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SL-C Manual: Brakes and the Pedal Box

Brake Rotors & Calipers

SL-Cs ship with the calipers and rotors loosely attached to the car and must be checked for fastener suitability and be properly torqued by the builder. If your car came with spacers on the rotors, be sure to always assemble the car with the spacer in place in order to maintain the correct relationship between hub, caliper, rotor and wheel.

Brakes are a key safety item, especially on a car with the speed potential this one has. If you are not experienced in braking systems, including repair, typical fittings and fasteners, soft and hard line routing, and general installation procedures, please get professional help here. As mentioned elsewhere in the manual, be especially vigilant about fasteners and fittings in the hydraulic system. It's better to be safe than sorry here!

Brake Ducts

Brake ducts are not needed on a street car, but for competition use, well-engineered brake ducts can reduce brake temperature and fade. The SL-C has openings in the front of the body to facilitate directing air to the rotors. 

The picture below of the factory race car shows how brake ducts can be run. The hose end connects to the openings in the front of the body to direct air to the interior of the rotor. 

If you elect to use brake ducts, be sure to route the air to the center of the rotor. Blowing air on the side or ends of the rotor does not help, and in some cases can actually cause the rotor to warp or crack because of uneven cooling. The picture below shows a properly-aimed brake duct hose.

Note that this picture shows the race swaybar, not the street set.

 

Pedal Box

The current pedal assembly from Tilton is shown below. 

Tools

  • 5/32 hex wrench

Consumables

  • Acetone (or similar)

Wipe the face of of the pedals with acetone (or similar) to and apply the self-adhesive abrasive.These do wear, and you should order replacements from Titlon if the car sees a lot of use. Note that the they aren't symmetrical from top to bottom, or you might be ordering replacements before expected. Attach the pedals with the button head bolts supplied by Tilton.

Note that the effective pedal ratio can be changed on these pedals by removing the two bolts holding the pads to the pedal assembly, and changing their position such that the pads are moved up or down relative to the pivot on the arm. A chart is supplied with the pedal set, and is printed on the brake pedal arm itself.

All Wilwood and Tilton master cylinders can be used interchangeably with either pedal set.

The recommended clutch master cylinder diameter for the Graziano, Porsche G50, G51, G52, G64, Ricardo and Albins transaxles is ¾”.
The correct master cylinders for the brakes are provided as part of the kit. Use the ¾” master for the front brake, and the 7/8” master for the rear. 

Depending on the length of the master cylinders you may need to shorten the threaded shaft. You should do this before assembly by cutting the shaft and then cutting an extended thread down the shaft with an appropriate die. If you don’t have a die, screw a nut onto the shaft before you trim the shaft, and when you unscrew the nut, it will act as sort of a poor man’s die. Clean up the shaft with a file or grinder to get good starting threads.

The later master cylinders have a black finish. One of these new types is just visible in the picture of the new pedal box on the clutch pedal. These are about 50 mm shorter, are lighter and allow the pedal assembly to be mounted about 2 inches further toward the front allowing more legroom for the driver. 

Again, use the ¾” master for the front brake, and the 7/8” master for the rear.

Some early pedal boxes require the builder to enlarge the mounting holes for the clevis on the clutch pedal. 
Photo of the shortened original-style clutch master cylinder shaft.

Assemble the brake master cylinders onto the pedal box before installing the pedal box in the vehicle. 

The pedals use studs, and only require washers and nylon locknuts.

Before you install the master cylinders, you may want to bench-bleed them. To do so mount each master cylinder in a vise, fill the reservoir with fluid, and pump the piston until only clean fluid and no air come out of the bleed port. This reduces the time needed to bleed system later.

Once the master cylinders have been attached push the brake pedal to check that the balance bar is adjusted to the middle. Both master cylinder shafts should start to move at exactly the same time. 

With the cylinders assembled, place the pedal box in the driver’s foot well. The exact location of the pedals is a personal decision, based on the ergonomics of the expected drivers. If you elect to mount the pedals in a fixed position, double check that the ergonomics are correct for your various driver(s), seat positions, relation to the steering wheel, knee and leg room, etc. This is an important issue and should not be rushed.

Use 5/16 AN hardware to attach the pedal set to the floor. The use of AN hardware makes possible the use of AN jet nuts, which fit perfectly in the castings on the pedal assembly. Regular nuts of the optimal bolt size won’t fit. Alternatively, you could use a longer regular bolt and create short spacers to space the nut up so it clears the pocket in the pedal assembly in which it would normally sit, but this is weaker and more complex than using the AN hardware.

If you do use jet nuts, be aware that they are essentially one-time nuts, and should be replaced after each use. This is because they deform on installation, and subsequent installations won’t have the same resistance to deformation as when they were initially installed, and the locking effect won’t be as originally specified. Thus, ordering spares is a good idea.
 
The pedal box mounting bolts should be assembled with the thread end up. This reduces the amount of fastener exposed to the elements below the car, and keeps the more delicate threads inside the car where they are not as likely to be damaged.

One option to consider is to use a bolt plate, which is a roughly 4” by 6” by .100” thick plate with the bolts welded to it so that the threads stick up. The bolts can be button heads, or even flat heads with the appropriate recess cut in the plate. Since the bolts are welded to the plate, installation is simpler; just push the threaded end of the plate through the holes in the floor, and fasten the pedal assembly in with jet nuts from the top. The bolts can’t rotate since they are welded to the plate, so installation can be a one-man job, and the plate stiffens the connection between the floor and the pedals to provide a firmer pedal feel.

If you choose not to use a pedal plate, consider using button head screws with large washers on the bottom instead of regular hex head bolts. These will smooth airflow, and provide less area to snag debris on the road.

You can grind the leading edge of the plate or the washers to reduce turbulence and make it less likely to snag on road hazards. 

In addition, for extremely long-legged drivers, it is possible to mount the master cylinders outside of the chassis, using longer rods to attach to the master cylinders and pedal boxes. One demo car was set up this way to illustrate the extreme leg room possible. In the following picture, the master cylinders are mounted on a bracket that is bolted to the 2x2 aluminum chassis tube, outside of the chassis, near the radiator.

Picture shows remote cylinders and remote reservoirs.

Recently, an optional extended pedal chassis mod has been offered from the factory to allow the master cylinders to extend past the normal chassis limits, which obviates the need for externally mounted master as shown above. Check with the factory for more details.
 
For adjustable pedals, the factory now offers a sliding pedal mount kit with specially machined adaptors as well.

The use of duct tape on the bottom of the assembly will reduce potential of scratching the aluminum chassis.

Throttle Actuation

The throttles on most modern cars are drive by wire (DBW), but some systems use a traditional cable to control the throttle blade. The Tilton pedal box accommodates either approach.

DBW is simpler, and not susceptible to heat-induced failure in the throttle cable. Tilton has a range of hardware that will adapt the pedal assembly to most cable throttles. 

A custom bracket supplied with the kit allows the Electronic Throttle Controller (ETC) to bolt to it, and then the assembly is bolted to existing holes in the Tilton pedal box. You will need to use small heim joints and threaded rod to connect the Tilton accelerator pedal to the ETC now mounted on the bracket. This is the solution that the 01 factory race car is using. A picture of this bracket is shown

The two holes at the bottom of the picture bolt to a matching set in the Tilton pedal box near the throttle pedal. The ETC bolts to the other three holes, with it's plastic bulge protruding through the large round hole in the bracket.

If you are using another engine, or one whose ETC does not fit the GM bracket discussed above, you will have to fabricate your own bracket.

Note that using this custom bracket in its intended place adds length to the pedal box, and limits pedal box placement. You can mount the bracket in other ways that do not suffer this limitation with additional fabrication.

If you are using a different engine controller you will need to fabricate a bracket to hold whatever ETC you are using.

You can also remove the throttle pedal entirely, and fab up a bracket to mount the ETC with its integrated pedal, though you lose the tight integration of the complete pedal box assembly, including the ability to easily make fine adjustments to pedal height.

Clutch Limit Stops

Don’t push that clutch pedal in for any reason until it is adjusted!

It’s crucial that you set the clutch limit stops on the pedal assembly.

Certain transaxles, particularly the Porsche and Mendeola variants, are very sensitive to clutch arm overtravel. The symptoms of this can be as varied as crank walk (in this case, the crank moving forward and backward too much), to graunching noises when selecting gears, to excessive clutch wear, and occasionally cracked clutch arms at the slave cylinder. Even cracked bellhousings on the transaxle are not uncommon.
 
What happens is that the driver pushes the clutch pedal all the way in, which in an improperly adjusted state, puts too much force on the clutch arm and cracks or breaks it, or pushes the clutch in too hard so downstream things (cranks, flywheel, etc.) are stressed, causing other damage.
 
While some transaxles are more sensitive than others, every SL-C builder should carefully adjust the clutch limit stops on their SL-C. This is a very important thing to do, and shouldn't be skipped.
 
Fortunately, the solution is easy. The excellent pedal system from Tilton that is part of the kit has built-in clutch pedal adjustment screws. These are very easy to adjust to get just the right engagement. Begin with these pedal limit adjuster screws backed all the way out so as to allow max travel. To get the clutch adjusted properly, do the following:

  1. With the car in neutral, the clutch OUT, and the engine off, have a buddy gently rock the car forward and backward while at the same time you are putting slight pressure on the gear lever to go into gear.
  2. Once it pops into gear, have your buddy rock the car again while you SLOWLY push the clutch pedal in. When the car starts to move, keep pushing the clutch in for another 1/4-3/8" after the car moves freely.
  3. Keep holding the pedal exactly where it ended up at the end of step 2, and have your buddy mark the position on the pedal cluster.
  4. Adjust the pedal limit screws on the Tilton pedal assembly to limit the pedal travel to the position you've found is 1/4-3/8" beyond where the car moves freely with it pushed in.
  5. Test the position by having your buddy push the car again while you push the pedal all the way in. The car should move freely just before you reach the end of the pedal travel.

In addition to preventing engine or transaxle damage, this also allows you to shift faster as your foot only needs to move enough to disengage the clutch and no more.

Brake Line Plumbing

The hard brake lines are delivered taped in place and mocked up on the chassis. You’ll need to run a few lines that are in a plastic bag, with the brake switch and residual pressure valves. See the pictures in this section for details on how they should be mounted and connected. All the lines need to be mounted to the chassis using the supplied P-clips.

Note: Don't use regular wrenches on brake fittings. It's much better to use specific brake line nut wrenches as shown in the following photo. These give a much enhanced grip on the hex nuts and fittings.

Before removing your brake lines from the chassis, take photos of their location. There may be differences between your lines and the photos below as the brake lines routing has been optimized over time.

The small blue anodized cylinders are residual pressure valves. These prevent pad knock-back (fluid pressure drop-off) due to the brake master cylinders being mounted at a level below the calipers. These are marked with the direction of fluid. The round switch with two terminals turns on the brake lights when the brake pedal is pressed and fluid pressure increases beyond switch’s threshold.

The rubber hoses that connect the brake master cylinders to the brake reservoirs should have rubber grommets fitted where they pass through the front cabin wall. Use 5/8” ID, 1” OD grommets.

The bolts required to attach reservoirs to front chassis extension are: 6 ea.: ¼” diameter x ¾” long button head screws with nylon lock nuts.

When you have assembled the hard brake lines as shown, attach the flex lines to the front calipers and the hard brake lines in the footwells, if they have not already been installed. Be careful not to install the flex lines with a twist, as doing so will dramatically reduce their life.

Similarly, attach the flex lines between the rear calipers and their hard lines. As with all brake line fittings, just assemble them dry- don't use teflon tape or pipe dope or any other sealant. If the fittings leak under pressure, tighten them. If they still leak, replace them.

In routing and positioning the flex lines make sure they cannot touch any part of the car over wheels and tires full range of droop and compression and their full turning angle.

a2

Any flex line that can touch another part on the car will fail so route carefully, use p-clips to hold the flex lines in place as needed and do not bend them beyond their minimum bend radius.

All non-NPT fittings should be able to be tightened with only finger torque until they seat. If you find you need a wrench to begin a fitting in the calipers, for example, STOP and validate the fitting and the part into which it is being inserted. You are responsible to ensure that the correct fitting is used in all cases. As noted before in this manual, approach all fasteners, even those supplied with the kit, with skepticism.

Mount the reservoirs on the inside of the radiator supports as shown in the next picture. Use the existing holes, already pre-drilled at the factory.

Clutch safety switch

A clutch switch is a switch designed to detect whether the clutch pedal is pressed. These are used for many reasons on production cars, and you should strongly consider one in your car. In fact, later cars have updated code in the Infinitybox system to expect a clutch switch (or neutral switch) in order to start the car.

Using a properly installed and programmed clutch switch prevents the car from starting without the clutch pedal pressed. This is a basic safety feature, and is very important, especially if you are using the one-button start capability built in to the Infinitybox system. As 

This function can be implemented in several ways. The preferred method is to plumb in a separate pressure switch- exactly like the brake pedal pressure switch- and run one wire to ground and the other to the preferred input on the Mastercell (Call Infinitybox for more info on the correct pin on the Mastercell). Use a standard brake pressure switch like this one, and use a standard brake tee like this one to plumb it in the clutch circuit.

Another option is to use the Standard Motor Products # SLS159T switch as it has contacts for both Normally Open and Normally Closed switch functions. One builder has used this to control both the clutch safety switch and cruise control. This switch is a mechanical one, meaning you won't have to plumb into the hydraulic system- just make up a small bracket to mount the switch on the pedal assembly. Wire it the same way as the pressure switch above, as only the physical actuation method differs.

Another, much easier method is to use the brake pressure switch you already have plumbed in for the brakes.  Instead of having to press the clutch pedal, you'll need to have the brakes on to start the car (presumably you'll have the clutch in too). With this approach, the Mastercell will need to be reprogrammed to use the brake pedal input instead of the clutch pedal in order for the Infinitybox system to allow the starter to operate. Only reprogramming, and no wiring needs to be changed with this approach.

Be sure to use one of these approached, or another similar one- otherwise your car could accidentally start and cause damage to it and other objects or people. This is mandatory in production cars for a good reason.

Brake failure warning lights

Some countries mandate that you fit a warning light for brake failure. One simple solution is fluid level switches. You will need two, one for the front brake and one for the rear brake fluid reservoir. The picture below shows ones with the yellow caps and wire connectors. These can be obtained from a number of sources, including Car Builder Solutions and others.

Note that the steering rack shown below also has an additional bracket at the bottom which is added to increase steering response.

Brake hoses

Be sure to use only the hoses supplied in the kit, or hoses approved for brake fluid to connect the master cylinders to the reservoirs. Such hose is often Teflon lined. Fuel line or other improper hose will degrade from the inside allowing debris to clog the circuits and they will usually leak externally as well, weeping brake fluid.

When all the brake components are in place and connected, you may fill the system with quality brake fluid and bleed the brakes. Good brake fluids include Castrol SRF and Motul 600.

The use of a pressure bleeder will make bleeding faster.

Alternatively, you can wait until the transaxle and engine are in place bleed the brakes and clutch at the same time.

Parking Brake

The installation instructions for the optional parking brake can be found here.