Every clutch has its window of safe reliable performance.
Any clutch taken or pushed outside of that window will often see rapid clutch wear or premature failure.
Most commonly we see clutch systems designed for a cool running street type use, used in competition, that results in rapid over heating of the clutch.
Second to this , we also see clutches coupled to flywheels, that are not suited for the vehicles HP , weight and type of use.
Motorsport Safety – Essential Advice
First and foremost: SAFETY should always be paramount in any vehicle seeing any competiton or motorsport application.
Original or factory cast flywheels have no place in competition vehicles.
Cast flywheels are susceptible to cracking and possibly exploding – due to heat cycling over time- or severe bursts of heat that are often seen in competition use. .
In our opinion, a quality billet steel (or alloy) flywheel is a must for any vehicles seeing any competition use.
Crack in cast metal flywheel – shown above
Photo above – Exploded cast flywheel
Strap driven covers / pressure plates
As a close second safety concern to the cast flywheel is the strap driven type pressure plates.
Most common clutch pressure plates (or clutch covers) utilize 3 or 4 sets of strap sheet metal to attach the pressure plate casting to the outer sheet metal of the pressure plate.
From time to time we see these groups of straps bend when subject to abuse type use ie hard launches, dropping of clutch , aggressive non rev matched down shifts and so on
This causes a safety concern as the clutch casting is then off centre inside of the pressure plate! Very dangerous!
We also see many of the strap driven systems , equipped with non billet type casting , that are of similar grade to stock cast flywheel material.
At Direct clutch we do offer billet casting upgrades to some common clutch covers with upgraded stap packs. Though nothing can substitute for the strength and safety of a complete billet clutch system, that utilizes a lug drive system .
A lug drive system eliminates the strap drive system completely.
A general guide of what we have found to work best
(contrary to common belief)
Generally speaking the lighter the weight the better for any clutch and flywheel components for any continuous hi rpm, circuit racing whether it be turbo or naturally aspirated form .
However we do need to place this into 2 catogories.
A: With out standing starts
B: With standing starts
A: A super light clutch, clutch discs and flywheel, not subject to standing starts or trailer loading, will usually see long an happy life, if kept under its HP rating.
B: A super light weight clutch , clutch discs and flywheel. will never be ideal for a standing starts. It will come at a price of high wear rate and easily over heated. We would then suggest other heavier options
Generally speaking in forced induction or naturally aspirated, we suggest clutch and flywheel components to be heavier the better!
We see this to have 2 advantages,
1 Inertia: A heavier flywheel at RPM will always provide a greater hit to the drive train and helping turn the back tyres
2 Heat capacity: A heavier flywheel will always offer greater heat capacity, obsorbing heat from the clutch and clutch disc.
*We would strongly recommend a quality billet steel flywheel over a stock cast flywheel to be used always in driftDrew, Direct Clutch
Worthy of mention, sprung hub verses solid….
We often have customers requesting a sprung hub in their DCS clutch set up..
A sprung hub commonly provides up to 6 degrees of twist , prior to hitting the stop pins. Repeated hitting of the stops too many times, we often see the stop pins tear out from the disc itself.
In our back to back testing, a sprung hub provides reduction in noise only. In our opinion a sprung hub is not the magic wand / drive train saviour that myth would have it
Below is an example of a sprung hub even from an organic clutch disc .
In the picture below the green arrow highlighting the stop pin already coming loose…Red circle shows the impact of the hub on the stops.
Generally speaking, we continually see benifit in a heavier clutch and flywheel assembly in most classes of drag racing.
This is manly due to the gains made in start line inertia and rpm stability off the line with a heavier assembly.
A lower assembly weight is a little more liklely to stall, and higher RPM is required, often making the launch more difficult.
We generally see gains with a medium to heavy weight flywheel in most hill-climb applications, purely due to the up hill starts and long climbs seen in many hill climb events
Lighter the better , due to the stop start nature of this type of motorsport, often on level tracks
If anything the lower over all weight flywheel and clutch assy would be of benefit to roll racing….
But with many roll racing cars being used for other duties, we would suggest to base the selection on the other use the car sees.
Due to the rolling starts on continuous hi RPM in speedway, we gnerally see gains in lowest clutch and flywheel assembly weight.
Despite common opinion, we would suggest medium weight for all NA strret cars and heavy for all turbo.
A low weight assembly can often see a street car more liklely to stall off idle, uneven engine charactistics at low rpm
We do not recommend driving any car onto a car trailer.
Many of the units that come to us for a service or rebuild , may have seen upto 25% of the wear as a direct result from loading the car onto the trailer via riding the clutch.
We strongly suggest winching your car onto your trailer.
Generally speaking the heavier the better . Though with the limits of many engines being tested, there have been some gains in lowered flywheel weights to assist with engine harmonics and ultimately reliability