Alloy wheel centre bore increase?

[ridds]

Anyone had this done or know of a machine company on the south coast or in the Midlands experienced in doing this without damaging the wheels?

[Evangelion]

Isn't this called something like 'centreless grinding'?

As it's not just a simple process like bunging something on a lathe, I'd have thought it would be quite involved (for 'involved' read 'expensive').

Better to just flog them and buy a set with the correct bore size shirley?

Or are they really special/rare?

[plasticman]

I am pretty sure you could just bung them on a lathe just you would need to find a very large one whereas any machine shop could turn down the hubs and probably lose some weight while you are there .

[ridds]

Unfortunately I need to lose 8mm of the diameter! So the hub isn't really an option due to lack of material.

[Nick1point9]

A machine shop will be able to CNC mill a bigger bore for you, but I'd be wary about doing it, any proof that the material loss won't affect the strength of the wheel?

Contrary to some shocking advice given on here before, the centre bore supports all the weight of that corner of the vehicle, not the studs. So I'd be careful about removing 4mm of wall....

[russell_ram]

"A machine shop will be able to CNC mill a bigger bore for you, but I'd be wary about doing it, any proof that the material loss won't affect the strength of the wheel?"

Correct, this is a simple job for a CNC mill.

"Contrary to some shocking advice given on here before, the centre bore supports all the weight of that corner of the vehicle, not the studs. "

This, however, is not true at all.

The 'weight' is transferred from the wheel to the hub/suspension by the friction between the wheel raer and hub flange faces. Providing the studs/nuts are tight then the vertical wheel force in normal operation will never by large enough to overcome that clamp load. The hub spigot merely centres the wheel while you do the nuts up, after that it plays no part at all in 'carrying' wheel loads.

[Nick1point9]

russell_ram said:

"Contrary to some shocking advice given on here before, the centre bore supports all the weight of that corner of the vehicle, not the studs. "

This, however, is not true at all.

The 'weight' is transferred from the wheel to the hub/suspension by the friction between the wheel raer and hub flange faces. Providing the studs/nuts are tight then the vertical wheel force in normal operation will never by large enough to overcome that clamp load. The hub spigot merely centres the wheel while you do the nuts up, after that it plays no part at all in 'carrying' wheel loads.

I'll be careful not to try to be too brash as I see you're a chartered engineer, but....

Why can fitting wheels with the wrong hub size shear wheel bolts? Why doesn't greasing the hub (massively reducing mu and therefore the load that can be transfered through the clamp load on the surfaces) lead to the hub/studs failing? Why will a wheel bolt that has been put in considerably below max torque not cause the hub/bolts to fail (if thread locked in to prevent it working loose)? Why would manufacturers bother fitting the spigot on hubs that have studs instead of bolts if it's purely for location?

[garagewidow]

in most cases i would say the spigot is there to minimize unwanted leverage forces on the outer bearing by placing it further out from the wheel/kingpin centreline.by doing this you have to enable the wheel to mount between the inner and outer bearing hence the being of the spigot.

[PhillipM]

Nick1point9 said:

Why would manufacturers bother fitting the spigot on hubs that have studs instead of bolts if it's purely for location?

Location's pretty important tbh! If the wheels off centre the oscillating forces can easily get high enough to shear bolts, especially if the wheel is resting against one of the threads...

And unless they were a tight press fit the spigot would only take load on one point it's touching, the bolts hold the wheel on, and they're massively overspecced, you could run half the wheelbolts the car normally takes and still have enough clamping pressure.

Edited by PhillipM on Friday 20th January 00:13

[Classic Grad 98]

russell_ram said:

The 'weight' is transferred from the wheel to the hub/suspension by the friction between the wheel raer and hub flange faces. Providing the studs/nuts are tight then the vertical wheel force in normal operation will never by large enough to overcome that clamp load. The hub spigot merely centres the wheel while you do the nuts up, after that it plays no part at all in 'carrying' wheel loads.

This is correct. My word there is some mis-information in this thread!
Enlarging the centre bore of the wheel probably won't be too easy. If you had a spare hub lying around you could make a boss which could be fitted to a large turning lathe- with tapered wheel nut seats you'll probably acheive better concentricity than factory manufacture. As you probably gather though, this is all a bit intensive and the simplest solution would be to buy wheels which fit!

[Classic Grad 98]

Nick1point9 said:

I'll be careful not to try to be too brash as I see you're a chartered engineer, but....

-Why can fitting wheels with the wrong hub size shear wheel bolts?
-Why doesn't greasing the hub (massively reducing mu and therefore the load that can be transfered through the clamp load on the surfaces) lead to the hub/studs failing?
-Why will a wheel bolt that has been put in considerably below max torque not cause the hub/bolts to fail (if thread locked in to prevent it working loose)?
-Why would manufacturers bother fitting the spigot on hubs that have studs instead of bolts if it's purely for location?

-It doesn't. Not without other factors.
-Because tapered nut/bolt seats also maintain concentricity
-Depends how many. If all of them were loose then the bolt would be loaded in shear and not in tension, and this would damage bolts/studs and mounting holes, just like any other mechanical fixing which isn't torqued. If you're relying on the spigot on the hub flange to do this then you should probably hand your license in. Torque them up.
-To make fitting a 10-20kg wheel/tyre assembly easier for the 95th percentile of adults that the manufacturer has to cater for when considering changing a wheel. To ease servicing and wheel fitting.

[K87]

Nick1point9 said:

Contrary to some shocking advice given on here before, the centre bore supports all the weight of that corner of the vehicle, not the studs. So I'd be careful about removing 4mm of wall....

Irony anyone.....

[ridds]

Wow, and what a lot of replies and not a lot of help about finding anywhere to do it or actually experience of doing it.

Well they are done, and and for a lot less than shelling out £1400 on a replacement set of wheels. They were laid on a mill, and the current hole centred by a tool in the mill head, then the tool changed to machine the diameter out to what was required.

For reference my 4x4 is running round on wheels that don't use the centrebore to support the weight and I've had no issues with that in the last year.

Happy days, pick the wheels up this week.

[The Black Flash]

PhillipM said:

Nick1point9 said:

Why would manufacturers bother fitting the spigot on hubs that have studs instead of bolts if it's purely for location?

And unless they were a tight press fit the spigot would only take load on one point it's touching

Absolutely, if it all hung on the spigot it'd have to be so tight that you'd need a hydraulic press to get the wheel on!
There are cases where the spigot does hold the wheel on, such as in knock-off wheels or those used in F1. Here, though, the wheel slides onto a tapered central stub axle, with a central bolt pressing it on. You'd never use a parallel sided fitting for this though.