Adam Dorey: The Stick Shift Mafia Wants You — Part 3
Like most things motorsports, a transmission is all about the combination — not the individual parts — to create a winning and trouble-free race car.
Assuming you’ve chosen your transmission, now we can look at your clutch program. There are many choices when it comes to types and manufacturers and all will depend on how much power you make and what your goals are with your ride. Your transmission program will be much different for a 2000 horsepower turbo car than it will for a 350 horsepower N/A car. For the sake of this article, I’ll talk about some of what I’ve seen first-hand, and rather than talk in manufacturer names, I’ll talk generally about types of products, and you can do your research on your own to complete your purchase with any number of qualified manufacturers.
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Street car: A lightly modified vehicle, maybe with some heft to it, where driving comfort overrides pure strip performance, a daily driver that can also do weekend dragstrip duty. This is the crowd with ‘full bolt-ons’, up to about 500 horsepower or a small blower/nitrous hit on the weekends. This kind of setup is exactly what I have in my Cadillac CTS-V, an N/A stick car weighing 4000lb. A TON of rides fit into this catagory, and I've got good news for you! Your clutch components can be had at your dealer! Since we’re living in the real muscle car war era, odds are good there’s a ‘hot rod’ version of your car out there, be it a Hellcat, Z06, GT500, or any other number of very powerful factory offerings. They’re also stuffed with stick shifts and have the fortune of being equipped with good clutches from the factory! These are built for both the factory power these rides make, but also are made for good drivability and road manners. They’ll be equipped with organic clutch material typically, which will work great without any heat, but won’t slip quite as easily, and will be packed with comfort features such as hub springs, a little bit of shock absorption right at the point of connection as well as a marcel, a big flat spring in between either side of friction material on the disc to further improve engagement comfort and lack of chattering. Stick with heavy steel flywheels for this kind of ride, especially if it’s heavy. Depending on the speed of your ride an OEM bellhousing can work here as well as a scattershield if you want the extra insurance/protection.
Aggressive to very aggressive street car: A heavily modified car, likely lighter than a street car, where racing takes priority over comfort. Turbo(s), blowers, single digit timeslips in the glovebox, but still a driver, up to 1000+ horsepower and sticky tires. You’ll be into aftermarket clutch territory here, and typically these clutches will be multi-disc, with two or three friction material discs separated by solid metal plates and a diaphragm pressure plate. The wearable part of the disc will typically be ceramic or kevlar at this level, and you will have lost spring hubs and possibly the marcel for smoother engagement in lieu of strength and heat-bearing abilities. These clutches tend to be more chattery during engagement due to the lack of hub springs or a marcel in the disc(s), and their range of engagement is typically a very small portion of the clutch throw; they’re basically an on/off switch. You can slip these clutches though, either utilizing your leg after you figure out where the launching “sweet spot” is, or by using an aftermarket clutch slipping device. There are many on the market, and they’ll work especially well with the non-organic disc materials in these clutches. Billet steel or aluminum flywheels are at home here, depending on the weight and main use of the ride, and you’ll be in scattershield territory here, as you’re not going to be one of the cool kids if your flywheel or clutch saws one or both of your legs off if they fail under power.
Race car that can street: Like the name suggests, these are FAST rides with tons of power. Depending on how deep your pocketbook is, the power capability of these clutches is unlimited, as cars like nitro burning top fuel dragsters and funny cars use a clutch and a single gear ratio to get down the track (literally eating the clutch up on the run to launch the car, keep it planted, and apply 100% of the clutch exactly where they need it to in the run). Here you will not be utilizing electronic means for slippage, but mechanical means with ‘turns’ in the base pressure (how much pressure the clutch is applying at static but engaged) and how much weight is put into the centrifugal pressure plate arms which will change the RPM where the clutch is applying maximum grip. These clutches will allow you to simply dump the clutch, and the clutch will take care of the rest. These are typically a sintered iron disc, which is noisy on the street and doesn’t grip very well until you build some heat into it. Unless you adjust it for the street for every drive, you won’t be able to ‘lug’ the engine, as the centrifugal weights won’t be adding pressure to the clutch at lower RPMs, so for a transmission with an/multiple overdrives, this type of clutch WILL need adjusted before attempting to drive on the street. These are available in single or multi-disc configurations for power handling as low or as high as you can imagine. Truly these are a clutch for any power or weight drag car, but they require a scattershield with a window in it to do your adjustments, and although they’re not difficult to adjust, they are time consuming to get it right, and it will add another variable in your tuning program.
If you’ve read this whole series so far, hopefully I’ve convinced you to use a stick shift in your ride. In party two you chose your transmission for your intended use, and now with part three you’ve chosen a clutch. Stay tuned for part four, the final part of this series, which will cover how to set up the rest of the car to be ready for the new third pedal, and you’ll finally be one of the cool kids!
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