sdh2903
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| posted on 25/7/12 at 09:15 PM |
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Brake test interpretation
I had my car at my friendly mot centre to have a few things tested, one of which was a brake test. The results were as follows:
Service brake
axle 1 NS 170 locks
axle 1 OS 160 locks
axle 2 NS 170 locks
axle 2 OS 160 locks
Parking brake
NS 90
OS 60
Balance
Axle 1 NS 140
Axle 2 NS 130
I did ask about the results and he did say that it would pass an MOT
I know that this wont help with regards to the IVA as its more a dynamic test but do these figures look about right? I hope to try and find a nice
quiet private road to try and do a lock up test.
I know the handbrake needs adjusting as it up by my armpits before it bites at the min
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AdrianH
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| posted on 25/7/12 at 10:27 PM |
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The results do not indicate how much effort it takes to get that much braking force into the wheels on the pedals.
On IVA my brakes were tested at 5 points. The tester fits a pressure gauge to the base of his/her foot and tests each wheel/axle to a point where
they start to lock up.
Say it takes 20 N to make the front axle to lock.
the tester may then do five tests on the front and five tests on the rear axle. He may pick, 3, 7, 12, 15 and 19 N pressure on the pedal.
At each pressure setting they obtain brake readings for both front wheels when testing the front axle and both rear when testing the rear axle. (Duh
obviously sorry for that).
Then they put it in a calculator and decide if the balance is correct.
They need a few other measurements, such as distances between axles, each axle weight and the height of the Centre of gravity. How they get the last
reading is probably from a table and height of wheel hubs etc.
The calculator will work out if at each of the 5 test points the front brakes have the correct balance to the rears. You typically want a static
70/30 to 6040 split. I think.
When at speed and braking the vehicle weight will transfer from the back to front axle and the split has to be more then this weight shift.
have a look at my IVA fail page as I posted a chart on there when I failed. I spent lots of time searching on the web for the calc and did a spread
sheet which is also there for anyone to use/ modify etc.
I used it to work out new rear size cylinders.
The retest I passed but this time they would not give me the results to confirm anything.
Sorry it is a long response and the IVA fail page is here:
http://www.tamarisktechnicals.com/pages/iva.html
Adrian
Why do I have to make the tools to finish the job? More time then money.
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britishtrident
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| posted on 26/7/12 at 11:33 AM |
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Other than proving your brakes are all working it doesn't tell you much apart from the fact the corner weights look not bad.
You need to do a slow speed brake test on a good clean dry tarmac surface.
Do a couple runs to find to check the front brakes reach lock-up point before the rears, rears locking before the fronts is bad news as it can
put you into a wall in the blink of an eye.
I half suspect you may find you are over braked on the rear axle especially if you have 9" drums or rear discs.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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