Keeping up speed going downhill


#1

Why do I have to use the gas pedal to keep up my speed while going downhill?


#2

Aero drag, frictional drag, tire drag to name the biggies.

The SUV us a barn door. LOADS of aerodynamic drag to be overcome. Big tires with lots of rolling resistance, AWD driveline with lots of frictional losses. That answer your question?


#3

I forgot to mention that if I quickly tap the brakes it will then gain speed going down the hill. None of the other AWD’s I owned ever did this. They all gained speed going down the same hills.


#4

Some of the newer vehicles will down shift a gear after you release the accelerator to provide a little engine braking to reduce the wear on the brakes. I find it a little annoying to have to hold the accelerator on roads that I usually coast on.


#5

Thanks. My feelings exactly. Save money on brakes & spend it on gas.


#6

Another idea, the brakes are dragging for some reason. Feel the wheels after a freeway drive with little braking involved. Do any of them feel really hot? You could also shift to neutral and coast (for testing purposes only) when this happens. If the car speeds up on down-hills shifting from D to N (assuming an automatic), it must be the transmission that’s slowing you down, not the brakes.


#7

I tried that once & it does speed up in N, but I would not do that for more than a second or two. My daughter has a 2017 Edge which does the same thing.


#8

Yep our Acura does that. If you wouldn’t let up on the gas, it wouldn’t engine brake so just keep a steady accelerator.


#9

My 2007 6-cyl 4-speed Impala would coast nicely. There’s a two mile stretch of a local road that was fun to “hypermile” coast most of the way with just one slight boost for a short hill. My 2014 4-cyl 6-speed Camry doesn’t coast the stretch of road although I’ve been able to coast part way.

The difference seems mostly a difference of gearing between the 4 and 6 speed transmissions and their shift points, as well as vehicle weight difference.


#10

I think it was back in 86 or 88 that GM had their fuel saving free wheeling transmission. You’d let up on the gas and it would coast endlessly. Wasn’t so much fun though on ice where you needed gentle deceleration without hitting the brakes.


#11

It is not so simple, some of the vehicle that I work on, sports cars and sports sedans go though front brake pads every 20,000 miles in city driving. It is generally the common vehicle that has this deceleration feature and the brakes last 50,000 miles. Vehicles with these multi-speed transmissions won’t slow well in high gear. The amount of fuel consumed while having to hold the accelerator at 1200 RPMs is insignificant.


#12

@Bing Yep. My '87 Olds had a free wheeling transmission. Nice except on ice, as you noted. Also, despite manually downshifting for steep mountain downslopes, engine braking didn’t really work. I had to be Very Careful going down Tioga Pass in Yosemite and several other places out west.


#13

Likely the reason these cars need brakes that often is due to who’s driving them and you never see the cars that don’t wear out their brakes.
An automatic transmission that does this would drive me nuts and have me looking for a way to disable this “feature”. My Yaris has a 5 speed manual and I usually coast towards red lights in neutral unless I’m going so fast that I need some engine braking. So I must be going through brakes every 20k or so, right?
Wrong!, my car has 195,000 miles on it and the original front brake pads still have plenty of life in them.
If coasting wears out your brakes, you didn’t start coasting soon enough.


#14

I measure and record the brake pads thickness every 5,000 miles so I have an idea which drivers get the most miles out of their brakes, it has more to do with the model and type of brakes, high performance brakes just don’t last very long in the city environment. The Yaris is equipped with ordinary brakes that are expected to last much more than 20K miles, different class of vehicle.

It really isn’t very noticeable or disturbing when automatic transmission downshifts to fifth gear at 40 MPH.