Volvo B12BLEA Brake Blending Problem

  • Thread starter Thread starter Brian Graham
  • Start date Start date
B

Brian Graham

I am looking for drivers who have experienced Braking problems with Volvo
computerised braking system, in either buses or trucks.

please contact me

My colleagues' and I are currently experiencing braking problems with
B12BLEA buses that VOLVO and our employer will not acknowledge, causeing
erratic braking performance.

[email protected]
 
Brian Graham said:
I am looking for drivers who have experienced Braking problems with Volvo
computerised braking system, in either buses or trucks.

please contact me

My colleagues' and I are currently experiencing braking problems with
B12BLEA buses that VOLVO and our employer will not acknowledge, causeing
erratic braking performance.

[email protected]
Click to expand...

I don't think you'll find much info on that here, this is the first I've
seen someone post regarding buses or trucks, most of us here drive cars.

Crossposting is very much frowned upon, there's separate newsgroups for a
reason.
 
Brian said:
I am looking for drivers who have experienced Braking problems with Volvo
computerised braking system, in either buses or trucks.

please contact me

My colleagues' and I are currently experiencing braking problems with
B12BLEA buses that VOLVO and our employer will not acknowledge, causeing
erratic braking performance.
Click to expand...
Such as what?

Every one I've driven, including one that had over 1.1 million km on,
have worked fine. (Tractor units..FM10/12, FH10/12 both 4x2 and 6x2
with ABS and EBD) As an agency driver, that's a fair few units. Must be
at least 20 different ones in the last couple of years.
 
Such as what?

Every one I've driven, including one that had over 1.1 million km on,
have worked fine. (Tractor units..FM10/12, FH10/12 both 4x2 and 6x2
with ABS and EBD) As an agency driver, that's a fair few units. Must be
at least 20 different ones in the last couple of years.
Click to expand...
1.1 million miles? Christ, where was that delivery? Mars?
 
Indeed. However it was only 6 years old and although it ran 7 days a
week, it wasn't double shifted.
Click to expand...

So just over 300 miles per day average.
 
So just over 300 miles per day average.
Click to expand...
Yeah..sounds about right. Got used less as it was older as they rotated
the work amongst the fleet when it was quiet.
 
Conor said:
Depends if you want to eat or not.
Click to expand...
Yes but do you really need to do that mileage with the truck, could you
not cycle or use horse & cart or even handcarts?
 
Tony Dragon said:
Yes but do you really need to do that mileage with the truck, could you
not cycle or use horse & cart or even handcarts?
Click to expand...
I suppose so but we'd have to bring over a few hundred boatloads of
"those nego folk" to do the work cos the locals won't want to.

;p
 
Conor said:
I suppose so but we'd have to bring over a few hundred boatloads of
"those nego folk" to do the work cos the locals won't want to.

;p
Click to expand...
I know of a bloke with a bike & cart who might help.
 
Just to return to the OP`s original request.
I notice its a B12BLEA...Is this an artic ?

Suffice to say that there are indeed "issues" surrounding Volvo`s "brake
blending" setup on it`s later B7 and even the newer B9 chassis.

To my knowldege this has presented as a most disconcerting "Snatch" at just
about the worst possible point in a Bus journey.....just as the Bus is
approaching a Bus-Stop of in Low-Speed Traffic.

The speeds involved are all in the sub 10 Kph bracket and result in much
discomfort for passengers and allegations of poor driving being flung at the
Busdriver !

Essentially it appears as if the Retarder cuts OUT at too high a speed which
requires the Busdriver to compensate by last minute rapid application of the
service brake accompanied by a certain coarse graduation of the delivery
pressure from the footvalve.

Again,AFAIAA Volvo are aware of these issues and have in some cases referred
to a "Software Modification" to addres them.

In my experience this modification IS successful,but it raises serious
questions as to whether such a critical component as Braking/Rertarding
should be the subject of research and development whilst actually in revenue
service.

Do they not have Test Tracks for this type of safety-critical issue ?
 
Alek said:
Just to return to the OP`s original request.
I notice its a B12BLEA...Is this an artic ?

Suffice to say that there are indeed "issues" surrounding Volvo`s "brake
blending" setup on it`s later B7 and even the newer B9 chassis.

To my knowldege this has presented as a most disconcerting "Snatch" at just
about the worst possible point in a Bus journey.....just as the Bus is
approaching a Bus-Stop of in Low-Speed Traffic.

The speeds involved are all in the sub 10 Kph bracket and result in much
discomfort for passengers and allegations of poor driving being flung at the
Busdriver !

Essentially it appears as if the Retarder cuts OUT at too high a speed which
requires the Busdriver to compensate by last minute rapid application of the
service brake accompanied by a certain coarse graduation of the delivery
pressure from the footvalve.

Again,AFAIAA Volvo are aware of these issues and have in some cases referred
to a "Software Modification" to addres them.

In my experience this modification IS successful,but it raises serious
questions as to whether such a critical component as Braking/Rertarding
should be the subject of research and development whilst actually in revenue
service.

Do they not have Test Tracks for this type of safety-critical issue ?
Click to expand...
I get a version of this on a 2002 B12B automatic coach, when the gearbox
goes into neutral (Volvo call it Bus Stop Neutral or summat, & it's a
pollution control thing they blame on the EU) under ECU control at just
below walking pace. Drive stops, but the brakes are still on hard
countering the drive, so there's a jerk at about 5kph. It's a deliberate
design feature, & there's no way to turn it off easily.

The one that *really* annoys me is on the Scanias, when the automatic
retarder cuts out at about 20kph, & half your brake force disappears
just when you're committed to stop in a certain distance, say, the
distance to a bus stop or stop line.
 
John Williamson said:
The one that *really* annoys me is on the Scanias, when the automatic
retarder cuts out at about 20kph, & half your brake force disappears
just when you're committed to stop in a certain distance, say, the
distance to a bus stop or stop line.
Click to expand...
IUt would have disappeared anyway as it relies on high engine speeds to
work. Any engine speed below 1500RPM isn't going to supply much
retardation. On my lorry when I use it, the autobox drops a gear or two
and takes it up to within 500RPM of the redline.
 
Conor said:
IUt would have disappeared anyway as it relies on high engine speeds to
work. Any engine speed below 1500RPM isn't going to supply much
retardation. On my lorry when I use it, the autobox drops a gear or two
and takes it up to within 500RPM of the redline.
Click to expand...
It disappears gradually with reducing input shaft speed, yes, much as
the effectiveness of an exhaust brake does. I can live with that, on our
Volvo autoboxes. On the Scanias, it's still quite noticeable in low
gears down to about 750rpm. That isn't too bad, but suddenly losing
*all* gearbox retardation from quite a high value isn't funny,it feels
to the passengers as if the vehicle is lurching forward just as things
are getting critical. Because of this, I disable the transmission
retarder function in town for more predictable braking. The normal
brakes run hotter & work harder, but the passengers get a much smoother
ride.
 
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