Getting the clutch right is usually the biggest part of getting radials to stick with a manual transmission. Too much clutch will knock the radials loose and make things very difficult.

When the clutch has more torque capacity than what the engine is putting out, that clutch pulls the engine down when you dump it, which in turn releases inertia energy from the rotating assy. For example let's say an engine is making 600 ft/lbs but the clutch has 800 ft/lbs of capacity. When you dump that clutch on the starting line, it will pull an additional 200 ft/lbs of inertia energy from the engine's rotating assy, and the net result is that the transmission's input shaft sees the full 800 ft/lbs of torque that the clutch can hold. If that 800 ft/lbs is enough to overpower the radials, they will get knocked loose with little chance of a quick recovery.

When dead hooking, that excess clutch capacity is also what determines how quickly the engine loses rpm after launch. If that 600 ft/lb engine above had a clutch with only 700 ft/lbs of capacity instead of 800 ft/lbs, the clutch would slip twice as long. The net result from that is the car has more time to gain speed before the clutch locks up, which in turn means the engine will only bog half as much as compared to the 800 ft/lb clutch. Not only does a closely matched clutch improve bog rpm, it also improves recovery rpm after WOT shifts.

Bottom line for radials- the better matched your clutch is to your engine, the more average power your engine will make, the easier your chassis will be to set up, the easier it will be to dead hook your radials, and the quicker your car will run.

All that said, my Clutchtamer eliminates that downside to installing a clutch that has more clutch capacity than you need. It basically makes it possible to temporarily dial back that excess capacity for a good launch. For me personally, it allows me to use a clutch that holds the torque when i'm spraying, but then allows me to dial back the hit of that same clutch for an effective NA launch at a zero prep event.

I'm a radial guy with a firm belief in dead hooking over wheelspeed, but this stuff can work with slicks as well.

Grant