Now I know some will say "Serve you right!" but I am going to share this nevertheless.
I am the owner of a single axle caravan. Last summer I thought I would replace the tyres as the originals were starting to crack on the sidewalls. I purchased 2 new rims and tyres which were balanced. I kept the old rims and tyres to store the van on during winter.
Anyway rims fitted bolts proressivly torqued to 65 ft lb. an off we go on our hols. 2 mile down the road and bang - nearside wheel now off caravan and on verge.
Now I'm no stranger to screwing wheels on having competed and serviced in rallies. I'm also paranoid with a torque wrench.
Anyway wheel put back on ( which ai'nt easy when its sat on its hub.) and limped back home.
Now I'm thinking I've been knobled. Back on road next day new rim and hub, mudguard reaffixed and a hole in the inner wheelarch gobbed up. This time I used my other Torque Wrench ( capitals because its a big mother ...... ). Would appear my smaller wrench is about 5 ft ibs down. Also fitted where some plastic straps which slide over and connect 2 nuts; the theory being that neither can unwind.
Travels down to Dorset and back - no probs.
Friday pulls caravan out of storage and puts the new rims back on complete with the plastic gizzmos and suitable torqued.
travels up to the North Yorks Moors. 1/2 mile from destination when - you guessed bang! One wheel on my wagon. Nearside again detached. Now it was my fault because I had heard a rattling 1 mile back but it couldn't be the wheel could it? Found 2 bolts and the plastic gizmos loose inside the hub cap.
With passing help managed to reafix the wheel and get to campsite. 4 new bolts the next day and use the damaged wheel and hub as I couldn't find the keys for the locks on the underslung carrier. Drove home today with frequent stops and checks with no problems. This time the caravan has sustained more serious damage as a hole has been punched through the floor along with other internal and external damage.
What I want to know is what the heck is going on. I've observed all the rules - cleaned and checked surfaces, progressivly tightened all the nuts and torqued them up to the correct. Those in the know say that it is a phenomina with nearside wheels that has been researched but the findings are inconclusive. All they can say that it is usually the nearside as the rotation of the wheel assists in the undoing of the bolts. The same thing happens with lorries. So why not cars? The only advice that can be given is to travel a short sistance re-check and then check evey so often on the journey.
Obviously the consequences of stray wheels could be dangerous to other road users. The only common denominator is that the wheels have been disturbed.
Fullchat
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Read this one with interest. I changed a wheel at the weekend on my caravan because of minor side wall cracking. I probably did it all wrong, but I used a trolley jack under the chassis, which enabled me to get the wheel off. However the hub & axle dropped by about a foot once it was off (it's designed to, apparently) and I had a helluva job getting it high enough to get the wheel back on! (Used a second trolley jack - which was trapped under the wheel once I'd finished, so without fully retracting the steadies I dragged the caravan forward with the car - and managed to dislocate one of the front steady machanisms. resulting in another 3 hours work yesterday - mobile tyre fitters next time for me!)
Anyway, having read your post I will make sure I do regular stops to check it. Having once had a blowout on the caravan, which turned out to be inconvenient but at least no damage/harm done, I'd sooner not be dealing with it at the side of a French motorway again...
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Fullchat,
I had a look at a modern 4 wheel trailer not long ago. It occurred to me that the wheel nut fittings would contravene motor car construction and use regs. It had wheel BOLTS without a spigot fitting. I might be wrong, but as I understand things, wheel nuts and studs can use the tapered seat of the nut and corresponding taper in the wheel to centralise the assembly. Wheel bolts must have a central spigot to centralise the wheel.
Most modern cars have both the spigot and tapered seats, but I don't know if the same standards apply to caravans.
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Interesting thought. There is definately no central spigot and the wheel is centralised by the 4 bolts being done up. Which bit of C&U regs did you think this contravenes? The only relevent bit I can think of is 'Using with dangerous parts or accessories' or something under the 'Fail to maintain' heading.
Had a chat with someone who examines such matters and the subject was bounced about the office. There was no definate conclusions on the subject other than a possible combination of stretched bolts and paint/rust debris around the seats. However this was a common occurance.
I then put a hypothetical case. If as a result of a wheel coming off a serious collision occured the the matter would be investigated. It would have been my fault but what could I be dealt with for. 'Fail to maintain', hardly as I had done everything by the book and a whole lot more to ensure safety. New tyres, rims, bolts and all properly torqued up. 'Using with dangerous parts and accessories'. An absolute offence subject to the opinion of the magistrates but again I had taken adequate precuations and was using equipment supplied by a manufacturer/dealer.
Of course the answer would be to fit left hand threaded bolts to the nearside. This has been done to some equipment. What also occured to me is why don wheels keep falling off cars with the same regularity?
HJ is there some mileage in this phenomina as an article?????
Fullchat
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Just a thought. Is the taper on the nut seat the same as on the rim, if not it's possible the friction area between the nut and rim is only a hairs breadth. The normal torque would then not hold it. Try chalking the taper and seeing if the whole seat is disturbed when you take the wheel off again. Don't forget to clean off all the chalk before using the wheel for real.
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Thanks. Yes that occured to me and will have a go, I have some engineers chalk somewhere.
Spoke to the insurance company yesterday and apparantly its quite a problem. They did some resesrch but thats as far as it got. When I suggested fitting LH threads to nearside they stated that this had been suggested but the manufactures did not seem overly interested.
Fullchat
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I'd be really interested to know when you finally solve the problem. In the meantime I think the left hand thread idea is a red herring. If you think about the force through the bolt/stud, it's not the same as a knock off wheel like F1 cars. On yours because the bolts are offset from the center there is a sideways force on them and not a twisting motion that would undo them. Cars witha single centre fixing do indeed need,and have, a lefthanded thread (as you obviously know). Best of luck.
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Many trucks and large vans-particularly those with double rear wheels use L/H threads on the N/S to attempt to overcome this.
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Also if you fit a new wheel(or newly painted/laquered wheel) you should retighten after 20 or so miles because you initially tighten down on the paint which crumbles.
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Have you considered having the wheels/tyres balanced?
Most caravan manufacturers and tyre dealers don't bother balancing them but having it done makes a difference to the smoothness as well as reducing any vibration forces which might undo the wheel nuts.
Caravan bearing hubs act as a spigot when wheel bolts are deployed, in exactly the same way as car wheels. Vauxhalls have used wheel bolts for years with no separate spigot other than the hub bearing. I haven't looked at luggage trailers or boat trailers so I don't know about them.
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May be well off track here... but it seems to me the clue is the new wheels. Are they IDENTICAL to the old wheels (apart from being newer, obviously!) - ie same centrehole size (should be exact fit over spigot if bolts to be used, rather than studs/nuts)?, is profile of taper identical on bolt/stud holes? Exact same Pitch circle diameter (otherwise bolt heads won't seat exactly?
Just a thought. I know if it was mine, I'd be a) refitting the old rims, albeit with new tyres and b) having a 'gentle factfinding chat' with the person who sold me the new rims...!
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Full Chat
As a safety issue is involved have you tried:
(1) Gateshead Tech where Police Accident Investigator (Mechanics) Course used to be held, or
(2) A word with a Metalurgist expert at your local Forensic Lab.?
DVD
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Fullchat,
My recollection of C&U regs is hazy, dating back to the 1970's Can't be certain about studs / bolts / spigots etc. but it's there in the back of my mind.
I don't know about modern HGV wheel nuts but in the past it used to be LH side = LH thread. All of the new vans, 3.5t and 7.5t vehicles I work on have all RH threaded wheel nuts / bolts - except for LDV. they use L & R handed threads. Lorry wheels do fall off occasionally but it's almost always the twin rear wheels and usually within a few miles of a wheel change. If the wheel(s) have been tightened correctly, the cause is invariably dirt / rust / paint etc between the mating surfaces.
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