MOT Break Test Results - Please Explain These Results
Discussion
The figures given for each wheel show the maximum resistance offered to the rolling road powered rollers by the cars braking system immediately before the tyre slips on the roller - which would be the brake locking the wheel. That is also noted.
The wheels are tested individually & then as an axle pair.
The figures are usually different between offside and nearside due to the weight of the tester who is sitting in the car whilst operating the rolling road. This is normal.
Link to the testers manual for you:
http://www.motuk.co.uk/manual_370.htm
Read through the link & its subsequent pages, you might find just how low the braking efficiency can legally be something of a surprise. In your case - dual line system with Parking Brake acting on the rear wheels - the service brake (footbrake) min is 50% & parking brake (handbrake) min is 16% so yours are well over.
The wheels are tested individually & then as an axle pair.
The figures are usually different between offside and nearside due to the weight of the tester who is sitting in the car whilst operating the rolling road. This is normal.
Link to the testers manual for you:
http://www.motuk.co.uk/manual_370.htm
Read through the link & its subsequent pages, you might find just how low the braking efficiency can legally be something of a surprise. In your case - dual line system with Parking Brake acting on the rear wheels - the service brake (footbrake) min is 50% & parking brake (handbrake) min is 16% so yours are well over.
Edited by paintman on Thursday 10th January 15:45
.EViS said:
Thank you for the reply. Will read though the manual to get some more info 
.
If the service break and parking break figures were below 50% and 16% respectively, what could the cause of this be? Worn break bads, discs, overly stretched parking break cable?
Not just the title!.If the service break and parking break figures were below 50% and 16% respectively, what could the cause of this be? Worn break bads, discs, overly stretched parking break cable?
Read the first page of the link.
Imbalance is measured when BOTH wheels on an axle are being powered by the RBT & its this that determines pass or fail, after first establishing that the individual wheel brakes are functioning.
As you can see from the manual, what you are looking for is that the braking forces on both wheels increase at about the same rate as the brakes are applied gradually without causing a wheel to lock & that when gradually released they decrease at about the same rate.
Maximum permitted variation is 25% at any time during the increase in application on the steered road wheels.
Imbalance is measured when BOTH wheels on an axle are being powered by the RBT & its this that determines pass or fail, after first establishing that the individual wheel brakes are functioning.
As you can see from the manual, what you are looking for is that the braking forces on both wheels increase at about the same rate as the brakes are applied gradually without causing a wheel to lock & that when gradually released they decrease at about the same rate.
Maximum permitted variation is 25% at any time during the increase in application on the steered road wheels.
Edited by paintman on Wednesday 9th January 00:11
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