Sudden Brake Shudder / Rapid Pulsing

[Mucci]

I've got about 11k miles on my '24 XLT hybrid and it did something the other day I've never felt before.

I was going about 40mph, pressed the brake coming up to a red light and the brakes rapidly shuddered. I can't imagine it was the ABS based on how aggressive it was and that I was on dry pavement and not braking hard at all. I'd say normal ABS is like a "buzzing" feeling. This felt like driving over a rumble strip, shaking the whole truck, however the pavement was smooth.

It almost felt like the truck couldn't decide between regen and hydraulic brakes and was rapidly switching between the two for about 1.5 sec. Truck was also cold which is when that switch over is the most jarring.

Anyone else ever experience this?

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[HeyBales]

Engine on or off (perhaps for heat)?

Do you recall how much into the brake you were digging - like still in Regen mainly or well beyond because it was a fast stop?

Was the shudder closer to the 40 mph side or the 0 side?

Was that 40 mph from coasting or even slight braking to keep it there due to downhill, until you needed to brake for light?

Do you use EV coach to know if you just had an almost full HVB, like full blue bar?

 

[Mucci]

Engine on or off (perhaps for heat)?

Do you recall how much into the brake you were digging - like still in Regen mainly or well beyond because it was a fast stop?

Was the shudder closer to the 40 mph side or the 0 side?

Was that 40 mph from coasting or even slight braking to keep it there due to downhill, until you needed to brake for light?

Do you use EV coach to know if you just had an almost full HVB, like full blue bar?

Don’t recall if the engine was on. Going to assume yes based on the road.

Shuddering started as soon as I applied brake. Pressure wise I’d say it was right on the cusp of getting into hydraulic braking.

Was probably cruising at 40 with foot on the gas before letting off to brake. It was a straight flat road.

Yea I use EV coach sometimes but not this time and dont know what the HVB was at. This was about 5 blocks from leaving my house.

 

[skinnyboy]

Was it possibly the ICE not shutting down smoothly? My 22 has done it a few times under similar circumstances. Rumble strip feeling is a good way to describe it.

Cheers.

 

[Mucci]

I mean it was a good 1.5sec of rapid jackhammer shaking. I hope that wasn’t the engine trying to shut down….

 

[HeyBales]

I'm going to make a guess just based on some actions.

Colder - so battery was perhaps being limited in the amount of regen it was allowed to take.
Or if engine already running because of cold, so HVB was already at max charge.

The braking regen power was not allowed to go to the battery since already at max.
This is when the engine would be used to waste that energy, by the generator motor changing it's RPM to engage it without it running, just spinning.
But it was running before braking.

So I've had those moments where 2-3 things are attempting to happen at once and the generator motor just can't get the RPM right it seems, and some roughness is felt.

So engine being brought off line - generator motor needs to switch from RPM for gearing, to now match traction motor RPM about 5000.
HVB at max charge, so generator motor now needs to change RPM for gearing to spin engine at right RPM to waste the energy from braking regen.

There has been comments of similar by ones hitting the exit ramp - so highway speeds engine on and HVB maxed.
Now massive braking and no regen going to happen and engine spun up.
It's an interesting time of interactions.

 

[skinnyboy]

I mean it was a good 1.5sec of rapid jackhammer shaking. I hope that wasn’t the engine trying to shut down….

Was on mine. Ugly feeling for sure, felt like it was hammering back and forth on the damper springs.

 

[Mrs.Smith]

I've got about 11k miles on my '24 XLT hybrid and it did something the other day I've never felt before.

I was going about 40mph, pressed the brake coming up to a red light and the brakes rapidly shuddered. I can't imagine it was the ABS based on how aggressive it was and that I was on dry pavement and not braking hard at all. I'd say normal ABS is like a "buzzing" feeling. This felt like driving over a rumble strip, shaking the whole truck, however the pavement was smooth.

It almost felt like the truck couldn't decide between regen and hydraulic brakes and was rapidly switching between the two for about 1.5 sec. Truck was also cold which is when that switch over is the most jarring.

Anyone else ever experience this?

Yes, this happens to me about once a week and I have no idea what it is. I have taken it to the dealer, but they can't replicate the issue when test driving and so no solution has been found.

 

[HeyBales]

Yes, this happens to me about once a week and I have no idea what it is. I have taken it to the dealer, but they can't replicate the issue when test driving and so no solution has been found.

Read the former post with questions.

Is it usually the same spot - like coming off a highway?

 

[Kenv24]

Read the former post with questions.

Is it usually the same spot - like coming off a highway?

Yes...it has happened about 3 times for me. And it WAS coming off of the 45-mph road to turn into my neighborhood for 2 of the 3. Truck was warm. It was pretty slight.....not a lot of bumping.....but you can definitely feel something odd in the braking. Almost like a little skip or the truck hit some speed bumps in the road....but didn't.

 

[wdancer]

Any updates to this? My truck just did it twice last week.

 

[HeyBales]

Any updates to this? My truck just did it twice last week.

Got answers to the prior post questions? - which may give a clue if an issue or merely interaction.

 

[wdancer]

IT happened at speeds of about 30 to 50 mph, pressed the brake moderately and the whole pickup shuddered like i was driving over a really bad washboard road. let off and hit the brakes again. It didn't stop until I was under 10 mph.

 

[HeyBales]

IT happened at speeds of about 30 to 50 mph, pressed the brake moderately and the whole pickup shuddered like i was driving over a really bad washboard road. let off and hit the brakes again. It didn't stop until I was under 10 mph.

These questions from prior post - otherwise I'd say warped rotors if no further details:

Engine on or off (perhaps for heat)?

Do you recall how much into the brake you were digging - like still in Regen mainly or well beyond because it was a fast stop?

Was the shudder closer to the 40 mph side or the 0 side?

Was that 40 mph from coasting or even slight braking to keep it there due to downhill, until you needed to brake for light?

Do you use EV coach to know if you just had an almost full HVB, like full blue bar?

 

[wdancer]

These questions from prior post - otherwise I'd say warped rotors if no further details:

No brake shudder before or since. Not warped rotors.

Engine on or off (perhaps for heat)?

Engine on

Do you recall how much into the brake you were digging - like still in Regen mainly or well beyond because it was a fast stop?

Past regen

Was the shudder closer to the 40 mph side or the 0 side?

Toward the 40 mph side

Was that 40 mph from coasting or even slight braking to keep it there due to downhill, until you needed to brake for light?

Slowing down uphill for light. Previous one was slowing downhill while merging to freeway

Do you use EV coach to know if you just had an almost full HVB, like full blue bar?

Yes I use the EV coach, was past the regen braking.

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