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Driving without a hub-centric wheel then you risk damaging your bolts if there was a bump (i.e. Mounting a kerb/big pothole). Bent bolts means vibrations, simple as. This is not true at all. Please see my earlier post regarding the mechanism of holding wheels on. The bolts are not loaded in shear. The load is transferred to the hub by friction. If that is true then please explain why I got a vibration without hub-centric wheels but fine after with the correct wheels? And no the wheels weren't buckled!
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The vibration is from bolting your wheels on slightly off-centre. They are still securely located by the studs/bolts. If the wheels were loose and wobbling around, they would be flying off the car and overtaking you on the hard shoulder.
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By the way, I have heard of some cases of people breaking wheel studs due to centre bore. However, in these cases, the centre bore was significantly undersized, hence the wheel was perched on the centre spigot and couldn't seat down onto the mounting face of the hub. Hence, when you torque the nuts down, you pull the wheel down out of true. This leads to high loads on the wheel studs, eventually causing fatigue failure and the loss of the wheel. One particular brand of alloy wheels in Australia was having this problem repeatedly due to incorrect machining of the centre bore.
If you can get the wheel seated properly on the mounting face of the hub, then you should have no problems whatsoever.
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kabman
Part of things
Posts: 348
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This is one of those subects that goes round and round on the internet. Anyone with any sort of mechanical engineering background imediately knows that the centrebore can't carry any vertical load unless it was a press fit on the hub. As a lot of people on here have pointed out, the bolts are never in shear once tightened; all loads are transfered by friction between the wheel and the hub. The centrebore is purely a manufacturing aid to locate the wheel while the bolts are fitted. Bolts are cheaper than studs and nuts and automated assembly is cheaper than employing people. If you've ever tried to fit older style wheels without a locating centrebore and get the bolts in the holes while propping up the wheel with your toes, you'll know what the centrebore is really for
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Last Edit: Nov 13, 2012 7:40:17 GMT by kabman
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g40jon
Posted a lot
Posts: 2,569
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With a wheel bolt set up the wheel hub is load baring and is therefore crucial for a snug fit or else you'll get a vibration through the steering at about 45mph+ BTW, with this post I'm not saying that the wheel'll fall off with the incorrect centre bore. No, that'd be a stupid thing to say/assume. It's just that the wheel bolts are only there to hold the wheels on. They are designed to handle lateral forces that push the wheel away from the mounting face. With the hub and centre bore being flush means the wheel can't move up or down on the mounting surface! Driving without a hub-centric wheel then you risk damaging your bolts if there was a bump (i.e. Mounting a kerb/big pothole). Bent bolts means vibrations, simple as. So yes, you could locate a wheel with oversized cb with self centring cone shaped bolts but you do risk damaging them! i think you are still confused. the bolts hold the wheel on yes. With a wheel correctly fitted the bolts are under tensile load, hence them being high tensile bolts. The only way you will ever bend a bolt is if the wheel is not correctly fitted. i.e. you haven't done them up tight enough or you have fitted a wheel with a slightly undersized centrebore, which results in the wheel face not mating with the hub face. With a wheel correctly fitted, there should be little or no shear stress affecting the wheel bolts, therefore they will not be snapping anytime soon. The wheel is kept in place by friction between the wheel mounting face and the hub face, if you can get the wheel to move, the friction is not great enough between the two faces, which means your bolts are not done up tight enough! A spigot ring is purely there to help centre a wheel. they are without doubt worthwhile, due to their low cost and the fact that it does make changing a wheel a whole lot easier. Think about it logically. If the spigot ring was load bearing, do you really think plastic would be a suitable material to take the load? Also do you think the fit would be suitable to take load. if you can get the wheel on and off with ease, it means there must be clearance between the two diameters. that means with the wheel fitted you could get a feeler gauge between the gap between the internal dia. of the of the spigot ring and the external dia. of the cars original spigot. If the spigot was meant to take load, the fit would need to be a close fit, maybe even an interference fit, else the gap would eventually cause deformation, due to the vibration involved with moving parts.
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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- Spigot rings are often plastic, and cheap soft plastic at that, if it had to take load in use it'd be destroyed pretty quickly. - Wander around the paddock at any motorsport event and you'll see more than a few car that don't use spigots, their wheels are subjected to much higher forces than most of our road cars. - The spigots are a loose enough fit that if there was regular movement in use they'd wear larger over time. - Up until the 80's a hell of a lot of production cars never even had spigots on the hubs, especially on rear drums, newer cars do pretty much all have them, but they also use bolts instead of stud, this is because the decision making is increasingly less the engineers job and more the accountants.
Basically, unless you have bolts that won't centralize the wheel them selves, or you have a habit of doing the wheel bolts up with zero care then you'll be fine without them from a safety point of view. As 10mpg has said, it can cause a slight wheel vibration, but personally I've found that doing the bolts up evenly and gently to locate the wheel before torquing them up can get rid of this, especially if you torque them up with the wheel still in the air.
I'd still run spigot rings my self, as they cost sod all and make life easier when changing wheels, but if I bought some new wheels and had to order the rings, I'd happily run them without until the spigot rings arrived, and I'd likely not bother to fit them until the wheels had to come off for another reason.
Without wanting to teach a hen to suck eggs, I think it's worth pointing out a good way to torque wheels up, as it's something I'm pretty fussy about. My usual sequence is to place the wheel on the hub/studs, get all the nuts/bolts started on the threads and in a few turns, then in an opposing pattern do them all the way up by hand (either directly on the nut or using just an extension on a socket, then nip them up with a ratchet held by the head/very close to the head. Then with the wheel still in the air, do them all up as tight as you can with a torque wrench set correctly, if you get full torque great, if not drop the wheel onto the ground but still mostly supported by the jack and torque up the rest of the way.
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Last Edit: Nov 13, 2012 8:37:15 GMT by RobinJI
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