Importance of hub spigot size to wheel.

[Guest SupraGTE]

Yes would say overtightening of bolts/nuts is a bigger issue, worked at alloy wheel company many years and seen allot, but many people take there boltgun or there 3m extension and tightens the bolt and then takes the torquewrench and check that it is 103 nm for example but in reality they are tihgtend waaaay to much as the mechanic has play almost RAMBO with the bolt gun before..ratatatatatat, and then check and fills in papers OK. but in reality NOK... but never seen a failure of a centre ring .... also wrong conical 30/45 nuts was a big issue

[Ian C]

Scott, I understand what you're saying and you have experience in metalworking whereas my teeth are put on edge filing my nails so I'm hardly the definitive source of info. Having said that, it sounds like your work a one-off clobber, much like an accident impact is, or at most ten, twenty impacts?

 

The scenario with the bolts holding on a wheel though is a different form of strain entirely. The stress on the bolt changes direction 360deg every rotation, so the load is continually shifting. In 10,000 miles the average 18" wheel will rotate approx 9.5 million times. I just can't see bolts or studs being ideal to support that even with frictional assistance Whereas a flush fitting spigot ring would be specced to deal with it.

 

Just my thoughts on it. I've got metal spigot rings and they are hard to remove from the hubs because they fit properly

 

-Ian

[Scott]

Scott, I understand what you're saying and you have experience in metalworking whereas my teeth are put on edge filing my nails so I'm hardly the definitive source of info. Having said that, it sounds like your work a one-off clobber, much like an accident impact is, or at most ten, twenty impacts?

 

The scenario with the bolts holding on a wheel though is a different form of strain entirely. The stress on the bolt changes direction 360deg every rotation, so the load is continually shifting. In 10,000 miles the average 18" wheel will rotate approx 9.5 million times. I just can't see bolts or studs being ideal to support that even with frictional assistance Whereas a flush fitting spigot ring would be specced to deal with it.

 

Just my thoughts on it. I've got metal spigot rings and they are hard to remove from the hubs because they fit properly

 

-Ian

 

I've got spacers on my car, i machined the spigots perfect for the alloy wheels i have (70.1mm), the bore is 60.1 as it should be. I'm not willing to take the chance on the spigot not supporting the load, I just don't think it does.

 

I know a lot of people who run non-hubcentric spacers without any issues. Jamie even commented on himself having no issues.

 

With regards to the forces being undertaken whilst driving. I think for something with enough force to knock the wheel off with the stud nuts appropriately tightened, without spigots, the rest of load impacted area's wouldn't hold up. Whether or not the wheel would go a tiny bit off balance is not for me to say or judge. I think the wheel would buckle before that happened though.

 

FWIW i remember a demo years ago regarding the shear strength of a wheel stud. I don't remember the manufacturer but they hung a car from one sticking out of a building. There are many parts of the subframe attachments that will give way long before the studs do.

[Ian C]

With regards to the forces being undertaken whilst driving. I think for something with enough force to knock the wheel off with the stud nuts appropriately tightened, without spigots, the rest of load impacted area's wouldn't hold up. Whether or not the wheel would go a tiny bit off balance is not for me to say or judge. I think the wheel would buckle before that happened though.

 

FWIW i remember a demo years ago regarding the shear strength of a wheel stud. I don't remember the manufacturer but they hung a car from one sticking out of a building. There are many parts of the subframe attachments that will give way long before the studs do.

 

You're still talking about single impacts/loadings though, I'm saying that 9.5 *million* wheel rotations, each of which moves a 75kg or so load per stud through 360deg, might eventually fatigue the bolt to the point where it lets go. With the load on the hub spigot, this rotational loading is removed completely.

 

I personally have had a wheel stud snap on the rear while tootling through town, and that was with wheels that fitted the hub correctly without spigots. The wheel didn't buckle and the subframes survived the episode intact... It would have to have been long term fatiguing, probably exacerbated by some monkey overtightening the nut. One, that shows they studs experience all sorts of loading changes during driving even when properly fitted, and two, I wonder how long the wheel would have stayed on if it had no spigot support and only four studs left...

 

-Ian

[AndyT]

 

Can anyone fill in the sizes for the standard wheel?

 

DIMENSIONS

 

‘A’ = TOTAL WIDTH OF WHEEL

 

‘B’ = BOLT UP FACE INTO CAR

 

‘C’ = BOLT UP FACE TO INNER EDGE OF WING

 

‘D’ = FORWARD PROTRUSION OF BRAKE CALIPER

 

EXAMPLE: IF YOU ORDER A 7.0 x 15” WHEEL DIMENSION ‘A’ = 8.0”

 

OFFSET

 

The amount of wheel going INTO the car from the wheel centreline is POSITIVE.

 

The amount of wheel moving OUT of the car from the centreline is NEGATIVE.

 

The drawing above shows the POSITIVE offset, along with dimensions ‘A’ ‘B’ ‘C’ and ‘D’

 

With this info. we'll be able to find decent manufacturers. I know it's easier to just fit standard wheels but I don't think they suit, aesthetically.

Edited November 7, 2009 by AndyT (see edit history)

[Terminator]

OK I'll throw my spanners in the works. In the past I have run cars with and without hub centric spigot rings and always torqued up the wheel nuts/bolts to correct torque and double checked after a few miles of use and then regularly there after/weekly/monthly. Never had any problems what so ever.

 

It is my personal belief that under normal conditions, the hub centric spigots ring's main function, is to centre the wheel on the hub. It is is frictional forces between the back of the wheel and the hub face created under clamping load that holds the wheel in place. If the thickness of the ring prevents the wheel and hub faces meeting, then to use such a ring would be suicide.

 

However, if, with the correct hub centric spigot ring in place, but clamping forces are reduced, ie partial loosening of bolt/nuts then the spigot will play a crucial role in keeping the wheel centred. If left unchecked the hub/wheel will shift position rotationally, which will introduce shear forces in the stud/bolts, which will lead to damage a potential failure. With the same degree of loosening on wheel with no hub centric spigot ring or an poorly fitting one, the situation immediately become exceedingly dangerous.

 

As drivers we have a responsibility to ensure our cars are road worthy. How many can honestly say they follow manufactures recommendations regarding wheel tightening and subsequent rechecking. How many have tyres fitted and never check the nuts/bolts for tightness. How many drivers would know how to check. I believe that incidents involving after market wheels and hub centric rings will involve more factors than the ring alone.

 

An incorrectly size ring is not necessarily dangerous in itself, if tighten correctly nut/bolts will pull a the wheel central. If the wheel remains in this position, there is not a problem. However if clamping forces decrease, then failure of the wheel nuts/bolt will be accelerated.

 

This is all very well for a theoretical technical debate. For responsible road use every precaution should be taken, therefore correctly fitted and fitting hub centric rings must be used when wheels do not match the hub in use. It is the car owners responsibility to find rings that fit correctly.

[beagle]

I remember reading that a while ago. I have driven a car without spigot rings before, the judder through the steering wheel was ridiculous. Only as they were off center though.

 

We can all agree to disagree. I don't think we will find anything concrete one way or the other.

 

My experience tells me that they would be fine without the spigot's, as long as they are centered. The weight will be on the cone of the nuts and the friction of the mating faces.

 

i had a calibra i got some 18s on it without spigot rings on ,you couldnt do over 40 mph with wheel wobble then i relies i needed the rings i put them on went down a45 went to a ton no wobble. next time you buy after market wheels on, wot need spigot rings on take rings off put wheel back on dont do up bolts tight and see how much play is in the wheel holes and bolts

[JustGav]

All interesting points, I've sent my daughter off with the task of finding out

 

Her response 'According to my college work and info, the spigot is used to take the weight and forces from the wheels and the wheel nuts are purely for clamping, tell them to buy the right wheels'...from a 15yr old doing mechanical engineering at college (I like her, she thinks the right way )

 

PS : The force that stops the wheel sliding against the hub is called stiction (And yes that is a word ) - http://www.answers.com/topic/stiction

Edited November 7, 2009 by JustGav (see edit history)

[Chris Wilson]

I am right, when I want another opinion I'll tell you what it should be

[Digsy]

Gav, tell your daughter well done

 

Theres a bolt preload calculator here: http://www.tribology-abc.com/calculators/e3_6a.htm I have no idea how good it is and I'd prefer to use the one at work but its Saturday so I'll have to assume this one is OK.

 

I did a rough calc assuming that the hub bolts are M12 (I think that's right?) The preload (clamping load) on a single M12 bolt tightened to 109Nm (I know the hub nuts are 103Nm but its close enough for this) is 45.5kN. Therefore the total preload from all 5 bolts would be 227.5kN - that's a lot of clamping.

 

If you multiply the preload by the coefficient of friction between the wheel and the hub - which will be about 0.15 - then you get the maximum vertical load the joint can take. In this case just over 34kN, or 3465kg

 

So each hub / wheel joint can take a vertical load of nearly 3.5tonnes just from friction alone.

 

Assuming you have tapered nuts / bolts or a hub-centric ring to help centralise the wheel, once it is clamped up then neither the ring nor the bolts take any load whatsoever. All the loads go through the friction face. Incidantally this is true of almost any bolted joint on an engine or car (i.e. crank pulley, flywheel, cam pulleys). Engineers usually transmit loads through friction faces, tapered shafts or splines.

 

Now, all this is fine unless something else makes the joint loosen, which is what sounds like happened to the guy mentioned in the OP. It sounds like he made a crap choice of hub ring which reduced the size of the friction face, which then fretted away or relaxed somehow, which then put all of the load into the bolts. In this case I'm not surprised the wheel fell off.

 

One other factor which is harder to calculate would be the vertical load due to the wheel hitting a bump and accelerating upwards. Its not going to be possible to determine this simply or without some measured data.

 

For the record, I have never used hub rings on my car, but I do always ensure that the wheel is as well centered as possible and the nuts are correctly tightened. Yes, it would certainly be safer with rings if something else went wrong - but they are not integral to the joint itself.

[Wez]

I use metal spigot rings on my Gram Lights, the holes in alloy wheels are larger only for the fact they fit several different cars, you then use the correct spigot ring to match your hub.

 

This is not rocket science.

 

Of course you can bolt a wheel to hub without them, just as you can put your head in an oven, drive off a cliff etc , doesnt make it right though does it.

 

 

At the end of the day if its good enough for Toyota with there massive R&D its certainly good enough for me.

 

 

I wouldn't mind but they are not exactly expensive either

[Scott]

All interesting points, I've sent my daughter off with the task of finding out

 

Her response 'According to my college work and info, the spigot is used to take the weight and forces from the wheels and the wheel nuts are purely for clamping, tell them to buy the right wheels'...from a 15yr old doing mechanical engineering at college (I like her, she thinks the right way )

 

PS : The force that stops the wheel sliding against the hub is called stiction (And yes that is a word ) - http://www.answers.com/topic/stiction

 

Gav, tell your daughter well done

 

Theres a bolt preload calculator here: http://www.tribology-abc.com/calculators/e3_6a.htm I have no idea how good it is and I'd prefer to use the one at work but its Saturday so I'll have to assume this one is OK.

 

I did a rough calc assuming that the hub bolts are M12 (I think that's right?) The preload (clamping load) on a single M12 bolt tightened to 109Nm (I know the hub nuts are 103Nm but its close enough for this) is 45.5kN. Therefore the total preload from all 5 bolts would be 227.5kN - that's a lot of clamping.

 

If you multiply the preload by the coefficient of friction between the wheel and the hub - which will be about 0.15 - then you get the maximum vertical load the joint can take. In this case just over 34kN, or 3465kg

 

So each hub / wheel joint can take a vertical load of nearly 3.5tonnes just from friction alone.

 

Assuming you have tapered nuts / bolts or a hub-centric ring to help centralise the wheel, once it is clamped up then neither the ring nor the bolts take any load whatsoever. All the loads go through the friction face. Incidantally this is true of almost any bolted joint on an engine or car (i.e. crank pulley, flywheel, cam pulleys). Engineers usually transmit loads through friction faces, tapered shafts or splines.

 

Now, all this is fine unless something else makes the joint loosen, which is what sounds like happened to the guy mentioned in the OP. It sounds like he made a crap choice of hub ring which reduced the size of the friction face, which then fretted away or relaxed somehow, which then put all of the load into the bolts. In this case I'm not surprised the wheel fell off.

 

One other factor which is harder to calculate would be the vertical load due to the wheel hitting a bump and accelerating upwards. Its not going to be possible to determine this simply or without some measured data.

 

For the record, I have never used hub rings on my car, but I do always ensure that the wheel is as well centered as possible and the nuts are correctly tightened. Yes, it would certainly be safer with rings if something else went wrong - but they are not integral to the joint itself.

 

 

You made different points. One said the rings are there to be used for holding the load, the latter said it isn't.

 

The latter, in my mind, is correct.

 

Edit: With regards to the wheel hitting a bump or a pothole. I don't think the vertical impact the wheel could take without moving off center would be less than other weak points in the setup. Take the upper wishbone, only held by 1 long stud. The shear strength of 1 of those will be more than 1 stud, not more than 5. I honestly believe the wheel would take a bigger hit than the mating face. Thats what tyres are for afterall, the bigger the profile the less of an impact the other components take.

Edited November 7, 2009 by Scott (see edit history)

[Scott]

You're still talking about single impacts/loadings though, I'm saying that 9.5 *million* wheel rotations, each of which moves a 75kg or so load per stud through 360deg, might eventually fatigue the bolt to the point where it lets go. With the load on the hub spigot, this rotational loading is removed completely.

 

I personally have had a wheel stud snap on the rear while tootling through town, and that was with wheels that fitted the hub correctly without spigots. The wheel didn't buckle and the subframes survived the episode intact... It would have to have been long term fatiguing, probably exacerbated by some monkey overtightening the nut. One, that shows they studs experience all sorts of loading changes during driving even when properly fitted, and two, I wonder how long the wheel would have stayed on if it had no spigot support and only four studs left...

 

-Ian

 

Plenty of time IMO. The fact the stud snapped tells me it was either old and needed replaced or it was overtightened.

 

They don't last forever.

 

Tell you what, look up the shear strength of an M12 tensile stud. Multiply that by 4 and see how long you think the wheel will have lasted.

 

What happened when it snapped? Did you notice? If you did something else was wrong IMO. Granted only having 4 nuts holding the wheel in place isn't as good as 5, clearly, but it still won't be as dangerous as you are making out. 2 studs at opposite ends would hold a wheel on sufficiently for normal driving.

 

I read of someone on here noticing their wheel wobbling. Got out to check and the wheel was being held on by the last few threads of one nut. If the shear strength was an issue it would have snapped off in no time. Improper tightening again, i think they lost 2 or 3 wheel studs and the others had worked themselves loose. That means that the car was driving on either 2 or 3 studs... with no nuts... and still held up.

Edited November 7, 2009 by Scott (see edit history)

[JustGav]

You made different points. One said the rings are there to be used for holding the load, the latter said it isn't.

 

The latter, in my mind, is correct.

 

I see your point, She was on the right track with the stiction stuff and the fact that the nuts hold no real load directly, spigot stuff I think she may have either got wrong or worded wrongly.. you try getting anything out of a stropy 15yr old (Still at least she has a clue compared to most )

[Scott]

I see your point, She was on the right track with the stiction stuff and the fact that the nuts hold no real load directly, spigot stuff I think she may have either got wrong or worded wrongly.. you try getting anything out of a stropy 15yr old (Still at least she has a clue compared to most )

 

Definitely on the right lines bud. Objective way of thinking about it too rather than "just because" as well.

 

Thats what you normally get out of 15 year olds

 

 

FWIW i think the nuts will take a bit of load as there will be flex in the alloy wheel. When you hit a bump the load won't all be transfered onto the face of the hub, the wheel will take some of the impact and flex. This is where the conical nuts will share a little bit of the impact as the wheel will try to bend off of the hub face.

 

Guess thats the reason for 30 degree nuts on aftermarket wheels.

 

The tophat ones on the toyota are even better as i believe the outer diameter is sized with the hole diameter on the wheels. Any vertical shift on the wheels flex will be met with the parallel diamater of the nut.