I have a 2008 Mazda 3 TS D. It's my first car, so I'm still unsure as to what is normal and what is not. I'm in the UK (Northern Ireland).

It recently (Saturday) passed it's MOT, but the parking/brake efficiency on the MOT certificate are as follows:

  • Service Brake 61%
  • Parking Brake 23%

Also, the following brake imbalance results:

  • SB. Axle 1 -> N/S: 2.91 -> O/S: 2.57 (Brake Force (KN)) -> 12 (Brake Imbalance (%))
  • SB. Axle 2 -> N/S: 1.79 -> O/S: 1.68 (Brake Force (KN)) -> 6 (Brake Imbalance (%))
  • PB. Axle 2 -> N/S: 1.74 -> O/S: 1.57 -> Nothing under brake imbalance

I had a full service done before the MOT (by Kwik Fit) and took all of their advice (including adding new brake pads). It was a bit pricey! It feels like these numbers should be a bit higher.

Do the above numbers look OK, or should I be expecting a bit better after quite a lot of (expensive) work after a full service?


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    Welcome to Motor Vehicle Maintenance & Repair! Nov 19, 2018 at 22:55
  • Happy to be here :) @Pᴀᴜʟsᴛᴇʀ2
    – JMK
    Nov 19, 2018 at 22:56

2 Answers 2


I believe that the minimum efficiency required to pass the MOT is 16%. The percentage is calculated based on the braking effort measured at the rollers and the weight of your vehicle. 23% is over the passing threshold. I realise that it's only a difference of 7% but that expressed of a percentage of the minimum required effort is 143% so if it were my vehicle, I wouldn't be worried.

Bear in mind that the design of the braking system will have a bearing on the theoretical maximum percentage that the system could ever achieve. It's not a scale which stops at 100%.

  • Thankyou, I'm just an idiot when it comes to cars so wanted to ask on here to get a bit more context. Will mark this as the best answer in the morning.
    – JMK
    Nov 20, 2018 at 21:17

Most people don't even use parking brake, even though it's illegal to leave your car without parking brake in UK. Your brakes will get better after new brake pads and maybe playing a bit with the brake cable settings.

  • I don't think leaving a car without a parking brake is illegal in the UK. Nov 20, 2018 at 15:02

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