C2 front caliper on a SC/Carrera?

[911st]

C2 front caliper on a SC/Carrera?

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What dose it take to mount a C2 Caliper on a 3.5" spacing Carrera strut if used with 24mm Carrera front rotors?

Will this clear a standard 7x16" Fuchs?

Will a C2 front rotor bolt up to a Carrera 3.2 hub?

Is there any difference between a C2 and C4 front caliper?

Would a turbo MC be needed on an 85 Carrera.

Should the rear pv valve need to be removed or any advantage to replacing w an adjustable?

Anyone know the difference in pad area from Carrera to C2?


I spent some time looking through old threads and could not find this info clearly.

Thank you in advance.

[spuggy]

Originally Posted by 911st

What dose it take to mount a C2 Caliper on a 3.5" spacing Carrera strut if used with 24mm Carrera front rotors?

There seems little point in putting bigger calipers on a 24mm 3.2 front rotor, because tire adhesion and thermal capacity of the rotor are the limiting factors.

The 3.2/SC calipers make 88% of the front braking torque of the 930 setup, on a rotor with 54% (SC) or 65% (3.2) of the front volume of the 930 setup (and thus thermal capacity).

Which is why you can overheat the 3.2 rotors with 3.2 calipers, let alone putting bigger, more powerful, calipers on the 3.2 rotor. And 3.2 calipers will lock the fronts, so "feel" (can be related to caliper stiffness, and/or pad area) and thermal capacity are the main reasons to upgrade.

The C2 calipers are designed to run with 298x28mm rotors, and these have a different offset to the 911 rotors. Bill V has written a lot of stuff here about the 964 rotors/calipers. The C2 setup has 98% of the torque of the 930 setup, and 88% of the 930 rotor volume (thermal capacity).

(I've long thought that the 930 setup is overkill in terms of thermal capacity anyway. It was off-the-shelf stuff for the 917 after they realized the 3.0 930 brakes turned to chocolate too quickly- but the 917 was an endurance racing car...)

If you fit 964 calipers on 3.2 rotors, there may be an issue with the pistons over-extending if the pads wear thin. Or not. Swept height of the C2 pad appears to be less than the 3.2/SC pads, so there shouldn't be an issue with pad overhang.

On the other hand, the 3.2 rotor is designed for a taller pad. So that might be an issue - you'll certainly not be putting that extra braking torque across the entire radius of the rotor.


C2 and 944T (and some 928) calipers are the same "basic Brembo", IIRC (gosh, I miss Bill V's brake page).

VCI does a kit to convert them for 911 use. Which includes making adapters for the calipers, because the 964 rotor offset is wrong for the 911, and the calipers work with that rotor.

Most people figure that it costs so much to adapt these for use on a 911 - and they're still lower spec than 930 brakes - that you might as well skip straight past them and get really serious (993TT, 996TT, Brembo GT-X) brakes for that same money that bolt straight on and definitely won't ever overheat.

Me, I think 996 are my sweet spot. Light, stiff, cheap wear parts and very close to 930 numbers for rotor volume, piston area. Far more swept pad area, IIRC. I just wish you could hog out the rear caliper pistons for slightly more rear bias.

Will this clear a standard 7x16" Fuchs?

If they're the same as 944T (951) calipers like I think they are, and the 951 Fuchs have extra space (and their own part #) to clear the calipers, I'd guess "probably not"...

Will a C2 front rotor bolt up to a Carrera 3.2 hub?

Believe so, but I seem to recall reading that the offset is wrong? It also gets very close to the A-arm, and you have to space the wheel or grind the A-arm.

IIRC, the '86 (pre-ABS) 944 turbo front rotor bolts up as well. It's the same dimensions as the C2 rotor.

Is there any difference between a C2 and C4 front caliper?

Fronts are the same between C2 and C4, at least in terms of pad dimensions, rotor and piston sizes.

Would a turbo MC be needed on an 85 Carrera.

If you need a 930 M/C for 930 brakes (which most people seem to agree you do, then "yes".

C2 front caliper piston area is in 930 territory (C2 is 2274 mm^2 as opposed to 2268.23mm^2 for 930 fronts), and the 3.2's single 42mm rear piston is 98% of the 930's rear piston area (1385mm^2 as opposed to 1413mm^2).

Should the rear pv valve need to be removed or any advantage to replacing w an adjustable?

Based on plugging your combination into my brake bias spreadsheet, I believe you should remove the P/V. It's about the same front bias as a 964RS, and more front-biased than a 930 (neither of which run a P/V).

See for yourself (these values are with the same coefficient of friction pads front and rear):

Anyone know the difference in pad area from Carrera to C2?

It looks like the C2 front pad has a working pad area (not including the backing plate, just the friction pad) of 98mm x 45mm ~= 4410mm^2.

As opposed to the 3.2/SC pads, which have a working pad area of 61mm x 54mm ~= 3294 mm^2.

But swept pad area isn't the issue.

What problem are you trying to solve?

[Bill Verburg]

If you are going to do it, do it right

to use 964 calipers you want 930 rotors and m/c, this is expensive and not easily done

my old setup, 964 calipers on 930 rotors




you are much better off just buying a set of 930s

[911st]

I guess I am back to reality again.

I have been hearing the SP911 guys are leaving the 930 set up behind for C2 front and 3.2 rear calipers both on 24mm rotors for the lower weight. There reported ballance has been very good without and adjustable system.

I was more after lower front pad temps that I hoped would come with larger pad surface area. My hope was if the front pad area was say 50% larger, that might make for lower peak temps at the pad material at the end of a big straight.

I do not seem to have a problem with total heat, kind of felt more like peak heat under a big stop at the end of a big straight.

Thanks again.

[Bill Verburg]

Originally Posted by 911st

..I have been hearing the SP911 guys are leaving the 930 set up behind for C2 front and 3.2 rear calipers both on 24mm rotors for the lower weight. There reported ballance has been very good without and adjustable system.

That is a fine setup as far as bias goes but you are not gaining much performance, it is simple to do, any***** can hog out the mounting holes and voila, instsnt BBK, but as I sais you haven't gained much, yes you have more pad area, but that does not lower pad or rotor temps, it does reduce the unit pressure on the pads and rotors but that isn't a problem.

The problem w/ stock 3.2 Carrera brakes is
1) bias, to fix this just install pre '84 M rear calipers and 20mm rotors
2) heat, the under sized front rotors get a real workout in track use, to fix cool the brakes + high temp pad & fluid + lighten the car or use 930 front rotors w/ whatever caliper floats your boat + high temp pads + brake cooling + high temp fluid

Originally Posted by 911st

I was more after lower front pad temps that I hoped would come with larger pad surface area. My hope was if the front pad area was say 50% larger, that might make for lower peak temps at the pad material at the end of a big straight.

I do not seem to have a problem with total heat, kind of felt more like peak heat under a big stop at the end of a big straight.

Thanks again.

bigger pads do not reduce pad or rotor temps

If I owned & tracked a 3.2 Carrera w/ 15 or 16" Fuchs i'd either budget $3-4k for a 930 setup or cool the fronts w/ large diameter ducts & scoops(you can not use enough cooling), use high temp pads & fluid, lighten the car as much as possible.

I'm torn about the rear calipers, it's great to get as much braking from the back as possible but the 3.2s have a bit too much, a really effective lsd would help a lot as does a lower stiffer suspension, before switching the rear calipers out i'd try an adjustable p/v and these things

[Steve@Rennsport]

Originally Posted by 911st

I have been hearing the SP911 guys are leaving the 930 set up behind for C2 front and 3.2 rear calipers both on 24mm rotors for the lower weight. There reported ballance has been very good without and adjustable system.

The PRC SP911 guys cannot use 930 brake components due to the rules,... Calipers are free but the stock (SC or Carrera) rotors must be retained. These folks retain the Carrera rear brakes without the PV to gain more rear brake bias and reduce some of the heat load from the fronts. LSD's make the car manageable but some experience is a real plus.

Given that "Necessity is the Mother of Invention", they make them work with close attention to cooling, choice of fluid and pads, as well as careful brake management during a race.

[911st]

Bill and Spuggy,

Thank you for your input. Project abandoned. Big brakes will be for another day.

For DE/TT's on my heavy weight 85 I am running stock rebuilt calipers, removed backing plates, Castor SPF, and a sport pad. I have brakes, my problem was uneven pad transfer to the front rotor (wrong pad and to hot).

Sold the C2 calipers and am going to race pads w stock calipers and for more cooling.

Again, thank you.

[911st]

Steve thanks. I did not understand there was different classes.

I guess SP911 is different that the PRC 911 spec class, PRC-GTS, or old Toyo cup class.

They had/have unlimited brakes. I guess the new SP911 class that was an out groth of this much have the rotor restriction you note.

I thought I had heard the Toyo Cup cars were converting from big brake set ups to Carrera rotors for better acceleration that came with lower rolling weight.

[KTL]

Bill's original C2 brake upgrade is definitely the biggest and best approach with respect to rotor choice for these calipers. That is, if you're going to do it? Might as well get a rotor with substantial gain in thermal mass. The 930 rotor or the Wilwood HD substitute clearly accomplishes that with it's 20+mm gain in diameter and 32mm width. The other upside to using these rotors is the alloy hat (a rather simple one, which is also a plus) which provides a nice unsprung weight benefit when considering the heft of the OEM rotors' one-piece construction with iron hat. Using this front setup with the stock Carrera rear is do-able with the stock master cylinder, so that's a plus too. But as Bill said, the cost of converting the calipers is quite high.

A slightly lesser alternative is the VCI-type C2 caliper installation. Here VCI takes the modified C2 caliper and uses it with the single model year 1986 944T rotor. To use this rotor, you must to space it out from the A-arm a bit due to the higher offset of the rotor hat. VCI makes 5mm spindle spacers that are installed onto the spindle, behind the OEM collar that is pressed onto the spindle. If you don't use these spindle spacers, the rotor will rub on the A-arm at the ball joint connection. Some slight clearancing of the ball joint housing on the A-arm helps to ensure adequate clearance.

These small Brembos clear a 16x7 Fuchs wheel no problem when using the VCI adaptation This is another nice feature that avoids the switch of wheels for some people. As has been said many times in other threads, the 930 is the best fitter of them all- even 15 in. Fuchs can hold them. Like Spuggy said, a lot of people go straight to the top and get the monster setup. I think these small Brembos used with the right rotor is a good solution to a small problem with the Carrera brakes. By using a slightly larger front rotor, but not something so big that requires new wheels, and most importantly some ducted cooling that actually works, you can get your brakes well-equipped for track use without dumping a boatload of money. Speaking of $, one other thing I like about the small Brembos is they use the 930 pad, which nowadays is cheaper than the Carrera pad when you are buying race pads. Cheaper pad that lasts longer adds up to be a substantial cost savings in terms of your track event consumables.

BTW, the C2 front rotor is not the same dimensions as the '86 944T rotor. The C2 964 and the C2 993 (these two aren't the same either) have much more offset than the '86 944T rotor. These 911C2 rotors have so much offset, that some brake upgrade creations like those of Steve Timmons (Instant-G) actually install the rotor on the front side of the wheel bearing hub vs. the normal installation that has the rotor fastened behind the hub.

[911pcars]

Kevin,
Good observations on your part.

I think more people "upgrade" for the red paint, the Porsche decal that peeks enticingly through polished Fuchs spokes and the requisite drilled or sloted rotors which scream "high performance" than any real gains in braking.

The factory equipped the RS models with ordinary factory brakes and found them very adequate. However, I imagine there are budding Jochin Rindt's, Vic Elfords .... or Chip Foose's among us who want a bit more.

Here's the typical Porsche hot rod brake upgrade path:
a. ATE Blue brake fluid, alternating with ATE amber BF @ $10/pt.
b. Turbo brakes or big reds @ $3000+ installation

Sherwood

[911st]

Thanks Keven.

Interesting to find out the C2's use the same pads at a cheaper price. $300 delivered for pads seems like a lot to me.

I am going to make the stock's work for now (no sheald, Castor SFP, race pads).

I am courious, what dose it take to mount the C2 Calipers to the strut up front? Is it just offset drilling them and or maybe spacers to off set them?

Also, some of the threads note putting C2 or 993 calipers on the rear makes for pad overhang. Why is that?

Thx all.

[KTL]

There's a good picture from VCI's site that shows how they mount the small Brembos to the strut to fit a properly sized rotor for these calipers. Bill has also shown us a picture of his Racetech caliper adapting done many years ago.

VCI

http://www.vehiclecraft.com/Brakes/VCI911_2_964.htm

Racetech



Agreed the cost of the A and M caliper pads is odd, considering the 930 pad is cheaper. I still won't complain though- 993 front pads are over twice the price and Big Reds take up another notch. All in all our cars are pretty cheap to equip with true race pads.

If you can't get ducting to the brakes, at least use some air scoops like those from the 993. Makeshift attachment with some zip ties is cheap and easy, and fairly effective (better than nothing)

993 brake cooling scoops on 911

The rear overhang issue is on account of the pre-89 rotor being a deficient in diameter. Our rear rotors are 290mm, whereas the later cars use a 299mm rotor. One would think that it shouldn't matter if you're modifying the caliper to fit the bolt spacing and the rotor. Yet whether you fill and redrill the holes, or you cut the mounting ears off and install an adapter on the rear Brembo, it doesn't matter. There's not enough room on the bottom of the caliper body to establish the mounting holes high enough into the caliper which would put it far enough down onto the rotor. So you end up with about 5mm of the brake pad (across the entire width) sticking above the outer edge of the rotor. It doesn't cause any problems with braking effectiveness or squealing, but it looks kinda hokey. I have the overhang setup on the rear of my car and have no issues with it other than occasionally having to grind off the excess pad chunk.

This is why the 930 rear rotor is the one Bill always recommends. It's offset is perfect and the rear Brembo fits atop it with no overhang. The only caveat is that if you cannot source the wide 965 rear caliper and intend to use more common 993 rear caliper, you need to grind the inside of the caliper to accept the heftier 28mm width of the 930 rear rotor because the 993 rear caliper is set up to fit a 24mm wide rotor. You also must shave the brake pads because, again, the 993 caliper isn't wide enough to hold the 930 rotor and the normal thickness of the brake pads. Pad shaving is easy with a belt sander. But man is it messy!

[KTL]

Sherwood,

I agree that a whole lot of people don't need these modifications. I've gotten better with my abilities where I too don't necessarily absolutely need the brakes for my car to survive track duty. Agreed people who do nothing but drive on the street certainly are wasting their money on this stuff. But when it comes to driving the car hard on the track on a regular basis, I think there is something to be said about putting more into the brakes so they're not so heavily burdened by the work they're doing.

Adding cooling to my brakes via the IROC ducting, plus the front Brembos with the '86 951 rotors, has eliminated any potential for heat issues with my brakes such that I have no need to ensure bleeding my fluid before each event and my pads, rotors, & caliper seals last much much longer. My brake hardware lasts at least 2-3 times longer than a friend with a similarly equipped car (big weight loss/dieted, streetable '87 911) and similar skill level, using the stock brakes.

Nonetheless, there no way around the cost. It's not cheap, even doing it as cheap as I can think of:

Brake hardware:

>'86 951 front rotor- $90 ea
>Used basic front Brembos- $100-$150 per pair
>Rebuild above calipers- $100
>Caliper modification- $500 from VCI + $50 for spindle spacer widgets

Brake cooling:

>Front bumper- $450 MA Shaw IROC narrowbody bumper
>Brake cooling backing plates + wheel hub/rotor blockoff plates $150-$200
>Cooling hose, fittings, clamps- $100
>KTL custom made sloppy copies of SmartRacing A-arm PVC pipe manifolds- 2 in. scraps of PVC pipe + your time figgering out how to cut and fit these suckers

Not cheap if you're buying all things new except used calipers. Maybe save some bucks scoring things used like I did. Still, you're EASILY into it for a grand. Not cheap! Most people will say you can buy a lot of brake fluid, pads and a set of rotors for $1000! Very true. But over the long term, it'll pay off. I figure my brake modifications will pay for themselves in about 4 years with savings in annual consumables like pads, rotors and caliper rebuilds. I still bleed the fluid all the time because it's just good to do it and i'm anal like that.......

[JeremyD]

Originally Posted by 911pcars

Kevin,
Good observations on your part.

I think more people "upgrade" for the red paint, the Porsche decal that peeks enticingly through polished Fuchs spokes and the requisite drilled or sloted rotors which scream "high performance" than any real gains in braking.

The factory equipped the RS models with ordinary factory brakes and found them very adequate. However, I imagine there are budding Jochin Rindt's, Vic Elfords .... or Chip Foose's among us who want a bit more.

Here's the typical Porsche hot rod brake upgrade path:
a. ATE Blue brake fluid, alternating with ATE amber BF @ $10/pt.
b. Turbo brakes or big reds @ $3000+ installation

Sherwood

Hey Sherwood - I resemble that remark -

Alright not completely - but try hauling a fat a$$ cabriolet down at the track - I know, I know - get a coupe and make it lighter...

[ShakinJoe]

KTL,

I am stuck with front rotor choice at this point. Does the 1986 951 rotor bolt on to our 87 Carrera? correct offset etc.....

[911pcars]

Jeremy and Kevin,
I didn't want to lump you guys into the street bling crowd. If there's a need, go for it.

I'm the last one to pronounce what is correct to accessorize one's car.

My only gripe with Turbo Brakes are the especially weighty 32mm rotors. They add a lot of heft to the unsprung weight of a 911. However, perhaps needed in a track situation. I would opt for the 28mm rotors for a good compromise for most. MHO.

ShakinJoe,
I believe Kevin mentioned a spacer is needed to move the installed 951 rotor slightly outward for clearance.

Sherwood

[KTL]

Originally Posted by ShakinJoe

KTL,

I am stuck with front rotor choice at this point. Does the 1986 951 rotor bolt on to our 87 Carrera? correct offset etc.....

Joe,

It does bolt onto the wheel bearing hub just fine. But the offset is a bit too deep and it hits the A-arm near the ball joint. So VCI uses a small spacer ring on the strut spindle to push the whole hub & brake rotor assembly outboard just enough to clear the A-arm. It still rubs when you turn the steering wheel to full lock, so some grinding on the A-arm to shave a bit of metal away is the remedy there.


The spacer is simply a machined ring that looks like a thick washer with a very large inside diameter. It goes behind the spindle collar shown in this pic.



You can avoid this spacer BS by using the 930 rotor like Bill mentioned, or use the Wilwood HD rotor. But i'd not use these small Brembo calipers with the 930 or Wilwood. Too much hassle machining the caliper and making the adapter. I'd use the 993/S4 caliper. Caliper is already suited for an adapter and the 930 or Wilwood HD rotor is a simple bolt-on that a 5th grader could install.

[KTL]

I agree the 28mm rotor is a nice compromise between stock and 32mm hefty rotor. However the 28mm selection is pretty sparse. It bothers me that the only rotor we can pirate from the 951 cars is from one model year. I suspect that in the years to come, this rotor could get expensive since it's from only one year of production.

There are of course other brands to choose from. AP Racing makes some 28mm thk rotors, as does Brembo, and they are NOT cheap. Wilwood makes an HD that is 298x28, but the size of the rotor face is not big enough which would create some pad overhang if this small Brembo caliper is used. I'm sure there's plenty of Wilwood calipers would fit a the 298x28 Wilwood rotor just fine, and probably save a good buck by avoiding the hefty cost of VCI modifying the Brembo calipers!

[JeremyD]

Kevin - is that Chris Streit's set up? I know he was using the 1986 944 Turbo rotors for quite a while - doesn't also add like 3 mm offset spacing too pushing the wheel out? I remember I considered the 944T route because I had a set of 964/944T calipers at the time but was put off by the offset issues.

BTW - Dave Walsh - who made my "kit" has a few new offerings with wilwood components. Some of which you can keep existing fuchs wheels.

http://www.probraking.com/BrakeKits.htm

[ShakinJoe]

KTL,

I like the Wilwood option using the rotor hat, but as you can see by this picture, the hat does not block off the air. Any air that I would push with the AJ style backplate would exit through here instead of the vanes as intended and needed...right? Do you use a different hat than shown?