An interesting conundrum....

Babalouie · Postby **Babalouie** » Thu Oct 04, 2007 12:38 am

You might remember that my new wheels fouled a bit of the brake caliper that sticks out. So I have to use a 5mm spacer.

My hesitation to use a normal slip on spacer was this...the new wheels don't have much of a \"hub\" so much of the wheel doesn't touch the spacer:

So I went and got the you-beaut german H&R TUV-approved ones:

Which look like this, installed:

Problem is...while the spacer itself is nicely hub-mounted, there isn't enough of the hub sticking out to support the wheel...

The irony is, I had a set of extra thick hubrings made up to give the cheapy spacers some extra support, and they DO stick out enough to support the wheel (or more specifically, the hubring):

So I wonder which is the more dodgy....hub mounted german spacer (which doesn't hub-mount the wheel) or cheapy spacer that does hub-mount the wheel?

Hmm....either way, the H&R kit came with extra long studs, so it's not a lost cause and I can put those to use...

bruce · Postby **bruce** » Thu Oct 04, 2007 12:20 pm

We need an engineers opinion on this ! Who on the forum is an engineer ?

Babalouie · Postby **Babalouie** » Thu Oct 04, 2007 12:49 pm

Ok, after sleeping on it, today my take on the situation is this:

The hub mounting of the wheel might not actually be that important. Even with oem wheels, the fit of the stock wheel onto the stock hub is quite a loose one (there is maybe a 1-2mm of play) and so I am thinking that it might be a furphy that the hub gives the wheel any significant support once you are moving.

And of course the aftermarket hubrings are plastic, so you would think that if the hub *really* had to support the wheel, then the plastic would just squash under the weight of the car during cornering.

But the German spacer does fit snugly over the 54.1mm hub, and so provides a stable, non-moving surface for the wheel to bolt onto. Whereas the cheapy spacer can move around a lot and hence the wheel can \"fret\" slightly on the hub (notwithstanding the fact that it might be hubmounted) and stress the studs.

So at this point...I am thinking that the German way is less dodgy. Mind you, tomorrow I may feel differently

Juffa · Postby **Juffa** » Thu Oct 04, 2007 1:11 pm

There has been a great number of disucssions on the big forum around the MX-5 wheels being hub centric or not.....with many (supposed) engneers giving their 2 cents worth. If I remember correctly the overall opinion is that the studs support the wheel/car and not the hub.

J

Benny · Postby **Benny** » Thu Oct 04, 2007 2:59 pm

I know that one of the most successful of our MX-5 racers hasn't worried about hub spacers for many years, and has never had a problem.
Seeing as his car does 1:04's at Wakefield, I would say that the studs can handle the load easily.
He runs aftermarket wheels which have a larger centre hole than the hub has, and just bolts them on and hasn't had a problem, so I wouldn't worry too much about it for street use.

Babalouie · Postby **Babalouie** » Thu Oct 04, 2007 3:05 pm

Cheers Benny. Yeah I figure that if it's TUV approved, that must mean that some German bloke in a white coat reckons it's good enough for barrelling down the Autobahn at godknowwhat.

So at the moment, it's Germany 1: China spacer 0

Babalouie · Postby **Babalouie** » Thu Oct 04, 2007 7:43 pm

Ok, found the threads, cheers Juffa:

http://forum.miata.net/vb/showthread.ph ... hubcentric
http://forum.miata.net/vb/showthread.ph ... hubcentric

Seems to be that you don't need hubcentric rings...Ok, Germany it is

tbro · Postby **tbro** » Thu Oct 04, 2007 9:55 pm

I've always found you only need hub mount spacers that inheritantly have balancing problems re:VL/VN dunnydores fitted with aftermarket wheels. MX5's have never been sensitive to wheel balance problems, so I wouldn't worry about the hub mount spacer, just stick to the wheel spacer.
Terry

ben wilson · Postby **ben wilson** » Fri Oct 05, 2007 12:22 am

Do you know anyone with a lathe?

It wouldn't take much effort to bore out the centre of the german spacers to fit your extra long hub rings.

Babalouie · Postby **Babalouie** » Fri Oct 05, 2007 1:04 am

ben wilson wrote:Do you know anyone with a lathe?

It wouldn't take much effort to bore out the centre of the german spacers to fit your extra long hub rings.

Yes but I waited 8wks to get a set of spacers with exactly the same 54.1mm centrebore as the MX5

Fabio · Postby **Fabio** » Fri Oct 05, 2007 3:00 pm

I'm not an engineer, but work with a few, and we all think that the taper on the wheel nuts will centre the wheel when tightened. If you make a hub extension and it is not concentric to the PCD of the wheel studs, then some wheel nuts will be side loaded. So what do you want to centre the wheel, the hub or the wheel nuts?

Caffeine · Postby **Caffeine** » Tue Oct 09, 2007 1:37 pm

Babalouie wrote:
ben wilson wrote:Do you know anyone with a lathe?

It wouldn't take much effort to bore out the centre of the german spacers to fit your extra long hub rings.

Yes but I waited 8wks to get a set of spacers with exactly the same 54.1mm centrebore as the MX5

I have access to some very nice machining equipment and a german machinist if you need some work done Kevin

BiX · Postby **BiX** » Tue Oct 09, 2007 6:57 pm

Allot of othere cars don't run any weight through the hub. its all taken by the stubs or wheel/hub interface.

Iam not sure where i remeber hearing it, but the majority of the load is taken by the wheel to hub interface. Eg the studs actaully clap the 2 together and that clamping therefore provides friction required to stop the shear stress. The wheel studs also act as extra support. But when you think about the cross sectional area of the steel studs and how much shear that could hold......

Myabe i will do some research with the mechanical guys tomorrow.....

Babalouie · Postby **Babalouie** » Tue Oct 09, 2007 7:35 pm

Fabio wrote:I'm not an engineer, but work with a few, and we all think that the taper on the wheel nuts will centre the wheel when tightened. If you make a hub extension and it is not concentric to the PCD of the wheel studs, then some wheel nuts will be side loaded. So what do you want to centre the wheel, the hub or the wheel nuts?

Basically that's the conclusion of Lance Schall on the big forum. He measured that the hub to wheel has so much play that it was the lugs that determined the position of the wheel, not the hub.

Caffeine wrote:I have access to some very nice machining equipment and a german machinist if you need some work done Kevin

Cheers Liam but I think a central part of how the german spacers are supposed to work is because they are themselves hub mounted and hence don't shift around....well I presume that's what the German dudes in the white coats were thinking when they gave it TUV certification

And loke Bix says, if the main thing is friction between the wheel and the whole face of the disc/hub, then the important thing is that the spacer doesn't move relative to the disc/hub...so machining a big hole in the middle of it would take away its exquisite german engineering

metris · Postby **metris** » Wed Oct 10, 2007 11:20 am

just something i found. i had new wheels put on, watched them balance em, they did a good job... no plastic hubcentric thingy tho and they told me id get bad vibration at high speeds... i didnt believe them. But i do get some pretty unfunny vibrations... not too bad, but bad enough to make a 3 hour hwy drive a task...

I cant think of what else might be causing it...

...just my 2c worth. :mrgreen: