Here’s a for instance for you. You’re sitting in your car at a red light, your foot pressing the clutch pedal firmly against the floor. You plan to annihilate the tires on your car as soon as the light turns green. You know your car can do it; you’ve got a turbocharger, a performance tune, and a set of gears to make it all happen. As soon as the light goes green, you side-step the clutch and start your smoke show. But, something doesn’t seem right. You see the smoke, but the smell is different. It doesn’t smell like tire smoke, and then you see it. You see the guy filming video of you trying to do a burnout, and smoking the stock clutch in your car. You my friend are about to go viral on YouTube as a fail.
While the OE clutch in your ride worked great when your car was all OE, upgrades tend to put more stress on parts—some of us learn that the hard way, but I digress. Anyway, your car came equipped with a single-disc clutch, which means that your “clutch” consists of a flywheel, clutch disc, and a pressure plate. When you push the clutch pedal, the pressure plate releases the pressure on the clutch disc, and you don’t move. When you release the pedal, pressure is applied, and your car moves.
Anyway, now that the only thing left of your factory clutch is the smell, you need to figure out how to fix this little situation. Replacing the clutch with another OE unit will heed the same results, so it’s time to step up. But, stepping up requires a little knowledge. How do you know what you need, if you don’t know what’s available?
As the performance of your car increases, so should the characteristics and durability of the clutch material. The following is a brief synopsis of clutch materials available, and when each should be employed.
Organically Speaking Organic material is what’s used in the making of stock clutch discs. This material works great in normal driving conditions and usage, but as operating temperatures rise, or under high loads (which is usually accompanied by slippage), they fade. This is because their coefficient of friction drops off. In addition, at high rpm and/or when they get hot, they tend to fail structurally.
Bullet Proof Kevlar material offers a much higher coefficient of friction than organic material, but with some loss in drivability (i.e. it gets grabby when releasing the pedal). As the coefficient of friction goes up in the disc material, so will the aggressiveness of the material when the clutch is engaged. This usually results in clutch “chatter.” Since Kevlar is compatible with stock flywheels and pressure plates, it makes a good upgrade choice for later model vehicles, but using it takes some getting used to.
Aggressive Grabber Bronze metallic is the most aggressive material in regards to your clutch friction. Since it is aggressive, it offers extended life by reducing static pressures, and usage results in a quick, clean clutch engagement. Since it is the most aggressive material, it will also cause the quickest wear of the flywheel surface, and should only be used with steel or nodular-iron friction surfaces (pressure plate and flywheel). If used on the street, this material will cause chatter when the clutch is engaged.
Iron Age Sintered iron is great for street use, as it has a great ability to withstand some slippage, and not lose its friction coefficient. Sintered iron is great for high horsepower applications, and for drag racing and truck pulling.
To Date Twins or Not
Not only do you have choices to make in regards to what material your disc needs to be, but you also need to decide if you need one or two—discs that is. When discussing clutches, you need to consider a few things; the inertia of the clutch, the clutch’s torque holding-capacity, the “feel” of the clutch when releasing the pedal, and the particular application or intended usage of the clutch. Clutches are generally rated by their torque holding-capacity. A single-disc clutch will have less holding capacity than a twin disc, based on solely on their surface area.
01 The new clutch-flywheel assembly is removed from the package and needs to be dismantled
02 The installed height of the pressure plate is the distance between it and the flywheel,
03 The floater plate; the plate between the inner and outer clutch discs, is connected to
04 Ram’s inner clutch disc (left) has no springs. To accomplish a cushioned smooth drive,
05 In this high horsepower application, the car’s owner requested an aluminum flywheel. Ma
06 The two main advantages of the Ram upgraded clutch over this original assembly are incr
07 After installing a new pilot bearing, the lightweight flywheel is hoisted into place an
08 Following the instructions, insert a clutch alignment tool into the pilot bearing in th
09 Between the clutch’s master cylinder and the internal slave cylinder (throw out bearing
Twin-disc clutches are designed to have a lower inertia, but have higher torque holding capabilities, as they spread the load out over more surface area. Twin-disc clutches tend to be noisier in comparison to their single disc counterparts, simply because there are more plates and separators in the “package.”
So, a good rule of thumb is that a single disc clutch is a good all-around performance clutch on a stock or mildly modified engine. Depending on the clutch material used, it will have OE-like engagement and shifting qualities. Twin discs are designed to handle a lot more torque than a stock or even aftermarket single disc; therefore they are a better fit in higher horsepower applications. To make the right choice, know the torque capability of your engine, and as easy as it is to do, consult the clutch manufacturer.
Finally, we can’t talk about clutches, and not mention flywheels. It’s simple; the flywheel not only has the teeth for starter engagement, it is an energy-storing device. A heavy flywheel will cause the engine’s rpm to climb at a slower rate than that of a lighter (aluminum) flywheel. But, since it also stores more energy because of its mass than the lighter flywheel does, the engine’s rpm will not drop as dramatically (like between shifts) as it would if using an aluminum flywheel. On the other hand, a lighter flywheel will allow the engine to spin quicker, but a more dramatic drop in rpm will be noticed (like between shifts), and the lighter weight could also cause an issue if daily driving your car. This is because the lower inertial mass of the lighter (aluminum) flywheel means that the car will be harder to get moving from a stop sign or traffic light. Aluminum is generally used in road race/drag race applications where the engine is kept at higher rpm.
Without a pressure plate, your clutch will not work. The pressure plate applies the clamping force that squeezes the clutch disc between the pressure plate and the flywheel. But, just like with the flywheel and clutch disc, you have a choice to make. For this article, we’ll focus on the three main types of pressure plates: the Long style, the Borg and Beck, and the diaphragm.
The Long-style pressure plate is identified by the three thin fingers that contact the release (throw out) bearing. The Long style plate is usually used in drag race applications, and will have a considerably hard pedal “feel.”
The Borg and Beck style is similar to the Long style, but while it too functions via three fingers, they can be identified by the somewhat wider three fingers that release plate pressure. The Borg and Beck also uses rollers under the pressure plate cover that are forced outward under centrifugal force. This increases the plate load (pressure), with rpm.
10 Reconnect the shift lever, as well as the shift lever mechanism. Then on the transmissi
11 Reinstall the cast crossmember, the drive shaft, and refit the exhaust.
Finally, is the diaphragm pressure plate. It uses a series of “fingers” (also called a Belleville spring), that completely encompass the center opening of the pressure plate. The main advantage to this style of flywheel, is that holding the clutch pedal in at a stoplight is much easier than it is with either a Long or Borg and Beck type pressure plate.
So, which flywheel, pressure plate, and clutch material do you think you need now that you’ve smoked your clutch and became a YouTube favorite? The car described at the beginning of this article is a combination that a lot of guys have built, so the popularity of this combination means that a readily-available replacement/upgrade should be available, correct? Well, it is, and Ram Clutches has just what was needed. The high horsepower application that we’re looking at made us take a serious look at a twin-disc unit, and according to the guys at Ram Clutches, “Ram Street Dual-disc systems are specifically engineered for today’s late-model performance cars, and [late-model] engine swaps into earlier vehicles. The purpose of these clutches is to provide smooth drivability [at] high power levels that was previously not available using aggressive friction material-prepped single disc clutches.”
So there you have it, we’ve let you know how to decide what you need, now it’s time for us to see how easy it is—or isn’t, to install.
Progressive Pedal Play
Though not a chronic problem, the clutch pedal position on some modern muscle cars can be
Install, and simply adjust the nut located on top of the hydraulic cylinder to lower the h