AP Racing - Master Cylinders (Formula Student)

AP Racing offer a range of master cylinders which are suitable for Formula Student use. Common options include the CP2623 family (and alternatives/variants) or the CP7854/CP7855 range. Although some teams do select other options. When selecting the right master cylinder for your requirements you should consider:

• Size - The space available for the master cylinders and pedal
• Mounting - The way the master cylinder will be mounted which could be to a bulkhead, trunnion or bearing
• Cost - The price difference between the ranges is quite large
• Required Bore - The bore size of the master cylinder makes a difference in the pedal 'feel' for the driver
• Plumbing - Different master cylinders require different fittings, most will use 3/8 and/or 7/16 UNF but some have metric threads

There are other considerations but these are the main ones. If your braking system uses ABS or similar there that does also effect the choice of master cylinders, please contact us for details.

Below are details of the various families of master cylinders used in Formula Student. Most of these master cylinders are available with a variety of different bore sizes and push rod threads/lengths.

CP2623
These are the most common master cylinders in use in motorsport. The CP2623 family are available in bore sizes from 14mm - 25.4mm. These master cylinders are also available with 5/16 thread UNF push rods (PRT) or M8X1.25 (PRM) at a length of 115mm or 160mmm. The PRT, 160mm are the more commonly available models and usually are in stock or have a shorter lead-time. The 160mm push rod length can be cut down to a required size. This master cylinder features 7/16 UNF inlet and a 3/8 UNF outlet.

The CP2623 master cylinder is a flange mounted unit with a short stroke. The CP5623, CP4623, CP4400 and CP9093 master cylinders are all similar to the CP2623 range but have different mounting options etc.

CP7854
This is a trunnion mounted master cylinder. The CP7854 family of master cylinders is available 14mm - 25.4mm bore sizes and with 5/16 UNF push rod thread. This master cylinder has a 3/8 UNF outlet and a 7/16 UNF inlet. The travel to cut-off distance on this master cylinder is extremely short allowing for more aggressive braking, however the CP2623 master cylinder would allow for more progressive braking. This master cylinder requires a trunnion type balance bar.

CP7855
This master cylinder is similar to the CP7854, however the CP7855 is a earing mounted design. This master cylinder is available in bore sizes ranging from 14mm to 25.4mm and with 5/16 UNF push rods. The outlet is 3/8 UNF and the inlet is 7/16 UNF.

Repair kits
Repair kits are available for all of the above master cylinders. Most race teams will have spare master cylinders and/or repair kits. However due to the limited running a Formula Student car goes through and the limited budget most teams are running on most teams will skip this. However these repair kits may be useful if you are re-using master cylinders from last years cars.

Reservoirs
Brake fluid reservoirs for the above master cylinders are available. For single seater formula cars most teams will use a reservoir which fits directly into the master cylinder. This is to help with centre of gravity and keeping the weight low in the car. For saloon racing and rallying often teams will use a remote reservoir which is mounted higher up in the engine bay and is easier to top-up. For Formula Student applications most teams will use CP4709 reservoirs and if the have the space they will directly mount these into the master cylinder. If you are using CP2623 master cylinders then please use reservoirs CP4709-10, CP4709-11 or CP4709-12. If you are using CP7854 or CP7855 master cylinders then you should use the CP4709-13, CP4709-14 or CP4709-15 reservoirs.
If you are planning on mounting your reservoirs remotely then you will need CP6614 hose and push on fittings for bother the reservoir and the master cylinder.

If you need any further assistance then please call or email us with details of your requirements.