MOT warning for 124 owners

[kth286]

Pleased my 1995 124 coupe passed Mot today.

Only one advisory as follows;

Front roll bar clamp bolts not clamped up all the way but no play.

Now here's the point.

Antiroll bars are fitted to help keep car level on bends, and if you look at the
arrangement as a schematic on a piece of paper, both with car level and with car leaning on a fast bend, you will arrive at the conclusion that as the lower wishbone changes angle on a bend it moves releative to the anti roll bar.

Therefore, to avoid the anti roll bar bushes from being destroyed prepaturely,
by being clamped too tightly onto the antiroll bar, the holding nuts only need to be done up sufficiently to keep the bushes snug onto the bar, and allow a sliding fit to allow the bar to both turn and slid within the bushes.

To reinforce the point, the Mercedes workshop manual states the nuts only be tightened to a max torque of 20 Nm.

Mine were just over that figure.

At that figure the clamps do not look fully tightened, and the MOT person
clearly was not aware the bar neds to move within the bushes.

I always leave a note inside the car for the mot tech, pointing out some of the foibles of the older Mercedes cars like mine; such as the fact that the front seat on my coupe lock only when both engine is running and doors are shut.

I will now be adding the anti roll bar torqe settings to the list.

I suggest you do the same to avoid the hassle of a potential fail in these ever increasing complex mot tests.

 

[jamesfuller]

I wouldn't worry too much, its not uncommon for an Mot tester to use an advisory to cover there back. As in, something that could wear further or work loose but cant be failed in its current state has been noticed so they have done there job!

 

[johnkyte]

I have the same advisory on my 89 Ford transit ambulance/ camper
Yet I assume That I could remove and throw away antiroll bar if I wished

Years ago when one was allowed to take tools to a HGV test station ,,I had a failure due to loose nut and bolt on tipper body.I cut off said nut and bolt with hammer an chisel---Result passed MOT

 

[kth286]

I have the same advisory on my 89 Ford transit ambulance/ camper
Yet I assume That I could remove and throw away antiroll bar if I wished

Years ago when one was allowed to take tools to a HGV test station ,,I had a failure due to loose nut and bolt on tipper body.I cut off said nut and bolt with hammer an chisel---Result passed MOT

I did that once, as I happened to have it off the car and was awaiting new bushes, so I thought it would pass without it.

The tester failed it, because ARB missing. They even checked (using my VIN)
with the dealer, that my car should have an ARB.

There is a clue on my car that an ARB should be fitted, because part of the
wishbone has a recess for it.

The garage got a quote from the dealer for approx. £600 for all the fittings for a new ARB including labour.

Went back a day later with newly purchased used bar (my own) and got the pass. I never did let on.

 

[del320]

Thanks for this - very interesting. Perhaps you'll remember my post from a year ago:

http://www.mbclub.co.uk/forums/part...144528-passed-mot-eventually.html#post1634095

Explains why the ends of my ARB were visibly worn. I had previously thought it worked like a torsion bar which would have required it to be bolted down fast.

As you will see, the whole service including supply and fit of ARB was just on £500.

 

[jamesfuller]

Our work 4x4s have the anti roll bars removed when we first buy and prepare them. Never had an issue getting an Mot. If they are fitted they have to be in a safe condition. Many Testers are over zealous and if they actually follow the book to the rule, it is very surprising what is actually allowed to pass. The official guidance with anything is 'if in doubt, pass and advise it'

 

[Paparazi]

It is like a torsion bar although both ends are fixed, typically to the lower wishbone.
The bar basically transferring forces from one side of the suspension to the other to minimize roll.
As one side of the suspension in compressed 'going around a corning' the ARB is turned in it's mounts transferring the rotating movement to the opposite side effectively compressing that side keeping the vehicle flatter and with less roll.

Martin

 

[coupe deville]

the front seat on my coupe lock only when both engine is running and doors are shut.


Get that every year, same test centre as well

 

[hotrodder]

I had previously thought it worked like a torsion bar which would have required it to be bolted down fast.

They are torsion bars. If they were bolted down fast they'd function as springs all the time instead of mainly countering roll. The bent ends of the bar are effectively levers with the straight(er) centre section acting as a torsion spring. When both wheels move in bump/droop together the bar just pivots in it's two inner bushes. In roll the ends of the bar are being bent in opposite directions and, being short, they're relatively stiff. Result is they twist the middle of the bar which fights back temporarily stiffening the suspension.

As said the ends need to allow some movement to account for geometry changes, the other (more common?) way is with 'drop links' where the ends of the bar are fixed to an additional linkage which connects them to the wishbone etc. The drop links add extra rubber bushes to the system allowing the necessary movement and/or alter the position of the ends of the bar so it's in more favorable position geometry wise to begin with, in theory at least- in practice some marques are infamous for eating drop links regularly. I've never really thought about the set up on a w124 before but if the sliding thing was done right it'd shorten the effective length of the 'levers' and progressively stiffen the bar