Noise during hard braking?

[jayvee]

I have noticed a somewhat strange sound upon moderate to hard braking, such as coming to a stop coming down a steep hill, or on more sudden stops. The only way I can describe it is the sound of thick rubber on metal - kind of a very short, low pitched "groan" or "grunt".

It happens just before the vehicle comes to a complete stop. For this reason, I suspect that it might be the regenerative braking disengaging right before the vehicle fully stops.

Is anyone else experiencing this type of noise? I have no history with previous gen Priuses, so I'm not sure if this is normal for the regen brakes.

Thanks!

[djasonw]

I think what you may be hearing is precisely what you described. It is more pronounced in the pre 2010 models. When you are slowing down normally and then get to say 10mph or so there seems to be a sensation of secondary braking power. The noise you may hear is the transition from regenerative to the actual standard brakes kicking in. Please correct me if I'm wrong.

[jayvee]

Originally Posted by djasonw

I think what you may be hearing is precisely what you described. It is more pronounced in the pre 2010 models. When you are slowing down normally and then get to say 10mph or so there seems to be a sensation of secondary braking power. The noise you may hear is the transition from regenerative to the actual standard brakes kicking in. Please correct me if I'm wrong.

Thanks for the reply - It doesn't occur when I'm moving that fast (although I think I know the sensation you describe) - it's only in the last foot or two before the vehicle is completely stopped. I'm going less than 1 mph at that point.

[Bobsprius]

Jayvee,

I believe the sound your hearing is what you have described. There are a lot of "New" sounds you will eventually aclimate to in time, once you have heard them. But the sound that you describe sounds to be the Regen Braking taking place before Friction Brakes are in full swing. It's doesn't sound abnormal to me. You can learn a lot as well by watching your monitor and seeing your in regen with the recharge in the monitor...

[jayvee]

Originally Posted by Bobsprius

But the sound that you describe sounds to be the Regen Braking taking place before Friction Brakes are in full swing.

Thanks Bob,

See my last post - it isn't when the regen brakes engage (at speeds >5 mph or so, as you describe) - it seems to be when they are releasing, a fraction of a second before the vehicle has come to a complete stop. (Think of the sound of a metal bumper car glancing off a rubber bumper on the track. Sorry, trying to find a way to describe this sound...) That's the sound, short and low-pitched, and right before the vehicle stops. It really sounds a bit concerning - but it may be totally normal sound when the regen brakes disengage during hard braking....

[Bobsprius]

Originally Posted by jayvee

Thanks Bob,

See my last post - it isn't when the regen brakes engage (at speeds >5 mph or so, as you describe) - it seems to be when they are releasing, a fraction of a second before the vehicle has come to a complete stop. (Think of the sound of a metal bumper car glancing off a rubber bumper on the track. Sorry, trying to find a way to describe this sound...) That's the sound, short and low-pitched, and right before the vehicle stops. It really sounds a bit concerning - but it may be totally normal sound when the regen brakes disengage during hard braking....

Sounds like your trying to describe a "groan" of the brakes, or RUBBING sound...Hmmmmm I have not noticed it my 2010, but then again, I have not experienced the backup brake issues. Do you think it is something with the Discs and needing adjustment??? I believe I understand now what your hearing I will have to listen to mine as well. Do you notice this with windows open and between cars/buildings to hear the resounding noise, or do you actually hear it in your car???? Do you feel you are applying the brakes hard or more moderate in the last seconds? I wondered since I will try it with my car on the way to work this afternoon and see if I can reproduce. I will also try in the lot tonight and let you know...

[jayvee]

Originally Posted by Bobsprius

Sounds like your trying to describe a "groan" of the brakes, or RUBBING sound...Hmmmmm I have not noticed it my 2010, but then again, I have not experienced the backup brake issues. Do you think it is something with the Discs and needing adjustment??? I believe I understand now what your hearing I will have to listen to mine as well. Do you notice this with windows open and between cars/buildings to hear the resounding noise, or do you actually hear it in your car???? Do you feel you are applying the brakes hard or more moderate in the last seconds? I wondered since I will try it with my car on the way to work this afternoon and see if I can reproduce. I will also try in the lot tonight and let you know...

It's not a "rubbing" or "groaning" sound - it's a short burst (0.1 second or so) - and almost a rubbery "clunk" sound (man, this is hard to describe... maybe I will try to post an audio file of the sound.....hmmm...) And yes, it really only is present at the very end of moderate to hard braking. Windows closed, I hear it IN the car. Sounds like it's coming from the engine compartment or the brakes.

I honestly don't think it has anything to do with the discs. It's not a metallic scraping or rubbing sound. It actually sounds a bit like loose/damaged engine mounts used to sound in older cars. But I don't think that's what this is - I'm sure the engine mounts are nothing like they used to be. Like i said, this might just be what the regen brakes do at the end of hard braking.

Anybody else hear anything like this?

[qbee42]

Originally Posted by jayvee

Thanks Bob,

See my last post - it isn't when the regen brakes engage (at speeds >5 mph or so, as you describe) - it seems to be when they are releasing, a fraction of a second before the vehicle has come to a complete stop.
<snip>

This is what Bobsprius is saying. You may want to reread his posts.

Tom

[jayvee]

Originally Posted by qbee42

This is what Bobsprius is saying. You may want to reread his posts.

Tom

Well, I thought I did read his posts carefully. They said this:

But the sound that you describe sounds to be the Regen Braking taking place before Friction Brakes are in full swing.

My sound takes place long after the friction brakes are fully applied. The vehicle is at almost a dead stop. And:

Sounds like your trying to describe a "groan" of the brakes, or RUBBING sound...

It is neither groaning or rubbing. It's a short burst of sound. Can you tell me what you are suggesting I'm missing in Bob's response (which I very much appreciate, by the way!)

Thanks!

[maxjlone]

I have 9,200 miles on my 300C Heritage and while at the Dealer (my Dealers name has changed, still selling DCX) getting my free oil change I told the Service guy I had a grind/clunk noise when brakeing, got the 23 point inspection, they found nothing, no charge.