300h - Transient Vibration during braking

[lexusinthecity]

brake pads look OK...wondering if this could indicate a planetary gear or some other problem with the regenerative braking system. Vibration only lasts for less than a second and occurs at varying phases of the braking cycle...

Warranty ends in July

Any ideas on how to further investigate?

L'city

[Zotto]

Sure it is not the noise from pump activating to restore pression in circuit
?

 

[lexusinthecity]

Its only begun recently...someone in I think a GS300 had it and was advised to check their ABS sensors...I'll see what its like with the ABS off'

[Dave748]

I've not had this on a Lexus as I've only just bought one but had this exact issue on quite a few other cars and all of them turned out to be warped brake disks.  I don't know how or where the regenerative system is applied but if anything is warped when it contacts I'm guess it will have the same affect.  Try slightly harder breaking to engage the calliper brakes and see if it makes it worse, not too hard though as I found this forces the warped part into alignment and hides the issue. 

[200h]

6 minutes ago, Dave748 said:

I've not had this on a Lexus as I've only just bought one but had this exact issue on quite a few other cars and all of them turned out to be warped brake disks.  I don't know how or where the regenerative system is applied but if anything is warped then it contacts I'm guess it will have the same affect.  Try slightly harder breaking to engage the calliper brakes and see if it makes it worse, not too hard though as I found this forces the warped part into alignment and hides the issue. 

braking on a lexus hybrid is quiet different to a normal car as the brake pads are only used during braking under about 8mph or if hard braking is required

and for this reason it wont be the discs

[rayaans]

The IS300H goes to brake pads much quicker than my RX does though, hence the masses of brake dust on the front wheels!

Could easily be warped brake discs so best to check them out.

But, also check your tyres. My ABS on the RX was kicking off like mad when I was on 3mm causing vibrations.

[200h]

with the vibrations lasting less then a second this says to me its not the discs, if it was the discs

the steering wheel would also wobble until the speed has been reduced then the wobble would stop.

you normally notice warped disc's when you leave a motorway and apply the brakes.

if you cant sort it soon contact the dealer

[Dave748]

46 minutes ago, 200h said:

with the vibrations lasting less then a second this says to me its not the discs, if it was the discs

the steering wheel would also wobble until the speed has been reduced then the wobble would stop.

you normally notice warped disc's when you leave a motorway and apply the brakes.

if you cant sort it soon contact the dealer

It depends how warped they are, if it's only very slight you may only notice during braking, if it is a much bigger warp then yes your steering wheel would be all over the place most of the time, especially between certain speeds when the warp most aligns with it's resonating frequency.  I've had both on past cars, it may also be worth looking for any marks on your wheels where the balancing weights are, one may have come off, I've had this too and it's a very quick and easy fix in any garage. 

[200h]

did you manage to find what the issue has been with your car lexusinthecity

[lexusinthecity]

not as yet. Haven't checked the tyre pressures for a while. I did notice the sensation just after I stopped at traffic lights and could hear the pump running then...think its going to have to be a service based solution

[lexusinthecity]

Lexus Service took it for a drive, advising that the vibration was within tolerance. On doing a bit of my own research via this article , one is advised:
Another common complaint for used hybrids is noise and pedal feel. Most two-mode hybrid vehicles, like the Prius, GM Two-Mode and Ford Escape, use a braking system that employs a high-speed electric motor/pump. Pump operation sometimes can be felt in the brake pedal as the system builds pressure. This is most noticeable to customers who start the vehicle with their foot on the brake pedal.

I'll keep looking into it...

 

[rayaans]

18 minutes ago, lexusinthecity said:

Lexus Service took it for a drive, advising that the vibration was within tolerance. On doing a bit of my own research via this article , one is advised:
Another common complaint for used hybrids is noise and pedal feel. Most two-mode hybrid vehicles, like the Prius, GM Two-Mode and Ford Escape, use a braking system that employs a high-speed electric motor/pump. Pump operation sometimes can be felt in the brake pedal as the system builds pressure. This is most noticeable to customers who start the vehicle with their foot on the brake pedal.

I'll keep looking into it...

 

Im confused about the "foot on the brake pedal" bit. I didnt think it was possible to start the car without having the foot on the brake pedal?

[lexusinthecity]

On 2/23/2016 at 11:21 PM, lexusinthecity said:

...This is most noticeable to customers who start the vehicle with their foot on the brake pedal...

 

the article was not written specifically for Lexus vehicles. I might attempt to contact another service centre(s) and run the scenario past each of them.