“Imagine” and “should not”. Yep, “sort of” is about the best you can do armed with that isn’t it 
How does it remove liability from the tester? The “Testers should take account of the vehicle’s drive configuration, transmission type and any Vehicle Specific Information…”. Sounds like if they decide wrong it’s their fault.
As for VOSA’s database - it doesn’t know if an LSD has been retro fitted to a car, so you’d expect it to contain false negatives, as well as mistakes. So the MOT chap will still have to use his jufgement. If you don’t trust the judgement of your MOT tester change your MOT tester to one you do trust.
The situation hasn’t changed - I still tell the MOT guy I don’t want it tested on the rollers. He has the right to refuse my business, but then he always has.
They’ve removed a specific instruction which did not rely upon any interpretation from the tester to implement other than to find out if the car had an LSD. It used to say,
“Vehicles not to be tested on a roller brake tester
Certain vehicles should not be tested on a roller brake tester, e.g. vehicles with
· Limited-slip differential”
Now there is no specific instruction about LSD. It is up to the tester whether or not to test vehicles with LSD on the RBT. My car had 4 RBT tests when the rules clearly stated none were to be done. The 2 test stations involved did not make their own judgement not to use the RBT despite the rules. They did not even follow the rules. They were wrong and may or not have caused damage but if any is found my case against them is much clearer than it would be under these rules.
This is a mess. VOSA are a professional organisation. Manufacturers of vehicles have a duty to ensure their vehicles are fit for purpose. If that includes limitations they may have with regard to MOT testing (a known part of their future use) they need to state those limitations clearly. This could be done via VOSA, included with the vehicle handbook and documentation, and/or stickered on the vehicle etc. The owner is not an expert and should not be expected to dictate testing procedure to anyone.
So what other cars should not be tested using the RBT? The original text used exempli gratia, not id est. I’ve written enough military documentation to know you can’t really use e.g., in a critical instruction, since it gives scope for mistake. If there was a definitive list, then i.e. would be used. But vehicle developments mean this list constantly changes. I imagine there are other vehicle configurations which have given problems, and this is communicated via “Testing Matters” or other similar documentation. The MOT testers are professionals; highly qualified motor engineers in their own right, so I see the new text as recognising that professionalism, and lending consistancy to the text, as there are other occurences where they are expected to use their professional knowledge to determine how a test is carried out.
I’m going to accept the opinions by knowledgeable individuals on this forum, and backed up from elsewhere, to determine that my Torsen differential will not be damaged by the RBT. Having said that, I might make up a small warning sign to be mounted to my dashboard along the lines of “Warning: This vehicles is equipped with a Tosen Limited Slip Differential”, and leave it to the MOT examiner to exercise his or her own judgement.
All of this will be sorted if the GB MOT switches to the Northern Irish MOT approach.
I don’t understand quite why you think the manufacturer should be responsible for an optional test their cars may be subjected to by mistake. This is VOSA’s problem, and the responsibility lies with either them or the MOT tester. The new wording seems to make the tester responsible. As the tester can see the car he is testing it seems to make more sense that his judgement is used rather than an obviously faulty database. I guess VOSA has realised it’s cheaper for them this way round, and the MOT testers are lumbered.
If your MOT tester mucks it up it’s their fault. Same as it was before, but without being able to point to a database and say “they didn’t tell me”. They have more responsibility now. Some LSDs will be fine, some won’t.
Frankly I think a potentially damaging test should not be the default for all cars - the default should be a road test unless it can be proven that a particular car can be safely tested on rollers. It’d be a massive pain for MOT testers though, and cars equiped with LSDs are a tiny minority.
In “your case” you seem to have used incompetant testers. I’m sure there is an official way of complaining about this.
I bought the car after 4 RBT tests. I had no input about what test was used but do not think the customer should be expected to have an input anyway.
AT, e.g. (for example) is read clearly as being inclusive of LSD. VOSA need to ensure their testers follow instructions. So far they have shown that in 4/4 cases they have not done that with my car.
Captain Muppet, the manufacturer needs to make their product fit for purpose (including later known testing) that is consumer law and may simply involve suitable labelling in documents and vehicle.
Perhaps indeed the default should be a road test if no way can be found of identifying vulnerable vehicles. That might sound retrograde until we consider how many vehicles now have LSD and 4 wheel drive compared to the 70’s when RBTs were introduced. VOSA are 15 to 20 years behind the curve on this.
It is clear, from discussions on this forum, and elsewhere, that not all LSDs are the same, and not all require a seperate, and lengthier method of testing. So the previous advice implied all cars equipped with LSDs should not be subject to the RBT. If VOSA decided that those owners who insist on buying LSD-equipped cars ought to stump up the extra cash for the bother, there would be no discussion. So maybe £50 for owners of regular cars, and those with vlsds, Torsens, and an extra £20 for the more awkward models.
I don’t want my MOT to take or cost any more than necessary because of the concerns of owners with an entirely different differential design.
It will probably be easier for Mazda to despec cars intended for the UK market; just fit them all with open diffs. The majority of owners won’t notice, or really care. Thats what I would do.
The MOT manual (which I’m pretty sure is just a summary of what is taught at MOT Testers School) is just a draft at the moment; why not submit your concerns to VOSA.
LSDs are fit for purpose*. They can also be tested in MOTs. They are also listed in the specification when you buy a new car (at least in the documentation I’ve seen). I see no legal liability for OEMs here.
That said - it wouldn’t hurt to cast “LSD” in to LSD specific housings, or add a sticker, or tick a box in the handbook if an LSD is fitted. Not least to let the used car buyer know what he has bought so he’d have some idea how to drive it. However, should the sticker fall off it’d be nice if the MOT tester still has to use his skill and knowledge to do the right test. Especially on 20 year old cars which may have had LSDs retrofitted, or in my case welded up entirely.
* excluding any which fall to bits causing poorly documented catastrophic failures
Our Mazda 2 is £30 a year road tax but our MX5 is £235 a year so I don’t think £20 on the MOT would be an issue or we would not own it. Nor do I mind that others have their tow bars tested for the same price as part of their MOT.
It seems to me that not road testing as standard is missing the point. A bit like testing all the parts in a TV for example but not looking at the picture. Heaven forbid actually testing the car for what it is to be used for! If a road test were standard a brake test could be included for no extra cost. Other things would be picked up too, a difficult gearchange or fierce clutch that might hamper driveability, a sun visor that dropped down unexpectedly, a mat that rode up under the pedals, under inflated tyres… some cars look fine but are shocking to drive.
So multiple castings for different markets. What to do in Germany, where LSD is generally recognised as an acronym of Lysergsäure-Diäthylamid, and where a LSD is called a sperrdifferential. Or just leave the LSD off UK cars, like what they did for the NA.
Is that car MOT’d? Do you use it on the road? Does your insurer know?
If your MX5 had an open differential, would you have still brought it?
An alternative model to MOTs might be the US approach; where most states have now eliminated vehicle safety inspections. This might sound crazy; imagine that, drivers having to take responsibility for the maintainance of their vehicles. Don’t maintain your car, and get in a crash? Go to jail for 30 years. The State doesn’t care how you assess whether your brakes are safe; its up to you, the owner, to make sure the brakes are safe. The private sector responds to worried motorists afraid to going to the Clink by offering brake testing services; fully underwritten of course in case they damage your car. It needs a change in this country to make that work, getting away from a dependancy culture, where people think just because they’ve got a bit of paper, their car is safe.
http://www.state.nj.us/mvc/PressReleases/archives/2010/071610.htm
New Jersey had a <6% failure rate. We get a 10-30% failure rate…
is that effectvely a live axle?
With regard to not knowing the difference or noticing the difference between a conventional and a LSD- I had this demonstrated by a competent driver at a Caterham handling day -with and without, the drive in and out of corners was spectacular with the LSD… granted this was at the extremes of performance and on a private track… The advantages for us in normal driving is minmal , but on that rare occasion when we can push the boundaries it will provide benifits. As for building a lower spec -how low do you go?
When you go into a Mazda dealer he will ask for your reg etc -he then apparently can revue the build spec of the car - why cant MOT centres do this?
Good points but I think that in practice the state needs to protect innocent people from others who will not test or service their cars properly otherwise. Our gaols are too full already without giving school run mums 30 year stretches. So I’m in favour of the existing annual MOT but would like to see a road test included as it’s then that an experienced tester will pick up on things that may otherwise go un-noticed.
Would I have bought my car without an LSD? I don’t know, probably yes if there was no LSD option and it felt safe to drive. There’s a lot more to a car than the diff, good geometry and axle location are probably more important as anyone who tried to get a tramping Cortina or Anglia handling in the old days will know! However, it has 160bhp and an LSD and pulling out of a junction or tight corner with both wheels gripping is a pleasure I do appreciate 
Here in Queensland, we don’t have an MOT equivalent.
The only time a car is tested is when it changes hands, and then it must have a valid roadworthiness certificate. Accidents caused by mechanical failure are far outwieghed by accidents caused by fools who drive in an unsafe and dangerous manner. The climate here means that cars are not so prone to rusting as in the UK, no salt on the roads etc. It’s quite normal to see a 1950s Holden being driven round by the original owner
90hp low.
I’m not sure Torsens or Fuji-Wotsit SuperLSDs really compare to something fitted on a Caterham. Mazda never called the vlsd a vlsd; only Miata owners called it that. Mazda was careful to call it a sports differential.
There is a really good explanation here about Torque Bias Ratios, and why the vlsd, TorsenI, TorsenII and TFS will never be the racer’s choice:
http://www.miata.net/garage/diffguide/index.html
Fact is, a lot of people don’t know if they have a Torsen fitted, otherwise they won’t be posting fairly regularly here asking if their Roadster has a Torsen fitted or not. And you also get the odd 1.8iS Mk1 owner who is utterly convinced they have a Torsen fitted, due to some misunderstanding of specs.
Well, less rust means longer vehicle lives, leading to increased chance of mechanical failure. But its a different mindset that means people maintain their cars rather better. I suppose there are many parts of Australia where a functioning car is literally a matter of life and death, so you look after your car. A few years back, I was staying with friends in the US. They had a trusty Mercury Sable wagon (a posher version of the 97 Taurus). My friend detected a slight hesitation in the shift of the slushbox, which by then had about 180k miles on it. But he had no hesitation in dropping it off at a dealership to get the transmission rebuilt at a cost of $3k. Over here, a lot of people will take the attitude of just driving the car into the ground, rather than fixing it properly.
Ireland never had a MOT until about 2000, when the NCT came in, using the GB model. I can’t say thats made cars in Ireland any safer (pre-2000, cars didn’t look like they were trundling around in an Albanian-state of disrepair), but its certainly put more money into the pockets of the government there.
You only need to drive 150ks west from my home to know the truth of that AT
According to this web page, my 2001 mk2.5 uk model Auto - comes with a Torsen LSD. Other web sites say that no NB autos have an LSD.
Any idea who is right (would help to know for MOT reasons)?
Automatic MX5s have never had an LSD from new, at least thats what I am lead to believe…
Dr. Eunos