DIY - How To Make 3-Piece Fuchs

[robcf]

Hi All,

Over the last few months I have periodically worked on a 3-piece wheel project, below I have shared my process. Please let me know if you have any questions.

Take four perfectly good wheels:



Introduce them to an angle grinder (be sure to use a aluminium compatible wheel). At this stage I wish I had access to a larger lathe as this was not fun!



You will need something to hold the wheel in the lathe, for this I made the below arbour. The arbour must be stiff, square and have little runout. Due to the size of the lathe I had to take the arbour out of the lath to machine the back side which required truing the setup each time.

I also used 997 wheel bolts rather than studs to hold the wheel to the arbour as it was relatively convenient.

[robcf]

Now the tricky part; setting up the arbour in the 4 jaw chuck so that the run out is as close to zero and is also square.

Arbour setup on the lathe and wheel mounted:




Removing some material. The goal here was to machine a flat surface for the rim to fasten to and create a centring spigot to suit a BBS or similar motor-sport rim. The centre bore for a 17" BBS rim is 321mm + a small clearance (0.1mm).






Measure measure measure!



Once the front side is down, flip the wheel/arbor over and machine the back side. Unfortunately due to forging shape there is not a lot of material to create a centring spigot for the rear rim. All I comfortably achieved was 1.5/2mm in depth as not to reduce too much material.

[rothaus]

Great ! Looking forward to see the progress on it.

Thanks for posting it.

Cheers
Engelbert

[safe]

Yep, looking forward. This is on my future todo list... way future.

[robcf]

Wheel ready for the mill and further sandblasting.





The DRO makes drilling the 6mm holes in the rim a lot faster! PCD is 325mm.



Finished wheel centre:

[safe]

Have you machined a groove for an o-ring, or do plan on sealing from the inside with RTV after assembly?

[robcf]

BBS Motorsport rims aren't widely available in Australia, however, there is a metal spinner located just outside Melbourne who does manufacture split rim halves.

For the 17 x 7.5"/9" wheel combination I was creating I ordered the following wheel halves:

Material: 4mm thick 6061-T6
Front Inner: 5" Front Outer: 2"
Rear Inner: 5.5" Rear Outer: 3"

Test fitting rims (there was a big moment of relief when everything when together as planned):





Now you might notice that the rims don't have any holes for the fasteners, unfortunately the metal spinner doesn't offer this service so off to make another jig:



The drill bushes (pressed in from the rear) will make for accurate location of the drill.

[robcf]

First rim on the drilling jig:



Flip the fim/jig over and using a battery drill proceed to drill the 20 holes.



Now for the inner rim barrel.





Test fit rims, wheel centre and fasteners.







And on the ground:



............More to come

[robcf]

Originally Posted by safe

Have you machined a groove for an o-ring, or do plan on sealing from the inside with RTV after assembly?

RTV - must be non-corrosive cure type, essentially a modern roofing silicone (Dow Corning 832 is what most use).

I like the idea of the BBS o-rings but at $80 a wheel they add significant cost to the project. Furthermore, they eat up a lot of space on the spigot bore which means more material off the wheel centre compromising strength and packaging. A good option if you can design around it.

[wayner]

The set I have has a sealing ring between the two hoops, and then the center bolts to the completed rim assembly

[tadd]

Very nice work and great shop. I am envious of you having nice tooling !!!

If I might ask, how come you don't just put the two rim halves together then the center in front or behind? That way you only have one seam to seal rather than two... thus one less place to leak. I think this is the way BBS does it IIRC.

[tributeventures]

Great thread. I could never understand the process of making 3 piece wheels.
If that is your home shop and equipment you are using?

[Dubbin']

Wow this is insane...

Good job man !

Mark

[PcarPhil]

Very nice.

Could you do us a favor and measure the radial and lateral runout at the flanges of the rim halves where the tire beads sit? I'd love to know how much runout (or lack of) are in these new wheels. Keeping in mind you can reclock the wheel centers and halves if tolerance stacking becomes an issue with runout.

[billjam]

Great thread, thanks for sharing. I'm a fitter and turner from way back and I just love seeing this stuff.
I have been considering doing something similar with four spare Fuchs I have. I'm eventually planning to fit some wide 17" wheels and turbo body panels to my Carrera and I looked into this method using Whitehorse? rim halves after I got prices for Fuchs style 17" wheels.

What size Fuchs did you start with and what size did you end up with?

[jpnovak]

That is a great writeup. If only I had access to (or owned) some of the machine tools you have in your arsenal of DIY equipment.

[clutch-monkey]

looks awesome. have considered widening my 16" fuchs but nobody local seems to do it, this looks ideal.

[Cory M]

Nice work, thanks for sharing.

[Porboynz]

I was right there with you when the angle grinder was used, after that I was overwhelmed with Workshop Envy. Well done, how did they spin up on the wheel balancer after such major surgery?

[robcf]

Hi Guys,

Thanks for the positive feedback, I am glad your all enjoying the thread.

A little about me:

I am a mechanical engineer, I work in the Australian automotive industry for GM's local brand Holden. I do not specialise in chassis components such as wheels, my main focus is design head lights and tail lights ect.

I own a 1988 Carrera (LHD) which I imported from Colorado nearly 2 years ago. I bought the car on this forum -

The pictures have been taken in my garage and at my friend Ross and Stewarts home workshop. Stewart recently purchased a 1985 Carrera and completed a road trip around the USA. I'm lucky these guys don't mind me coming around using their shop.

More about the wheels:

I started with 16x6 Fuchs, the part number suggests they are from an SC. If you read around on Pelican the SC Fuchs have a flatter forging where the rim will fasten too.

The final specs are 17 X 7.5" ET28.4 and 17 X 9" ET15.6. I used the information on this forum provided by Bill V to create a fitment envelop in CAD. This enabled me to determine what was a reasonable wheel width based on the limitations of the original forging and my design targets. I benchmarked as many 3-Piece Fuchs that I could find to determine what I thought were reasonable dimensions.

In order to minimise any runout at the the rim (after assembly) I decided that both rim halves had to be centered on a spigot. In order to engage both rim halves and maximise the wheel flange thickness (the area sandwiched between the rims) I was forced into this design. The trade off is that there are two sealing surfaces and the flange thickness influences the width of the wheel.
There simply isn't enough material on the back of the rim to machine a deep enough spigot to centre both rim halves without reducing the strength of the wheel centre.

Billjam: The rim halves are manufactured by whitehorse industries, the cost differential compared to Bob Woodman once considering shipping and exchange rate was significant. However, Whitehorse will not machine the bolt holes for the PCD or the valves, this would be an added cost and if you cannot do this yourself it may influence your purchasing decision. If you ever do go down this path I may be able to drill the holes for you !

I will measure the runout when the wheels are together. The OEM specification (ISO standard) is +/- 0.25mm for radial runout and the difference between both beads cannot be more than 0.25mm (composite tolerance). I doubt this style of wheel can achieve these tolerances due to the manufacturing process and assembly stack-up, however, the target clearance wheel to rim is 0.125mm. I'm not sure if the bases of the ISO standard is NVH or tire fitment, ideally the less runout the better, FYI the service limit for the forged Fuch is 1.0mm.

NEXT STEPS

- Drill the valve stem holes (BBS motorsport).
- Clear anodize the outer rims. This will dull the finish and hopefully achieve a similar appearance to the stock wheel.
- Paint wheel centres.
- Assemble and seal with silicone.