vehicle road worthiness tests

[Ex contributorParticipant @mgnbuk]

From this, I don’t think that there is a MOT measured relationship between pedal pressure and braking efficiency.

I think the “efficiency” is derived from the weight on the wheels. Where I used to have motorcycle MoTs carried out, they used a spring balance arrangement to drag the bike forwards against the applied brakes – before this test each wheel of the bike was weighed by pushing each in turn over a weigh scale. The results were entered in the MoT computer on completion of the inspection and an “efficiency” worked out. The pass value was low – about 20 or 25% “efficient” IIRC. The tester said that on one occasion he was able to ride a scooter around the carpark with the brakes fully applied without much effect on performance, but that it still passed as the caluclated “efficiency” when tested was above the test pass requirement.

My current MoT tester (the one I used for many years passed away a couple of years ago) uses a rolling road which I think has an integrated weigh scale & reads out the “efficiency” directly.

Nigel B.

[Robert Atkinson 2Participant @robertatkinson2]

On brake pads and disks I had a MkII Fiesta Diesel van as a works vehicle. It went in for 1st service and needed new front disks. I queried disks not pads and they said yes. Pads are OK. They did replace them under warranty. Next service, new disks required. Would not cover under warranty as I was “braking too hard” ! Id id notice that on hard (not excessive) breaking you could get a bit of brake fade. Van was not heavily loaded, we doing aircraft radios so a briefcase size tool kit and a couple of test sets.
They then bought a couple more vans and I noticed that they had ventilated front disks (probably off the XR2). These were much better and had normal wear. I can only think that the original brakes suffered from fade with the weight of the diesel engine and Ford “fixed” it by fitting hard pads. Thus disks wore out before pads.

I’ve had lots of issues with Quik fit. Onect took a car to them for a exhaust check (lifetime warranty) and they told me I urgently needed new front disks as they worn and “could explode”. I asked how thick they were and he said “Huh? they re worn out” I asked how they measured them and got another Huh?. I asked for the manager and he said that was him. I explained that I’d measured the disks the precious day with a micrometer and they were at least 3mm over the manufacturers replacement thickness (I’d measures closer to the edge than specified and the disk is thinner there). The manager then changed the subject….

[HOWARDTParticipant @howardt]

I suspect many  of us on here can remember when cars were purely mechanical and spent many a happy hour tinkering and getting to know what made them work.  Unfortunately we are in the minority now and all new cars are heavily dependant on electronics with sensors for indicating potential problems.  I find that if you have a relatively new car and take it into a main dealer they assume that it is a company car and treat all worn items as replace as the customer is not paying for it and will just blindly agree to it.  i had a Renault twenty odd years ago bought new and on the second service with about 18,000 on the clock wanted to replace all discs and pads as well as numerous other items, a quick add up and it came to over £1200, needless to say I told them what to do with their suggestion, the pads got to 50,000 and the discs 80,000.  Most of us will be aware of how we drive and the wear and tear we induce on a car, so with past experience know what life we can expect of wearable items and can work on that without getting ripped off.

[noel shelleyParticipant @noelshelley55608]

Having spent a large part of my life in the trade running my own business though as the world went electronic I moved into other areas of engineering !

Some scams to watch for, changing spark plugs, brake pads and discs, shock absorbers, tyres, all often tighed into other work. Doing a bit of homework eg Know the minimum thickness of discs, and having at least a basic idea of things will often stump conmen. ALWAYS ASK FOR ANY REMOVED PARTS and point out that you will query the bill if their not available.

One thing one doesn’t so often hear of is the changing of brake fluid, recommended every 3 years ! Often put forward as the reason for unexplained crashes, some fatal when brakes would suddenly fail, only on inspection to work fine ! I only came across one case in my work, a Range Rover, after 15 miles, at a roundabout, no brakes ! Elderly driver, who had his head screwed on and went for the hand brake, in this case a shaft brake ! Drove home VERY carefully then found the brakes worked fine ! CAUSE ! NORMAL Brake fluid will absorb moisture. In this case the front N/S caliper was dragging just a touch and over the 15 miles had heated up, boiling the water/moisture to steam in the fluid – a compressable gas- = no brakes ! As the system cools the moisture is reabsorbed and the brakes work fine again ! There is a cure from new BUT this would involve the manufacturers in cost !  Normal DOT 3 or 4 fluid is glycol based and is hygroscopic ! silicone fuid does not have this tendency but is much more expenseve !

Having an MOT does NOT absolve you from the requirement for the vehicle to be in roadworthy condition AT ALL TIMES ! Though it does reduce the likelyhood of you being stopped.

Ah well, better light the fire ! Noel.

[noel shelley]

On noel shelley Said:

…

One thing one doesn’t so often hear of is the changing of brake fluid, recommended every 3 years ! Often put forward as the reason for unexplained crashes, some fatal when brakes would suddenly fail, …

You might appreciate this, Noel … as an interesting alternative failure:

Sometime late1970s, early 80s … I was driving my Reliant Scimitar Coupé and ‘making good progress’ when I noticed a small cloud of brilliant white smoke behind me [no, it was not for a new Pope].

As the next tight bend rapidly approached me: I suddenly discovered that I had no brakes.

After limping gently home I discovered that there was no fluid in the system !!

The single point of failure was the [Lucas, I think] Servo, which had perforated its diaphragm, and allowed the engine to schlurp  the lot.

MichaelG.

 

[noel shelleyParticipant @noelshelley55608]

It was late one evening, fast approaching closing time, I was driving a bedford truck ! Hard and fast down the straight,brake for the T junction turn lt, 150yds 1st half of the S bend brake, 2nd half brake  300yds to a tight Rt bend, brakes cooked, warned passenger, hand brake and gear change to2nd, followed by a hard Lt bend, needed all the road and 50yds to pub – we made it – JUST ! It was the only time I had brake fade ! Noel.

PS To add to my previous post glycol brake fluid is highly inflammable and will flash easily, another cause of vehicle fires following an accident as the fluid spills on a hot exhaust, A leaking cluch master cylinder being topped up in a ford V4 proved this one – in a filling station !

[Paul Mills 4Participant @paulmills4]

While in Northern Ireland the MOT test centres  was surprised to find mot test centres were not in local garages but were run by the government, the other surprise was that a vehicle did not require a test till it was 4 years old. My wife ended up having to bring her car back to Scotland to get its first MOT as it was still registered here, and they would not test it as it was only 3 years old, even though the swansea joke shop said it needed a test.

The other thing that surprised me was, (pre covid) that you stayed with the vehicle and operated it as instructed by the examiner, although was told if I was worried about being able to hold the weight of the bike while operating the brakes for the efficiency tester then they would have someone do it.

[Perko7Participant @perko7]

Here in Queensland Australia we are not required to have regular roadworthiness inspections for cars and light commercial vehicles unless the vehicle is being sold. I have always taken my now-20-year-old Subaru to the local Subaru dealer for all the regular servicing. Anything major that needs work I will always research online to see if it is something I can do myself. So for I have done many things like brake discs and pads, wipers, lamps, alternator, radiator hoses, fuel hoses, and various body bits like window rubbers, drivers seat, gear lever bushes etc. I’m not afraid to tackle those tasks as I’ve done them all (and a lot more) previously on older cars I have owned. I do balk at engine repairs though as the plumbing and wiring on modern engines is too confusing.

It is amusing when I take the car in for a scheduled service and they repeat all the advisory repairs that were listed on the previous service report which I had attended to in the interim. I usually let them off the hook but sometimes it’s fun to mention the fact that the car was fitted with a new such-and-such just 2 weeks ago but they have noted it as needing replacement. It appears that unless they did the work it does not get recorded on the service history.

[Iain DownsParticipant @iaindowns78295]

Not directly related to MOTs, but I took my car a few years ago to a local tyre place (national chain) for a puncture repair.

OBVIOUSLY, it was to bad to repair and I needed a new tyre.  In fact I can’t remember the last time a tyre could be repaired, they must be much more fragile than they used to be…

They took a few hours longer than they said and when I popped back to pick up the car, the battery had gone flat.  ‘Oh dear, the battery must be flat!’.  I was somewhat suspicious and walked away, picked up some jump leads, jump started the car and 5 or so years later the car is still running on the same battery!

I should probably have complained to head office, but I doubt it would do much good and it would probably have been hard to actually prove it was criminal action.  And most likely I would have found some large men with crowbars waiting for me somewhere.

I’m still mad about it.

 

Iain

[noel shelley]

On noel shelley Said:

PS To add to my previous post glycol brake fluid is highly inflammable and will flash easily, another cause of vehicle fires following an accident as the fluid spills on a hot exhaust, A leaking cluch master cylinder being topped up in a ford V4 proved this one – in a filling station !

That was why there was a spate of vehicle fires after accidents collisions when they brought out push in master cylinders. They flew off, fluid went everywhere and wooof. The fix was a cable tie. !!!

[noel shelleyParticipant @noelshelley55608]

Yes I remember it well Dave. It was the plastic push in reservoir !

Used to take the Austin Champ in for MOT with out the windscreen on, No windcreen = no need for wipers or washers ! Being vacuum they were never great ! Watching the untrained try to reverse was always a laugh – there was NO reverse in the box, just 5 gears ! Reverse was on another lever and was in the rear axle and reversed the whole box – I took it to over 40 in reverse – just once !  Noel.

[Robert Atkinson 2Participant @robertatkinson2]

I’ve had a main dealer put cheap basic oil in and charge for fully synthetic. Put the wrong battery in the car, a old looking “BIG” in place of a 3 month old Yuasa. Fortunatly I had a receipt for the battery.
They also changed the brake fluid and when I checked the reservoir and cap were still covered in grime and road grit. After some “discussion” incuding showing them the instruction in he owners manual to clean the cap area before opening, they cleaned it off, drained the reservoir flushed the system and re-filled it.
I only used them becuase it was a condition of the extended warranty.

[mark costello 1Participant @markcostello1]

Across the pond in My State of Ohio We have no car inspections ever where I live, none when bought or sold. Another part of the State has a yearly pollution inspection, We have none. If involved in an accident then one would be in fault for an unsafe vehicle, if it was the one causing the accident. Problems? None. Drivers doing bad things are the biggest problems. Diesel pickemups rolling coal are around and never seem to be ticketed although I think They should be. Clouds of smoke are a bit much.

[Tim StevensParticipant @timstevens64731]

The remainder of the material on the pads (40%) is certainly enough for several thousand miles, but … there is always a but, isn’t there? The brake pads act as insulators between the hot disc and the hydraulic fluid. As long as you know this, ie that the ‘reserve thickness’ is not there to be all used up and then changed – and you bear it in mind when you go to the Alps with your caravan, all well and good.

And re Bob and heavy pedal – immediately above – the old pads were likely to be contaminated (oil, grease, mud, brake fluid, etc) and the discs (with rust), so what he says makes sense. And there really cannot be a quoted ratio of pressure and efficiency (even if they were in the same units) because cars, and uses, and conditions, vary so much. That is one reason why MoTs are done by real people and not by AI. Look out when this is changed, though!

Have a good year, just in case it is your last.

Tim Stevens

[noel shelleyParticipant @noelshelley55608]

Another one to remember, many if not all modern car requiring synthetic oil do so because ordinary mineral oil and it’s additve pack will poison the cat or DPF, resulting in VERY large bills, I was quoted £2200 for a DPF and this from a discount house ! The oil may be expensive BUT ! Noel.

[Mark RandParticipant @markrand96270]

Had advisories that the brake pads were getting near their limits for the two years before the most recent MOT. Changed the discs and pads after the MOT this year and the worst pad probably had another couple of thousand miles on it.

Note to the engineering minded:- brake discs make very good lapping discs either when new or after re-facing of worn out ones. I needed a couple of new lapping discs!

[Roderick Jenkins]

On Roderick Jenkins Said:

Can a garage really do an MOT in £55 worth of time?  If we had MOT only centres the cost would surely triple.

Rod

No, it only goes up by about 10%. For many years I took my car to a Council-run MOT only depot near Chasetown, then switched to a private MOT-only garage in Burton upon Trent.

Now I use the guy who does all the families cars and in many years he’s never ripped us off.

[Ex contributorParticipant @mgnbuk]

The brake pads act as insulators between the hot disc and the hydraulic fluid

Not always.

I have worked on motorcycle calipers that had isnulating “pucks” that sat in the hollow pistons to bear against the pads. IIRC the standard pads used were of the sintered maetal type, so the pads would not have been very insulative.

One of my former colleagues complained that the front brakes on his company Escort estate were “very noisey”. The garage found that not only had the pad friction material been totaly worn away, so had the steel pad back plates & the pistons were well on the way to being consumed as well ! Yet he did not complain about lack of braking efficiency or brake fade or the pedal becoming spongy, just that they had become “noisey”.

Nigel B.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I have never had any pressure from MOT test centres, when advisories have been added to the report, and seeing that I have always done my own servicing, they wouldn’t have got any joy from me if they even tried, and as has been said, an advisory is nothing more than that, it’s certainly not an indication that the vehicle is in an unroadworthy condition, so it’s up to the person to head it or not. An MOT only states that the vehicle is roadworthy at the time of the test, but does not guarantee it remains roadworthy, once it has left the test centre, and it is the duty of any driver to ensure it’s roadworthy at all times, whether you are the owner or not.

Regards Nick.

[Rod RenshawParticipant @rodrenshaw28584]

Thanks to everyone who contributed thoughts and experiences to this thread. On balance I think i will leave both the worn brake pads and rusting springs until the next test and see how things are then. I don’t think I will leave the pads until they are very thin though  that sounds a lunwise. And I will get a local independent garage to give me a second opinion on the springs.

Rod

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