Footbrake quicker than transbrake

[treessavoy]

Originally Posted by Alan Roehrich

Over the years I worked in a transmission shop in Nashville, I worked mainly on racing transmissions, and in around 90% of the Super Stock cars, a foot brake transmission was always measurably quicker, consistently. We even built identical transmissions, except for the valvebody, and in nearly every case, the foot brake setup went quicker, regardless of how the chassis was adjusted, even in 4 link cars. We also tried changing rear end gears and low gears in the transmissions, as well as torque converters. In many cases, I think it may be that the engine is happier with the RPM held well below the flash speed, so that the converter flashes hard/higher and does a better job of multiplying torque. Also, a torque converter really needs to be built for the way you intend to use it, either with a transbrake, or foot braking.


I think the modified cars, and maybe some others with high RPM small displacement engines that need a very high stall speed may be quicker with a transbrake, if the car can be adjusted for it, simply due to how hard it is to make the converter work well. I know they are easier to drive well with a transbrake.

Alan,

When you say the footbrake was quicker, do you mean footbraking while leaning on the convertor or launching from an idle?

JimR

[Alan Roehrich]

Originally Posted by treessavoy

Alan,

When you say the footbrake was quicker, do you mean footbraking while leaning on the convertor or launching from an idle?

JimR

Pretty much various degrees of both. Most guys are "swapping feet", ie, holding the RPM at around 1/2 of the flash RPM (as low as 2000 or so, as high as 4000 or so) while holding the brake down hard, then matting the accelerator pedal while dumping the brakes.

It is extremely important to note that I'm talking about a very well tuned car, if you have a car you just can't get to rev up or flash quick and clean, it's not going to run well foot braking.

[Dave Cook]

Don't forget the rollout difference when comparing your ET's.

If the transbrake launch is picking the fronts straight up out of the beams rather than getting the run at it rolling out, it could be a .03-.05 difference.

[Patric Fox]

The Carter carburetor in the AMX does not have enough acclerator pump shot to foot brake. That could be a problem in other applications, making the transbrake faster.

[Myron Piatek]

I was told about one variable that makes sense. A footbrake trans can be quicker than a transbrake trans because the transbrake requires a higher line pressure. That would create a slight parasitic HP loss throughout the run. I haven't run a brake even years ago in brackets, but it seems like a footbrake carb set-up can be more finely tuned.