968CS / winter mods & repairs / Front brake upgrade
I like strong brakes and am used to lightweight cars on large rubber that stop very very quickly. Once I discovered that my 968 brakes needed refurbing I decided to go the whole hog and upgrade the front calipers to something a bit more beefy. Note though that when the standard OEM 968 system is working well with decent pads and fluid and no plate lift, the braking ability should be perfectly adequate for normal fast road use.
968 brake upgrades are one of the most popular mods for the car but it all gets very confusing very quickly and there are also various misunderstandings that get pedaled around the internet so lets first clarify all the available upgrade paths and idiosyncrasies.
First of all, to upgrade your brakes you are essentially upgrading your front calipers, changing to larger units that have bigger pistons and use larger discs and pads than stock. Now this might in turn demand that the rear calipers need upgrading but we will deal with that later. First of all, consider the the 3 different front caliper upgrades available to the 968 owner:
see bottom of page for part numbers
The first thing to note is that unless you have proper M030 steering knuckles fitted (unlikely) you will have to use machined adaptors to mount any of the above calipers. The standard 968 caliper mounts axial meaning the bolts go through the caliper and into the knuckle left to right in the direction of the width of the car or the axle. M030, big reds/blacks all mount with the bolts pointing forwards in the direction of the rear of the car to the front. You could of course buy M030 knuckles/spindles but at 1100+vat each its not really worth it !
Calipers are available from various specialists for about 80 to 150 pounds. Ninemesiter used to make their own and I know Promax supply them and are very knowledgeable when it come to what bolts you will need. Many adapters have the caliper mounting hole offset by 5mm to make up for the top hat offset when going to 45mm top hat discs.
All the discs you use for any of the above will be 32mm, 4mm thicker than the stock 968 28mm discs. The adapters work slightly differently depending one whether you use 45mm or 40mm top hat discs. For 45mm top hat discs, the outer face of the disc will be in the same position as a standard 968 setup so that means the thicker disc will sit 4mm further in towards the car.
When using discs with a 40mm top hat (993TT, 993RS) the outer face of the disc and the caliper will be 5mm further out than normal towards the inner face of your rim. The disc is thicker though as stated so the inner face of the disc is only out by 1mm when compared to standard. Some people prefer the latter setup because it means the disc is not pushed too close to the track rod end. There have been no actual reports of problems with this but its been said that on paper, one would avoid having them too close for heat transfer reasons.
Some adapters require the use of a ring spacer with 40mm top hat discs. This sits inside the disc and pushes it out by the correct amount. Some adapters have the caliper hole offset so you can turn them around 180 degrees and they will work both 40 and 45mm discs.
In all instances, consult the seller of the adapter and also ensure that you get the correct bolts. The knuckle to adapter bolts will most likely be a custom affair not supplied by porsche. If these don't come with the adapter then you can either use a second set of the caliper mounting bolts but cut them down to size, or source the corret length bolts yourself. Namrik are a good source of high tensile zinc plated bolts and set screws. You will want M12 with a fine pitch of 1.5 and the length will depend on adaptor type.
These calipers were originally fitted to the 928 S4, then later on certain 944 turbo models and the 944 S2 M030 option and of course 968cs spec'd with the factory M030 upgrade option. They are large black calipers with 36 & 44mm pistons and mount 'trailing' the disc in the same way as the stock 968 brakes, i.e. behind the disk furthest to the rear of the car when you look at the car from the side. They provide considerably better braking performance than stock and with correct pads and fluid are perfect for the trackday punter.
Most users don't report any fade or issues at trackdays even after long sesssions and long days. The general consensus of opinion seems to be that unless you have very big horsepower upgrades, bigger calipers might not gain any additional benefit and the extra unsprung weight added will almost certainly outweigh any small positives gained. They state that if you're trying to improve upon the M030 setup then fine tuning the pads to something like Performance Friction 97 compund might be the best move.
Out of the useable discs, the factory OEM option is to use proper cross drilled M030 discs. These look the part but are hideously expensive at over 200 pounds each plus vat. A cheaper and common option is to use OEM 928 S4 non-cross drilled discs which come in at around half the price. After that there are various non cross drilled after market discs from the likes of zimmerman and sebro... Eurocarparts.com is your friend here. Sebro do make an inexpensive but elusive cross drilled disc but you might have to wait decades for them to arrive in stock anywhere.
The M030's are the natural choice for a 968 brake upgrade. They were the calipers that Porsche fitted to the hot M030 versions and there is more chance you'll maintain or even increase desirability when you sell the car on. Bear in mind that full factory M030 968's are very very rare and command a big price premium so if you can mimic the spec to some extent then you're likely to have a far easier time if you ever want to move the car on.
However, its not quite as simple as that because for some strange reason M030 are to this day, more expensive than big reds or blacks. At over 360+vat GBP per corner, many people opt for big blacks. This may be something to do with the fact that Brembo class them as a motorsport item and the big reds & blacks as a road item.
One word of caution about M030. There does exist a very early M030 caliper that is referred to at type I. It came from very early 944 cars and can be identified by the thicker, bulkier porsche lettering (much like the bulky blocky letters of 968 calipers). These calipers are best avoided if you see them. They have a different seal design and a scraper and the parts for them cost a lot more than the more common M030. If you try and refurb a set it just will not be cost effective and will probably work out a similar price as a brand new set. Also, they are rather old so will undoubtedly be really seized up and difficult to revive.
These are slightly larger in physical size to the M030. They have the famous red paint and come from the 993 twin turbo. They were also fitted to the wide bodied 993 Carrera 4S cars and also the 3.6 964 turbo (not the earlier 3.3 964 Turbo). The pistons are the same as the M030 but the discs used are bigger and the pad, although the same length, is deeper by 1cm. The pad surface area for ecah corner is 151 cm2 compared to 112.5 cm2 for M030 .. so quite a difference.
For road use on the 968 they are most certainly overkill by anyone's standard. As you can imagine, with the 993 turbo being a weighty 184mph supercar, they provide gargantuan stopping power and even if you go to bigger 18" rims and wider 275 rubber by all accounts they will still show up the tyres as the weak link. On standard 17' tyres they will most likely lock up the fronts long before you ever reach the full pressure of their braking force... kind of frustrating and annoying I would have thought.
For the track though, these or big blacks could arguably be the right choice especially for supercharged 968's. Although they add more unsprung weight, they will definitely allow you to lap for hundreds of miles all day long without any threat of fade or degredation in performance. Most people have defualted to a big red or big black setup not because of the extra pad and disc area however, more because they are cheaper than M030 and easier to find on the secondhand market.
Note that Big reds are a leading mount. That is they are fitted before the disc. This means that to use them on a 968 you have to swap them around using the left one on the right wheel and vice versa. Of course this introduces a few anomalies. Firstly the bleed nipples are upside down, the pad retaining clip is also upside down and clips in at the bottom of the caliper and finally, the offset brake hose connection will be in a slightly different place. The hose placement can matter with some 944 models that use a rigid connection but the 968 uses flexible hoses so its not a problem. The upside down nipples can also easily be swapped with the cross over tube so that they sit once again on top. Not a big deal then, just something to be aware of.
Common disc options are the expensive genuine 2 piece 993 turbo discs, 993 rs cross drilled discs, 1 piece 964 turbo cross drilled discs or the one piece non-cross drilled 928 GTS discs. The 928 GTS are the cheapest. The 993TT and 964 turbo look as sexy as one another but the 993TT are lighter and more expensive.
These are from the 928 GTS. They are physically the same as big reds... same caliper body, same pistons etc.. The only differences are that they mount in the normal 968 way, trailing the disc. They therefore have none of the associated nipple/hose placement issues. These days they are also cheaper than the big reds from Porsche (and of course the M030). The main difference of course is that they are black and therefore less noticeable and in many people's eyes, less desirable and sexy.
The one last brake upgrade I know about is a 996 GT3 upgrade that a chap from sweeden developed making some custom brackets to match the awkward caliper bolt spacing and addional brakcets to allow proper handbrake cable functioning. 6 piston stopping power ! Definitely bonkers and OTT but interesting nonetheless. See the link here if you're keen.
UPGRADING THE REARS
There are various schools of thought about balancing the rear stopping power with increased front stopping power. First of all, you'll probably know that you do not want to go too mad with this because a car that locks at the rear before the front is highly undesirable.
Some people are happy to use the M030 with standard 968 rears. A factory M030 968 was supplied with the exact same stock rear calipers but the rear discs were also M030 spec. The rear M030 968 disc is the same size as a standard rear disc but it just has the fancy drilled holes and is crazy expensive. Also, I think I am right in saying that the M030 968 from Porsche had a non standard 5/33 brake bias valve to shift a little more power to the rear. This is easily fitted to the top of the ABS control unit inside the left of the offside wheel arch. I am personally going to try my M030's without this. My car is not a trackday car and I quite like a bit of nose dive action.. it can be useful if you want to aggressively make the back go light into a corner. If I feel that the car is too unruly then i'll fit the valve as recommended by Porsche.
With Big reds and blacks there is no doubt that the front braking completely over dominates the rear. Without having tried it I can't comment personally but whilst I have spoken to some people who have kept the rear standard on track with no ill effects, my feeling is that you would almost certainly want to be upgrading the rears in some way to make for a more composed car under braking and into corners.
Some people do it with pads, using a higher performance pad on the rear and keeping the pads on the front reasonably sensible (e.g. RS29 on the front and stock Textar on the rear would probably be asking for trouble). Most big red owners though seem to advocate changing to a 5/33 bias valve as an absolute minimum, but then others suggest that the 5/33 still does not send enough force to the rear. Also, another popular mod is to put the stock front 968 caliper onto the rear. The front has slightly larger pistons so you will get more braking force at the rear doing this. This method has come under some criticism though including negative reports about heat build up but then others have had no problems. Best thing is to test for yourself.
Here are my new M030's. I took the trouble of unscrewing the caliper bolts and removing the thread lock applied by Brembo at the factory. I also placed some silicon sealant between the plate and the body to better safeguard them against water ingress and corrosion. See my plate lift page for information about this hazard.
The rear Goodridge hoses went in easy enough. Someone had been kind to my brake line connectors and they were easily undone. Although access is a bit of a pain here using axle stands, its a very simple job. Just watch for the outermost retaining clips. Because they probably trap damp against the aluminium trailing arm, nasty corrosion can build up and make them difficult to budge. I used a chisel and mallet to force them up and off and then made a point of rigourously cleaning all the corrosion away with a wire brush.
I decided to remove my brake pad wear indicators. They have a tendency to crumble when taken out and given that i'll be checking the brakes periodically like any normal enthusiast, there are pretty pointless. Of course when the circuit is broken the dash light will illuminate so you can't just pull the plugs out. You need to connect the circuit. I opted to cut the plug wires at their origin, solder them together, seal with a little heatshrink and then affix them back into the sockets that are held by the plastic carrier that also houses the abs sensor plugs.
nearside wheelarch with liner removed, showing M030 adapter in place, note that thdisc backing plate has been cut off and then the excess bent backwards (it tends to rub against the bigger M030 discs)