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| TexasRover Member Since: 24 Nov 2022 Location: Paris Posts: 1039   
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I just did the MOT in France for my Series and I have been trying to understand what these numbers mean. I can see how the put the car on the roller for brakes but then they vibrate the wheels up and down at different frequencies.
Surely what they measure there is the damping, which will be combination of the unsprung weight (axle wheel) the spring stiffness and obviously the damper. Springs are just dumb steel they sag maybe but especially for coils their stiffness does not change. The only remaining part are the dampers (shocks). They do wear over time (less damping), and are easy enough to change. In France they they seem to make things overly complicated. They use the measurement 'ripage' m/km (-8 to +8m/km). Only seems to be measured at the front and then they measure the symmetry (<30%). I don't understand what is this unit m/km? EDIT: ripage has to do with the geometry and how far your car veers off the straight line. Nothing to do with damping, which it seems is not measured other than deviation between left and right They also measure the vertical force in daN (which is 10 newton). I guess that will give you the weight:. my 110 was Front 1032 daN and aft 1220 daN so 2252 daN or 2296 kg? The brake force is then measured in daN and the total brake force must be more than 50%(?) I presume this means the total brake force needs to be 50% of the vehicle weight. my 110 had 51% while my Series on drums had 67%!!! Of course 0 information online |
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26th Jul 2024 2:20pm |
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| Mdm Member Since: 11 Sep 2013 Location: Sunny Lancashire Posts: 1597 
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it does depend if they set the brake tester to 4wd rather that 2 wd
brake imbalance is usually tired or sticky calipers. |
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26th Jul 2024 3:57pm |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3414  
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Brake imbalance is calculated by subtracting force generated by one side from the other side and then divide by the largest force.
Example for front of the OP, it is calculated as (90-55)/90 x100% = 61.111% So it does look like the left front brake is not generating enough braking force. Could be a sticking caliper as mentioned earlier, but also oil contaminated discs / pads. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
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26th Jul 2024 4:11pm |
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| Olaf Member Since: 09 Feb 2024 Location: Ramelton, Co. Donegal Posts: 6  
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TexasRover
Thanks for your input. I think that 'ripage' m/km is the same as slippage here in Ireland which is a measure of drift over a KM and related to tracking alignment (tolerance of +/-14m/km here in Ireland). Foot brake has to have an efficiency above 55% and handbrake above 16%. Looks like test tolerances are a bit tighter in France than in Ireland. Unless I'm wrong the UK MOT doesn't include a suspension bounce test and a UK Government website mentions problems of doing bounce tests on Defenders. Martin |
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26th Jul 2024 6:15pm |
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