Trailer. Hub or stud centric wheels?

[T i m]

Hi all,

I have been given an old dinghy trailer (with a dinghy on it I'm about to give away ) and before I move it from it's current location I felt I should check the running gear.

It was obvious the tyres were perished and because the rims were rusty, I considered complete replacement wheels (tyre + rim) to be the best solution.

However, it doesn't look like any of the 400 x 8 sized rims that I can find to suit a 4" x stud PCD using 10mm studs has a suitably large centre hole diameter of 66mm, but a more common / smaller 65. ;-(

Now, I (believe I) understand that these sorts of wheels are typically 'stud centric' and that means all the load is carried via the clamping force of the rim to the hub (via the studs / wheel nuts etc), rather than with a hub centric solution where the load is carried by an interference fit between the hub and the centre hole in the rim, the fasteners really just holding the wheel in place. As is happens, the existing rims do seem to fit the centre hub fairly closely so I can't say 100% that they aren't actually 'hub centric'?

So, if I can't find replacement rims with the right sized centre hole (as I want a spare wheel in any case) my options are (no particular order):

Open out the centre to allow it to fit the existing hubs. *If* the wheels are stud centric I could safely do this by hand, or, if I can be bothered, turn up a suitable back plate and get them in my mates lathe and bore them out concentrically (to the studs).

Put the (cast iron) hubs in my lathe and turn down the shoulder slightly (66 > 65mm) so that the stock wheels will fit. This means that if I do refurbish the existing rims they will be used in a stud-centric setup.

Replace the hubs with something that will fit stock wheels, assuming I can find something with the right dimensions etc (25mm stub axle).

My only concern re spending too much money on this 'project' is I'm not sure what condition the suspension units are and these are actually formed into the main axle, rather than being bolt-on independent units etc.

I don't mind spending the money on the hubs now , if they were likely to fit new suspension units, should I have to replace them later on.

Basically I have a couple of boats I need to sell (for the family) and need a trailer to get them out of storage and possibly deliver them. Because we will still have some boats after those two have gone and it's not as easy to put bigger boats on the roof of the car these days (bars are narrower and cars generally higher (and we are older)), having the trailer would still be handy.

I may also email the likes of Indespension on the stud / hub centricity matter.

Cheers, T i m

[Bill]

In message , T i m writes

As no-one else has answered, I wonder if they are really too far gone for you to have ruled out cleaning and painting the existing rims and fitting tubed tyres.

Our big trailer came with 4 wheels that were similar to, but not quite the same as old Land Rover types. I asked around about a spare wheel and the local long-established family owned tyre place suggested a small yard that might help. Went there and he moved tons of stuff and came out with a matching wheel at a very, very good price.

ATS sourced tyres and tubes, but then made a complete pig's ear of fitting them over about 4 attempts, trapping tubes etc.

Our Rangie came with the wrong wheel nuts all round. On-line experts said it was dangerous, but the local Indy RR garage said "What's the problem?". I replaced all the nuts anyway.

I'm not sure a tiny eccentricity would matter on a small trailer.

[T i m]

What the other members of uk.d-i-y?

No, I don't think they are beyond recovery Bill but that still doesn't deal with the issue of no spare wheel? ;-(

The reason for looking as new complete wheels was because of the time and effort required recovering the old rims over the extra fiver it will cost per wheel to buy a complete new tyre (that I need in any case) and rim? The last time I had some prepped for me I was quoted £5 each just to get them shot blasted (the blasters don't like powdercoat so I took them away and burnt them off myself in a brazier).

Both tyres are currently holding air and may well be tubed in any case. If not I don't think the insides will be an issue, certainly once I have removed any remaining powdercoat.

Result. ;-)

Great. I think that sort of thing comes under the 'old skool' craft (and doing cycle and older motorbike tyres).[1]

That was another issue I have previously encountered. I was supplied with a 'this is what you need sir' and the stud holes in the rim were too big. When you used the stock wheel-nuts the tips of the cones would 'bottom' on the hub before the cone had actually contacted the rim. Again, I could nip the tops of the nuts off in the Myford but that would mean they had been 'modified' and should something happen in the future (however unlikely).

'Advice is worth what you pay for it' they say. ;-)

Quite. I might be able to do that with the other trailer (find wheel-nuts with a more shallow cone) but again, I'm modding it ...

Whilst it may not, getting that sort of thing as right as possible is what I just can't help doing. However, the question of hub or stud centric was more to do with how the wheel was supposed to transfer the load to the trailer rather than general concentricity as such.

eg, With many car wheels (especially alloys and those that haven't been serviced regularly (eg 'Main dealer serviced')), you remove all the wheel nuts / studs and you have to hit the wheel off the hub with a club hammer and a block of wood on the inside of the rim. This means that the wheel could probably transfer the stationary load of the vehicle, even without wheel fastenings!

In contrast, 'stud centric' wheels rely on the friction generated by the clamping force of the fastenings to allow the load to be transferred to the hub, not requiring (or even having) and contact between the vertical edge of the wheel hole and the hub. This is fine if that's how they were designed but not a good thing to do if they weren't. I think this is one of the reasons why many aftermarket wheels come with Spigot Ring / adaptors.

I have emailed a big trailer manufacturer to see if they can shed any light on it.

In the meantime .. I may look into turning the rib on the hub down slightly to allow me to take a stock wheel as the old ones will still fit and the best (rim) could be kept as a spare etc (and I can't see the trailer ever carrying anything like a 'heavy load').

Cheers, T i m

[1] A mate has just had a new pair of tyres fitted on his work Transit and he was surprised to see they *had* lined up the balance marks (their regular tyre fitted didn't even know what the marks meant!). ;-(

p.s. I know an eccentrically mounted smaller diameter wheel won't create as much centripetal force as a bigger one but it will spin faster and so could still put undue forces and wear on stuff?

[Fredxx]

For a constant road speed, force is proportional to radius.

[Roger Mills]

But these adapters are usually made of plastic. I don't know how much load they would take. AIUI, their purpose is to locate the wheel so it's concentric with the hub - but you still need the clamping force of the studs to support the vertical load and to transmit drive (not on a trailer) and braking torques.

[FMurtz]

When I built a trailer I fitted hubs that were the same as the car,then I could use the car spare or swap the tyres round any which way.

[T i m]

So the rpm has no bearing on that (genuine question)?

Cheers, T i m

[T i m]

Many are but the 'better ones', are made of alloy.

Well there are plastics and plastics of course, some being very strong (especially in compression)

Understood, that is definitely one of their roles.

Ok. Take a wheel off a car (that is 'hub-concentric) that has not been off for some years. Often, even after removing all the fasteners it could actually be driven on (slowly) without any issues. How much

*vertical* load (eg the mass of the vehicle and the spirit of this question) in that instance is being carried by the fasteners? (The answer is obviously 'none').

Of course, but I am only really discussing the basic principles of the difference between stud (lug) and hub centric wheel fitting.

Most wheel nuts are conically faced, as are the mating points on the rim and so should (potentially) 'centre the wheels on the hub as they are tightened up. However it seems they often don't for those running aftermarket wheels without spigot rings (or even bad spigot rings that don't provide a reasonable interference fit to the wheel centre and hub).

So, are you saying that in fact any wheel on any (conventionally wheeled) car wouldn't need to rely on hub-concentricity, once the fasteners were tightened correctly ... if the spigot ring could be removed after the wheel was fitted?

Cheers, T i m

[T i m]

As did I. Unfortunately, whilst I still have (and use) the trailer, I've long since sold my Morris Minor van and so found that even finding tyres to suit the trailer isn't that easy (as in range of manufacturers and so good price / model choice).

It's not that easy to get the tyres I want for the Kitcar. When we built it 30 years ago it was a fairly common size (185/80/14) and so we were even able to get the choice of several off road / M&S type patterns, even in remoulds. The tyres we have now are still M&S but nothing like the sort of aggressive look that really suits the vehicle design.

Cheers, T i m

[Fredxx]

There are two classic formulae of interest:

F = m . w^2 . r - 1

w = rotation in rads/s where V (at perimeter) = w . r

F = m . v^2 / r - 2

Proving I was incorrect, where force is actually inversely proportional to radius of wheel. The only saving grace is a smaller wheel is likely to have less out of balance mass.

[T i m]

Thanks for that.

True.

FWIW, our local bike shop can't balance many small / scooter wheels because they use a spindle rather than some form of hub or carrier. So I made up a balancing spindle (two width adjustable cones on a hardened steel axle some fine bearings on the end and something to rest the assembly on) and *all* such wheels I have balanced have required some balancing weights.

These seems to work as you can feel the difference when running a balanced versus unbalanced wheels, especially at moderately high speeds. [1]

I'm also interested in how true a tyre is and will even tweak a tyre (especially on a cycle) to ensure it sits as true as possible before full inflation.

Back to the hub v stud thing, I've remembered that some (many?) and especially (exclusively?) ally wheels use a flat washered wheel nut / bolt that wouldn't offer anything in the way of concentric wheel mounting so would *have* to be (initially) centred (at least) via the hub.

From what I have Googled so far it seems there were some older vehicles that weren't ever hub centric (VW Beetle to name but one) but it could be that any vehicle designed that way may have had heavier or more bolts or some such?

I'm not talking about what you might be able to get away with here but what the 'right thing' is (assuming there is such a thing etc). ;-)

Just because it's a 'trailer' still doesn't absolve my responsibility re the RTA or C&U rules, something many 'lads' found out to their cost after modding their vehicles then having a bad accident.

Cheers, T i m

[Roger Mills]

Yes - provided that the wheels and nuts have conical mating faces. It might be a different story if the wheels and nuts had flat faces (were any ever made like that?).

I'm aware that wheels can stick on the spigot rings, and take a seemingly lot of (human) force to remove. But I don't think you'd get far if you started driving round with the wheel nuts removed.

[T i m]

I think many ally wheels are like that Roger and hence rely 100% on hub-concentricity to give accurate alignment and (potentially) 'support'.

Repeatedly hammering the rim outwards from the inside with a 2lb club hammer and after the application of a release agent, yes. ;-)

No, but the fact that you could drive *at all* suggests that the fit between wheel and hub was far more than 'trivial'?

I think the nut type does help define the expectation / system.

A conical / rounded wheel-nut face and mating dished_wheel_socket means that the wheel could be 'stud centric' and may or may not also have an interference fit at the hub (and if it does it's likely to be more tolerant to high shock loads like hitting the kerb etc).

A flat faced nut / stud is very likely to be hub-centric as there would be no other way to ensure the wheel was mounted concentrically.

If you ever bolt two things together where the mating faces are basically flat and the bolt holes offer reasonable clearance, I would say you could make one move compared with the other (holding one in the vice and hitting the other with a hammer at 90 degrees to the joint) more easily than you could pull one away from the other?

It will be interesting to hear what the trailer manufacturer says (assuming they say anything).

Cheers, T i m

[Roger Mills]

Agreed.

Interestingly, many years ago I needed to replace both half-shafts (don't ask!) on my 1938 Morris 8, and was given a pair of shafts from an older model. My originals had flanges which were a tightish fit on the wheel studs but the older model must have had shouldered studs because the flange holes were much bigger - "prick in a shirt-sleeve" fit on my wheel studs. Anyway, I centered them on the studs and then fitted the wheels and tightened the wheel nuts. On subsequent wheel removals there was never any evidence of movement, so the clamping force must have been sufficient to hold it all together.

[T i m]

I did one on my Moggy Minor. ;-)

Ok. ;-)

I'm sure it could well have been (I read of clamping forces in excess of 20 tonnes on a single lorry stud!) but 1) that was 'only' a Morris

8 (so hardly 'a performance vehicle') and 2) you may not have ever have 'pushed' the clamping forces hard enough (going up a kerb or over a brick at speed?) or had a situation where the clamping forces were lessened over time (heat-cycling of the hub)?

FWIW, *I've* never seen any signs of that on my stud centric vehicles either, however that doesn't mean it can't happen or really answer my core question.

I believe we are supposed to re-check the torque on our wheelnut after a wheel has been changed and after a few miles / hours 'in case' the wheel has settled tighter to the hub and therefore reduced the fastener clamping force?

What makes the wheels come off the 'Star in a reasonably priced car' cars on Top gear (as they seem to do quite regularly)?

Cheers, T i m

[T i m]

Update:

It looks like this was all down to poor description of the product.

I took the hub to the trailer shop and offered my 66mm OD hub into one of their '65mm ID / centre hole' wheels and it was a fairly loose fit!

So, I suspect the nominal OD of this range of trailer hubs is '65mm' and that the wheels designed to fit have and ID of the centre hole of more like 67mm, designed to *fit* a ~65mm OD hub.

Had I not previously had this very issue (wheel hot fitting because the centre hole was too small by a mm or two) I may not have measured my hub and would have just bought a couple of the 400 x 8, 4" PCD,

3/8" stud wheels and found them to fit fine (as it happens).

What might also have been nice was if my supplier actually *measured* the ID of the wheel they were offering (rather than by going by what it may have said on their suppliers invoice etc)? Now, because it's a fairly small wheel and quite dished it's not 'easy' to measure the diameter with some basic vernier calipers but I think even a tape measure would have shown they were bigger than 65mm ID!

So, because the fit of the new wheel on my old hub is fairly slack, it may also answer my 'hub or stud centric' question (in this case) ... as I think by the time the wheel had moved far enough for the inside of the rim centre hole to touch the shoulder on the hub, all 4 studs would have been sheared off. ;-(

Cheers, T i m