Mike88 Posted May 15, 2011 Share Posted May 15, 2011 I wonder how Airides are regarded for MOT purposes. They are obviously not standard equipment so a manufacturer's advisory to VOSA would have no affect. Link to comment Share on other sites More sharing options...
Mel B Posted May 15, 2011 Share Posted May 15, 2011 Air-ride suspension aids - we had these on our Rimor Sailer 645TC and it went through the MOT no problem. Link to comment Share on other sites More sharing options...
George Collings Posted May 15, 2011 Share Posted May 15, 2011 Cart springs or leaf springs are relatively cheap and robust and can simultaneously suspend the load of the vehicle and locate the axle, they come come in an infinite variety 1/4 eliptic ( mainly rears-1920s Austin 7, Mk1 AH Sprite, Mk II Jag) . 1/2 eliptics, (More than half the worlds HGVs and most pre 1980s RWD cars). 3/4 eliptics ( rarely later than 1930 cars) Full eliptics ( high class horseless carriages but occasional veteran cars) They can be curved down or up. (1950s BMC cars rears curved up) They can be transverse ( Model T Ford , MB Sprinter front) or longtitudinal, ( and then not necessarily parallel). Resilent bump stops are normally fitted to the chassis over the axle to limit the axles upward travel and cushion the impact against the chassis but in most designs even at the maximum designed load there should be reserve travel left in the suspension before contact with the bump stops. In recent years some hybrid designs use leaf springs to both suspend and locate the axle but augment it with an auxiliary resilent spring where the bump stop would normally be. To provide the additional travel this unit is usually upward of twice as long as a bump stop and the axle contacts it when the vehicle operates at or just short of its rated load. It does not take a genius to see that there is still a reserve of suspension travel due to the length of the auxilliary spring. If the AS is heavily compressed with little reserve suspension travel then an MOT fail is warranted. Making judgements on wear and corrosion etc are part and parcel of an MOT testers job along with an up to date knowledge of current practice. Been there done it, but alas no free T shirt. Sorry, I will put the soap box away now. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 16, 2011 Share Posted May 16, 2011 Mike88 - 2011-05-15 4:53 PM I wonder how Airides are regarded for MOT purposes. They are obviously not standard equipment so a manufacturer's advisory to VOSA would have no affect. Presumably Airride-type units would be assessed for MOT-test purposes under Section 2.4.D (Fluid/Gas/Air Suspension). See http://www.motuk.co.uk/manual_240.htm though such units provide assistance to the rear springs rather than being genuine "air suspension". However air-bellows air-assistance units are treated, they won't come under the 2.4.A regulations that can cause difficulties when the vehicle has the long 'bump stops' mentioned in this thread. Link to comment Share on other sites More sharing options...
paul2 Posted May 20, 2011 Share Posted May 20, 2011 Hi Some news that should make the Judge happy and Derek you were right . Today i read this in Matters of Testing VOSA's magazine for MOT testers. Taken from Matters Of Testing May 2011 Issue 50 Page 13 Hot Tips The Knowledge Spring assisters and bump stops Quite a few van manufacturersuse 'spring assisters' to support the base spring, especially on models which have low load heights or are usually run full or part loaded. Typical examples include motorhomes, which use the the basic chassis/cab with quite a heavy body, and vehicles such as the 'tool van' which always have a fair amount of heavy stock on board. Spring assisters are usually either exxtra leaves (more common to heavy goods vehicles) or rubber / polyurethane cones - alsoknown as Aeon springs (more common on the types of vans we see for MOT testing). Both types act by stiffening the suspension once deflection of the base spring reaches a certain point, affording maximum comfort whether the vehicle is empty or loaded. On vans,the preferred method is to use a rubber cone, which keeps unladen weight down and allows a low load height. These cones look like oversized rubber bump stops but work in a different way.The centre of the cone is hollow and when the suspension oscillates, the rubber compresses - effectively dampening the spring oscillation. The compression rate is progressive until eventually - at full load - the cone is fully compressed and then acts as a bump stop. When the suspension rebounds, the cone decompresses and re-froms to its natural shape. Because of their size and design characteristics, these cones may sit very close to or even on the base spring ,yet the suspension appears to be in its normal running position. This is, in fact, a design feature - but some testers interpret it as a failure under IM2.4A1: ' inadequate clearance between bump stop and chassis or a suspension unit so weak that the body or other part of the vehicle fouls a road wheel or would do so if the vehicle was laden'. Befor failing a vehicle under this RfR, testersshould first determine if a spring assister is fitted, and wherther the suspension really is so weak that the body would foul a road wheel. You can view this magazine as a PDF on the VOSA website www.vosa.gov.uk/matters-of-testing Hope this is usefull Paul Link to comment Share on other sites More sharing options...
Shaun Posted May 20, 2011 Author Share Posted May 20, 2011 Very useful, Paul! That's the first time I've been able to picture what exactly the tester is looking for. It makes perfect sense that if a suspension has sagged so much, it risks fouling the rear wheels, which could obviously have safety implications. However, given that bump stops don't actually have to be fitted, why is the emphasis, from the MOT perspective, so much on them? Surely what's much more relevant is the distance between axle and underside of chassis? Going back to my tester, he took one look under the van and concluded the rear suspension was not only shot, but had never been fit for purpose. Yet if he'd looked at the way the van sat - even under its constant load - there was an obvious vertical gap between rear wheels and their arches. Common sense you'd think would suggest the suspension was doing its job, yet this particular tester (and it seems there are many others) was wholly focused on the distance between axle and (what he perceived to be) the bump stops. One bad MOT rule, with testers who follow it blindly, and the ramifications are far-reaching for owners of these newer suspension designs. Shaun Link to comment Share on other sites More sharing options...
paul2 Posted May 20, 2011 Share Posted May 20, 2011 All testers should read this so in the furture they should now be aware of this suspension .Having said that i've put the mag in my van ready for my mot in 2 years time! Paul Link to comment Share on other sites More sharing options...
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