Increasing center bore of alloys

[DavidStrawhorn]

Hello,
Is it possible to grind out the center bore of a set of alloys so they fit over the center hub on my mk2ph2?
The alloys are 56.1mm and the hub in the clio is 60.1mm so would need to grind 2mm all round.
Anyone done or heard of this being done?
~David

 

[syko6288]

good machine shop with a decent lathe could i pressume

 

[AshleyJames1990]

Its easy enough I'm a CNC machinist I've done it to a set of BBS wheels, just need a big enough lathe. Its possible

 

[DavidStrawhorn]

I've read of people using a grinding drill bit, marking where they need to grind to with a pencil then grinding away the excess down to the line?
In theory it should work, or am I over looking something?

 

[Steven103]

In theory it should work, or am I over looking something?

...that the hole will never be round (let alone the centre bore being at 90deg to the mating face on the inside of the wheel) and will be something more like 60.1 +-1.5mm which is, frankly, awful for what is supposed to be a "close running" fit.

Why, given the severity of a wheel having a large imbalance or eventually falling off (for example), you'd do it in your shed rather than the £50 per hour (couple of hours) a machine shop would charge is questionable.

Paying for peace of mind...

 

[NorthloopCup]

I've read of people using a grinding drill bit, marking where they need to grind to with a pencil then grinding away the excess down to the line?
In theory it should work, or am I over looking something?

I would imagine they all wear Stetson hats and spurs on their boots as well mate! Proper cowboy way of doing things!

 

[DavidStrawhorn]

What exactly does the center bore do for the wheels? I was under the impression that it was the bolts that take the strain. And if I made the center too large by say 0.5 - 1mm then it won't be too bad as the bolts will pull the wheel true and it'll sit right on the hub.

 

[NorthloopCup]

What exactly does the center bore do for the wheels? I was under the impression that it was the bolts that take the strain. And if I made the center too large by say 0.5 - 1mm then it won't be too bad as the bolts will pull the wheel true and it'll sit right on the hub.

The centre bore is what the wheel actually sits on mate and transfers the load into the hub. You want the fit to be as close as possible so as it centralises the wheel on the hub as well. If its not, you will suffer with vibrations and the wheel bolts will be forever coming loose.
The bolts are there to keep the wheel secured to the hub.

 

[Llewellyn]

I've read of people using a grinding drill bit, marking where they need to grind to with a pencil then grinding away the excess down to the line?
In theory it should work, or am I over looking something?

Seriously mate don't even bother, the centre bore does exactly what it says, it centres the wheel.
If contact between the centre of the wheel and hub wasn't important, spigot rings wouldn't exist!
Take it to your local machinist and have it done properly, I was quoted about £100 to remove a small amount from the centre bore on a set of 4 wheels.

 

[not normal dan]

I would imagine they all wear Stetson hats and spurs on their boots as well mate! Proper cowboy way of doing things!

Made me laugh.

I paid around 70 quid a few years back to have some ats cup wheels done at a local machine shop, doing it with a drill or dermal is the most ridiculous thing I've ever heard tbh.

 

[Chip-mk1]

What offset are they? We fitted vauxhall wheel using adapters which I had made which altered the centre bore.

 

[Chip-mk1]

...that the hole will never be round (let alone the centre bore being at 90deg to the mating face on the inside of the wheel) and will be something more like 60.1 +-1.5mm which is, frankly, awful for what is supposed to be a "close running" fit.

Why, given the severity of a wheel having a large imbalance or eventually falling off (for example), you'd do it in your shed rather than the £50 per hour (couple of hours) a machine shop would charge is questionable.

Paying for peace of mind...

You could just make sure its comfortably oversize and then rely on the wheel bolts to locate it, as they are tapered fit and will actually centralise the wheel more exactly than the centre bore does anyway. The centre bore just aligns it roughly right in the first place to make it easier to put the bolts in.

 

[DavidStrawhorn]

They are et45

 

[DavidStrawhorn]

You could just make sure its comfortably oversize and then rely on the wheel bolts to locate it, as they are tapered fit and will actually centralise the wheel more exactly than the centre bore does anyway. The centre bore just aligns it roughly right in the first place to make it easier to put the bolts in.

That's what I was thinking mate. I'll probably just sell them on as don't have the money to get them drilled :/

 

[Chip-mk1]

They are et45

Then I would just make some adapters as they will sit looking a bit lost anyway if they are just bolted straight on.

 

[NorthloopCup]

Yeah me too tbh. Any decent machine shop could knock you some up with different sized centre bores mate.

 

[Chip-mk1]

Yeah me too tbh. Any decent machine shop could knock you some up with different sized centre bores mate.

I got some vw ones that were 58 or so mm, then got an engineer to turn a mm ish off inside and outside (so 2mm off diameter in each case) to make them into renault inner and vauxhall outer of 60.1 and 56.1 (or whatever the exact values are I dont remember now)

 

[Coops Mk1]

believe Winston used a dremel in the park on the BBS he put on the illiams, worked fine

 

[C2kev]

Cant you just use 5mm non hubcentric spacers to clear the hub center?

 

[Adamm.]

Cant you just use 5mm non hubcentric spacers to clear the hub center?

This would put an unsafe amount of strain on the bolts, certainly not how I'd do it.

 

[C2kev]

This would put an unsafe amount of strain on the bolts, certainly not how I'd do it.

Read post 12

 

[Adamm.]

Still not something I'd want to do.

 

[Steven103]

PCD of wheel bolts & chamfer on wheel bolts will just be a plain toleranced distance rather than a toleranced fit of the centre bore & wheel. Seems incredibly unlikely that the flange on the hub wouldn't bear any load (especially if you're torqueing wheel bolts with the car on the ground, as is usually most practical)

Would be very interesting to know the clamping force of 5x M-whatever bolts at however-many NM?

 

[mad in general]

Read post 12

This doesn't sit well with me.

I am far from an expert but I have always understood that the spigot/centre bore has to be a very close fit. This after all is what takes the weight of the car, the bolts deal with rotational and sideways load.

Please do correct me if I am wrong.

 

[C2kev]

Im no expert either, but, i ran my car for about a year with aftermarket wheels and no spigot rings
after the tyre fitting place left them off. Caused no noticable difference to driving/handling and i only realised when changing my brake discs. I wouldnt run it like that by choice though

 

[len_beach]

Cant you just use 5mm non hubcentric spacers to clear the hub center?

You could just grind the lip off of the hub.

 

[Chip-mk1]

This doesn't sit well with me.

I am far from an expert but I have always understood that the spigot/centre bore has to be a very close fit. This after all is what takes the weight of the car, the bolts deal with rotational and sideways load.

Please do correct me if I am wrong.

you are wrong. Most aftermarket wheels the spigot ring is plastic for example and even the standard wheels aren't an interference fit so if the spigot was taking load the wheel wouldn't be located exactly it would move about.
Its the clamping force that takes 100% of the load.

 

[mad in general]

you are wrong. Most aftermarket wheels the spigot ring is plastic for example and even the standard wheels aren't an interference fit so if the spigot was taking load the wheel wouldn't be located exactly it would move about.
Its the clamping force that takes 100% of the load.

That is fair enough Chip, from lurking on here I gather you are a knowledgeable chap.

To be honest though I do still disagree, I won't pretend I know the finer details to be able to explain why.
My logic tells me differently.

With regards to plastic spigot rings, surely the fact that they are clamped In such a solid cavity means they cannot go anywhere even if they do crack. This means they would be perfectly useable until you remove the wheel. Could even be refitted as long as they are not in too many pieces.

My wheels certainly seem to be an very tight fit, spigot wise.

Do you have any idea where I could research this subject? Google would probably be easiest I suppose.


One more question, sorry.
Why do people buy hubcentric(sp) spacers instead of just universal ones?

I am genuinely interested I learning.

Cheers

Dave

 

[Chip-mk1]

That is fair enough Chip, from lurking on here I gather you are a knowledgeable chap.

Im old, its a side effect of being into cars for over 2 decades, lol

To be honest though I do still disagree, I won't pretend I know the finer details to be able to explain why.
My logic tells me differently.

Your logic is wrong mate IME, the spigot isnt designed to carry load, its there to help you locate the wheel when fitting, I know lots of people including myself who have used aftermarket wheels without a spigot ring on stud and nut conversion (so you dont need it to locate the wheels anyway) and none of us has ever observed the sort of out of balance wheel wobble you would get if there was any movement.
thats why the spigot ring in the wheel is ally or plastic, and the tapers for the studs/nuts are steel inserts, cause its them carrying the load.

With regards to plastic spigot rings, surely the fact that they are clamped In such a solid cavity means they cannot go anywhere even if they do crack. This means they would be perfectly useable until you remove the wheel. Could even be refitted as long as they are not in too many pieces.

The plastic isnt particuarly hard, so getting it to compress by a few thou (all it would need to move by in order to feel out of balance) wouldnt be an issue if the studs/bolts clamping the wheel on wasnt sufficient to hold it in place.

My wheels certainly seem to be an very tight fit, spigot wise.

If you take them on and off a lot so everything is nice and clean you will normally be able to feel a VERY small amount of play in them which proves its not them locating it as if it were that there would be a small amount of movement and when you next removed the wheel it would look polished on the back where it had been moving slightly and rubbing.

Do you have any idea where I could research this subject? Google would probably be easiest I suppose.

You could look into the clamping force of the wheel bolts, which will be many tonnes, and then find the friction coefficient of ally against steel, and see if any movement is possible, but I can save you a lot of time and tell you that so long as the studs/nuts are properly torque it isnt going to be given the sort of loads your car will see in normal use.

 

[ben lee]

chip is correct its the clamping force between the wheel face and hub that holds the wheel on not the centre hub . if the wheels relied on the centre hub to take the weight they would have to be a very tight fit if not the wheel would move and loosen the bolts over time.


i have after market wheels without spigot rings that are way over 60mm bore and use the wheel bolts to centre the wheel had no issues with them.

 

[ben lee]

if it was the centre hub that took the weight/force then it would need to be a interference fit and would need to stick out further so more of the wheel sat on it.

 

[mad in general]

Im old, its a side effect of being into cars for over 2 decades, lol


Your logic is wrong mate IME, the spigot isnt designed to carry load, its there to help you locate the wheel when fitting, I know lots of people including myself who have used aftermarket wheels without a spigot ring on stud and nut conversion (so you dont need it to locate the wheels anyway) and none of us has ever observed the sort of out of balance wheel wobble you would get if there was any movement.
thats why the spigot ring in the wheel is ally or plastic, and the tapers for the studs/nuts are steel inserts, cause its them carrying the load.



The plastic isnt particuarly hard, so getting it to compress by a few thou (all it would need to move by in order to feel out of balance) wouldnt be an issue if the studs/bolts clamping the wheel on wasnt sufficient to hold it in place.



If you take them on and off a lot so everything is nice and clean you will normally be able to feel a VERY small amount of play in them which proves its not them locating it as if it were that there would be a small amount of movement and when you next removed the wheel it would look polished on the back where it had been moving slightly and rubbing.


You could look into the clamping force of the wheel bolts, which will be many tonnes, and then find the friction coefficient of ally against steel, and see if any movement is possible, but I can save you a lot of time and tell you that so long as the studs/nuts are properly torque it isnt going to be given the sort of loads your car will see in normal use.

Thats fair enough mate, thank you for taking the time.

I know that I will never take the chance of no spigot or oversized centre bore because I believe that if you effectively have two flat faces clamped with bolts then you run the risk of these bolts sheering upon heavy impact,like a large pothole at speed.

As I said though, thanks for replying.

Dave

 

[Chip-mk1]

Thats fair enough mate, thank you for taking the time.

I know that I will never take the chance of no spigot or oversized centre bore because I believe that if you effectively have two flat faces clamped with bolts then you run the risk of these bolts sheering upon heavy impact,like a large pothole at speed.

As I said though, thanks for replying.

Dave

Shearing force is around 5 tonnes PER bolt, so 20 tonnes of force on that one wheel to get anywhere near shearing them, and when installed you have not just the shear force of the bolt to contend with but also the friction of the clamped surfaces as you arent applying the force directly to the wheel, so I would expect it to probably be more like double that, the alloy wheel would internally split and fall apart way before then if you ever did try and put that load through it by hoisting it 200ft in the air and dropping it from a crane or similar, and the spigot in particular would be the equivalent in that mix of trying to re-enforce an armoured vest by wearing a football shirt over the top of it to "help stop the bullet just in case" yes it WOULD have an effect, but its SO tiny it just isnt worth considering.

 

[Alex Conway]

I'm a curious chap so I'll probe further. Firstly, that 5 tonnes shear force is a static load, the studs under go fully reversed fatigue loading. This probably isn't a problem as shock loading will be more than double what "generic" loading is and steed has a beautiful endurance limit. I'd also be very surprised if you couldn't generate some ridiculous shock loads through, think hitting a pothole hard. Bolts are also by nature covered in stress raises.

Finally, if this is the case then why are hubcentric spacers even a thing? I've been heavily involved in upright/hub design and manufacture for a race car before and have seen hub failures due to not using spigot rings, though we do have a pretty marginal factor of safety on some things. We always use the spigot to locate and take load.

Edit:
On hubcentrics being a thing, bar the need to centre the spacer on the bolt to hub type.

 

[mikes86]

I'm a curious chap so I'll probe further. Firstly, that 5 tonnes shear force is a static load, the studs under go fully reversed fatigue loading. This probably isn't a problem as shock loading will be more than double what "generic" loading is and steed has a beautiful endurance limit. I'd also be very surprised if you couldn't generate some ridiculous shock loads through, think hitting a pothole hard. Bolts are also by nature covered in stress raises.

Finally, if this is the case then why are hubcentric spacers even a thing? I've been heavily involved in upright/hub design and manufacture for a race car before and have seen hub failures due to not using spigot rings, though we do have a pretty marginal factor of safety on some things. We always use the spigot to locate and take load.


Edit:
On hubcentrics being a thing, bar the need to centre the spacer on the bolt to hub type.

I was under the impression hubcentric is purely to locate and center the wheel. While possible without it, i would assume you would get more vibration through the wheel.

 

[jenic]

Ok this is going to sound really pikey but here goes.

Can a spigot ring be widened with a lathe? Or are they not suitable as from the pictures I've seen they aren't a flat inner edge.

The only reason I ask is I have bought some wheels, which come with proper OZ spigot rings which have an inner bore of 57.1mm. The official OZ ones lock in I believe, and would cost £60 for a set delivered from Italy. I know I can get aftermarket cheaper but it would be nice to have official ones if I could machine these to 60.1mm.

 

[Alex Conway]

What's the OD? If you can keep sufficient wall thickness it should be a dead easy job.

 

[jenic]

What's the OD? If you can keep sufficient wall thickness it should be a dead easy job.

I don't know yet as they aren't with me, I'll have them Thursday hopefully.

I believe OZ changed from 68.1 to 75 at some point so either of them, I'll only know when the wheels arrive and I can measure them.

 

[Alex Conway]

I don't know yet as they aren't with me, I'll have them Thursday hopefully.

I believe OZ changed from 68.1 to 75 at some point so either of them, I'll only know when the wheels arrive and I can measure them.

Should be plenty then, if push comes to shove you could just get some ally ones made up (6000 series should suffice). It really is a dead easy think to make.

 

[jenic]

Should be plenty then, if push comes to shove you could just get some ally ones made up (6000 series should suffice). It really is a dead easy think to make.

Ok, thanks for that.

I'll pop them out and take them to my uncle as soon as they come as he has a lathe. Saves me spending £60