NCT failure for suspension test imbalance

youtheman

My wife's car failed the NCT because of the front axle imbalance. The nearside was 49 Mm and the Offside was 33 Mm, a 33% imbalance (limit is 27%).

So she got both shocks replaced (with new units from the Fiat garage). The car passed the retest, BUT the readings are now 48 Mm and 35 Mm (a 27% imbalance, which is near the fail limit).

I would have thought there would be zero imbalance with 2 new identical shocks.

Am I missing something?. Don't know whether to tackle the garage or the NCT centre.

Mar4ix

it is strange. after i changed shock absorbers, and after 1 week went to test, it was only 4 percents imbalance. rear was 0. i was blaming that front tires had different air pressure.

My advice would be go back to garage, and show your nct test report, as really something wrong with one of shock absorbers. Actually, you have to look on them yourself, see, if they look new. if they both new , and not faulty, id be blaming springs, maybe one is too old and worn, but not sure it would make such difference, somebody here could correct me.

I believe, that NCT center test equipment is genuine tested and certificated, and i believe, you didnt use same line in nct center when did re-test. .

youtheman

Went back to the NCT centre. Very nice bunch of lads I must say. The supervisor suggested that the shock mounts might be the problem, and possibly they were not changed out. Checked the wife's car, and the original shock mounts seem to be still in place.

So I'll be on to the garage first thing in the morning. Not sure how much the shock mounts cost, but i would expect they would have at least inspected them.

And the downside, of course, is that maybe the original fail was due to the mounts, and I might have paid for two new shocks when there was no need to do so !!!!!.

Nissan doctor

The effect that a worn shock mount could have on the suspension imbalance would be tiny and if worn enough to cause any imbalance there would be obvious issues when driving such as creaking or knocking.

Its much more likely that one of your springs is weak and that this was the problem all along. The new shocks are likely masking the problem just enough to have passed the test but over time the weak spring will wear that shock quicker then the other side.

n1st

Is there a workaround for imbalance?
mine failed last week, it is 32% imbalance and the max allowed is 30%

To repair is 200+ euro, the car is over 10years old and driving perfectly, is there something I can do myself to decrease the imbalance?

Nearside Offside Imbalance
Rear Axle : 36Mm 53Mm 32% Imbalance Ablove 30% fail

jelutong

Anything over 30% imbalance is a failure.

jetfiremuck

Had the same issue with a discovery. It was the shock bushings. If you watch them doing the test the wheels barely move up and down during the test? I'd now replace bushings before shocks in the future.

jelutong

My car failed on suspension imbalance.
Front axle imbalance: 32%. Failure/ refusal.
Rear axle imbalance % Pass.
Couldn't get shocks to fit the car. Spent €200 on a pair of Bilsteins. That's another story.
Decided to put it through again with the original shocks.
Retest results.
Front axle imbalance: 29% Pass.
Rear axle imbalance:10%.Pass.
The only change I made was to fit a set of winter tyres.

n1st

Re-Test passed.
Gave the car a good drive, and over a few speed bumps, re-test results showed only 7% imbalance.

jelutong

Happy days. The imbalance went from 32% to 7%. That's amazing.
Mine went from32% to 29%.

dooroy

Before fitting new shocks its a good idea to move each piston up and down as far as it will go 5/6 times . This kind of 'primes' the shock .
If this hadn't been done with yours then the drive over the speed bumps could have had the same effect - hence the improvement in performance and balance.

Jimmy Bottlehead

Sorry to dig up a necro-thread, but I have the same issue so felt it best not to make a new thread. Front suspension was imbalanced by 33%, so 3% above the fail limit. No other issues on the NCT.

Anything I could do before bringing her to a mechanic?

biko

Old thread lock, start a fresh one.