Pumpers really pump?

[Reaper1]

Unfortunately if you put a car on jackstands...or just free-spin the wheel on a wheel balancer or anything else, you WILL feel a breeze...regardless of the possible "pumping" effect. Even then that doesn't tell the whole story because the wheels are inside of a wheel well while the car is moving. The interaction between the aerodynamics of the car and *just* the wheel will be pretty much impossible to discern. Suffice it to say that there is a possibility that the wheels do in fact help evacuate air from behind them to help aid in cooling the brakes, but I don't think any of us would be able to quantitatively determine if that's true or by how much.

Bakes, the better cooling you saw on you GLH was probably a combination of different things. #1, the wheels are larger in diameter, so there is physically more space for air to flow around the brakes. #2, because the wheels are larger, I do believe they are heavier equating to more mass to act as a heat sink. #3, also because the wheels are larger, and because of their design, I'd venture a guess that there is more surface area to dissipate and absorbed heat.

[supercrackerbox]

Perhaps a better visual could be had by having someone follow you with a camera (or a body mounted Go-Pro) while driving in a heavy rain. One thing I have noticed with the Daytona and Charger (both of which wear 16" pumpers) is when driving in heavy rain, the brakes do tend to get "wet" requiring heavier braking. This condition is much less pronounced when I have the crab wheels on the Daytona. I don't know if that means anything or not.

[Reaper1]

Just means there's more room for water to get on the brakes, honestly.

[supercrackerbox]

I'm sure you're right, but it was a thought.

[contraption22]

I would think anything that would be somewhat effective at drawing enough air would add significant drag. Thinking like an engine driven cooling fan.

First thing to do would be to determine that you're going to have a problem. If you do, then I'd take at look at what the manufacturers of rear and mid engine vehicles have done to address it.

[johnl]

Waaah, Alan forgot me.

Willow big track, Streets of Willow, Las Vegas. The GLHT, GLHS, and Ramerati - they've all been out there. Not lately, though, and just track days, not real races. And, while I do have a set of 16" pumpers, never ran them on the track, the good tires were on the 7x15 Fiero wheels, which are hybrids - cast centers welded to forged hoops.

And, generally forged wheels, pound for pound, are stronger than cast, and that means they can be made lighter, size for size.