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| This Quartermaster twin disc clutch has all carbon friction surfaces. Even though this is a racing clutch with no springs, low inertia and no Marcel, it is exceedingly smooth. |
The latest in disc friction material technology is carbon-carbon. This refers to all of the friction surfaces of the clutch from the disc or discs, the pressure ring and the flywheel surface all being made from amorphous carbon (solid carbon, not like laid up carbon fiber like in your hood). Carbon is an impossibly good friction material. It is strong and very burst resistant, very light, very smooth – silky smooth in fact, and it has excellent grip that gets better at higher temperatures. It lasts the longest of any friction material and it is non-abrasive. Carbon only has two drawbacks, one is its ultra expensive, and two it tends to wear faster at lower temperatures. There are reports of carbon clutches wearing very quickly on the street for this reason. Carbon clutches are used exclusively in high-end motorsports applications and would otherwise be used everyday if it weren’t for the cost. A slightly cheaper alternative is carbon-steel. In this case the disc is mostly carbon with some friction modifiers but the pressure plate and other surfaces are steel. This is a cheaper alternative that works pretty well.
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| This Exedy twin disc clutch is a carbon-steel type. Carbon steel has many of the advantages of carbon carbon but a lower price because it uses half of the carbon. The carbon must have friction modifiers added to it to help it grip the steel but carbon steel clutches are still very smooth. |
Friction Material Characteristics
(Rating 1-5, with 5 being best)
| Material Type | Smoothness | Burst Strength | Mu Cold | Mu Hot | Life | Abrasiveness |
| Organic | 5 | 1 | 5 | 2-1 | 2 | 5 |
| Kevlar | 5 | 3 | 4 | 2 | 3 | 5 |
| Semi Metallic | 4-2 | 3-4 | 4-2 | 4-3 | 3-4* | 4-2 |
| Copper Ceramic | 2 | 5 | 2 | 4 | 2-4* | 2 |
| Sintered Iron | 1 | 5 | 2 | 5 | 2-5* | 1 |
| Carbon | 5 | 5 | 2 | 5 | 2-5* | 5 |
* The smaller number is street use, the higher number is racing use
Sources
Nukabe Automotive
Cusco Clutches
www.napsusa.com
Jim Wolf Technology
Nissan Clutches
www.jimwolftechnology.com
Centerforce
www.centerforce.com
Clutch Net
www.clutchnet.com
Clutch Masters
www.clutchmasters.com
Exedy
www.daikin-clutch.com
Fidanza
www.fidanza.com
Unorthodox Racing
www.unorthodoxracing.com
