Downhill braking problem.

I would say that is not normal unless you were using the breaks for very long periods without stepping off them. I also live in the mountains and have not experienced this issue with my 2020 Rav4. The way I like to handle descents is to start off from the top of the slope going slow and allowing the car to engine break on the way down with supplemental breaking when needed.

DevSeanD said:

I would say that is not normal unless you were using the breaks for very long periods without stepping off them. I also live in the mountains and have not experienced this issue with my 2020 Rav4. The way I like to handle descents is to start off from the top of the slope going slow and allowing the car to engine break on the way down with supplemental breaking when needed.

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Yeah, I didn't have that option. With a car behind me there wasn't the option to slow down too much. The speed was 35, and I had the CC set to 35, but the engine couldn't keep it below about 43 so I had to brake. Grade is 10%.

This appears to be more of an observation than a problem. It only becomes a problem if the brakes fail to slow car down. Car relies on motor/generator to slow car when descending a hill by shunting excess energy into traction battery. Once battery is fully charged during a particularly long descent then generator freewheels and brakes have to be applied to reduce speed. This has happened to me several times on a long downhill grade near my home.

pahiker said:

Yeah, I didn't have that option. With a car behind me there wasn't the option to slow down too much. The speed was 35, and I had the CC set to 35, but the engine couldn't keep it below about 43 so I had to brake. Grade is 10%.

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That's pretty steep. In that scenario, since braking cancels the CC, I would put the shift lever into the sequential/S mode, and downshift as much as needed or possible, and then switch between engine braking while letting the brakes cool down, and then firm pedal braking back down to 35, rinse repeat. I'd either just let the guy behind me deal with that, or if he's a jerk, I'd find a spot to pull off and let him rush to his own funeral. I certainly appreciate the rare driver like you who is actually aware of traffic behind, rather than just the people in their way, btw.

dbump said:

That's pretty steep. In that scenario, since braking cancels the CC, I would put the shift lever into the sequential/S mode, and downshift as much as needed or possible, and then switch between engine braking while letting the brakes cool down, and then firm pedal braking back down to 35, rinse repeat. I'd either just let the guy behind me deal with that, or if he's a jerk, I'd find a spot to pull off and let him rush to his own funeral. I certainly appreciate the rare driver like you who is actually aware of traffic behind, rather than just the people in their way, btw.

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Thanks. I wasn't aware of the "S" mode at the time, will give it a shot next time. I'm guessing the brake pads aren't very big on a Rav4, my Jeep never had this problem. Something to get used to.

RobertB said:

This appears to be more of an observation than a problem. It only becomes a problem if the brakes fail to slow car down. Car relies on motor/generator to slow car when descending a hill by shunting excess energy into traction battery. Once battery is fully charged during a particularly long descent then generator freewheels and brakes have to be applied to reduce speed. This has happened to me several times on a long downhill grade near my home.

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If the brakes are burning then I consider it a problem. Depending on the build of the rotors, and how hot the brakes get, they can glaze the rotor surface, then the brakes don't grip well. The pads definitely need replaced at that time, and the rotors need to either be cut or replaced.

pahiker said:

Thanks. I wasn't aware of the "S" mode at the time, will give it a shot next time. I'm guessing the brake pads aren't very big on a Rav4, my Jeep never had this problem. Something to get used to.

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Yeah "downshifting" to S2 or S1 should solve your problem

ddox said:

Yeah "downshifting" to S2 or S1 should solve your problem

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Thanks. I live on the edge of the Alleghenies (Foothills), so any trip east gets into the mountains and some pretty steep grades. Westward is flatter, the hills there aren't a problem.

pahiker said:

If the brakes are burning then I consider it a problem. Depending on the build of the rotors, and how hot the brakes get, they can glaze the rotor surface, then the brakes don't grip well. The pads definitely need replaced at that time, and the rotors need to either be cut or replaced.

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I was recently in the Ozarks area doing some hikes out there, where you needed to drive down steep grades for miles and engine braking (putting the car into S and gear 1/2) is the only way to save the brake pads from heating up/burning up. We were at a trailhead with a steep down grade lacing up our boots and every other car coming in had the burnt brake pad smell. Engine braking should be more known about, but sadly isn't

ravvyguy said:

I was recently in the Ozarks area doing some hikes out there, where you needed to drive down steep grades for miles and engine braking (putting the car into S and gear 1/2) is the only way to save the brake pads from heating up/burning up. We were at a trailhead with a steep down grade lacing up our boots and every other car coming in had the burnt brake pad smell. Engine braking should be more known about, but sadly isn't

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Yeah, I didn't find any reference to it in the manual I have. It talks about S-Mode (after hunting it down) but not as a reference to braking. Seems to think it's more of a sport-driving thing.

With CC on, I'm guessing cruise control, wouldn't the system auto adjust by using both brakes and engine to try to maintain the speed?

I had a similar situation where I set the dynamic radar CC to 60mph (I think) as I approach the mountain road with a vehicle ahead in range. The RAV4 followed the vehicle ahead up and down the mountain adjusting speed without me manually applying brake or acceleration. Of course I kept my foot ready to do so but didn't need to at all.

badankles said:

With CC on, I'm guessing cruise control, wouldn't the system auto adjust by using both brakes and engine to try to maintain the speed?

I had a similar situation where I set the dynamic radar CC to 60mph (I think) as I approach the mountain road with a vehicle ahead in range. The RAV4 followed the vehicle ahead up and down the mountain adjusting speed without me manually applying brake or acceleration. Of course I kept my foot ready to do so but didn't need to at all.

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CC=Cruise Control. I'm guessing at 60 you weren't hitting 8-10% grades.

pahiker said:

CC=Cruise Control. I'm guessing at 60 you weren't hitting 8-10% grades.

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Yeah, I don't know what the grade was up/down that section. I was set at that speed on US 33 prior to the start of the climb up onto the Blue Ridge Mountains peeking at the Skyline entrance then down the other side. Along the twists and turns we had to get down to 35 mph.

This is is new tech to me so was really happy how it worked without intervention, but I'm still not sure I'm fully comfortable with it. LOL

I've used the cruise control on 6% grades (steep sections of highway in Colorado mountains) and have been very impressed with the ability to keep the car at the set speed. I don't know if it actually engages the brake calipers or if it's able to maintain a set speed entirely through a combination of regenerative braking and engine braking/compression. I'm also very curious if the brake lights are activated in that scenario.

dbump said:

I've used the cruise control on 6% grades (steep sections of highway in Colorado mountains) and have been very impressed with the ability to keep the car at the set speed. I don't know if it actually engages the brake calipers or if it's able to maintain a set speed entirely through a combination of regenerative braking and engine braking/compression. I'm also very curious if the brake lights are activated in that scenario.

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Yeah, me too.

S mode is basically the settings for engine braking. In my experience, S-1 and S-2 are sufficient to keep the car below 25 mph on pretty steep gravel and dirt. That's the only place I've used it consistently since I didn't want to rely on brakes to moderate speed on a loose surface.

I think that if you used S mode to moderate engine braking, you should be able to just use the brakes as normal. S mode should take enough of the braking load off and moderate your speed so it shouldn't be an issue.

Also, if it helps, I haven't had this issue on any drives I have done, and I routinely drive the Los Angeles crest highway (which takes you from ~1,500 up to 5,000) and up and down from the colorado plateau in AZ (which is fast driving with elevation varying from 1,500 to 7,800).

Your issue sounds like a function of the steep grade and the low speed combining to cause high-energy braking with limited air cooling.

Anyway... try S mode.