I 70 sucks

[pchewn]

When I'm at Colorado National Speedway, only the high end classes brake hard enough to light up the rotors. The amount of heat produced is roughly inversely proportional to the speed of the car. A few of the fastest drivers hardly or never light up their brakes at all, while some of the slowest ones look light they're about to explode into flame. I think it's a complex combination of driver skill, chassis setup and individual gearing of each car.

I believe the amount of heat produced is proportional to the SQUARE of the speed of the car.

A car braking from 40 to 0 will produce 1/4 of the heat of a car braking from 80 to 0 .

The kinetic energy of the car is given by the formula E = 1/2 m V ^2

Intuitively, the amount of heat cannot be inversely proportional to the speed of the car: More heat for a slower car? I don't think so.

 

[jmeb]

Intuitively, the amount of heat cannot be inversely proportional to the speed of the car: More heat for a slower car? I don't think so.

I think @Don in Morrison wasn't referring to absolute speed, but cars that are being driven with more proficiency -- i.e. less braking. Same in mountain biking -- the fastest rider the one who relies on their brakes the least.

 

[Don in Morrison]

I think @Don in Morrison wasn't referring to absolute speed, but cars that are being driven with more proficiency -- i.e. less braking. Same in mountain biking -- the fastest rider the one who relies on their brakes the least.

That's right. A skilled driver with a good chassis set-up can carry more speed into the turn with less braking. Less than optimum chassis set-ups might require more braking, even with a good driver. Some drivers just don't have the nerve, or the skill, and they end up braking harder and entering the turn at a slower speed. Then there are the ones with a set-up so bad they have to lift early and brake lightly so they don't swap ends going into the turn.

 

[tball]

Descending from the Tunnel to Denver at speeds of 60mph+ in 4-7000# vehicles is on the edge of an "extreme" driving scenario for most vehicles. It is common to warp rotors and burn through pads doing so. Sure -- if there was no traffic maybe you could brake very strategically to avoid this -- but there is always some traffic on 70.

This is worth emphasizing.

Also, not only will using your brakes to control your speed on I-70 wear them out much faster, your emergency stopping distance will be longer due to your hot brakes.

Control your decent speed with your engine, and only use your brakes for traffic.

 

[Dave Marshak]

Also, not only will using your brakes to control your speed on I-70 wear them out much faster, your emergency stopping distance will be longer due to your hot brakes.

Now you’re just making stuff up. Overheating brakes isn’t really a thing for passenger cars anymore.
Downshifting to control speed is never necessary anymore, and never provides better control than brakes, at least not with modern cars.

dm

 

[jmeb]

Sorry @Dave Marshak . You're just factually wrong. The reason why I've replaced several sets of friends' warped front rotors in the last few years is because they overheat them on long descents from the tunnel. There is no other reason you'd see such frequency of warped rotors among a wide variety of otherwise fine, modern cars besides heat.

Lets not even get started on spirited driving. I can produce brake fade in my Miata on downhill canyon runs no problem.

Is it typical driving in flat lands? No. Is it a fact for larger passenger vehicles descending I70. Yes.

 

[scott43]

Another pet peeve of mine is the warped rotor thing. They don't warp really. Mostly it's improper installation. My motorcycle rotors heat cycle endless times and end up permanently blue. No warping. Go to a better shop...

 

[Dave Marshak]

Nope. @jmeb Downshifting is obvioiusly easier on the brakes, but brakes are always better for control. FWIW I don't recall ever downshifting or overheating the brakes on I-70 in any of the rental cars I've driven to Summit County. I can't tell you how long those brakes lasted, but the car stayed in control.

dm

 

[Dave Marshak]

FWIW my rotors rust away before they wear out, but I travel a lot and my cars sits at the airport for weeks at a time.

dm

 

[tball]

Now you’re just making stuff up. Overheating brakes isn’t really a thing for passenger cars anymore.
Downshifting to control speed is never necessary anymore, and never provides better control than brakes, at least not with modern cars.

Really? Then why do they stop you and check the temperature of your brakes half way down Pikes Peak?

 

[slowrider]

Sorry @Dave Marshak . You're just factually wrong. The reason why I've replaced several sets of friends' warped front rotors in the last few years is because they overheat them on long descents from the tunnel. There is no other reason you'd see such frequency of warped rotors among a wide variety of otherwise fine, modern cars besides heat.

Lets not even get started on spirited driving. I can produce brake fade in my Miata on downhill canyon runs no problem.

Is it typical driving in flat lands? No. Is it a fact for larger passenger vehicles descending I70. Yes.

Engine braking is always better. That's why class 8 trucks have aux braking devices. Exhaust & transmission braking devices. I've got hot brakes off of mt grades before. That'll make you pucker up. Some people are untrainable regardless of the facts or experience. After 4 million miles I'm just talking out my ass.

 

[RachelV]

Really? Then why do they stop you and check the temperature of your brakes half way down Pikes Peak?

Hah, you beat me to it. I was very proud when I didn't have to pull into the mandatory brake cool down lot after the Pikes Peak ranger checked my brakes with a thermometer gun. Interesting experience all around.

 

[scott43]

Pad selection is the primary driver of temperature range. Passenger car are really the worst vehicles to try and pad appropriately. You need both cold and hot performance with no noise or shudder. Having said that, today's brake pad technology is really very good. Buy OEM rotors and pads and you're likely at the best place for all around performance.

 

[jmeb]

@Dave Marshak -- Your opinion about brake performance is as an infrequent visitor to I70 using rental cars.

Mine is as someone who travels up/down I70 80-90 times a year, and works for an operation that spends the winter operating a fleet of full-size trucks up/down mtn passes. Collectively we cover about 100k mi a year. Our umbrella agency we fleet share with does well over a million.

Each fall we go through reminders of how not to cause unnecessary wear on the vehicle. Engine braking is covered every time.

 

[scott43]

Really? Then why do they stop you and check the temperature of your brakes half way down Pikes Peak?

Partly because people drive poorly modified and maintained vehicles.... For instance every lowered vehicle ever....

 

[scott43]

@Dave Marshak -- Your opinion about brake performance is as an infrequent visitor to I70 using rental cars.

Mine is as someone who travels up/down I70 80-90 times a year, and works for an operation that spends the winter operating a fleet of full-size trucks up/down mtn passes. Collectively we cover about 100k mi a year. Our brother agency we fleet share with does well over a million.

Each fall we go through reminders of how not to cause unnecessary wear on the vehicle. Engine braking is covered every time.

Engine braking used sensibly is fine.

 

[jmeb]

Hah, you beat me to it. I was very proud when I didn't have to pull into the mandatory brake cool down lot after the Pikes Peak ranger checked my brakes with a thermometer gun. Interesting experience all around.

If you were driving the Sienna that is a feat. Those things eat brakes for those without technique...

 

[Dave Marshak]

Engine braking used sensibly is fine.

I agree with that. Engine braking as your first or only choice for slippery road conditions is obsolete.

dm

 

[Dave Marshak]

... operating a fleet of full-size trucks up/down mtn passes. Collectively we cover about 100k mi a year.

Each fall we go through reminders of how not to cause unnecessary wear on the vehicle. Engine braking is covered every time.

Full sixe trucks are different. Jake brakes save lives.

dm

 

[scott43]

I agree with that. Engine braking as your first or only choice for slippery road conditions is obsolete.

dm

Well you wouldn't want to be doing anything silly engine braking in a front or rear wheel drive vehicle in slippery conditions.. too hard to modulate lock up except at very slow speeds. And really brakes aren't that issue at low speeds.. but in normal conditions, have at it.