A word of warning about relying on roller brake test results

I read with interest in your last issue the emphasis placed on routine roller brake tests in ensuring the safety of vehicles, drivers and passengers.

I find this very troubling.

For those of us with an understanding of physics and engineering, roller brake tests are all but worthless. I have personally had a reading of thirty-something percent on my local brake rollers, and yet passed the MoT with ease.

How so? The reading will depend more on the condition of the abrasive surface of the rollers than on the brakes themselves. If the wheels lock, which they will do on most rollers — and do with ease on a worn roller — that is a ‘pass’. And that tells you nothing at all.

I once had a reading of 700% on an MoT, which was impressive. But the know-nothing examiner didn’t query it, because it had the word ‘pass’ printed at the bottom of the document, and that was all he cared about. It was good enough for him, even though it made no sense.

There is also the matter that DVSA doesn’t seem to know what the standard is for handbrake efficiency. Half of my test results over the decades have specified the ‘pass rate’ as 16% of laden weight; the other half give it as 16% of un-laden weight. I have been asking DVSA for years which one is correct, but nobody there seems to know. It would appear that half of my test results are incorrect, but again, DVSA’s approach has been one of ‘don’t know, don’t care’.

I had an even more worrying experience when one of my vehicles developed a violent snatch to the left when braking. I thought we had fixed this prior to the MoT, but the fault returned with a vengeance on the journey to the test station. I decided to proceed anyway, and to my utter astonishment, the vehicle passed. I pointed out to the examiner that he had just issued me with an MoT for a vehicle that was virtually undriveable. His reply will remain forever etched in my brain — completely unconcerned. Oblivious to the irony of the situation, he told me that had it been a private vehicle (class V) or a car, it would have failed, but that “we are not required to test the front brake balance on PSVs.”

Sure, they measure individual wheel effort, but not both front brakes together, which is what matters. So as soon as I got home from the MoT test, I had to strip the brakes down to make the vehicle roadworthy.

Yet roller brake testing is what the Traffic Commissioners apparently expect?

Hugo Miller

Horsham