Wheel Spacers

Competition engines and ancillaries - general discussion
Post Reply
Rallyroller
Posts: 89
Joined: May 31st, 2011, 2:40 pm
Contact:

Wheel Spacers

Post by Rallyroller »

I have put this in as a new thread as it is more general preparation than specific to the rally preparation thread.
Wheel spacers- which option is the best?
The works rally cars had wheel spacers on the homologation papers. They were 10,20 and 30 mm wide. ( Giving 20,40 and 60mm increase in track width.)
You will see on the attached file the design of these spacers. Basically they bolt to the hub using “normal” wheel bolts, and then the new wheel fixings have wheel studs and nuts to secure the wheel.
wheel spacers Hom doc0001.pdf
Homologated wheel spacers
(513.87 KiB) Downloaded 574 times
I have a set of these that I had made many years ago made in stainless steel. They are 25mm wide each.
I am now looking at what is available on the market and I can get good quality aluminium spacers from a couple of German suppliers. However, I now have a slight dilemma.
The aluminium spacers are of a similar design except that they recommend using the original bolts to secure the wheels. The problem with this is that a) it is more difficult to locate the wheels when changing - i.e. it takes longer, and b) the number of wheel changes on a competition car would soon cause wear on the aluminium threads in the spacer.
One company offers a steel insert in the spacer thread to give a stronger fixing. I am not sure if it is stronger or it will just reduce the possibility of wear on the thread.
One option 1 - Convert to studs in screwed into the spacer. The stud will only be inserted once, so reducing the problems of possible wear on the spacer thread. However, all of the studs I have seen on the market only have a 10mm thread to screw into the hub or spacer in this case. While this may be strong enough screwed into a steel hub, will it be ok into aluminium? Would screwing into aluminium require a more coarse thread or a longer threaded section? The answer to this would probably be special manufactured studs, but that may be difficult to get the correct quality and strength.
Option 2- Buy readily available long studs. These would be inserted into the original steel hubs, and then the spacers would be drilled and reamed to fit over the studs, and the wheel bolted secured with nuts , so in effect the spacers are clamped between the wheel and the hub. You could also secure the spacer to the hub to stop it coming off with the wheel.
Question which option would be stronger? This is a rally car so different than a road car. It will not have the same stresses as a circuit racer, and running in MSA events is limited to the width of tyre even on tarmac, so we are not talking super wide soft slicks here. However, I do not under estimate the strains that the setup will be required to withstand.
Any comments would be appreciated.
GC_13
Urbancamo
Posts: 317
Joined: August 8th, 2011, 1:04 pm
Location: Finland
Contact:

Re: Wheel Spacers

Post by Urbancamo »

Every single older rally car I see around here has just longer studs inserted into original hubs. They are usually the ones you insert from behind with press or similar tool.
Of course if you use wheels wich doesn't require spacers, you have to use open ended nuts.

I personally do not recommend using aluminium spacers wich have threads cutted straight in to the aluminium. Use the ones with steel inserts.

Others can give their opinions about material strength, I don't handle those things.
GC_25
WhizzMan
Posts: 459
Joined: August 13th, 2010, 8:05 pm
Location: Amsterdam, the Netherlands

Re: Wheel Spacers

Post by WhizzMan »

Take good care about shear forces and what those spacers will do regarding these. You wouldn't be the first to shear off entire wheels due to improper torqued wheels or bad engineering.
Book #348
Rallyroller
Posts: 89
Joined: May 31st, 2011, 2:40 pm
Contact:

Re: Wheel Spacers

Post by Rallyroller »

Thanks for the views. Certainly the shear forces are of concern.

Using long studs with spacers placed on them gives me some worries. If you look at the press in studs, ( as fitted to Escorts etc) many of the extended versions seem to have a plain section with wheel nut threads only at the end. The extended screw in type all seem to be threaded for the whole length of the wheel nut side, which I think would significantly reduce the strength. Has anybody seen extended screw in studs with plain shanks?

One other option is to use the press in extended studs. (like the Escort. ) has anybody tried to do this on a Fiat axle/ stub axle?

If not then I may go for the bolt on spacers with the steel inserts to screw in the studs. I think the main concern with these type is to ensure that the spacers do not come loose. Regular checking would certainly be required.
GC_13
pastaroni34
Posts: 58
Joined: June 26th, 2006, 10:53 am
Location: Texas, USA
Contact:

Re: Wheel Spacers

Post by pastaroni34 »

As a manufacturer of wheel spacers, I'll recommend the following:

1. Don't thread into an aluminum spacers directly, this is fine for occasional use but with parts like wheels that are constantly bolted on and off, studs would be better. Threaded inserts aren't much better than bare aluminum threads. Just use studs.

2. Shear shouldn't be a problem with longer studs/bolts assuming you have them properly torqued. In addition, good spacers will be tightly toleranced around the bolt holes. The spacers will act like a sleeve around the bolt keeping it from bending. If you're still concerned, pin the spacers to the hubs so they can't rotate. For that matter you can pin the wheels to your spacers too. Of course, quality studs are paramount, there's so much junk out there in this category.

3. Press in studs: keep in mind the brake rotor centers itself on the OD of the wheel hub. The head on most pressed in studs is too large and will extend beyond the OD of the hub when installed. You'll have to trim the head for clearance. Some companies sell 'clipped' studs that have a flat side on the head to accommodate this already. You'll also have to machine the back of the hub flat for the studs to seat properly. Also there isn't much room between the wheel bolt holes and the OD of the wheel hub, this is an area which is likely to crack, i've seen it before. Machining the rear axle for this is a relative pain also.

As much as I like press in studs, pressing them into the OE wheel hubs is too problematic. You can install them on thicker wheel spacers (20mm+) without the concerns addressed above but then you pay a weight penalty because you have twice the wheel hardware (bolts from hub to spacer, then spacer to wheel).

4. Whatever you do, make sure your spacers are hub centric.
-Jason Miller
Miller's Mule Machine and Design Inc.
Houston, Texas - USA
Rallyroller
Posts: 89
Joined: May 31st, 2011, 2:40 pm
Contact:

Re: Wheel Spacers

Post by Rallyroller »

Jason

Thanks for the comments. I am looking at a number of options and will take all comments on board.
one question- hub centric- the original wheels are not hub centric on the 124. The original works spacers ( bolted to the hubs and fitted with studs) were not hub centric. So if the spacers have hub centric fitting for the wheels but the hubs are not hub centric for the spacers to fit onto, what would the outcome be?

Nigel.
GC_13
pastaroni34
Posts: 58
Joined: June 26th, 2006, 10:53 am
Location: Texas, USA
Contact:

Re: Wheel Spacers

Post by pastaroni34 »

Nigel,
if the spacers have a nose/hub for the wheel to fit on, you should be able to install them and indicate them in on the rotating axis so that they are hub centric, then tighten the bolts that hole the spacer to the hub. If you don't do this, then they're certainly not hub centric.

I am not as familiar with the Abarth 124 but on the standard 124 the front certainly has a hub to center the wheel on. Depending on what rear axle you have, there is a hub to center on, others, unfortunately have nothing. I feel a hubcentric setup is more important (or more noticeable) on the front wheels rather than the rear.

I find it interesting that the works spacers are not hub centric but then again, I know a few higher end racing teams that never bother balancing their wheels. They claim that whilst racing they get flat spots and become unbalanced anyway.

-Jason
-Jason Miller
Miller's Mule Machine and Design Inc.
Houston, Texas - USA
TomLouwrier
Posts: 333
Joined: July 28th, 2010, 3:09 pm
Location: Leiden, The Netherlands
Contact:

Re: Wheel Spacers

Post by TomLouwrier »

As far as i can see in the picture there definitely is a nose in the centre, the one on the right even holding an 'Abarth' grease cap. That would be centering the wheel, right?

regards
Tom
GC_29
Rallyroller
Posts: 89
Joined: May 31st, 2011, 2:40 pm
Contact:

Re: Wheel Spacers

Post by Rallyroller »

Jason- Tom

Many thanks for the reply. Loooking at the "works" spacers , there is a lip on them. ( The Abarth cap is the grease cover on the hub itself).
I have now checked the front and rear hubs in more detail. On the early (pre 1978) spiders, the brake disc itself locate on the outside of the hub flange (front and rear). At the front, the disc brake then covers the hub centre, as does the 6mm spacer fitted to most cars. This part of the hub centre that these two items cover is 58.6m diaeter. There appears then to be 2 further diameters on the hub, protruding out of the brake /spacer. The part right next to the brake/spacer is 57.8 diameter. This is around 4mm in depth. The hub then reduces to 57.6 mm diameter for the rest of its length. From this I assume that the steel wheels locate on the 57.8 diameter. However, the slight chafer on the alloy wheels I have ( various Cromadora) would not, in my opinion, locate onto this 57.8 diamter, only on the 57.6 diameter. ( I have checked 4 hubs and they all have this double diameter). This is of course for the front wheels and hubs. The back axle has non of this for wheel locaiton.

I notice that many of the spacers avaiable state 58.1 as the hubcentric dimension. Is this dimension of the the hub ring, or the wheel bore?
How accurate does a wheel location have to be? What tolerance would there be between the hub centre ring and the wheel itself? Obviously on the rear axle it is down to location by wheel bolts so is dependant on the maching tolerances and the positioning of these wheel bolts. I have never measured the radial run out on a wheel to consider what is good or bad.

While on this subject of wheel location, hubs and things, what about location of the brake disc. The standard Fiat discs locate on the outer diameter of the hub. ( or half shaft flange at the rear). My V8 Jag front discs just fit over the wheel studs. So when I fit uprated discs do they need to be a close fit to the hub, like the originals, or will reasonably accurate location be achieved on the studs? Obviously the studs actually take the breaking force, so if the disc is accurately located on these they should be ok?

Your very welcome and informative comments have made me think a bit deeper now, just what this forum is great for.

Nigel.
GC_13
TomLouwrier
Posts: 333
Joined: July 28th, 2010, 3:09 pm
Location: Leiden, The Netherlands
Contact:

Re: Wheel Spacers

Post by TomLouwrier »

hi guys,

There's a similar discussion going on about Miro's hubs, brakes and spacers over here:
viewtopic.php?f=5&t=1240&start=465

As far as I'm concerned bolts and studs are springs and should not take shear or bending loads. You may use them for location but they should have a shank of sorts with reasonable precision. Same shank -if it exists- could take some shear, but basically it's the friction between the disc and the hub that transfers the braking force, not the bolt! The bolt only provides the clamping force.

I must look up the details for the 124 front hub on my own car, will be back on that.
Looked up Brembo drawings for the original 227mm Fiat disc, it has an interior face that locates on the hub as you say, dimensioned at 117,020 - 117,100mm. The friction surface is tolerated to both this locating face and to the one sitting on top of the hub at 0,05mm. This gives you an indication of normal runout tolerances: less than 0,1mm.
Attaching the drawing, it's from their public aftermarket web catalogue.

Don't forget that your wheel nuts are tapered so they too provide location while torquing up.

regards
Tom
Brembo specs Fiat 227mm disc.jpg
Brembo specs Fiat 227mm disc.jpg (84.4 KiB) Viewed 10871 times
GC_29
pastaroni34
Posts: 58
Joined: June 26th, 2006, 10:53 am
Location: Texas, USA
Contact:

Re: Wheel Spacers

Post by pastaroni34 »

This is what I have for the front 124 hub:
Fiat 124 Front Hub Dimensions
Fiat 124 Front Hub Dimensions
Front Hub Dimensions.jpg (183.97 KiB) Viewed 11074 times
There are two different rears from what I can gather, I only have specific dimensions on one of them:
Fiat 124 Rear Hub Dimensions
Fiat 124 Rear Hub Dimensions
Rear Hub Dimensions.jpg (567.15 KiB) Viewed 11074 times
I cut 124 hub centric spacers to 58.5mm. X1/9's and Lancias are 58.1mm, I have seen many many places quote them incorrectly. I do not have direct experience with 131's so I can't give any dimensions there.
-Jason Miller
Miller's Mule Machine and Design Inc.
Houston, Texas - USA
volumetrico
Posts: 18
Joined: July 24th, 2006, 11:24 am
Location: London
Contact:

Re: Wheel Spacers

Post by volumetrico »

Hello all,
I thought I would throw something else in here, the intention is not to go off topic, but this seemed related to some points being discussed.
On the Gr.A Delta, Abarth use tapered studs to locate the wheels. There is no centre raised section/shoulder/lip. The threaded ends are 14mm (versus 12mm for OE) and the tapered part in the middle of the stud is 16mm at its widest. The wheel is centred on the 4x16mm stud sections. The wheels have special steel inserts that I presume are are nominally larger than 16mm.

Melo
GC #162
Uros Piperski
Posts: 60
Joined: September 4th, 2006, 10:55 pm
Location: Belgrade, Serbia
Contact:

Re: Wheel Spacers

Post by Uros Piperski »

Hi guys,
Just one small thing to note - the threaded part of the bolt/stud is not weaker than the rest of the stud. It may be even stronger on a high quality item with the thread rolled after the heat treatment.

Uros
Guy Croft
Site Admin
Posts: 5039
Joined: June 18th, 2006, 9:31 am
Location: Bedford, UK
Contact:

Re: Wheel Spacers

Post by Guy Croft »

I only just got time to read this one. Some good work by all.

1. Studs preferable. Should be metric fine grade according to shear stress non plated with rolled threads both ends. Metal (hub) end must have 1.5 x dia engaged thread. They should be secured by Loctite Studlock 270

You will never find anyone who can make 12.9 grade but 10.9 grade there is UK mfr I know who can make them.

2. The nuts must be one grade lower eg: 8.8 grade on 10.9 stud or 10 grade on 12.9 grade stud and have min 1.5 x fully engaged threads.

3. No reason bolts cannot be used - grade according to load but it makes changing wheels harder and constant removal degrades the hub threads. If in doubt go 12.9 grade rolled thread - no plating (it degrades the material). You can plate 10.9 grade however.

The wheel must center on the hub not the fixings.

Some math on normal shear should be performed on this, the K (stress concentration) factor needs to be quite high I would suggest x 3

G
Guy Croft, owner
Post Reply

Who is online

Users browsing this forum: No registered users and 41 guests