Situation: You have an UrS4 with the four spoke airbag steering wheel and you wish that you had the 3 spoke UrS6 airbag sport steering wheel. (Note: UrS6 folks with the early four spoke steering wheels can just remove it and install the 3 spoke sport wheel). As a result, you need to figure out how to convert a 3 spoke sport airbag steering wheel to your UrS4 column.
The main issue is the signal light cancellation tab on the clockspring is in the wrong position on the UrS6 clockspring to work on the UrS4 steering column switches. Orignally there was one method (Method 1) that involved cutting the UrS4 cancellation ring off the UrS4 clockspring and glueing it to a trimmed UrS6 clockspring. I did this on a conversion for my UrS4 years ago. Subsequently, I came up with Method 2 and then Method 3. I did a Method 2 (better than Method 1). I ran out of clocksprings and somebody else (Steve Y.) did Method 3 using my sketches. These are documented at the link below, along with a link to an excellent DIY for Method 3 written by Steve Y. Of the three clockspring modification methods, Method 3 is by far the best.
Link to a description of Methods 1, 2 and 3: http://forums.quattroworld.com/s4s6/msgs/24345.phtml
Method 3 during a test fit, prior to the application of epoxy:
A month or so ago, some one pointed out an alternative documented by Martin Newiger on the German AudiV8 forum. I translated this method (with the help of Google translate) and became intrigued by it. (Link to the translation at the end of this post).
In Martin's case, he wanted to install an UrS6 sport three bag airbag steering wheel in his Audi V8. Rather than modifying the UrS6 clockspring signal cancellation tab, he decided to keep the V8 clockspring and modify the UrS6 steering wheel to accept the V8 clockspring (same as the UrS4/C4 100 clock spring).
Here is Martin's end result:
Besides looking good, here the main reason why I want to add a sport steering wheel to my 94 S4 V8 avant - Thicker steering wheel rim (and nifty thumb notches too).
So having a spare UrS6 steering wheel to use as a guinea pig and my old UrS4 steering wheel and a 94 100 clockspring to use as a guide, I re-read Martin's instructions a couple of times and then started into it.
First thing would be to disassemble the OE UrS4 steering wheel to get the clockspring and clockspring mounting plate off it, to use as a template for the modifications to the UrS6 steering wheel.
OE UrS4/C4 100 clock spring mounted to UrS4/C4 100 4 spoke air-bag steering wheel:
Here is the plate on the inside of the steering wheel with its 3 Phillips screws that hold the clock spring into/onto the steering wheel.
Here is the clockspring separated from the UrS4/C4 100 four spoke steering wheel. Note the three mounting lugs. They are used to both position and attach the clock spring to the steering wheel.
Here is a view of the back side of the UrS4/C4 100 clockspring mounting plate, showing that there is a significant height/depth of a centre ring that need to be accomodated in the UrS6 sport steering wheel.
Here is the front side of the interior of the UrS4/C4 100 steering wheel showing the features of the steering wheel hub area that have to be reproduced in the UrS6 steering wheel in this conversion method:
Here is the back side to the UrS4/C4 100 steering wheel showing the features of the steering wheel hub area that have to be reproduced in the UrS6 steering wheel in this conversion method:
Here is a view of the UrS4/ C4 100 steering wheel hub "nose" showing the key dimensions that need to be used as a guideline for modifying the UrS6 steering wheel hub nose. Note that the UrS4 /C4 100 hub nose is parallel-sides whereas the UrS6 nose widens. This is one of the main issues when making this modification. The UrS4/ C4 100 hub nose is approximately 31 mm in diameter and that diameter continues for ablut 19.5 mm until a rounded fillet flares out for another 3.3 mm of depth (total of 22.8 mm from the top of the nose to the bottom flats of the steering wheel hub).
With that background, now the work can begin on the UrS6 sport steering wheel:
First thing would be to gut the UrS6 steering wheel, as per Martin's instructions. Everything out of the inside. Once that is clear, the firs thing is to create the champfer on the inside of the steering wheel:
You need to grind out the champfer so the UrS4/C4 100 clockspring mounting plate fits completely down into the centre area of the UrS6 steering wheel. Champfer at roughly 45 deg and grind off anything that sits noticeably proud of the general flatness of the inside of the steering wheel. This includes the date casting arrows and any other bumps that prevent the plate from fitting fully and completel down into the centre area of the UrS6 sport steering wheel.
Keep working at the champfer and associated areas until you can get the UrS4/C4 100 clockspring mounting plate to sit down nice and flat, no rocking in the centre area of the UrS6 sport wheel. Then, as close as you can, centre the plate in that space (looking at the hole in the plate and the splines in the inside of the hub). Then mark the location of the holes in the UrS4 mounting plate with a felt pen. Then drill pilot holes big enough to take the mounting screws.
Once I got the pilot holes marked and drilled I tried the UrS4/C4 100 mounting plate on the wheel. I showed that I had been too impatient and had not ground enough around the champfer and the areas beside it. Of course I ignored this and carried on. (This was a mistake and it resulted in some extra work later).
Once the work on the initial work on the front side of the steering wheel hub, the next thing was to turn the wheel over and start trimming the nose so its sides were parallel (no taper) and about 31 mm in diameter:
After several hours and numerous Dremel cut-off disks and sanding drum replacement tubes, I had this:
Finally I got to the holes for the three mounting lugs on the UrS4/C4 100 clock spring. Martin called for 10.5 mm drill bit. I went a bit larger and used a 7/16" Bosch Titanium-coated drill bit (Very sharp and easy to drill with). Unfortunately, due to my impatience with getting the champfer area on the inside of the steering wheel perfect before I marked and drilled the pilot holes, when I drilled the larger holes, I found out that they were NOT quite in the right location. This necessitated grinding and filing to get the room for the lugs to fit properly.
Here is how the UrS4/C4 100 clock spring looks from the front side before the mounting plate is added.
And with the mounting plate:
Here is the back side of the UrS6 steering wheel with the UrS4/C4 100 clockspring, side view, showing that the clockspring isn't sitting fully down into the steering wheel. Not quite sure what the issue is, so I ignored it for now.
Here is the final (interim) product. I took it out to the 93 UrS4 and mounted it (ish - it has UrS6 column covers now and they are not compatible with the UrS4 clock spring). The key thing was the steering wheel moved and turned the wheels and the clock spring cancelled the signal lights in both directions. No grinding to be heard.
WHAT I WILL DO ON THE NEXT ONE:
1. Either get a machinist to work on the champfer area or have more patience before I mark where the pilot holes need to be drilled.
2. Have a machinist turn the nose on the UrS6 steering wheel on a lathe down to 31.5 mm constant, 23 mm high/deep.
3. Consider having some of the larger UrS6 holes on the steering wheel hub area welded up and ground flat before the drilling of the three necessary lug holes (and/or horn wire hole).
Steering wheel conversion - a translation of Martin Newiger's original German post:
The main issue is the signal light cancellation tab on the clockspring is in the wrong position on the UrS6 clockspring to work on the UrS4 steering column switches. Orignally there was one method (Method 1) that involved cutting the UrS4 cancellation ring off the UrS4 clockspring and glueing it to a trimmed UrS6 clockspring. I did this on a conversion for my UrS4 years ago. Subsequently, I came up with Method 2 and then Method 3. I did a Method 2 (better than Method 1). I ran out of clocksprings and somebody else (Steve Y.) did Method 3 using my sketches. These are documented at the link below, along with a link to an excellent DIY for Method 3 written by Steve Y. Of the three clockspring modification methods, Method 3 is by far the best.
Link to a description of Methods 1, 2 and 3: http://forums.quattroworld.com/s4s6/msgs/24345.phtml
Method 3 during a test fit, prior to the application of epoxy:
A month or so ago, some one pointed out an alternative documented by Martin Newiger on the German AudiV8 forum. I translated this method (with the help of Google translate) and became intrigued by it. (Link to the translation at the end of this post).
In Martin's case, he wanted to install an UrS6 sport three bag airbag steering wheel in his Audi V8. Rather than modifying the UrS6 clockspring signal cancellation tab, he decided to keep the V8 clockspring and modify the UrS6 steering wheel to accept the V8 clockspring (same as the UrS4/C4 100 clock spring).
Here is Martin's end result:
Besides looking good, here the main reason why I want to add a sport steering wheel to my 94 S4 V8 avant - Thicker steering wheel rim (and nifty thumb notches too).
So having a spare UrS6 steering wheel to use as a guinea pig and my old UrS4 steering wheel and a 94 100 clockspring to use as a guide, I re-read Martin's instructions a couple of times and then started into it.
First thing would be to disassemble the OE UrS4 steering wheel to get the clockspring and clockspring mounting plate off it, to use as a template for the modifications to the UrS6 steering wheel.
OE UrS4/C4 100 clock spring mounted to UrS4/C4 100 4 spoke air-bag steering wheel:
Here is the plate on the inside of the steering wheel with its 3 Phillips screws that hold the clock spring into/onto the steering wheel.
Here is the clockspring separated from the UrS4/C4 100 four spoke steering wheel. Note the three mounting lugs. They are used to both position and attach the clock spring to the steering wheel.
Here is a view of the back side of the UrS4/C4 100 clockspring mounting plate, showing that there is a significant height/depth of a centre ring that need to be accomodated in the UrS6 sport steering wheel.
Here is the front side of the interior of the UrS4/C4 100 steering wheel showing the features of the steering wheel hub area that have to be reproduced in the UrS6 steering wheel in this conversion method:
Here is the back side to the UrS4/C4 100 steering wheel showing the features of the steering wheel hub area that have to be reproduced in the UrS6 steering wheel in this conversion method:
Here is a view of the UrS4/ C4 100 steering wheel hub "nose" showing the key dimensions that need to be used as a guideline for modifying the UrS6 steering wheel hub nose. Note that the UrS4 /C4 100 hub nose is parallel-sides whereas the UrS6 nose widens. This is one of the main issues when making this modification. The UrS4/ C4 100 hub nose is approximately 31 mm in diameter and that diameter continues for ablut 19.5 mm until a rounded fillet flares out for another 3.3 mm of depth (total of 22.8 mm from the top of the nose to the bottom flats of the steering wheel hub).
With that background, now the work can begin on the UrS6 sport steering wheel:
First thing would be to gut the UrS6 steering wheel, as per Martin's instructions. Everything out of the inside. Once that is clear, the firs thing is to create the champfer on the inside of the steering wheel:
You need to grind out the champfer so the UrS4/C4 100 clockspring mounting plate fits completely down into the centre area of the UrS6 steering wheel. Champfer at roughly 45 deg and grind off anything that sits noticeably proud of the general flatness of the inside of the steering wheel. This includes the date casting arrows and any other bumps that prevent the plate from fitting fully and completel down into the centre area of the UrS6 sport steering wheel.
Keep working at the champfer and associated areas until you can get the UrS4/C4 100 clockspring mounting plate to sit down nice and flat, no rocking in the centre area of the UrS6 sport wheel. Then, as close as you can, centre the plate in that space (looking at the hole in the plate and the splines in the inside of the hub). Then mark the location of the holes in the UrS4 mounting plate with a felt pen. Then drill pilot holes big enough to take the mounting screws.
Once I got the pilot holes marked and drilled I tried the UrS4/C4 100 mounting plate on the wheel. I showed that I had been too impatient and had not ground enough around the champfer and the areas beside it. Of course I ignored this and carried on. (This was a mistake and it resulted in some extra work later).
Once the work on the initial work on the front side of the steering wheel hub, the next thing was to turn the wheel over and start trimming the nose so its sides were parallel (no taper) and about 31 mm in diameter:
After several hours and numerous Dremel cut-off disks and sanding drum replacement tubes, I had this:
Finally I got to the holes for the three mounting lugs on the UrS4/C4 100 clock spring. Martin called for 10.5 mm drill bit. I went a bit larger and used a 7/16" Bosch Titanium-coated drill bit (Very sharp and easy to drill with). Unfortunately, due to my impatience with getting the champfer area on the inside of the steering wheel perfect before I marked and drilled the pilot holes, when I drilled the larger holes, I found out that they were NOT quite in the right location. This necessitated grinding and filing to get the room for the lugs to fit properly.
Here is how the UrS4/C4 100 clock spring looks from the front side before the mounting plate is added.
And with the mounting plate:
Here is the back side of the UrS6 steering wheel with the UrS4/C4 100 clockspring, side view, showing that the clockspring isn't sitting fully down into the steering wheel. Not quite sure what the issue is, so I ignored it for now.
Here is the final (interim) product. I took it out to the 93 UrS4 and mounted it (ish - it has UrS6 column covers now and they are not compatible with the UrS4 clock spring). The key thing was the steering wheel moved and turned the wheels and the clock spring cancelled the signal lights in both directions. No grinding to be heard.
WHAT I WILL DO ON THE NEXT ONE:
1. Either get a machinist to work on the champfer area or have more patience before I mark where the pilot holes need to be drilled.
2. Have a machinist turn the nose on the UrS6 steering wheel on a lathe down to 31.5 mm constant, 23 mm high/deep.
3. Consider having some of the larger UrS6 holes on the steering wheel hub area welded up and ground flat before the drilling of the three necessary lug holes (and/or horn wire hole).
Steering wheel conversion - a translation of Martin Newiger's original German post:
(sometimes appealing).
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