ABSOLUTELY :thumb:

Here's one:

No it doesn't.
It only demonstrates that either:

1. 'they' don't know;
2. 'they' aren't prepared to commit;
3. you are only going to listen to someone who you believe knows best.

Why start a thread and then exclude anyone except "the big names" ?

Take a hint or 2:

• No "big name" has stated that I'm incorrect;
• An MoT tester has stated the same as I did ie. always use a Tapley and avoid ANY doubts and comebacks.

I wonder if you'll be so confident next MoT????????????????????????

(And of course we'd all be eager to know :D).

I'm sorry if I don't take your point of view as gospel (you being a relatively newbie an all) and lets be honest, most of your posts are just long winded dribble anyway chap... (no offence intended)
The thread has had lots of views with only a couple of people of the opinion that standard brake rollers should not be used.
So why would I take your opinion as correct ??

There are some 'big names' on here that not only myself but many others trust and respect the knowledge they have. People like Ali, Alyn, David etc etc.... I'd like to see what they say.

As I said in my original post, there's been lots of threads about this over the years and not one had a definitive answer. Some (like yourself) said don't do it but then others said it's perfectly fine, I've even been told by MOT stations that it'll be fine.
Not one of the threads I've seen on the matter have had responses from long time known experts in the world of impreza's.

And just to clarify, I'm not excluding any opinions from anyone, infact the more response the thread gets the better. However, not only myself but most others will take note of long time known and trusted tuners opinions over someone like yours chap.

Maybe there is no definitive answer because there is no "definitive" 4x4 system

Like I posted earlier, I don't see a problem with a standard open centre diff (which I was under the impression most impreza's have)

Which, under extreme circumstances is simply 1wheel drive, in the same way that a 2 wheel drive cars are

But there are several type of centre diffs allowing varying amounts of slip etc (DCCD)

Certain car manufacturers (Volvo I think was one) insisted that all tyres had to be replaced at the same time to ensure the same rolling diameter and thus avoid differential damage due to different rotational speeds


Maybe MOT testers that don't use rollers are just playing safe rather than working out the exact type of diff

I have had 4x4's for the last 20 years and always assumed (maybe wrongly) that they were tested on rollers

I don't think you'll find I said "don't". I said "shouldn't".

And the reason you'll get different opinions is because there are different systems - as per advice from other poster(s). One man's 'safe' diff is another's knackered up car.

Fwiw a JDM Hawk is 'safe' to put on rollers (provided DCCD is left to auto of course). And that IS from experience.
Some things you only have to do once to be as knowledgeable as others.
Obviously you aren't, by the very fact that you've posted seeking advice on a particular subject.

With regard to a lot of the irrelevant content of the quoted post I'm sure I've got under enough people's skin that had I posted something even slightly incorrect you'd have had a 10-pager.

Not exact a vibrant thread is it?

Oh I don't know, compared to your Cheshire Car Sales thread it's a hive of activity :lol1:

Many respected guys have given given their opinions on it loads of times. Personally I've got to the to the point that I tend to ignore these threads as it very tired and very old ground and my answers can easily be found via search. I'm sure Alyn and David have given their opinions in the past too.

Heres a few comments I've given over the past 11years on the subject:

https://www.scoobynet.com/scoobynet-...r#post11433190

https://www.scoobynet.com/scoobynet-...r#post10545715

https://www.scoobynet.com/scoobynet-...r#post10545538

https://www.scoobynet.com/non-scooby...er#post5247990

https://www.scoobynet.com/scoobynet-...er#post2752603

But to repeat myself. For MOT purposes, I don't recommend roller brake testing for any car with a limited slip differential...be it 2WD or AWD. Regardless of if the roller spins one wheel at a time or not.

http://www.motinfo.gov.uk/htdocs/m4s03000701.htm

Im a tester and anything 4wd i use a taplow. There is nothing in the mot that says brake rollers MUST be used. Ive used a taplow on some low 2wd cars too.

Id rather not risk harming someones pride and joy no matter how small the risk.

And as above anything with an lsd doesnt go on either.

Its not for the tester to switch the car from 4wd to 2wd.
The car should be tested as presented.
There are so many different systems its impossible to know whats safe and what isnt unless you work on one brand

Well, that's at least 2 MoT testers that have given their professional opinion.

So is a car with the DCCD in auto safe then ???
According to the above posts that would appear not, but you said it is from your experience...

I started the thread to see if there was a definitive answer but it appears not. In Ali's links there is still two opinions. Alan Jeffery says it's fine to run an impreza on standard rollers for instance.
You say a car with DCCD in auto is safe.
Ali says it shouldn't ever be done.
Others say it's fine if the rollers are fancy 4x4 ones.

Who knows hey, all I know is I won't allow my car on rollers after this.

"But to repeat myself. For MOT purposes, I don't recommend roller brake testing for any car with a limited slip differential...be it 2WD or AWD. Regardless of if the roller spins one wheel at a time or not."

Suggests it is not the drive configuration 2 or 4 but the amount of "slip" present in the diffs that is the issue

Surely it's not about damage to the car but that the results on the rollers will be meaningless. So if one brake was low on effort the other brake will compensate via the LSD. Just think of the forces on a diff on the road when braking hard mid corner or with a damp road. Or even with one wheel on the grass verge or a track kerb. Diffs would be smashing every time we drove a car.

Definite answer right there, don't ****ing do it. I won't.

If you put your car on a brake tester doing one axle , it can burn the centre diff out , same as you cannot do a suspended tow if you break down , even a dccd centre diff will not open fully , so can be damaged.

Comprehension eh?

I think what I said was 'as long as the DCCD isn't locked'.
That means that IF the diff is locked you would risk problems. It DOESN'T mean you won't get problems if it's left to auto.
In MY experience a JDM Hawk with DCCD on auto doesn't have a problem.

This is consistent with almost everything said.

• I've said that Subarus/4WD "shouldn't" be tested using rollers.
  The simple, plain common sense logic is that if you don't expose a car to risk then there won't be any;
• this is a point stated by at least 2 professional (in all senses of the word) contributors to this post - they always use a Taplow.

The latter point is, I suggest, the key one.

You wanted a definitive answer and that's it.
If you don't want risk, or don't have the confidence to believe in what you've researched then don't allow brake testing using rollers.

A very useful thread on here gave me a warning about the possible effects of testing Subarus using rollers, so I wanted a Taplow.
I couldn't find anywhere in my area that used a Taplow, so I did a fair bit of research and came to the conclusion that my pride and joy would be OK tested on rollers.

I had the balls to allow it to be so, and didn't have a problem.

But my car's unique. Even owners of the same model probably have something different. How do I know what they've got ? How can I tell them 'yes, go ahead, it'll be OK' ?

My 'safe' diff configuration could be their knackered drive train.

But I guarantee it wouldn't be if you ensured that your MoT tester used a Taplow gauge.

The reason for the differences of opinion is simple.
Those whose cars have been OK on rollers will obviously say 'mine's been OK on rollers, so what is the problem?' (just like I have).
Those who aware of the potential problems will quite properly say 'it is too risky.

Which is what has come out in this thread, people saying that there's various configurations, what MoT tester knows every possible configuration, what's OK for 1 isn't necessarily OK for another etc. etc.

And in order to avoid even more misunderstanding, although I'm happy for mine to be roller tested I'd NEVER say it's OK to anyone else with a similar model.
It would always be 'Taplow - better safe than sorry'.

Finally, can I suggest that it doesn't help when you put words in my mouth - sorry, posts.
You have clearly either misunderstood or misrepresented what I have said and/or implied.

I'd hate for someone to ignore what I've written on the basis that you, the op, consider my contribution unworthy for whatever reason, and for them to consequently suffer loss as a result.
I believe we all have a responsibility to collectively be as informative as possible. Where someone fails occasionally another(s) can correct it.
Simply using someone's number of posts and/or length of membership as a yardstick to the amount of credence and credibility they have is quite frankly assinine.

Just dropped off car to fail it's mot
Asked the old fella that took the keys how he's gonna do the brake test
I'll drive it down the road he says we won't put imprezas on a roller

At least 3 professional opinions now then.

Btw is "the old fella" a 'big name' on here, so we can terminate this thread? :D

PS - hope it's not too expensive to get yours back through :thumb:

:)

Give it a rest pal, you're the one who thinks it's 'safe' to put an impreza on the rollers if the DCCD is in auto even though others above have all said it's still a bad idea.
You have as much knowledge on the subject as me but still you post your dribble.

And another biter gets bit :D

Why are you trying to spoil the OP's thread? You had your say, but then your last few posts are posted for no other reason than to needle him. Trolling I think they call it. As the OP said give it a rest.

Thanks Chris but to be fair I shouldn't of taken the bait, he's obviously a bored old man with nothing better to do than troll the Internet.
Come on LWC, take off your glasses and climb into bed mate because we've had enough of your nonsense this evening.

Let's close the thread as after all the posts and opinions it's now clear that there is not a right or wrong answer to my original question.
The safest bet is to not allow our cars to be tested on the rollers, that way we can be sure no damage or stain is being put on the diff's.

Thank you for the input guys.

Fundamentaly if an mot tester put a 4wd on.a 2wd brake rollers and the gear box fails then
the garage will have to pay for the repairs so

My boss would nt be to happy if I told oops sorry just broken this guy's 6 speed gear box on the rollers that's 100quid you owe him.

Always use deaccelerometer on 4wd vehicles end of.

Oh I'm an mot tester aswell.

What's the gearbox got to do with it, surely it's in neutral with the clutch disengaged

If you put a 4wd on 2wd rollers the car will try to leave the rollers as the other axle gets driven via the centre diff.
All this has been covered by the land rover guys years ago. Basically there are multiple reasons. Safety being one and risk of damage to the diffs (but if a diff is in good condition it will take it) also the fact that the results are meaningless. Also applies for 2wd with a LSD.

:thumb:

I asked my MoT man about this yesterday, prior to seeing this thread, and for 4WD he uses the decelerometer.

They only test 2WD cars on the rollers, and one time a Golf 4Motion was tested on there it damaged the grip coating on the rollers, not the car.

not if is an open diff - try it, jack the front wheel(or rear) up and try and turn the wheel

if you can (which on most Scooby's you will) - then you have an open diff - all torque is going to that wheel - whether by your own efforts or the engines

if you have a locked or limited slip diff you will not be able to because I doubt you will have the strength to overcome the slip (or turn the wheel that are on the ground)