Thread: Brake upgrade
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spuggy spuggy is offline
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Join Date: Jul 2003
Location: Glorious Pac NW
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Originally Posted by gsmith660 View Post
So I am doing some reading and I surmise all I need to upgrade the 911 brakes to 996 brakes is the calipers, new rotors, and adapters and misc. hardware right?
Not quite. There's various ways to do it; I kicked it around for 4-5 years, and finally went with the kit from Instant-G for the 996NA brakes. The monobloc calipers are stiffer than the two-piece calipers (e.g. 993 and earlier), I feel. They're also lighter, I believe. And the 996TT I felt were both overkill for a light car, and too front-biased. I didn't want to faff with a twin master setup (which would require to either ditch the booster for an SC RS setup or go with a boosted Fabspeed or similar). Many people who need the thermal capacity (track) are running twin masters anyway. Those who just bolt in 996TT brakes with no ABS generally report that the front locks up very easily - e.g. not optimal. Because they're 1.92:1 bias, rather than the more street-optimal 1.6:1, or the lower ratios preferred by the factory for the RS cars...

Two things you don't mention above are "hubs" - 911 hubs won't accept 996 rotors, and if you machined them down enough that they would, they'd be dangerously thin - and "wheels" - you can't fit 996 rotors under anything less than 17" wheels.

Just FYI, 996 N/A calipers without spacers are tight on the backside of 8J Rufs - they'll squash your pinky. But they fit, just. The modified hubs also pull in the wheel by 10mm or so - if you're rocking 225/45/17 up front with rolled fenders, you'll have MORE fender clearance afterwards. And slightly more restriction on lock due to tub rub inside the fender well.

You can supply your own calipers if you want. 996 N/A & Boxster S are exactly the same thing, except Boxster S are red - and usually slightly more expensive. I went with red. Contrasts nicely on a black car.

The Instant-G kit provides all appropriate hardware (including fasteners of the correct rating) except hard lines IIRC (which are easy to source from your FLAPS). I also had him supply a set of new 996 rotors (Bolo, OEM for MB/BMW) - they were packed in Sachs waxed paper inside the boxes and were stupid cheap - $200 for all 4 drop-shipped, IIRC.

The front is easy bolt-up with the appropriate hubs (necessary to accept the 996 rotors), and a 0.5mm-1mm shim on the caliper mount lines it up perfectly over the rotor centerline. Which you could happily ignore.

The rear requires the removal of the dust shield, and the tab on the banana arm it bolts to. Then you start fitting the adapter (as in the old sense of the word "fitting"). Go to bolt it up, figure out what fouls, machine it down. Go to bolt it up again, figure out what fouls, machine it down. Apparently the same adapters are supplied for the 993/993TT/996/996TT rears - and there's minor differences between the 911 years as well.

So you just make 'em fit. Eventually it all bolts up - pretty tight. But it fits.

The 911 handbrake shoes do hang out of the 996 rotor by a small amount, but plenty of meat left for engagement. No issues there.

Use a 930 M/C. The '77 originally had a 7" booster, so I switched to an 8" 930 booster at the same time, but wouldn't have bothered if I'd had an SC or 3.2 - although the 930 booster has slightly different specs to the 8" 911 booster, I probably would never have noticed. 930 brake light switches don't match a 911 harness. Not a biggie. And tired brake light switches are notorious for lighting up late anyway.

To tweak the front/rear bias slightly, I used Pagid Yellow (RS19) up front and the more aggressive Pagid Black (RS14) pads in back - good for perhaps 0.05:1 or so - I forget exactly, but still have the spreadsheet if needed. From completely cold, the rears bite momentarily faster than the fronts, but the car hunches down flat/even. Oh, and It. Just. Stops. No drama.

BTW, you CANNOT bed these pads on the street, because they just will NOT get hot enough to gas off - even after 100's of miles of "real" driving. Once they're bedded, they'll squeal/ring if you're toying with them - like lightly slowing down for lights. They shut up completely when you're using them for real. Dust slightly more than factory stock - but not to the point where it's an issue.

What's it like to drive? Well, I was never very impressed with my 3.2 brakes. The 996 brakes are totally different. The pedal moves an inch or two, then felt like there was a block of wood under it after the 3.2 brakes.... Really sensitive, good modulation - pedal hardly moves even under hard braking, so heel'n'toe is much more predictable. I no longer bother to bleed the brakes before (or after) track days... It's incredible how fast they'll haul it down after the straight at PIR. The rotors don't show any wear at all, and the pads look fine.. Amazing how tiring repeatedly braking hard can be...

Only thing to be careful of is transitioning immediately from accelerating hard to braking - like when someone changes lanes in front without warning. If you jump on the brakes too fast - e.g. while the front is still light - it'll just push along in a huge cloud of rubber smoke....

My car can tolerate large amount of rear bias - lowered, stiff TB's (21/30), 40/65 LSD, 255/40/17's at the rear (fat for a 911). I ran 3.2 brakes without a P/V for years - which is about 1.3:1, supposedly far too much. Never caused me any issues, even on greasy roads. I probably will go dual masters eventually - I suspect that the ideal f/r ratio for me would be somewhere around 1.45:1, but can certainly live with the 1.6-mumble:1 I have now.

Mulling it over for years (and considering/rejecting for various reasons many different approaches), I settled on the Instant-G kit, and 996 versus 996TT. Few weeks before I pulled the trigger myself, Peter Bull documented his own install in a rather excellent thread here The mother of all IB brake upgrades?.
'77 S with '78 930 power and a few other things.
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