Some or many of you may already know this, but I wanted to share this after the amount of research and digging I went through. I recently took notice that the lug bolt caps on my 1995 SL500 sat noticeably recessed into the eight-hole wheels, I began researching whether this was correct. This vehicle has been in my family since it was brand new in early 1995, and I recalled when my mother drove it during the early years that the lug bolt heads were virtually flush with the outer edge of the wheels.
Every original Mercedes-Benz brochure and period press photograph I could find showed the lug bolt caps sitting almost flush with the face of the wheel.
That started a rather interesting investigation.
VIN: WDBFA67E1SF115894
Factory 8-hole wheels
Mercedes describes this as a spherical collar screw. It is a relatively short wheel bolt with the spherical seating surface directly beneath the head. When installed, the plastic lug caps sit noticeably recessed within the wheel.
This is what most dealer-serviced cars wear today because it is the current superseded part supplied by Mercedes-Benz.
Original Mercedes wheel bolt: A124 400 07 70
Characteristics:
His response included: “I was always under the impression they sat flush with the face of the wheel.”
I also discussed the issue with Matthew in the Parts Department at Mercedes-Benz of Portsmouth (New Hampshire). He explained that Mercedes eventually discontinued the extended-shank bolt because the thinner shank was more prone to snapping, superseding it to the current shorter design. While I have not located a Mercedes engineering bulletin documenting this change, it aligns with the supersession history in EPC.
Original wheel bolt
A124 400 07 70
↓
Later supersessions
A126 400 00 70
↓
Additional supersessions
A203 401 03 70
A210 400 01 70
↓
Current Mercedes-Benz replacement
A000 990 48 07
Because I wanted to return my SL500 to its original appearance while still driving it regularly:
The pictures I've attached show the whole side profile of the car before I figured out the lugs had been swapped out at some point when my mom had the car, and the return to factory look when the original OEM versions of the bolts arrived today.
I hope this saves another owner the many hours of research it took to piece together.
Every original Mercedes-Benz brochure and period press photograph I could find showed the lug bolt caps sitting almost flush with the face of the wheel.
That started a rather interesting investigation.
My Vehicle
1995 Mercedes-Benz SL500 built 01/95VIN: WDBFA67E1SF115894
Factory 8-hole wheels
What Mercedes-Benz EPC Shows Today
Looking up the VIN in the Mercedes-Benz EPC points to the current wheel bolt: A000 990 48 07Mercedes describes this as a spherical collar screw. It is a relatively short wheel bolt with the spherical seating surface directly beneath the head. When installed, the plastic lug caps sit noticeably recessed within the wheel.
This is what most dealer-serviced cars wear today because it is the current superseded part supplied by Mercedes-Benz.
What I Found
While researching, I located several independent sources that all pointed toward an earlier design.Original Mercedes wheel bolt: A124 400 07 70
Characteristics:
- 95 mm overall length
- Extended reduced-diameter shank
- 20 mm threaded section
- Ball-seat wheel bolt
- Plastic caps sit nearly flush with the wheel face
- Original Mercedes-Benz parts listings
- R129.co
- Period used OEM parts
- Multiple dismantled R129, W124 and W126 vehicles
Independent Evidence
During the investigation I contacted Stuart Webb at The SL Shop in the UK.His response included: “I was always under the impression they sat flush with the face of the wheel.”
I also discussed the issue with Matthew in the Parts Department at Mercedes-Benz of Portsmouth (New Hampshire). He explained that Mercedes eventually discontinued the extended-shank bolt because the thinner shank was more prone to snapping, superseding it to the current shorter design. While I have not located a Mercedes engineering bulletin documenting this change, it aligns with the supersession history in EPC.
Part Number Progression
Original wheel bolt
A124 400 07 70
↓
Later supersessions
A126 400 00 70
↓
Additional supersessions
A203 401 03 70
A210 400 01 70
↓
Current Mercedes-Benz replacement
A000 990 48 07
Appearance Difference
Original A124 400 07 70- Long reduced shank
- Lug caps nearly flush with the wheel
- Short spherical collar
- Lug caps sit deeper inside the wheel
What I Chose
Because I wanted to return my SL500 to its original appearance while still driving it regularly:
- I purchased an original OEM set of A124 400 07 70 bolts from R129.co.
- After confirming their fit and appearance, I ordered twenty-five brand-new FEBI Bilstein 100940 wheel bolts for service
- Preserve the original Mercedes bolts as a reference set.
- Install twenty new FEBI bolts.
- Keep five new FEBI bolts as spares.
Final Thoughts
If your R129, W124, W126 or related Mercedes has recessed lug caps on eight-hole wheels, there is a good chance it has been updated to Mercedes’ current superseded wheel bolt. That does not mean it is incorrect or unsafe. However, if your goal is factory-original appearance, the earlier A124 400 07 70 geometry (or its OE-equivalent, FEBI Bilstein 100940) appears to reproduce the original look shown in period Mercedes-Benz literature.The pictures I've attached show the whole side profile of the car before I figured out the lugs had been swapped out at some point when my mom had the car, and the return to factory look when the original OEM versions of the bolts arrived today.
I hope this saves another owner the many hours of research it took to piece together.
