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182 
BRAKE REACTION REVISITED
Page 100
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• Oh dear, it seems that I have upset Mr Dickson Simpson with some of my comments, but at least we now know who wrote "Stopping true" (CM 23-29 August). Of course, l don't feel he is the odd man out; we all need better brake performances specially on trailers and I believe the time is fast coming when all trailer manufacturers will be forced to conform to much narrower and higher brake performance bands.
This would be of great assistance in the compatibility problems which face us today.
We are all well aware that trailers are not subject to Type Approval as such, but Mr Dickson Simpson has failed to mention that all axles currently used by trailer manufacturers are subject to EC brake approval.
I have no wish to enter into a public argument with Mr Dickson Simpson, but in his letter he has made some serious assumptions (CM 30 August-4 September).
I am very aware that predominance valves are fitted to tractors by manufacturers, but I am not aware that anyone fits a valve with a 1.8bar predominance, the usual being about 0.5 or 0.6bar.
He must also be taken to task for his complete misunderstanding of my paragraph about brake reaction or application times; at 75% of asymtotic value considerable retardation of up to, say, 0.6G is taking place, not as he states "unrestricted travel".
Heaven help us if that was the case.
I am sure that Mr Dickson Simpson would agree that the most important factor at the end of the day is clearly stopping distance, and a reduction in this can only be achieved when we have brakes that are reliably modulated at each wheel and are actuated by electronic means in well under 0.5 seconds.
AHJ Ruffles M1RTE,
Bury St Edmunds, Suffolk.
The subject has been thoroughly aired. This correspondence is now closed — Ed.