My 2008 Mazda 3 TS D passed it's MOT, but with seemingly low service/parking brake efficiency. Should I be worried?

Question

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?

Cheers

Answer 1

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%.

Answer 2

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.