Mounting Aftermarket Alloy Rims

[MBGraham]

Job is to choose best lug bolts in order to install aftermarket alloy rims on a 98 Mercedes.

- Original rims used 12x1.5mm 40mm shank lug bolts with R12 ball heads. Bolt protrusion 17mm, boltholes 13mm.
- Aftermarket rims are thinner and require 26mm bolts to get same 17mm protrusion
- Aftermarket rim boltholes are drilled 15mm and have R13 seats.
- Rims are hubcentric. Bolt torque 75-80 ft.lb.

Bolts provided were 12x1.5mm, R12 ball and nominally 28mm long (but actually closer to 29mm). Protrusion was ~21mm. Too long and would have to be cut down by ~3mm to avoid contact with parking brakes at rear.

Questions:
1. Is there any problem in using 12mm bolts with rim boltholes drilled to 15mm?
2. Would it make sense to add a 13x15mm sleeve between the bolts and the rim?
3. Could the 12mm R12 ball lug bolts be used, given that seats are R13 and bolt hole is 15mm?
4. If not, would R13 bolts be satisfactory given bolt holes are 15mm?

 

[TugboatEng]

The diameter of the hole is unimportant here. As for the seats, if there is any mismatch it's likely plastic deformation will correct it during the first tightening.

 

[BrianPetersen]

This is safety-related. The rims are incorrect for the vehicle. Get correct ones. It is not acceptable for wheel bolts to have 3mm clearance around them.

Audi wheel bolts are commonly M14 R13 and that is probably what those rims are meant for.

 

[TugboatEng]

The bolts aren't body bound. The clearance should have zero impact on performance.

 

[BrianPetersen]

I'm more concerned with the reduced clamping area due to the smaller remaining clamping area due to the oversized holes, plus the ball-radius doesn't match. It looks like the combinations that exist are M12 R12 and M14 R13, with the car originally equipped with the former and these wheels being designed for the latter.

This is not a place where you want to expose yourself to liability - be it a failed MoT inspection, or heaven help an inspection by investigators subsequent to a crash or other incident.

I still say, get the correct wheels for the vehicle, which won't have this issue.

 

[TugboatEng]

Having been a child of the '70's vicariously through my parents I am well versed in the "MAG Wheels" (shoulder lugs with flat washers). OP's situation is already infinitely better and the mag wheels were already good enough.

 

[MBGraham]

Thanks for the input so far!

In buying these rims, I bought ones that were supposedly replicas of the OE rims, but as it turns out, they are not. The only "correct" rims for the car would be from Mercedes. They would cost several times the value of the car! I do still have a set and in another post asked about sealing them to eliminate leaks. These aftermarket rims use the same tire size and were specified as being suitable for my car. As such, I could switch back to OE later.

The bolts are 12mm diam. The rims have R13 seats and 15mm bolt holes. Nothing can be done about either.
Bolts are available with R12/R13/R14 radius heads.
I was provided with R12 head bolts.

As Brian mentioned, the combination of oversize bolt hole and incorrect radius head mean that the bearing surface on the rims is very small and near the edge of the bolt hole.

I was at first told R12 bolts in R13 seats would be OK. Probably true, but with the 15mm bolt holes, perhaps not?

I can't easily return the rims. I would like to make them work, at least until I am sure the OE rims are properly restored. Choices seem to be:
- Use as-is ????
- Get R13 head bolts (hard to find in 12mm diam and 26mm length)
- Add a sleeve around the bolt shank (would reduce deflection if rim/hub was to move)

As I understand it, the mechanics of this are:
- Rims are prevented from moving against hub by friction between the respective faces.
- The bolts are torqued so that the friction is sufficient to prevent movement during, for example, hard braking.

The OE design had 0.5mm radial clearance between bolts and rim holes. So some clearance is tolerable. I have 1.5mm clearance.

 

[MBGraham]

I found these bolts from a Japanese company. These are R14 with 12x1.5 thread, so not correct for my needs. But if R13x 12x1.5 bolts were available, the concept seems like it might work with my rims.

 

[MBGraham]

I have had some discussions with the rim vendor. This is part of what they said:

As for the lug hole size of 15 mm, this is to accommodate the later generation Mercedes-Benz models which as of 13-15 years ago all switched to 14x1.5 mm bolts. For this reason virtually all wheels sold for your vehicle today have this same lug hole size, however in our case it's important to note that we have performed full SAE J2530 testing for both Radial and Axial fatigue with 12 mm hardware and the torque retention remains consistent even after 1,000,000 cycles, so you can be confident that this is a safe combination.

This is presumably when using the bolts they recommended which were M12x1.5 26mm with R13 to match the rims. Not what they provided! I received R12 heads and 29mm long bolts that I had to cut down.

If I can get R13 26mm bolts, I think I will feel safe given the testing they say they had done.