NCT fail, shock imbalance, possible workaround? Tyre pressure?

pauldavis123

I failed my NCT on a 2002 Toyota Previa.

The values were 54mm nearside and 37mm offside, resulting in a 31% imbalance (>30% = fail).

Since this is a shock test can it be influenced by tyre pressure as they are part of the overall suspension system on the car.

New front shocks are coming in at €300 and since the current ones only fail by one percent its an expensive near miss.

Any thoughts. I'll PayPal you a couple of pints for some good info :rolleyes:

Avns1s

pauldavis123 wrote: »

I failed my NCT on a 2002 Toyota Previa.

The values were 54mm nearside and 37mm offside, resulting in a 31% imbalance (>30% = fail).

Since this is a shock test can it be influenced by tyre pressure as they are part of the overall suspension system on the car.

New front shocks are coming in at €300 and since the current ones only fail by one percent its an expensive near miss.

Any thoughts. I'll PayPal you a couple of pints for some good info :rolleyes:

The best advice you'll get, is to get them replaced. They're not an NCT fail for nothing. Now, where do I get them pints!!:):):):):pac::pac::pac:

quadrifoglio verde

Your car will drive incredibly better with new shocks! Replace them

corglass

If you do go down the cheaper route of chancing a retest and hoping for the best, lower the tyre pressure to about 26 to 28psi. That'll help dampen the vibrations produced by the machine.

Just ensure the tyres don't look noticeably deflated.

No pints necessary

shietpilot

The problem is a year later the imbalance will probably be much worse. Get them replaced, it's the best way of spending your money. Tyre pressures won't do much to be honest.

pauldavis123

quadrifoglio verde wrote: »

Your car will drive incredibly better with new shocks! Replace them

A Toyota Previa will never drive well



It's getting scrapped otherwise, definitely not worth spending money on at its age and tax band

pauldavis123

corglass wrote: »

If you do go down the cheaper route of chancing a retest and hoping for the best, lower the tyre pressure to about 26 to 28psi. That'll help dampen the vibrations produced by the machine.

Just ensure the tyres don't look noticeably deflated.

No pints necessary

I'll give that a shot and let you know.

Nice one, shame to get rid of her

porsche boy

Don't scrap her. PM me if you want rid of her

jelutong

My car failed the imbalance test last year. Put it through again with without changing the shocks and it passed.

unklerosco

jelutong wrote: »

My car failed the imbalance test last year. Put it through again with without changing the shocks and it passed.

My car failed after I replaced the shocks.. I did some research on it and as the above poster says, a load of cars pass on a second retest. Some people swapped wheels around etc.

For me it was the top mount bushing had deteriorated, cost €12 to replace... Sorted.

pauldavis123

Just checked my tyres, the two front are both at 36psi!

Garage gauge must have been way off.

If reducing the pressure is advised then even at thirty psi it would probably pass!

I'll report back when it's retested.

visual

The imbalance check is very crude test that only detects imbalance

At 31% one if not both shocks are faulty. It's not just handling it also makes a difference braking.
Considering the size of your people carrier I really hope your not able to fool the test.

Ideally the imbalance should be in single digits %. 31% is a lot off even a reading of 29% should be prompting you to change shocks

pauldavis123

visual wrote: »

The imbalance check is very crude test that only detects imbalance

At 31% one if not both shocks are faulty. It's not just handling it also makes a difference braking.
Considering the size of your people carrier I really hope your not able to fool the test.

Ideally the imbalance should be in single digits %. 31% is a lot off even a reading of 29% should be prompting you to change shocks

I agree with you in theory but

This:

http://www.boards.ie/vbulletin/showpost.php?p=88471764&postcount=1

This:

http://www.thejournal.ie/road-safety-boss-nct-claims-flaws-2729212-Apr2016/

This:

http://www.boards.ie/vbulletin/showpost.php?p=100468619&postcount=4

And the inability to find any info on the MahaMeter unit which the test uses leads me to think that this test is somewhat flawed.

I ordered 4 new tyres using the same money as one was at 3mm and 2 were over 5 years, I think that is a better safety investment

Squidgy Black

Imbalance test wouldn't necessarily indicate a blown shock.

I know as I recently failed because of a leaking rear shock and the car was still well within the imbalance allowance :pac:

visual

The point being there is something seriously wrong with suspension. If springs, rubber bushing etc.. are fine then its down to shocks. Probably the most likey component. Like anything else needs to be checked what is actually faulty before replacing but varying tyre pressure to cover up fault isnt good way of dealing with it.

NCT imbalance test will actually pass a car with two faulty shocks if there is no visible leaks and the imbalance falls within 30%.. While RTE program on NCT was unjust and poor investigation at best it was missing the point the NCT is the most basic of safety tests and isn't a substitute for properly maintaining a car.

The girl that died because car had two faulty rear shocks that manage to pass a nct a number of months previous was very sad case. The previous owner bears some responsible. There was a case that there should be more strict test that specifically tested shocks but RTE went off on tangent with less than creditable experts. So nothing has changed.

Cars that scrapes through NCT most basic tests on the day are perceived to be perfect by public almost like a guarantee until next year when it's gets another test. As a result most only get an oil change between NCT tests and no inspections, no preventable maintenance or even repairs.

The 300 euro for front shocks I suspect includes labour.

wonski

pauldavis123 wrote: »

I agree with you in theory but

This:

http://www.boards.ie/vbulletin/showpost.php?p=88471764&postcount=1

This:

http://www.thejournal.ie/road-safety-boss-nct-claims-flaws-2729212-Apr2016/

This:

http://www.boards.ie/vbulletin/showpost.php?p=100468619&postcount=4

And the inability to find any info on the MahaMeter unit which the test uses leads me to think that this test is somewhat flawed.

I ordered 4 new tyres using the same money as one was at 3mm and 2 were over 5 years, I think that is a better safety investment

There could be some flaws in the way your shocks were tested, but other cars pass it without a problem

There must be something wrong with your car suspension, regardless of what you think of the test itself.

If spending 300 is making it uneconomical repair to you then I am not surprised insurance companies don't want to touch 10+ years old cars.

Makes perfect sense now.

shietpilot

I wouldn't drive around with busted shocks anyway. They are what makes the tyres stick to the road on uneven road surfaces and bumps and they are not just for comfort.

Agricola

Had a rear imbalance of over 50% recently. One shock was clearly in bits and leaking oil. Managed to pick up a good second hand one with plenty of resistance and the re-test came in at 3% imbalance. Will do the job for now til I get around to replace both.

Renegade Mechanic

I doubt lowering the pressure will work much on the mechanism controlling the oscillations.
Not unless it's down to something like 10 psi.

Anyway as far as I remember, the NCT boys walk around the car with an air hose to check the pressure on the day

Renegade Mechanic

shietpilot wrote: »

I wouldn't drive around with busted shocks anyway. They are what makes the tyres stick to the road on uneven road surfaces and bumps and they are not just for comfort.

Amen to that. Hit the brakes with fubarred shocks?

BU-BU-BU-BU-BU-BU-BU-BU-BUMP!!!

pauldavis123

Just as a matter of interest, I redid the NCT and lowered the new tyres to 28psi from the 36psi they were at in the last test.

Passed with a 15% shock imbalance.

Definitely a flawed test!

keyboard_cat

pauldavis123 wrote: »

Just as a matter of interest, I redid the NCT and lowered the new tyres to 28psi from the 36psi they were at in the last test.

Passed with a 15% shock imbalance.

Definitely a flawed test!

What were the new mm values ?

shietpilot

This ladies and gentlemen is why we cannot have cheap insurance. The NCT test is not flawed. It will show imbalance correctly but OP chose to cheat it and then say it's flawed!

If you've ever braked hard in a car with busted shocks, you will know that the wheel isn't in contact with the road probably 50% of the time. Ridiculous carry on...
.

Bazzy

shietpilot wrote: »

This ladies and gentlemen is why we cannot have cheap insurance. The NCT test is not flawed. It will show imbalance correctly but OP chose to cheat it and then say it's flawed!

If you've ever braked hard in a car with busted shocks, you will know that the wheel isn't in contact with the road probably 50% of the time. Ridiculous carry on...
.

The test is flawed.

The tester should check the tyre pressure?

pauldavis123

shietpilot wrote: »

This ladies and gentlemen is why we cannot have cheap insurance. The NCT test is not flawed. It will show imbalance correctly but OP chose to cheat it and then say it's flawed!

If you've ever braked hard in a car with busted shocks, you will know that the wheel isn't in contact with the road probably 50% of the time. Ridiculous carry on...
.

If I had 31% at 36 PSI and 15% at 28 PSI then at the correct PSI I would still pass.

Seriously the test is the problem here.

PSI is not checked and the test is incorrectly named as its suspension not shock imbalance.

dr.fuzzenstein

pauldavis123 wrote: »

I ordered 4 new tyres using the same money as one was at 3mm and 2 were over 5 years, I think that is a better safety investment

So you did spend money on 4 new tires by saying it is a safety investment.

wonski wrote: »

There could be some flaws in the way your shocks were tested, but other cars pass it without a problem

There must be something wrong with your car suspension, regardless of what you think of the test itself.

If spending 300 is making it uneconomical repair to you then I am not surprised insurance companies don't want to touch 10+ years old cars.

Makes perfect sense now.

But this is the crux of the issue to me. If your shocks are knackered, you can spend all the money you want on new tires, but you're just pissing in the wind. What you are doing is the equivalent of this:



Also, you should not just rely on the NCT to tell you what's wrong with your car. Considering Irish servicing, those are probably still the original shocks (since maintenance and the NCT are regarded as scams on this beautiful isle), so after 14 years they will be well knackered. Shocks and brakes don't get changed just for a laugh, they are crucial items.
This whole "oh the car's not worth it" attitude is idiotic in the extreme, any car is worth replacing safety items, why do you think I put front springs, all new shocks all round and new brake discs all round into my car? Because I wanted to increase the value? Because I made sure it wouldn't cost more than the car is worth? No! I did it because it needed to be done. That is why my car has done 380k km in 10 years and drives like new (well, ish, but really quite good considering the age and mileage) unlike a car under Irish servicing that is 5 years old and knackered.

shietpilot

Bazzy wrote: »

The test is flawed.

The tester should check the tyre pressure?

I agree. The tester SHOULD check the tyre pressures however, the owner shouldn't also take the piss and mess around with tyre pressures to pass a suspension test.

The NCT test doesn't include a suspension test so they can fail you and steal 28 bloody euro for a retest fee, it's there to tell you that you have components that just don't cut it and will put you at risk if you don't change them.

pauldavis123 wrote: »

PSI is not checked and the test is incorrectly named as its suspension not shock imbalance.

Great defence for not changing shock absorbers, jeeeeesus christ.

grogi

pauldavis123 wrote: »

If I had 31% at 36 PSI and 15% at 28 PSI then at the correct PSI I would still pass.

Seriously the test is the problem here.

PSI is not checked and the test is incorrectly named as its suspension not shock imbalance.

The test is still showing a severe problem with the car, but you are just happy it passed...

Clearly something is flawed, but it is not the test...

selectamatic

Tbh at present both sides of the argument going on here are wrong. The test isn't flawed per say it should however take Mm readings into account. Likewise there quite possibly is not a severe problem with the car or it's shocks only the Mm reading will show that.
My slightly less dramatic assumption is that the passenger side shock is slightly more worn than the drivers side (a common issue with rough verges on Irish roads)
Painting a picture of completely blown shocks and scenarios where the op can't stop their car is overly dramatic very few people drive with completely blown shocks as the racket the make is cronic.
Now it certainly could be the case that ops shocks are that bad but I doubt it and jumping straight to the worst case scenario is nothing more then scare mongering.
If the op puts up the Mm readings then we'll know for sure.

Bazzy

shietpilot wrote: »

I agree. The tester SHOULD check the tyre pressures however, the owner shouldn't also take the piss and mess around with tyre pressures to pass a suspension test.

The NCT test doesn't include a suspension test so they can fail you and steal 28 bloody euro for a retest fee, it's there to tell you that you have components that just don't cut it and will put you at risk if you don't change them.



Great defence for not changing shock absorbers, jeeeeesus christ.

Fully agree it should be checked.

Some people a lot of people dont know how to check tyre pressure so it should be included

Bazzy

Furthermore the major flaw in the test is

Both shocks can be fcuked and once they're as fcuked as each other they will pass.

Que ordinary Joe leaving the test centre thinking he has a bullet proof car for two years

The reading should have a tolerance for suitable use if they go over a certain resistance pressure they deem them a fail and need to be replaced.


I recently had a car fail on a coil spring the smallest bit at the top was off i'm talking a couple of centimeters to be fair to the first guy he spotted it.

I took it back to a seperate smaller test centre and an older guy was on it was busy and I commented how busy it was and he said he would rather it was quieter as he was retiring

I had the receipt stapled to the fail sheet he knew the guy who done the work and was only short of passing it there and then

I do think they need a bit of an overhaul in the NCT centre and the test the tyre pressure should be added at the very minimum

jimgoose

Bazzy wrote: »

Furthermore the major flaw in the test is

Both shocks can be fcuked and once they're as fcuked as each other they will pass.

Que ordinary Joe leaving the test centre thinking he has a bullet proof car for two years

The reading should have a tolerance for suitable use if they go over a certain resistance pressure they deem them a fail and need to be replaced...

Turns out this is a little tricky. There's quite a good thread about that whole business here: http://www.boards.ie/vbulletin/showthread.php?t=2057587793

jimgoose

jimgoose wrote: »

Turns out this is a little tricky. There's quite a good thread about that whole business here...

And this is a good post, from a different thread. I think it's useful to give some inkling into how complicated this can get:

http://www.boards.ie/vbulletin/showpost.php?p=94956515&postcount=25

grogi

Bazzy wrote: »

Furthermore the major flaw in the test is

Both shocks can be fcuked and once they're as fcuked as each other they will pass.

Que ordinary Joe leaving the test centre thinking he has a bullet proof car for two years

For mother of all Gods - NCT does not guarantee road-worthiness. It is designed to catch the worst of the bad and force people into making an effort of maintaining the cars at least every one/two years.

If a car fails the NCT test, it is really bad and unsafe. If it passes, nothing wrong was found and it might actually be safe, but no guarantee is given.