Potentially a very stupid question...

[Barnett]

Ok, so I bought a set of alloys off ebay after several messages back and forth between me and the seller in order to establish if they'd fit my car. They're the correct pcd (4x100), offset and width are fine and then he said that they had previously been on a clio so I thought great! However, I got picked them up and the centre bore seems to be too small. Judging by the VW centre caps he gave to me with them, the centre bore is probably 57.1 rather than 60.1.
The deal was done outside of ebay so can't get my money back. Plus due to the amount I spent on them and the distance I travelled to get them, it's not worth me taking them back. I'll most likely sell them on it I can't get them to fit.
Anyway I went to trial fit them today just to check, and they seemed to fit ok due to my spacers, which essentially negate the centre bore (see pics). Since there is no centre bore to actually sit the wheel on top of, would it be possible to safely fit these wheels to my car? It is my understanding that it is the bolts alone that secure the wheels to the car and that the centre bore is mainly there to make it easier to put the wheels on, not for safety purposes.

However, the front spacers do have little bit protruding that would emulate the centre bore, surely I could just get the same ones as are on the back for the front?

Alternatively, does anyone know of anyone in the Bristol area who could re-bore these wheels, and roughly how much that would cost?

Thanks for any replies, despite the fact I'm expecting to be burnt at the stake for such a proposal.

 

[Daniel]

No no no no no no.

The centre bore is what keeps the car in the air! Otherwise, over a ton of metal will be resting on 16 wheel studs.

This is why DIY mods are so bloody dangerous! Remove those rear spacers, buy some proper hubcentric ones and then send the wheels to get bored out.

There used to be a machine shop in kingswood (gone bust now) that used to charge £30 for a set of four wheels to be machined.

 

[Barnett]

Pretty much exactly the response I was expecting, except yours was actually helpful, thanks!

I understand your point but with regards to the small ring on the front but not on the rear spacers, does that really make such a difference? I remember one of them falling off due to the weight of the wheel resting on it when I was putting a wheel back on on my old car. Surely it can't do that much structurally?

I had no idea it'd be so cheap! For the sake of £30 it's a no brainer to just get it done properly.

Thanks again.

 

[f0xy]

As above - http://en.wikipedia.org/wiki/Wheel_sizing#Centerbore

 

[Daniel]

Pretty much exactly the response I was expecting, except yours was actually helpful, thanks!

I understand your point but with regards to the small ring on the front but not on the rear spacers, does that really make such a difference? I remember one of them falling off due to the weight of the wheel resting on it when I was putting a wheel back on on my old car. Surely it can't do that much structurally?

I had no idea it'd be so cheap! For the sake of £30 it's a no brainer to just get it done properly.

Thanks again.

I think you're confusing the actual metal that the wheel sits on with the hub nut cover; a thin piece of tin that's there to prevent the ingress of s**t into the hub nut hole and then the bearing.

 

[Barnett]

I think you're confusing the actual metal that the wheel sits on with the hub nut cover; a thin piece of tin that's there to prevent the ingress of s**t into the hub nut hole and then the bearing.

I'm referring to the metal bit that the wheel sits on, very crudely pointed out in the above picture. Since the centre bore takes some of the load, how can such a thin piece of metal provide structural support? Surely it isn't as strong as the centre bore itself. So my point/question is, why is there a need for me to replace the rear spacers? I apologise for my naivety.

 

[Daniel]

Remove that s**tty spacer and look at the actual original part. It's a load baring part.

*edit, is that a spacer or silver paint??

Either way, i'm right and that's what matters. Someone with more of a grasp of physics will be along to explain it properly.

 

[Barnett]

So the front spacers are s**tty too? They're hubcentric, which I thought is what you said I needed for the back?
I'm no longer debating the role of the hub, my issue is with the little aluminium protrusion on the spacer itself. My point is that this cannot provide the exact same load baring potential that the hub does, so why is it essential?

Edit in response to Mr.Potato's Edit: That is a spacer, around the same thickness as the ones on the back, but these ones still have the hubcentric part intact.

I'd just like to clarify at this point that I'm most certainly not going to do what I suggested doing in my original post. I will either be selling the wheels or getting them rebored to the correct fitment. Thank you Jord and Mr.Potato for steering me in the right direction.

 

[ThomasBrentnall]

Those wheels look tiny

 

[Saner]

Thank you Mr.Potato

Worth checking this thread out just for that.

 

[Daniel]

Chip-mk1

Come in and explain this please??

 

[Barnett]

Those wheels look tiny

Yeah they do in that picture. They are 15"x7J though, I even measured them myself to make sure.

 

[Steven103]

Either way, i'm right and that's what matters. Someone with more of a grasp of physics will be along to explain it properly.

Well I'm sorry to say... you are partially quite wrong :rasp:


This misconception has come up on here before. I'm sure they'll also be a lot of stuff on the internet about this classing it as a "common misconception."

Let me first make this clear - I would still keep the OEM design for a number of reasons. The following is just an explanation for those are interested, I mean after all it does sound counter intuitive.

Road wheel bolts are not designed to take the vertical (due to the vehicle weight) or rotational load (traction/braking). They do however take significant tensile load (tension) to create a clamping force and hence "friction" between the mating face of the wheel and hub due to the clamping force provided by the road wheel bolts. A few ways of thinking about it without using loads of equations:

The major diameter (just over 12mm) of the road wheel bolts is small enough relative to the PCD bore that this section of the bolt doesn't even make contact with the wheel. The only part of the bolt that actually touches the wheel is a very small area on the chamfer on the underside of the bolt's head. Wheel bolts/nuts are chamfered to help locate the wheel centrally onto the hub.

The type of bolt/stud chosen for wheels & circular bit in the middle are a very long way from "good engineering practice" for taking vertical and rotational loads. And that's because they don't. It's probably got a thickness of about 2mm. It's very short (10mm, whereas the centre bore of the wheel is maybe 20 - 30mm). It's actually a very loose fit compared to the centre bore - this would mean that if it was load bearing, only a tiny fraction of the circumference at the bottom would take any load. Put a washer on a bolt and pull the bolt down (representing the weight of the car) and pull the washer up (representing the wheel centre bore) and you'll see a tiny bit of daylight around probably 3/4 of the bolt.

When you brake, what stops the brake disc locking and just spinning around the hub? When you place the disc over the hub and put the road wheel bolts through, there is still a fair amount of rotational play until you put a wheel on and "clamp" it by doing the road wheel bolts up.

Now think about centre lock designs in motorsport - these are the opposite way around with significant rotational & vertical load taken by "drive pegs" as a result the design is completely different. The centre bore often does not make contact with any part of the stub axle at all. The "drive pegs" in these cases are designed to take some rotational and vertical load (since there are MASSIVELY higher forces involved with slicks - and I don't mean the forces you get with slicks on a Clio, think 300mm wide tyres & 1000kg of downforce etc) and hence are of a totally different design to road wheel bolts or even stud-conversion kits which are not designed to take the load.

 

[Steven103]

*However I still agree with the Potato on not using spacers that look:

A) 1000 years old
B) Aren't hub centric so are a right pain to fit and centralise
C) Threads that appear worryingly short and more to the point look as if they're made of cheese?

 

[Chip-mk1]

As explained very well by Steven above, the centre bore is there purely to easily locate the wheel in the first place, it's not intended to take load.

 

[Daniel]

Well don't I feel like a c**t! Lol.

So how has my track car sat for two years with no bolts in the rear wheels then? This is not me being awkward, I just want to understand.

 

[Spinksy]

Well don't I feel like a c**t! Lol.

So how has my track car sat for two years with no bolts in the rear wheels then? This is not me being awkward, I just want to understand.

Pure luck and that fact you haven't moved it

The centre bore will have 'wedged' itself into the rear of the wheel and will be held purely by that

 

[koi]

Isn't the bore of aftermarket Oz's usually big and spigot rings used to reduce the size to suit. Maybe the VW one's are still stuck in yours.

 

[Barnett]

Thanks for the many replies. As previously stated, I will be getting the wheels re-bored.

There are no spigot rings in them. I don't believe they are Oz wheels but I could be wrong, I have no idea what they are, just thought they looked alright so worth a punt for the price.

 

[Chip-mk1]

Daniel, most aftermarket wheels have a brittle little easy to break plastic spigot adaptor. Deffo wouldn't take load.

 

[Alex Conway]

I'm personally pro centre spigot, bolts are turd loaded in single shear. A thread is just a massive stress raiser! Hideous engineering practice.