12 replies to this topic

[Ed Tomlinson]

My car is a 1983 Austin Mini Sprite and has a pressure reducing valve for twin circuits mounted on the bulkhead. Car was MOT today (last mandated one as soon to be forty years old) Tester said handbrake was absolutely fine but rear hydraulics weren't providing enough stopping power. I mentioned the Pressure REducing Valve but they didn't know anything about this. Everything else about the brakes are fine, no loss of fluid, no warning light, rear wheelcylinders are fairly new. If this system is working OK how should it perform on an MOT brake tester? Is it different from normal? As I understand it, under heavy braking the flow to the rear brakes should be restricted. Should they be tested only with light braking? How can I tell if my unit is faulty or correct. Any MOT testers out there who know the answers to this one. Many thanks Ed

[Spider]

I have looked through a small handful of factory publications for the Mini to see if they gave a description of the Brake System. Sadly, I couldn't find anything.

 

They did include such a description in the Metro's Workshop Manual, which does make reference to the rear valve;-

 

 

I would think somewhere, there would have to be something similar for the Mini. Surely that would help at MOT time.

[imack]

Compared with modern cars, minis hardly give a reading on a roller brake tester on the rear brakes. From memory they only used to raise about 50kg of effort on each rear wheel.
A lot of younger mot testers are not familiar with the peculiarities of old cars.
With the rear wheels off the ground and the hand brake off, if you apply the foot brake and can't turn the rear wheels there's probably not much wrong with the rear brakes.

[Ed Tomlinson]

Thanks for information, I've found some info about how they are supposed to work in my Haynes manual, will post something on here later, I'll also just check with wheel off the ground and check inside the drum to see if they are nice and shiny and some brake dust although it's not getting much use at the moment. Interesting to know about readings, is there somewhere official that this sort of data is available to MOT testers. Cheers Ed

[cal844]

My 1980 CE gives roughly 50kg on each rear wheel. Did the wheel lock or not?

[sonscar]

I thought the pass/fail brake performance was listed per vehicle.I have had the comment that it was a pass but they should be much better in the past.Steve..

[weef]

Section 1 of the MOT Inspection Manual , available on line, gives directions to the MOT tester as to brake performance figures and efficienty and how to calculate same although the modern brake roller tester does this calculation for the MOT tester and generates the performance figures and hence the Pass/Fail result.

The rear circuit on the Mini does not generate a big braking effort and you have to squeeze as much out of it as you can. 

If the efficiency figure is low then its time for an inspection and although there may be no apparant faults, leaking fluid, sticking wheel cylinder, pull off springs and brake shoes fitted correctly and all correctly adjusted it may be that the brake drums are worn out of spec. It is surprising how much they wear and often go unoticed. Fitting new drums and shoes may remedy this fault.

[imack]

There's no requirement for the brakes to lock, but the braking efforts both sides must increase and decrease relatively equally. Overall braking efficiency is a calculation of vehicle weight and total braking efforts on all wheels.

[cal844]

My 1980 CE gives roughly 50kg on each rear wheel. Did the wheel lock or not?

There is MOT Data as part of the official guidance possibly available online

Edited by cal844, 14 July 2023 - 03:03 PM.

[absx2]

Minis are very old and basic with no fancy load sensing compensators or ABS so the rear braking has to be a happy medium for ALL conditions so it should be obvious to say that if the rear brakes had any sort of stopping power the rear of the car will overtake the front and you could end up dead in a ditch.

 

Of course give the rear brakes and good going over but my guess would be there is nothing wrong with them and again if they had any stopping power the car would be dangerous in a wet emergency stop situation.

 

As far as I`m aware they can still use a Decelerometer in the MOT that sure as hell won`t be testing the rear brake efficiency.

 

I use adjustable rear brake valves on my minis and my 1990 Cooper is set to not lock the rear wheels under very heavy braking and I have never had to readjust it for the MOT in 30 years of ownership so again I`m guessing the MOT inspector is not clued up on minis but again get the brakes checked.

[Ethel]

Sure there used to a chart on the testing station wall back in the day that gave figures for the rollers for the common models, Expect it's all computerised now. Do testers still hang off the roof gutter to stop yer Mini's rear riding off the rollers? 

 

https://www.gov.uk/g...hicles/1-brakes

[lordcakes]

Just had my mini tested today and they test the rear brakes quite progressively and then take the highest reading. Last year I had zero braking effort at the rear and it failed. I hadn't noticed as there is so little braking effort at the rear. It turned out to be the bulkhead valve not allowing any fluid through to the rear circuit. As this valve was the original (1985) it was replaced as there is no real testing that can be done on it.

[Ed Tomlinson]

Brilliant feedback, thanks everyone, the MOT testers passed mine but advisory on rears, Think I'll have another discussion with them as I'm interested to know what the braking effort was and did they do it progressively. Will also check the brakes to make sure there is some hydraulic pressure, the cylinders are relatively new and linings even newer so interesting to see if they have bedded in. Maybe a week or so until I can have a proper look but if I find anything interesting I'll post back on here. Cheers Ed