Hi,
Can one of our gurus confirm whether NA wheels are hub centric or lug centric?
Thnx!
They are lug centric even though they have a sized bore. The conical seat on the nut centres the wheel to the stud. Effectively every wheel that bolts on is this as even if you have a sized spigot it is the clamping friction through the force applied by the fixings that holds the wheel in place. The Load does not go through the spigot even with commercial vehicles using washer face nuts.
This is something I wrote on MX-5 Nutz a while ago. It is not answering this question as asked, but the principal is exactly the same.
Are we on to this again?
For the mechanically inept there is a nice diagram on the VOSA website differentiating the different types of wheel fixing.
For those that still believe that the centre spigot is there to take dynamic load consider this, there is a clearance between the outer diameter of the spigot and the inner diameter of the ring, just as there is on the out side diameter of the ring to the wheel just like there is on the studs to the wheel. OK it is smaller, but a clearance or gap in non engineering terms, none the less.
For that spigot to take load, the weight of the car, the car is going to push downwards through its weight, through the suspension and hubs, through the spigot on the hub, that would push the the spigot to the bottom of the spigot ring and in turn the spigot ring to the bottom of the diameter in the wheel. Just like standing a 10p and a 2p upright together on a table you have a gap at the top.
Now for that spigot ring, or even wheels with sized centre bores, when that car rolls forward half a turn, that gap is now at the bottom and the weight of the car is not supported by the spigot, or spigot ring. The only way for that to happen is for wheel to slide across the hub face and remove the gap again. Roll your 2p and 10p across the table together and you can see that the only way for there to be no gap at the bottom is for one coin to be sliding across the other. The spigots do not support the load or weight, the clamping friction applied through the nuts and studs does. That is the same as gluing the two coins together. In addition, any sustained enthusiastic use of the brakes usually puts enough heat into the plastic ring to see it disintegrate.
Yes there are all sorts stories of studs breaking “because no spigot ring” but this is because of other issues like leaving fixings loose, over tightening fixings and snapping or stripping fixings, damaged mounting faces, wrong fixing, wrong hole centres, forcing 108 PCD wheels onto 110, wrong nuts, the list is almost endless.
Does the OP need spigot rings? Not if everything is in order.
Hi Nick,
Thanks for your reply - that’s exactly what I’m looking for.
I’m fitting non-OE wheels with a bigger bore, and need to use hub adapters as PCD and offset are different. I was concerned about finding suitable parts if the original setup was hub centric.
Your nutz post mentions hub rings - given that the wheels are lug centric, would you say they are a pointless addition?
Many thnx
MnB
You are into different territory if you are fitting a different PCD or hole pattern wheel. You would need to either modify or have new hubs and or fit a proper bolt on adaptor at which point you could have the spigot on this made to fit the wheel.
All that said the principal is the same, the spigot does not take the load, it is the clamping force achieved through the fixings. The spigot is there to help locate the wheel.
Most alloy wheels use a 60 degree cone seat and the wheel nut will have a matching 60 degree cone. Ignoring tolerances, when you fit the first nut, the cones will mate and remove 5 of the 6 degrees of freedom the unfitted wheel has. The second nut then removes the remaining freedom to rotate about the hub. (obviously there are more nuts) The issue will not come from the wheel centre bore being over size but the centring on any hub spacer bolt combination you fit or if any of the mounting holes in the wheel are damaged, worn etc.
Hi,
That’s very useful info. I’ve been looking into H&R PCD hub adapters, which seemed the most likely.
Bestregards!