I seem to have problems finding MOT testers who know how to assess play in wheel bearings. I'm talking about common adjustable taper bearings .Not many people seem to know that there should be a noticeable amount of play in a properly adjusted wheel hub as this allows for expansion of parts due to heat transferred from brake components.
I have an engineering background and have been working on mine and others cars for over 25 years and have several times come up against testers who insist that wheel bearings that are properly adjusted are too slack.
In the past I've never made a fuss - sometimes I've let them play around and set them how they think just so as to get the car through with little fuss, other times if other stuff has been required I've just nipped them up a bit to get them through the test and then adjusted them properly afterwards.
One occasion on my own car I adjusted them a bit tight to get through with no problems and forgot to slacken them later, - and managed to ruin the bearings on the next long run that I did. Surely this creates a situation that is more dangerous than a slack bearing?
Now today I've just had my car fail an MOT retest on this same issue. After the original retest I did the same as usual - adjust them just as tight as I can to still be safe, yet the tester is still not satisified has refuesed an MOT and has gone on holiday for the next week - by which time the Tax will have run out!
Understandably I'm a bit fed up. Can anyone tell me what chance I have of getting a satisfactory appeal? and does anyone know where I can find the relevant MOT standards to argue my case?
Cheers Rob.
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you also have to see the testers point of view, he passes a bearing with a bit of play which is subjective, you sell car and new owner gets dave down pub to check it over with his vono spanners and man doing mot gets it in neck........
i had a fiesta pass its mot monday afternoon wed morning went to work and a rear shocker had exploded and dumped its oil in one big go (never seen this before) could you imagine if i sold the car tuesday with its full mot.
You havent said what make of car fwd rwd etc so difficult to give an exact answer to your appeals idea
(im not an mot inspector by the way)
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Free play is essential in taper roller hubs and is a sign of wear in angular contact or parallel ball bearing hubs.
Any MOT tester worth his salt will know which type of hub he is examining and judge accordingly.
659.
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Free play is essential in taper roller hubs and is a sign of wear in angular contact or parallel ball bearing hubs. Any MOT tester worth his salt will know which type of hub he is examining and judge accordingly.
Absolutely !
If anyone remembers the Austin Allegro (all-aggro), there were a number of instances of these sheding their entire rear wheel hub and brake brum assembly due to vertight taper roller bearings. This was caused by mechanics mistaken assumption that like the Mini and Austin 1100/1300, the cvar had straight bearings with a stepped stub-axle, whence the crown-nut should be tightened quite tight when refitting.
As a result of this BMC had to put a waring sign on the hubs that said 1/16 th" freeplay required in bearing.
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Is it possible that there is a happy medium between the obviously incorrect tight play-free setting of a taper hub and the degree of play that you are obtaining?
The reason I ask is that while there should be some clearance in a taper hub, it should only be very slight play - for example, I can't see much justification for total play of more than about 1mm at the rim of a typical car.
How does this compare with your settings?
Number_Cruncher
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Hi,
Thanks for the replies so far.
The car is a Mk2 Golf and Im'talking about the rear wheels.
The manual for this car says "Hand tighten the securing nut to the point where the thrustwasher can just be moved with a screwdriver and finger pressure but without levering it" which is fairly vague, but I have actually set it as tight or tighter than this, due of course to the fact that i did not want any problems with the re-test.
So there is no doubt - the bearings are not set too slack. What there may be is a small amount of stub axle wear as I notice that the small amount of play that there is (and yes this is less than 1 mm at the rim) is only apparent in the vertical plane rather than the horizontal plane. But I ask "so what?" there is no safety issue here, just maybe a bit of wear.
When I asked what the garage what complaints procedure was I got a very vague response, it appears they should be able to supply me with a form VT17 which I have to fill in , and send off with another fee and then they send someone out. So that's whats going to happen next.
Cheers Rob.
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I'm sure if you look at the failure notice that the complaint procedure is documented.
You make an appointment at a VOSA testing station, paying the full price, and they will test the vehicle.
What happens next depends on the result.
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he says hes got play in the stub axles martint123 therefore car is dangerous and shouldnt be on the road.....
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Without being offensive, if i can be.....
But if you are from engineering background and have found wear in stub axle and you are unsure of why tester has failed car for wear at bearings not necessarily in bearings?
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Quick Update,
I took the car to a largish while you wait place this morning and explained the problem. No less than three chaps looked at it and all agreed the play was within tolerances. The car now has a new MOT certificate.
Moral of the story to me is that there are some testers out there that don't know what they are on about..
Cheers Rob.
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It's not strictly essential for a taper roller bearing to have free play, but you must be able to move the washer behind the castle nut with a screwdriver quite freely. If you cannot then it's too tight, and if being able to move it means free play then so be it.
I'm not totally sure just how skilled modern vehicle technicians actually are, but that's an argument perhaps for another day....
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I've had exactly this problem over the years, and have come to realise that virtually every MOT tester has a weak point, or at least some pet component he gets obsessive or over critical about.
A tester recently commented that one of my front wheel bearings was a bit slack, but not enough to fail or even give a formal warning about. When I got home and checked it I could detect virtually no play at all - I had deliberately set them a bit tight, intending to slacken off after the test.
I've had another tester who didn't understand how a traditional rear wheel drive axle worked. Again, he didn't realise that each half shaft is supposed to have a bit of end play, and he thought the feel of turning a single wheel indicated axle wear, rather than just the usual noise you get from the chunky straight-cut differential gears.
Yet on other items each tester was knowledgeable and very fair, and ready to take a reasonable line on points that could perhaps have been marginal.
I wonder if they get some kind of psychological carry-over effect from the previous test? They fail a car that really does have very worn bearings, so are in a "bearing mood" when they do yours?
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Up to a point Cliff Pope is right, but testers are only human.
In my past life as a tester I came across many other testers who seemed to have an obssesion with various components.
I've met the wheel bearing king, He used to check driven axle wheel bearings with a stethescope - and a road test.
Then there was the number plate king, almost every car he tested had an insecure or slightly insecure plate.
There are loads of pad and disc merchants about, anything less than nearly new is an automatic failure to them.
The tyre man was good, he could spot a suspicious tyre at 100 yards. He once found a small closed up split in a tyre, dug his screwdriver in and wiggled it about until he thought he could feel the cords, then failed it. The customer pointed out that the garage had repaired a puncture in that tyre a few weeks before. Tyre was removed and sure enough there was a perfectly good recent patch on the inside.
I've worked with the tester who overtightened a worn Fiat front taper roller bearing so much that 20 miles later the stub axle sheared off on a motorway.
I've met many testers who don't even spin the wheels to check for roughness, a quick rock top and bottom and side to side is enough for them.
Customers can be just as bad though, a few years ago I failed a VW camper van on a loose and noisy N/S/F wheel brg. A couple of days later he's back having repacked with fresh grease - it's just as bad. Next day he's back again, says he has replaced outer bearing - inner seemed ok and it's nice and quiet. A quick check revealed a very rough and noisy bearing. Off he goes, returns some time later having replaced the whole bearing assy with a kit. And it's just as bad. I invited him into the workshop so that he could listen for himself. As I spun the wheel he looked a bit bemused and said " I thought the N/S was the side nearest the driver".
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my current mot man is a disc man to the core
last one wiper blades
before that suspension bushes (anything with a ford badge he hated)
before that ? well that man lost the plot and went to live abroad...............
its the job that does it i think..........
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