My rs2000 4x4 has got its mot very soon. When they do the brake test, how does it work with the 4x4 - as i remember they only put one set of wheels on rollers at a time?? Cant be good surely.. i'm probably just paranoid but i've never had it mot'd before..

cheers

 

cant test 4x4 cars unless they have specilaist brake tester ! and if they do try tell them to get F**ked they use a big metal thing thats goes on the passenger footwell and he goes up the road and stands on the brakes and it gives him a reading

 

Im sure when the cars in the 1 set of rollers, the car is in neutral, so the 4x4 system won't be engaged. Then he just presses the brake and watches his readings.

 

all my 4x4 saff,s have been road tested for brakes

 

noooo!
the 4wd is permanently engaged, rear wheels are linked to the front by the centre diff and viscous coupling.. if you try and drive one pair of wheels without the other you will risk damaging the centre viscous coupling. Although Ford quote that it's ok provided the wheels aren't driven over 5mph for 30 seconds, it's much better not to do it at all.
They will normally put a Tapley meter in the footwell and drive the car on the road to test the brakes. The Tapley uses g-force to measure braking retardation.

The Tapley Brake Testing Meter


The Tapley Brake Testing Meter is a pendulum-type decelerometer especially designed for convenience of use in motor vehicles on the road. It is accurate and robustly constructed to give long operational life. No special skill is required for its use and reliable results can be obtained with it by following simple instructions.

The meter has only three principal working parts. A heavy pendulum is pivoted at the top so that normally it hangs vertically inside a box which is filled with special oil to damp the movements of the pendulum so that vibration does not affect the indication given. The pendulum is a powerful permanent magnet and when it moves, a light armature follows its movements exactly.

The armature is joined to a toothed segment which in turn drives a pinion to which is connected the circular scale. The scale is read through an opening in the top of the casing and a light ratchet retains the scale at its maximum displacement. The whole mechanism is mounted in a casing carried on pivots which incorporate a fine adjustment so that the casing can be set level before a test. The pivots in turn are mounted on a heavy metal block.

 

that was what i was trying to say

 

lol looks im wrong then lol, cheers good to know.

 

testing viscous driven 4x4 systems on a roller brake tester is fine for the time period it takes to carry out the test, dont worry just get it tested

 

They're suppose to use either bi-directional rollers or the old way as in the pendulum tester, the metal thing that swung. Most just run it up regardless

 

well mine dont get tested by either of those means

 

They just run it up regardless then

 

no they drive it onto what looks like a 4 post ramp without the posts and brake and the comp gives them a reading dont ask me how it works as i haven't got a fookin clue

 

so ok , let me put it another way , youve got one of your front wheels on the grass and you accelerate away , it spins up , what happens ?

youve got both your front wheels on the grass/ some loose surface and teh backs are on tarmac with plenty of grip ? what happens ??

trust me , at 5mph on a roller brake tester for 15 secs will NOT damage your diffs in any way what so ever

 

fixed plate tester , very cool units

 

100% agree but my MOT tester likes to go for a test drive with that thing on the seat


























That way he turns a blind eye to me not having a cat

 

dont know what you mean

 

maybe but how the fook do they work

 

its a simple calculation of vehicle weight and braking force , what happens is , the car gets driven onto this plate , you hit the brakes , i think its at 10mph iirc, the plates moved and the force is calculated in kgs of how much the plate moved , then the plate weighs the vehicle and then its just vehicle weight over braking force !!

 

always had me wondering that did

 

 

yup in my mot bay i got the ye olde stylee tapley meter/decelorometer to test 4x4's wiv hth

Dave

 

Never thought of this before

I get mine tested on a normal MOT brake tester (2x Rollers) not had any problems as yet.

 

my local place did that .... it launched itself into the front of the footwell as the muppet had put it just infront on the passenger seat thatll learn him to go up the road at 30 mph and stamp on the brakes ..
good ol ap 6 pots and 330mm discs