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Posted By Steve Buxton
I am a volunteer officer with a voluntary aid society, and my main responsibility is for our Ambulance Group. One of our members has said that because the torque ratings are marked on the wheel arches of our ambulances, and because there is a "tendency" for wheels to drop off vehicles, we should be checking the torque on a regular basis.
The ambulances are new (one very, one 18 months) and do relatively low mileage, and are serviced and MOT'd in a County Council Maintenance Depot.
Apart from when wheels are changed, do we need to do any more in the way of checks on torque on the wheel nuts ? If so, can we do this ourselves or should we drop them in to the nearest tyre depot ?
This is my first post so please be gentle !
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Posted By Brett Day
The vehicles handbook should give you some specific information, also call the manufacturer, most motor companies have a technical department; but the general guidance is normally that bolts should be checked after tyres have been replaced (within ten miles or so or the same day, really to ensure that the fitter did do them up properly) and monthly thereafter.
You can buy 'Nut movement indicator tags' though by the time you can see the movement in the tag the nut is already loose enough to be a hazard.
Alternatively once you know the torque rating from the manufacturer or handbook, by a torque wrench and do it yourself, it'll be cheaper than putting it into a tyre fitters
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Posted By Brett Day
Just re-reading your post, given that the vehicle is regularly service in a council depot ? why are the nuts dropping off, might be worth having a chat with the people servicing the vehicle, they may a: not be doing the nuts up to the correct torque - allows them to come loose or b: they may be using an air gun and overtorqueing the nuts, this can strip the threads or stretch the stud again allowing nuts to come adrift.
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Posted By Steve Buxton
We have never had a problem, but one of our members is keen to pass on any nugget of information he has found from the internet etc and whilst he is often correct, many times I am left running round in circles for no reason.
I think perhaps buying a torque wrench might keep him quiet and give him a new toy to play with.
Thanks.
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Posted By Chris Pope
Steve
Welcome to the forum.
There was a posting on this subject on the 22 November 2004.
To save you struggling I've emailed direct the main content
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Posted By Nigel Singleton BSc
I was always under the impression that nuts on vehicle wheels are threaded 'counter' to the direction of rotation of the wheel, which has the effect of tightening the nut whenever the wheel is in motion.
Any loosening of a wheel nut must therefore point to human intervention or a serious problem with the wheel itself.
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Posted By Paul Adams
The "American" style ambulances in the UK have been plagued with this problem.
Suggest you contact your local ambulance station who will put you in contact with their maintenance department. Find out what they do.
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Posted By John Webster
Nigel
Not so. Wheel nuts and studs thread the "normal" way, ie clockwise to tighten. The main hub nut may have opposite threads on each side of the vehicle, and is often secured with a split pin, but not the wheel nuts.
Steve
Are you sure it is the wheel nut torque marked on the wheel arches? This is usually where tyre pressure is marked on fleet vehicles.
Note that overtightening is far more dangerous than undertightening. Overtightening can lead to sudden catastrophic failure of the studs or of the wheel itself, and is most likely to occur when cornering. Loose nuts will usually cause vibration or knocking - a warning to the more alert driver, with the wheel more likely shaking loose on the straight.
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Posted By Steve Buxton
Thanks for all the responses.
The vehicles are Renault van conversions, not the American style boxes on wheels.
I have come to the conclusion (without yet having chance to check the manufacturers info) that common sense rules.
If the wheels have been changed, or if it goes in for service/mot etc, then get the torque checked. Otherwise should be no problem.
Both the tyre pressures and the torque are marked on the wheel arches which is why the subject arose from one of our members in the first place.
I will now wait for his next area of concern !
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Posted By Andy Petrie
Put some marker tags on the nuts (like the ones you see on HGVs) when a nut becomes lose the tag moves and can be easily spotted
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