Saving on vehicle costs

[travelover]

The initial reason to increase the rim diameter was to meet new mandated braking performance. Bigger wheels allow for bigger brakes. After that, further increases in rim diameter were primarily driven by styling.

 

[Finance Dave]

The initial reason to increase the rim diameter was to meet new mandated braking performance. Bigger wheels allow for bigger brakes. After that, further increases in rim diameter were primarily driven by styling.

One of these days we'll move to electromagnetic braking completely, thus doing away with rotors and calipers. Today some of the electric cars have 'regenerative' braking, but it's supplemental to the regular brakes...thus it saves no weight/complexity/cost.

 

[Finance Dave]

20. Do you know that feeling you sometimes get in a car where you press on the brake pedal lightly to stop, and the car sort of stops and goes…almost like a vibration, but more like a “wobble”? As the car slows, the "stop and go" slows…and if you let off the brake pedal it stops completely. This is due to “rotor runout”. It’s not dangerous…so if it doesn’t bother you, keep on driving. But if you want it fixed, the proper fix is to have the rotors resurfaced, which is where they remove them from the car and grind them down flat. Unfortunately, rotors are often made so thin that they cannot be safely resurfaced, as there is a minimum thickness…and in this case you’ll have to buy new rotors. A typical rotor resurfacing would cost about $60-$80, and new rotors with labor would cost about $160 or so. You do not have to change the brake pads when you do this, but often the brake pads are either worn or glazed…so whether you do or not depends on the specific situation…talk to your mechanic and ask questions. Typically I would NOT change rotors, but completely understand there are times when you must.

If you're looking for ways to avoid having the rotor runout issue, read some of my other posts on brakes...avoid getting them hot in one place using the techniques I mentioned, use a torque wrench when tightening wheels, and avoid driving through large water puddles when the rotors are very hot.

 

[Finance Dave]

21. Ok, so related to my post on rotor runout, what causes brake rotor runout to happen? The answer is excessive heat. So why are they getting too hot? When you press on the brake pedal, two pads (or sometimes shoes) squeeze a metal disc called the rotor. You can often see the rotor if you look through your wheels…it’s shiny. That friction creates heat. The pads only squeeze it in one area making up about 20% of the total “swept area” as it rotates. Let’s say you’re going 50 mph down a hill, and there’s a traffic light at the bottom of the hill. You see the light change yellow…so you apply the brakes. Those pads squeeze the rotor…and the entire rotor heats up as the rotor “sweeps through” the pads. Then when you get to the traffic light, you hold the brake pedal on, which keeps the hot pads against that hot rotor…while the remaining 80% of the rotor sits in the open air, cooling off. Voila…you’ve created a situation where one part of the rotor is heated more, and thus it’s size/shape changes slightly, and you get rotor runout. Multiply this over the thousands of times you stop your car, and you can see how this happens.

Another potential cause is where you get the rotors hot by braking a lot, then drive through a puddle of cold water…the water splashes up on the rotor, shrinks it quickly in one area…and voila…you have rotor runout again.

Another cause could be overtightening of lug nuts whenever wheels are bolted back on the car...use a torque wrench. Proper torque varies by the type of wheel and the type of lug nut (shank lugs require more torque and actually a re-torque if new than conical lugs - although most factory lugs are conical).

So why don’t they make rotors thicker so they can handle this? Excess weight reduces fuel economy.

Is there a way to prevent it? Yes, when you stop at a traffic light after a hard stop….inch forward 2-3 inches every 10 seconds or so, exposing all parts of the rotor to the air, cooling it evenly. Or, if you are on flat ground and have a manual transmission, simply take your foot off the brake pedal. I have manual transmission cars…and I’ve not had a rotor runout issue in 25 years…ever since I learned this trick.

 

[Finance Dave]

22. Tire size/info reading - ok, rather than me writing a long expose on this, let me just provide a link.

Tire Tech Information - Tire Size Guide

LOL

 

[Nords]

One of these days we'll move to electromagnetic braking completely, thus doing away with rotors and calipers. Today some of the electric cars have 'regenerative' braking, but it's supplemental to the regular brakes...thus it saves no weight/complexity/cost.

I don't know if there's a standard regenerative braking system, but the Prius only clamps the pads onto the rotors below 6 MPH-- or if the driver really stomps on the brake pedal. Otherwise the electric motor-generator does all the work when the driver's foot presses the brake pedal. It's like spinning up a heavy flywheel.

This is supposed to help the Prius brake pads last up to 100,000 miles. I guess it would minimize rotor runout too.

We'll know in about 10 more years...

 

[Finance Dave]

I don't know if there's a standard regenerative braking system, but the Prius only clamps the pads onto the rotors below 6 MPH-- or if the driver really stomps on the brake pedal. Otherwise the electric motor-generator does all the work when the driver's foot presses the brake pedal. It's like spinning up a heavy flywheel.

This is supposed to help the Prius brake pads last up to 100,000 miles. I guess it would minimize rotor runout too.

We'll know in about 10 more years...

Good info, thanks Nords. Yes and my understanding is that it charges the battery that way. What I'm not sure on is the thermal efficiency...in other words is there any heat generated during the part where the pads are not clamped? My guess would be no other than slight battery heat...but not sure.

 

[Nords]

Good info, thanks Nords. Yes and my understanding is that it charges the battery that way. What I'm not sure on is the thermal efficiency...in other words is there any heat generated during the part where the pads are not clamped? My guess would be no other than slight battery heat...but not sure.

No, I think the generator is just spinning from the rotation of the front axle on the chain of the CVT that's connected to the common shaft of the generator/engine. (Not sure what's happening to the back axle.) It's a big drag, and the heat is the normal heat produced by the resistance of the generator windings and the battery's chemical reactions as the current charges the battery.

I'm not sure how much the generator weighs, or how much torque it takes to spin all the gears & shafts, but whenever the car is coasting it's spinning the generator a little (and recharging the battery a little). If the car is coasting at faster than 41 MPH, the ECU actually spins the engine as well (with no gas to the cylinders) to prevent the generator from overspeeding. (I'm not sure exactly how the gearing achieves that.) Of course the car coasts quite well, and I've coasted down off the Ko'olau at up to 75 MPH with the battery getting a ferocious charge from the spinning wheels.

When the braking shifts over from electrical/regenerative to mechanical at 6 MPH, there's this momentary feeling that the brakes have slipped. It's a little exciting the first time you experience it-- usually about 10 feet from the car in front of you. It's even more exciting when your daughter is behind the wheel learning how to drive (while you're in the passenger seat) and instinctively pulls her foot off the brake...

 

[NW-Bound]

There are highways that descend a few thousand feet non-stop in just a few miles. I have driven on some with 10% and even 16% grade.

I wonder if the EV or hybrid car batteries would have enough capacity to store all that energy that is converted to electric. If and when the battery is full, the mechanical brakes must get activated. And as there is no combustion engine in a true EV to provide the drag, the brakes must then absorb a lot more heat. And in a hybrid, the combustion engine may be too small to provide the needed drag.

I am sure car makers have worked this all out, but I am curious about the details.

 

[Finance Dave]

23. Fluids you will find in a car
a. ----
b. Windshield washer fluid is light blue translucent
c. Anti-freeze is typically green/yellow and translucent. Typically it is recommended to mix 50/50 with water, although some stores sell “pre-mixed” fluid that can be used “as is”.
d. Brake fluid is clear and slightly viscous when new, but brown and slightly viscous when used. Brake fluid will eat paint…do not get it on any car finish. Brake fluid is hydrophilic, which means it attracts moisture out of the air. Once you open a sealed can, throw away any you don’t use within about a week or so…even screwing the cap back on the can is insufficient protection.
e. Oil is light brown and viscous when new, and dark brown/black and less viscous when used…also less viscous when heated in the oil pan
f. Gear oil is typically 80W-90…very thick viscous light brown fluid.
g. Automatic transmission fluids vary widely…many of them are red translucent, but in many front wheel drive cars they use motor oil or gear oil. See your owner's manual for the correct fluid.
h. Gasoline is very slightly brown translucent and has a distinctive, well-known smell

 

[Finance Dave]

That's my final "pre-written" post. I may have to start a new thread on a new topic in a few weeks...there is some exciting news coming.

 

[travelover]

That's my final "pre-written" post. I may have to start a new thread on a new topic in a few weeks...there is some exciting news coming.

This was an interesting thread - thanks.

Congratulations in advance.

 

[ERD50]

There are highways that descend a few thousand feet non-stop in just a few miles. I have driven on some with 10% and even 16% grade.

I wonder if the EV or hybrid car batteries would have enough capacity to store all that energy that is converted to electric. If and when the battery is full, the mechanical brakes must get activated. ...

I think this came up on Tesla's blog - one of the developer cars was used by a high level employee who lived on the top of a hill. So you charge overnight to 100%, and then go down a hill, and it won't use regen as you'd overcharge the batteries.

Not sure if they did anything about it, I suppose he could set it to charge to 95% or something.

Brake fluid is hydrophilic, which means it attracts moisture out of the air. Once you open a sealed can, throw away any you don’t use within about a week or so…even screwing the cap back on the can is insufficient protection. ...

In this day and age, isn't there some alternative brake fluid that would not absorb moisture? Moisture is a real safety issue. It turns to steam when it gets hot, and steam is compressible. Hydraulic brakes count on the non-compressiblity of fluids - so the brakes don't work (or not very well). Plus, the moisture leads to corrosion.

And +1 on thanks for starting this thread, some great points.

-ERD50

 

[samclem]

Not sure if they did anything about it, I suppose he could set it to charge to 95% or something.

When the battery gets full they could shunt the electricity to a BHR. "Big Honking Resistor."

In this day and age, isn't there some alternative brake fluid that would not absorb moisture?

Yes. Many cars still use DOT3 and DOT4 brake fluids, which are based on glycol and absorb water (which causes the boiling problems and the corrosion problems you noted). DOT 5 type fluids are based on silicone and don't absorb water, so they work at higher temps and they do a better job of protecting against corrosion in the brake system. Don't just switch over if your car's manufacturer doesn't specifically recommend DOT 5: The seals and other rubber components aren't always compatible. Also, if it gets into an engine (e.g. through a leaky brake booster, etc) the DOT 3 and DOT 4 fluids burn off harmlessly, the DOT5 burns to a gritty substance that is not good for the internals of an engine.

 

[bolt]

Hi you might find this link helpful True Cost to Own (TCO) Calculator on Edmunds.com True cost to own a auto.

 

[Finance Dave]

I think this came up on Tesla's blog - one of the developer cars was used by a high level employee who lived on the top of a hill. So you charge overnight to 100%, and then go down a hill, and it won't use regen as you'd overcharge the batteries.

Not sure if they did anything about it, I suppose he could set it to charge to 95% or something.



In this day and age, isn't there some alternative brake fluid that would not absorb moisture? Moisture is a real safety issue. It turns to steam when it gets hot, and steam is compressible. Hydraulic brakes count on the non-compressiblity of fluids - so the brakes don't work (or not very well). Plus, the moisture leads to corrosion.

And +1 on thanks for starting this thread, some great points.

-ERD50

Yes there is, DOT 5 silicone...but it's a whole different animal and I'd suggest 99% of the population stay away from it. I have it in my '69 Camaro.

There are a few cars that receive this from the factory...I think the Corvette is one.

 

[Finance Dave]

When the battery gets full they could shunt the electricity to a BHR. "Big Honking Resistor."


Yes. Many cars still use DOT3 and DOT4 brake fluids, which are based on glycol and absorb water (which causes the boiling problems and the corrosion problems you noted). DOT 5 type fluids are based on silicone and don't absorb water, so they work at higher temps and they do a better job of protecting against corrosion in the brake system. Don't just switch over if your car's manufacturer doesn't specifically recommend DOT 5: The seals and other rubber components aren't always compatible. Also, if it gets into an engine (e.g. through a leaky brake booster, etc) the DOT 3 and DOT 4 fluids burn off harmlessly, the DOT5 burns to a gritty substance that is not good for the internals of an engine.

+1, didn't see this until after I made my post above.

It took me 2 days to switch over my Camaro to DOT5. Too many things can go wrong if you don't REALLY know what you're doing.

 

[bld999]

When the battery gets full they could shunt the electricity to a BHR. "Big Honking Resistor."


Yes. Many cars still use DOT3 and DOT4 brake fluids, which are based on glycol and absorb water (which causes the boiling problems and the corrosion problems you noted). DOT 5 type fluids are based on silicone and don't absorb water, so they work at higher temps and they do a better job of protecting against corrosion in the brake system. Don't just switch over if your car's manufacturer doesn't specifically recommend DOT 5: The seals and other rubber components aren't always compatible. Also, if it gets into an engine (e.g. through a leaky brake booster, etc) the DOT 3 and DOT 4 fluids burn off harmlessly, the DOT5 burns to a gritty substance that is not good for the internals of an engine.

Beware, however, DOT 5.1 brake fluid is not silicone, but glycol. It should have been designated 4.1 or something. I don't know if it is widely available, but certainly some people are going to have a bad day with it.

 

[dennygt]

We go to Florida for three months (January - March) and have only one car. Not too bad, just got to plan the trips. It can be done!

 

[Nords]

There are highways that descend a few thousand feet non-stop in just a few miles. I have driven on some with 10% and even 16% grade.
I wonder if the EV or hybrid car batteries would have enough capacity to store all that energy that is converted to electric. If and when the battery is full, the mechanical brakes must get activated. And as there is no combustion engine in a true EV to provide the drag, the brakes must then absorb a lot more heat. And in a hybrid, the combustion engine may be too small to provide the needed drag.
I am sure car makers have worked this all out, but I am curious about the details.

The Prius battery system has a sophisticated and proprietary charge controller that the enthusiasts are perpetually trying to reverse engineer. (So are the makers of the aftermarket EV conversion kits.) Toyota doesn't share and it's a mystery, but it's based on both voltage and on the number of electrons that have flowed out of the battery during a certain amount of time. (Literally a coulomb counter.) I don't know the details.

But when the charger says the battery's full, the generator dumps its output somewhere else. There's also a special "B" gear for "Braking with the engine" (that I've never used) designed for extended downhill mountain driving.

I'm going to have to look those up on PriusChat and in my owner's manual.

Windshield washer fluid is light blue translucent

I've stopped using it.

I use distilled water or the water out of our whole-house conditioner, but I don't add anything to it. Of course it never freezes on our part of the island, so I can get away with "just" water.

 

[NW-Bound]

When the battery gets full they could shunt the electricity to a BHR. "Big Honking Resistor."

But when the charger says the battery's full, the generator dumps its output somewhere else. There's also a special "B" gear for "Braking with the engine" (that I've never used) designed for extended downhill mountain driving.

There we go. A simple solution! As the power to be dissipated can be many tens of KWs, I am willing to bet that the "BHR" would need forced-air cooling. I would look for a metal box with a fan at the inlet, and a directed exhaust.

 

[meierlde]

There we go. A simple solution! As the power to be dissipated can be many tens of KWs, I am willing to bet that the "BHR" would need forced-air cooling. I would look for a metal box with a fan at the inlet, and a directed exhaust.

Which of course is what diesel locomotives do. Look up regenerative braking in the context of diesel locomotives. Some locos have what is called a bonnet where there are large fans that blow air past a set of resistors. Of course if one were to install an overhead wire one could reclaim the energy and pass it to trains going uphill. I don't think up till now the economics have panned out on Cajon Pass or over Techapai pass (Bakersfield to Mohave) or over the Sierra.

 

[dennygt]

Ethynol is garbage, sorta like using hamburger helper.

I notice the decrease in mileage on my 4 cyl camry. It seems to be about 1 to 1 1/2 miles per gallon less with the ethynol.

To me it's just another scam from the oil companies to increase profits. JMHO

Actually, it's not the oil companies, it's the US gov't. being bought out (ok, lobbied) by the ethanol industry, and leading the charge is ADM (Archer Daniels MIdland). Over 40% of their profits are from federal subsidies, a significant portion of that amount from its ethanol production.

Just last year the Feds allowed up to 15% (was 10%) ethanol allowed in gasoline, for newer models only.

 

[ls99]

Light rail vehicles use regenerative braking down to about 5 MPH, then friction brakes are employed for stopping. If the line is receptive, then power is dumped into power lines or third rail depending on configuration.

On Ward Leonard powered AKA Diesel Electric Locomotives, at night the braking resistors really light up, and the cooling fans kick in at a ferocious rate, too keep them from burning up.

 

[travelover]

On the Ford Escape hybrid, when the battery is full and more regenerative braking is needed, like on a steep grade, the generator on the wheels powers the electric starter motor on the internal combustion engine and spins it at a maximum safe RPM. Of course, the friction brakes are the ultimate backup. There is no big honking resistor.