tractor/trailer/tanker air brake time to pressure up

[DGC1]

on a 7.1 - 8bar system how long should it take to build pressure to 7bar at the trailer/tanker after brakes are applied?
got one tractor that's taking 16 seconds to get to 7bar
and another that's taking 23 seconds
and another that's taking 78 seconds
all of these tractors are big tractors and under 2 years old
compared to commercial lorries it seems that certainly at 78seconds the braking is not as it should be
>
also one tanker seems to be wearing rear shoes out but fronts not needing adjusted
its on the tractor that is taking 78seconds to go to 7bar but could there be another factor?
abs and load sensing all look to be working fine
pressures front and rear look to be equal from tests done.
sister tankers on other tractors are wearing evenly

 

[Andrew]

on a 7.1 - 8bar system how long should it take to build pressure to 7bar at the trailer/tanker after brakes are applied?
got one tractor that's taking 16 seconds to get to 7bar
and another that's taking 23 seconds
and another that's taking 78 seconds
all of these tractors are big tractors and under 2 years old
compared to commercial lorries it seems that certainly at 78seconds the braking is not as it should be
>
also one tanker seems to be wearing rear shoes out but fronts not needing adjusted
its on the tractor that is taking 78seconds to go to 7bar but could there be another factor?
abs and load sensing all look to be working fine
pressures front and rear look to be equal from tests done.
sister tankers on other tractors are wearing evenly

You mean it takes 78 seconds for the air system to build up to 8 bar from empty?
Or
When the system is up to pressure, it takes 78 seconds from pressing the brake pedal, for the cylinder pressure to reach 8 bar?

 

[DGC1]

the above times are when the tractor is fully charged and this is how long it takes to build to 8bar when the pedal is pressed
we have tested at the rear of the tractor and out on the tanker and times are the same
i know that at 78 seconds something is wrong but even 16 seconds seems quite a long time
the 16 seconds is on a nearly new fendt 718

 

[Andrew]

the above times are when the tractor is fully charged and this is how long it takes to build to 8bar when the pedal is pressed
we have tested at the rear of the tractor and out on the tanker and times are the same
i know that at 78 seconds something is wrong but even 16 seconds seems quite a long time
the 16 seconds is on a nearly new fendt 718

If you have the tanker disconnected how long before the yellow line hits 8 bar? Anything over a couple of seconds would be too long.

 

[DGC1]

its taking 16 seconds to go to 8bar on yellow line on fendt718 !
it hits 7bar at app 7 seconds

 

[s~~t shoveller]

I would check very carefully for kinked plastic airlines if it was mine,that’s what slowed our air down on a tanker,took a day to find!only found when we cut the cable ties off and released where it was pulled up tight into a corner.

 

[Andrew]

I would say definitely something wrong somewhere. What pressure gauge are you using? Could the gauge / valve lifter / gauge pipe etc be faulty?

 

[GFA]

Since the new mother regulations the brake pressure is a lot slower. on a fendt 820 as soon as the brake lights come on there's 2.4 bar then the pressure increases the further you push the pedal down. On a 2018 724 the pressure is about 0.8 bar then slowly increasing so there is a noticeable difference in brake performance. Also on the tanker jack it up and see if the front axle is actually braking had a flat trailer where the s cams were the wrong way round from new so wasn't pushing the shoe's out.

 

[njneer]

Since the new mother regulations the brake pressure is a lot slower. on a fendt 820 as soon as the brake lights come on there's 2.4 bar then the pressure increases the further you push the pedal down. On a 2018 724 the pressure is about 0.8 bar then slowly increasing so there is a noticeable difference in brake performance. Also on the tanker jack it up and see if the front axle is actually braking had a flat trailer where the s cams were the wrong way round from new so wasn't pushing the shoe's out.

This is a current bone of contention with all the major tractor manufacturers at the moment as the new progressive application rate set out in the mother regulation , coupled with the fact the current trailers are now not compatible with the new mother reg brakes on the tractors , is causing complaints about insufficient performance of the trailer brakes.
The AEA ( Agricultural Engineers Association) of which all major manufacturers are members are currently in discussion with government officials regarding this matter .
I was told this by someone who works for a manufacturer last week.
Tractor are currently compliant with the law and old trailers are not .
Trailers do not have to meet the new regulations for another year or so and as such there is a big mismatch now between tractors and trailers.
It’s a joke , the truck industry would have had everything changing at the same time so no mismatch.

 

[njneer]

Also check the probe on the yellow line is not worn , not unknown for them to trail on the ground and wear the tip off and the probe does not open the lifter fully and restricts flow to the brakes on the yellow line .