NCT tester driving off premises

jordanfaf

Had my car in for NCT test in one of the Dublin offices (won't name for now) after testing the car I watched the technician drive out to the carpark and then caught a glimpse of him driving by the front of the test center on the main road... He was only out of my view for 30 seconds max before driving back by and into the carpark, leaving the car in the usual collection lanes.

I'm more curious than anything, why would he have drove off premises and are they permitted to do so. He was clearly a car enthusiast as he was asking questions and complimenting the car when giving me the pass sheet.

mickdw

jordanfaf wrote: »

Had my car in for NCT test in one of the Dublin offices (won't name for now) after testing the car I watched the technician drive out to the carpark and then caught a glimpse of him driving by the front of the test center on the main road... He was only out of my view for 30 seconds max before driving back by and into the carpark, leaving the car in the usual collection lanes.

I'm more curious than anything, why would he have drove off premises and are they permitted to do so. He was clearly a car enthusiast as he was asking questions and complimenting the car when giving me the pass sheet.

Some 4 wheel drive cars have to have brakes tested off the rollers so it involves a brake test while driving.
What type of car do you have?

jordanfaf

mickdw wrote: »

Some 4 wheel drive cars have to have brakes tested off the rollers so it involves a brake test while driving.
What type of car do you have?

Ah thatd makes sense, its an Audi S3, so quattro/Haldex system would need the road test i suppose. Thanks !

Del2005

jordanfaf wrote: »

Ah thatd makes sense, its an Audi S3, so quattro/Haldex system would need the road test i suppose. Thanks !

Yes anything with a limited slip diff or four wheel drive can't use the rolling road for brake testing. They put an accelerometer in the car and get up to 25km/h and then brake.

Pops_20

Del2005 wrote: »

Yes anything with a limited slip diff or four wheel drive can't use the rolling road for brake testing. They put an accelerometer in the car and get up to 25km/h and then brake.

How do they know if the car has a limited slip diff? My car has a viscous LSD and has been on the NCT rollers twice now.

kona

Pops_20 wrote: »

How do they know if the car has a limited slip diff? My car has a viscous LSD and has been on the NCT rollers twice now.

You should tell them at least. I always make sure they know.

Melodeon

I always stick a note about this on the steering wheel.
That said, the person checking me in has always mentioned the issue as it appears on their computer.

The older version of the NCT Test Manual (2014) had this note under the Service Brake Performance section (page 37):

8. The use of a roller brake tester is not appropriate on hybrid vehicles or on vehicles with a permanently
engaged four wheel drive, limited slip differential or belt driven transmission.

Interestingly, the current version (NCT Test Manual 2018) doesn't appear to provide this sort of detail, merely stating on page 41 (Service Brake Efficiency):

2. If the tester has any doubt regarding the service brake configuration then a Decelerometer test must be
conducted.

...and:

Decelerometer Test
If the vehicle is of a type that cannot be tested on the roller brake tester it should be subject to a decelerometer test
as follows:

...and this bit on page 8:

Where the brakes cannot be tested on a roller brake tester, due to the design of the vehicle, a road test must be carried out using a decelerometer to evaluate brake
efficiency.

Does anyone know if the details of what type of transmission/braking systems are unsuitable for the rollers are officially published anywhere?

ohnonotgmail

Can anybody tell me if this applies to my car? It is a 2008 Renault Koleos. It uses the 4x4 system from the Nissan X-Trail so it can be switched 2wd, auto or 4wd mode. It has its NCT in a few months so should i stick it in permanent 2wd mode for the test?

tossy

ohnonotgmail wrote: »

Can anybody tell me if this applies to my car? It is a 2008 Renault Koleos. It uses the 4x4 system from the Nissan X-Trail so it can be switched 2wd, auto or 4wd mode. It has its NCT in a few months so should i stick it in permanent 2wd mode for the test?

You should insist on them doing the brake test outside just to be 100% sure.

I've tested a rake of 4wd cars at this stage and always found the testers very knowledgeable and cooperative.

ION08

I usually find the testers quite knowledgeable ..

When I put my A4 Quattro through it's NCT I had planned on leaving a note on the steering wheel but forgot to do so. (It's not usually the type of car you'd expect to be AWD)

I remembered as the car was being inspected and asked one of the other testers to mention it to the guy testing my car that the cars is AWD ... the guy just shrugged and sayid "Don't worry, he'll know"

Sure enough he did and took it outside for a brake test.

Pops_20

What is the issue with doing the rolling road brake test with an LSD?

The only thing I can think of, is that the wheels are locked together during braking, and if each wheel is braking at different rates then the car will skip on the rollers.

I don't think this would be much of an issue with a viscous LSD as it doesn't lock during deceleration (could be wrong).

Wibbs

Wondering this myself. My car has a mechanical LSD and has never been taken outside. Just does the usual NCT thing in the lane. Including the brake test where it hops like any other car. And having talked with a few of the testers down the years they all know what it is and what it has. Could the difference be it's front wheel drive? I dunno, genuine question.

jordanfaf

When getting my previous car tested (Renault Clio RS197) the tester walked off the lane and asked me if it had an LSD. It dosnt but it looks like the kind of car that should!

gtturbokid

I've had a few Japanese cars with lsd fitted in the box and unless I told them about it they would test it on the rollers, now i'm driving a Quattro Audi a5 and actually never mentioned about the road test

galwaytt

Same with my Audi TT's over the years: I've seen mine tested using the decelerometer - indoors ! - twice.

LariToper

Curious about this too. I have a Mini with factory mechanical LSD and it was tested on the rollers, never even occurred to me that it should be any different. But as above I don't see why it should make any difference for a 2wd car

Guy:Incognito

Havnt hade a 4wd to get tested but I did watch as there was some confusion with the handbrake test on the Xantia before someone else was called over and they switched to the front axle

I left a note the next time but the lads in the Naas centre knew anyway.

antodeco

Interesting. I've a RWD Torsen LSD and the car has always been out through the rollers!

Pops_20

I've done some research online and can't find a definitive answer on this.

Some people saying that LSDs are not allowed on the rollers as they can damage the rollers themselves, not the diff. Others saying that they have seen diffs explode to bits when being tested.

I didn't pay any attention last time I was at the NCT centre, but I think the brakes on each axle are tested at the same time, therefore each wheel is spinning as it would be under normal road operation.

I think the real issue is testing a 4WD car with a locking centre differential. When the rollers are spinning the rear wheels, the engine is not powering them, so the centre differential is not spinning. Therefore the rollers are forcing the rear wheels to spin against the stationary center diff, which isn't good...

galwaytt

Pops_20 wrote: »

I think the real issue is testing a 4WD car with a locking centre differential. When the rollers are spinning the rear wheels, the engine is not powering them, so the centre differential is not spinning. Therefore the rollers are forcing the rear wheels to spin against the stationary center diff, which isn't good...

On the TT, which is a Haldex part-time system, if you drive the rear wheel on the rollers, the haldex unit 'locks', the front wheels engage...and off she pops off the rollers.

I would have thought any AWD/4WD would do similar: i.e., it's not possible to drive one axle, alone.

I did hear, years ago, that this was pointed out to the NCT at tender time (seeing as the gear is German....), but some bright spark thought the 2wd roller testers would save a few bob................lolz.

What happens on an electric car, even an AWD electric one ?

Cee-Jay-Cee

In the past I've had several Integra Type R's tested on the rollers and they have helical LSD without any issues.

The testers have always done the brake test in AWD Subaru's I've owned outside in the carpark.

Wibbs

Cee-Jay-Cee wrote: »

In the past I've had several Integra Type R's tested on the rollers and they have helical LSD without any issues.

Same here. Mine's done 12 NCT's and the LSD hasn't fallen out. Yet.