Pierre Gillet Posted June 16, 2003 Share Posted June 16, 2003 Just had my Contrôle technique done (Mot). I noticed that the efficiency of the braking system is globally lower by 20% than 2 years ago. The main difference between the 2 tests is that wheels are now shod with 021Rs. Brake pads (standards) are of course a litle bit more worn but still not to be replaced in terms of thickness. Can the better grip developed by the A021Rs ( Vs Michelin Pilots) explain an apparent decrease of braking efficiency? Pierre Link to comment Share on other sites More sharing options...
Sheds Moderator Posted June 18, 2003 Share Posted June 18, 2003 No. They put the car on rollers covered in high friction material and measure the brake efficiency that way. If the tyres slip on the rollers they get a man to sit on the car and stop them slipping. The brake test is just that, tyres are different. If you have lost 20% you may have glazed pads. Take the car out and give it a good thrashing until the brakes are very hot. This should restore lost efficiency. Alternatively, fit better pads, you may have chocolate ones in at present. Link to comment Share on other sites More sharing options...
Graham Perry Posted June 18, 2003 Share Posted June 18, 2003 Did the guy manage to lock them ? If so ignore the guage as you cannot get better than locked. I watched my father carry out many MOTs over the years and the guages should only really be used as an general indication of braking efficiency on a light vehicle, where the design of the rollers is supposed to be for vehicles weighing about a tonne. With some vehicles we used to use a tapley meter to manually test deceleration as the rollers were not always the answer I used to get involved with testing heavy trucks where this problem is exagerated further. A light truck on a set of brake rollers designed for a 10 tonne axle load will often show poor efficiency. The ministry testers just say that as long as you can lock the tyre and the roller continues to rotate, then they can ask for nothing more. It is similar for a Caterham Link to comment Share on other sites More sharing options...
Pierre Gillet Posted June 18, 2003 Author Share Posted June 18, 2003 Do you mean that 'locked wheels' means 100 % efficiency of the braking system? Pierre Link to comment Share on other sites More sharing options...
stevefoster Posted June 18, 2003 Share Posted June 18, 2003 They should use a Tapley meter to check brakes / handbrake on the LSD axle but never seem to... See http://www.pwds.co.uk/tapley/intro.htm My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Link to comment Share on other sites More sharing options...
Graham Perry Posted June 18, 2003 Share Posted June 18, 2003 No, within the limitations of the testing system it is the best you are going to get unless you start putting lots of extra weight in the vehicle being tested. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 18, 2003 Share Posted June 18, 2003 Braking efficiency is proportional to the vehicle weight, so a lighter car needs less braking force to reach the same braking efficiency. I can't remember if pedal effort is important. Link to comment Share on other sites More sharing options...
Pierre Gillet Posted June 18, 2003 Author Share Posted June 18, 2003 Good point , between the 2 tests I indeed dropped the spare wheel, and fitted carbon protectors 😬 Pierre Link to comment Share on other sites More sharing options...
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