve in your graph?

 

There are four steel pins holding the pads in place in stead of the steel plates on the earlier calipers. You can see outer ends of the pins as depressions in the side of the calipers.

 

I haven't taken the effect of the proportioning valve into account. The graphs are used as a first guess on how to adjust the proportioning valve.

 

Peter - what is pad availability and pricing like for 996 size pads?

 

I got Performance Friction PFC01, which were quite easy to get, but rather expensive.

 

/Peter

[Peter Bull]

After the first season with the new brakes I am mostly positive to the update. On the negative side; the PFC 01 squeals like mad when driving in regular traffic. I haven't had the opportunity to run the car on a race track, but the brakes work great in auto cross and spirited street driving. They're easy to control, and I've had no problems with the fronts locking up too early.

 

/Peter

[Peter Bull]

It took quite some time to get some quality track time. But now its happened, and I thought I'd post a quick update on how the new brakes have worked. In case anybody wonders, or thinks about getting 996 brakes.

 

I've been at two tracks this season and had a couple of hours effective track time at each occasion. One track is quite curvy and somewhat demanding on the brakes. The other is a faster track with maybe three curves that require hard braking, but there is a good distance between them for cooling the brakes.

 

At the first track I did provoke the brakes seriously to see if they started to fade. They didn't. At the other track I didn't bother with the provoking, and the brakes didn't show any tendency to fading.

 

The brakes were quite linear and easy to control, but that might be as much due to the pads as the brakes.

 

I had no problems with the front wheels locking up. Or the rears for than matter. I am running r-compound tires which makes it possible to brake rather hard.

 

/Peter

 

For the curious ones, both tracks are located in Sweden. The first is called Gelleråsen, and the other is called Mantorp.

[Richard Hamilton]

Are the front disks on the right side? I appreciate the calipers are the other way up, but it looks like the disk in your photo is a LH disk fitted to the RHS.

 

Old thread, I know.....

Edited September 9, 2013 by Richard Hamilton

[Peter Bull]

Now that you mention it ... But considering how well they work I don't know it it matters that much.

 

/Peter

[Richard Hamilton]

I think you'll get better cooling if you fit them the right way round. The flutes in the vent slots will work better.

[Peter Bull]

I had to take a close look at the discs the last time I took the car out, and the front discs are mounted as they should be. Honestly The images in this thread are from when the parts were being fitted, so all the brake parts went on and off several times before I could use the car.

 

/Peter