The sun is in their eyes too..
Enjoying the show :-)
Ha!

True dat, but there is one, so obvious that it's easily missed, basic principle of physics that, when elucidated, produces an inevitable, Uhh, ermm, well yeah, of course!!!

Ha! :D.

Think about it...you'll get it. SmileWavy

Braking is more effective going uphill

I grew up on top of a great hill climb. Highway 84 from Woodside up to Skyline Blvd. Some of you know it. I used to race it flat out when I was young and foolish.

All I know is that when going downhill, the rear of the car had less weight on it and felt more squirrelly. I had to be more careful. Not so going up hill. Has to to with weight distribution and centers of gravity, I believe.

Yup.

Driving uphill is driving 'into' the hill; more downforce/greater traction than on level.

Driving downhill is driving 'off' the hill; less downforce/traction than on level.

If the uphill direction produces the faster times, then the answer is not physics, but psychological.

Braking would indeed be improved uphill, but acceleration would be degraded . A possible aid to acceleration would be weight transfer to the rear wheels, assuming RWD .
, but I doubt the increase in traction would offset the demands of power to offset gravity.

What remains is nerve.

Best
Les

While that answer does seem obvious to me, I think there is another answer to the question as the original question did not mention uphill v. downhill. The dynamics of the radii in the turns will favor speed in one direction over the other even assuming that the road is secure and you can use all of it.

But, the idea does bring up an interesting idea. Race Pike's Peak downhill. I wonder how far off his record Loeb would be.

The answer actually is physics. On a winding road with adequate runoff areas (go as fast as you want, if you spin off it won't matter), assuming horsepower adequate for the task, uphill runs will always be faster.

Because uphill v. downhill is the basic answer to the original question. Bill Douglas answered it in the first post.

Assuming the car is set up to turn equally well, left and right, how would you explain that? If by "dynamics of the radii" you mean increasing and decreasing, those dynamics are the same going uphill as downhill.

A whole lot!

I don't think so.
Driving uphill you have gravity helping you brake, so braking times are less and "on the throttle" times are greater and with ample HP that = faster times. But I don't see how a car has " more downforce/greater traction" pointing one way on a hill vs pointing the other.

Assumes rear-wheel drive.

Crest a hill and a car "goes light" as its forward momentum lifts it "off" the road surface. Begin an incline and a car "goes heavy" as its forward momentum drives it "into" the road surface. Doesn't matter which of the cars wheels are driven.

I'm now wondering whether anyone here seriously believes that Pike's Peak can be run anywhere near as fast downhill as uphill.

Hehe, sorry I should have started off with "The corners are slow in fast out one way..."

So, if I have it correctly, you are saying on the uphill, you are accelerating the car upward, so there is increased traction available for cornering and in the downhill runs, because the car is in some way "lighter" on its tires, there is less traction available for cornering, acceleration and braking.

If this is indeed the case, I wonder at what velocity it becomes relevant.

Best
Les

Racing velocity, when you are at the limit of adhesion. An easy way to think about is with a helux, like in an airport parking garage. That would be easy to try because hp wouldn't matter much and the radius is tight and continuous. You could easily increment up speed.
Of course knowing that going down your accel due to gravity is subtracting from normal force to tires, versus adding in the uphill direction should be enough.
Probably why hill climbs are so popular.
Fun little question darisc, thanks for the provocation.

Many years ago, a gasoline company had a well known TV on-air personality drive a car from A to B with generic gas.

Then from B to A with Chevron with techron. Got almost 5 mpg better mileage.

Played the ad for weeks before the lawsuit. Even the TV guy was sued.

A was Los Angeles.
B was Las Vegas.

A to B is uphill all the way

B to A is downhill all the way.

The ad disappeared.

What ends in Vegas stays in Vegas.

What returns from Vegas can be sued. :cool: