NCT Suspension Test Measurement Units

cletus

So, passed my (free) NCT last night, and I was looking over the report to make sure nothing was borderline, or nothing stood out.

It occurred to me while looking at the suspension test that I don't know what measurement unit is used in the suspension test. The sheet says Mm, but is it actually millimeters?

The reason I ask is, we all know that two equally bad shocks on one axle can pass, but I wondered if the results could be used as an absolute, to see if there were issues with a set of shocks.

My front axle had an imbalance of 7%, with absolute readings of 30Mm and 28Mm.

The rear axle had an imbalance of 5%, with absolute readings of 55Mm and 52Mm.

Can I deduce from this the reader shocks are on the way out, or are there stiffer shocks at the front to allow for engine weight, or some other scenario.

Any thoughts

buggy beag

The lower the reading ,the better they are ,so your front shocks are good and rear shocks are half way but still alright for the minute

cletus

buggy beag wrote: »

The lower the reading ,the better they are ,so your front shocks are good and rear shocks are half way but still alright for the minute

Cheers,I figured that, but what I'm wondering is are they absolute figures. Is there a scale? your post would assume a scale of 1 - 100, but is this the case

doolox

Which is a unit of force.

They are Maha Metres. A unit made up by the manufacturers of the test equipment.

I'm not sure that lower is better.

jimgoose

I think that's "Nm", which is Newton-Metres.

cletus

doolox wrote: »

Which is a unit of force.

But what is the measurement. The only SI unit I can find attached to Mm is megametres, which is a unit of 1000 km, so unlikely to be what they are using

cletus

jimgoose wrote: »

I think that's "Nm", which is Newton-Metres.

I thought so too initially, but its definitely Mm.

cletus

[Deleted User] wrote: »

They are Maha Metres. A unit made up by the manufacturers of the test equipment.

I'm not sure that lower is better.

Thanks Songok. Do you have any more info on how the measurement works, is there an absolute scale, is it relative, exponential etc

jimgoose

cletus wrote: »

I thought so too initially, but its definitely Mm.

Hmm. It seems each shock just gets a precisely-calibrated wallop and the resulting deflection is measured. It is actually millimetres.

cletus

jimgoose wrote: »

Hmm. It seems each shock just gets a precisely-calibrated wallop and the resulting deflection is measured. It is actually millimetres.

If this is the case, do you know if any given set of shocks have an absolute limit of travel attached, so that this measurement could be used to determine their state.

jimgoose

cletus wrote: »

If this is the case, do you know if any given set of shocks have an absolute limit of travel attached, so that this measurement could be used to determine their state.

Any shock will bottom-out if hit hard enough, but I expect the NCT wallopers are a reasonable approximation of actual road.

cletus

jimgoose wrote: »

Any shock will bottom-out if hit hard enough, but I expect the NCT wallopers are a reasonable approximation of actual road.

Sorry, what I meant was, for example, can you buy a set of shocks that will say any more than 60mm of travel and the shock must be replaced

jimgoose

cletus wrote: »

Sorry, what I meant was, for example, can you buy a set of shocks that will say any more than 60mm of travel and the shock must be replaced

Not to my knowledge, not quite so straightforward. You can tell somewhat by feel when the damping and/or spring is shagged, and suspension specialists like VMtek in Oysterhaven have special test jigs that measure this, that and the other.

CiniO

jimgoose wrote: »

I think that's "Nm", which is Newton-Metres.

Nm is an unit of torque so that doesn't have any relation to shocks.
However in SI system Mm would be mega metres, which is one million metres (1000 km). Equally nonsense.

Quick google search shows that no one know what Mm in shock test it.

challengemaster

CiniO wrote: »

Quick google search shows that no one know what Mm in shock test it.

Eh...

Deleted User wrote: »

They are Maha Metres. A unit made up by the manufacturers of the test equipment.

CiniO

challengemaster wrote: »

Eh...

Nothing about it on the internet except from few quotes from discussion forumes, half of it from boards.ie
Nothing on a wikipedia.

I have grounds to believe that no such thing as maha meter exists.

Renegade Mechanic

I'm not to sure myself.. But I can guess..

Lets say that the suspension vibration plate puts out a set, oscillating force on all vehicles. (At the end of the day, it's the same size bump, whatever car hits it) and the "Mm" is indeed a millimetre measurement.
Basically, a worn shock wouldn't resist the movement of the plate, allowing it to move up/down by, say, 70 millimetres. Whereas a good shock will resist that oscillation to a higher degree, only allowing 40 millimeters of movement under the level of force that the machine exerts.

All shock have a full travel of much, much more of course, but you'd be exerting much more (potentially damaging) force to get it.

That's my take on it anyway

challengemaster

http://www.backroads.ie/forums/showthread.php?7467-NCT-Suspension-Imbalance-Test/page2

It's Maha meter, there was no scientific measurement for shock testing so the makers of the equipment made there own. makers being maha.

http://www.maha.de/

Email them and ask

jimgoose

challengemaster wrote: »

http://www.backroads.ie/forums/showthread.php?7467-NCT-Suspension-Imbalance-Test/page2

Bejabers, I thought your man was taking the piss. So the walloper is an actual shock-dyno. I'm almost impressed!

buggy beag

I work as a vtn inspector with the maha gear.the lower the mm reading the better the shock is

Tragedy

CiniO wrote: »

I have grounds to believe that no such thing as maha meter exists.

http://www.asanetwork.es/doc_equipos/maha_banco_suspensiones_sa2_fwt1_en.pdf

What were those grounds CiniO?

cletus

buggy beag wrote: »

I work as a vtn inspector with the maha gear.the lower the mm reading the better the shock is

Is there an absolute upper limit to that, or is it a relative scale do you know

* edit* sorry,l looked at that above pdf again, I see the maximum reading is 100 Mm.

Buggy beag, as a tester who used the equipment, at what reading would you recommend changing the shocks.

Looking at the fail standard, it seems that if both shocks were reading in the 80's they would still pass, as long as they were within 30% of each other.

buggy beag

The lower the mm reading is the better the shock is

gofaster_s13

buggy beag wrote: »

I work as a vtn inspector with the maha gear.the lower the mm reading the better the shock is

Not true, by that reasoning a vehicle which is solidly suspended ie no suspension at all which gives a result of 0mm is the best suspension of all.

There is no correlation between the amount of travel and how good a damper is. Using the Maha equipment I have seen that a new performance car ie a BMW m3 etc will give a very low reading and a new standard saloon car such as a BMW 520d will give a much higher reading both are perfect but just designed to give different damping characteristics. The test is only used to measure imbalance between left and right and not as a test of performance.

The test isn't carried out with a single wallop as described earlier, it's a cam driven oscillation of the suspension which is measured as a frequency over a timed period.

jimgoose

gofaster_s13 wrote: »

Not true, by that reasoning a vehicle which is solidly suspended ie no suspension at all which gives a result of 0mm is the best suspension of all.

There is no correlation between the amount of travel and how good a damper is. Using the Maha equipment I have seen that a new performance car ie a BMW m3 etc will give a very low reading and a new standard saloon car such as a BMW 520d will give a much higher reading both are perfect but just designed to give different damping characteristics. The test is only used to measure imbalance between left and right and not as a test of performance.

The test isn't carried out with a single wallop as described earlier, it's a cam driven oscillation of the suspension which is measured as a frequency over a timed period.

Understood and well-answered. Thank you.

cletus

@gofaster, thanks for the explanation. Would it be safe to say that the figure in Mm cannot be used to accurately assess the condition of a single shock?

Also, would you expect to see similar figures for the front and back axle of any given vehicle, or to put it another way, given the figures in my first post, works out be safe to assume my rear shocks are on the way out

challengemaster

cletus wrote: »

@gofaster, thanks for the explanation. Would it be safe to say that the figure in Mm cannot be used to accurately assess the condition of a single shock?

Also, would you expect to see similar figures for the front and back axle of any given vehicle, or to put it another way, given the figures in my first post, works out be safe to assume my rear shocks are on the way out

Even just look at the physical appearance of front and rear shocks and you'll know you can't compare readings from them.

cletus

challengemaster wrote: »

Even just look at the physical appearance of front and rear shocks and you'll know you can't compare readings from them.

This is what I would have assumed challengemaster, but you know the saying about assume, it makes you look like a prick

I initially imagined that the front shocks would need a greater damping effect given the weight of the engine, but considering the contradictory viewed on just the measurement units in this thread,I thought asking the question of those more informed than I couldn't hurt

CiniO

Tragedy wrote: »

http://www.asanetwork.es/doc_equipos/maha_banco_suspensiones_sa2_fwt1_en.pdf

What were those grounds CiniO?

They must be gone underground together with my face - I feel like an ostrich now.

Stand corrected.