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Discussion Starter #1
i've just purchased a set of 18" mono block amg allows for our 1994 R129 SL320 mercedes
Unfortunately i haven't the studs to fit them to the car, is there anybody out there that could tell me the type bolt, diameter and
length that i require for these wheels.
I have contacted two mercedes benz dealers that can't help me with this problem.
 

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SL's & 500E's
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Easy one if you tell us (or post a pic), what exact Mono-block wheels these are, there are many styles in 18", and several models that may not be compatible on a SL R129. There are 18" monoblock wheels for a w140 that can look identical to the similar SL wheel, but they won't fit right.

First of all, look on the back side of the wheels, cast or stamped into the backside are the 3 sizes of the wheels, and if staggered you'll need the numbers off the front and back. Front - 8Jx18H2 et31; Rear - 9J x 18H2 et 35 for example. Also look for part numbers that will identify the wheels. Look in this link, do you see your wheels here?


Actually the lug bolts from the stock wheels may fit. If you do have SL mono-block wheels. they most likely they will take 39 or 40mm length shanks, so here is a guess that can be firmed up when you identify the wheels.

12M x 1.5 R12 39mm

The above means;
  • 12M bolt diameter, (all R129's are 12M)
  • 1.5 thread size - (almost all MB's are 1.5)
  • R12 is the Ball Seat radius
  • 39mm is the shank (thread) length, base of ball seat to end of threads, Not the overall bolt length
By comparison, W140 wheels will take larger diameter bolts 14M 1.5 R14 39mm

Finally when you have confirmed that you indeed have SL wheels, you check the shank length needed with one simple measurement.

Take any old lug bolt you have laying around, if you don't have one, remove one from your SL.
Stand one of the wheels up and insert the test lug bolt into one of the sockets and hold it firmly in place with one hand.
With your other hand measure the length of threads sticking out the back side of the wheel. It should be between 17mm and 20mmm, roughly 3/4" give or take.

If your measurement is close to 3/4", then the test lug bolt is the correct length lug-bolts you need. If too long or too short, do simple math based upon the measurement you took. Would help a lot to have a scale in mm. If you measure 30mm for example, that means your test bolt is 10mm to 13mm too long, etc. so if your test bolt shank length was 50mm, subtract 10mm and you need 40mm shank length bolts.

If the mono-block wheels you bought are indeed R129 wheels, I'd bet the bolts on your stock wheels are perfect, but measure to be sure.

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Post back the sizes and part numbers on the back of your mono-blocks, and a picture will help as well.

I have a set of 18" AMG I's and AMG II's in the storage building, I'll measure what the bolt lengths should be for them tomorrow morning.

If you need to buy new lug bolts, the guys in the link below are the best, they have everything and will get you the perfect fit bolts..


Good Luck
 

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1999 E320, 2003 E320 Wagon, 2005 C230K SS, 2010 Accord LX w Eibach & Koni FSD's
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If your rims have 14mm holes, you can get 12mm adapter bolts with 14mm ball seats.
 

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I know, I have those custom bolts on my 2000 SL500, with R230 22 spoke wheels. But that's advanced stuff, he needs to identify exactly what wheels he has purchased for now, hopefully they are not S class wheels, the ET on W140 wheels will require spacers to fit on an SL if so. This happens more times than you would think, as S class wheels sell cheaper that SL wheels normally, so cheaper is better thinking kicks in. If you don't understand wheel compatibility, then you find out you need spacers and the extra long custom lug-bolts. Always better to buy wheels that don't need spacers, there are so many wheels that do actually fit right, you shouldn't have to buy non compatible wheels.

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2002 Black SL500, 2000 Azure blue SL500, 2005 Silver (A209) CLK500
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I purchased similar wheels...nightmare.
Shop made a big mistake...wrong lug bolts...backed out of the shop...rears locked up...studs were to long and damaged the emergency parking brake system.
Lesson learned.
Shop did repair the system and installed the correct lug nuts.
 

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Discussion Starter #6
i've just purchased a set of 18" mono block amg allows for our 1994 R129 SL320 mercedes
Unfortunately i haven't the studs to fit them to the car, is there anybody out there that could tell me the type bolt, diameter and
length that i require for these wheels.
I have contacted two mercedes benz dealers that can't help me with this problem.
Hi Folks, As you suggested Aero 1, have attached pics of the wheels. these wheels came off a R129 SL 500
 

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SL's & 500E's
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WOW, I would not have guessed you had these SL600 option 2 piece wheels, rare and expensive.. very nice find...👍

So all you need to do is just make that measurement I described earlier in this thread.

I actually have a set of these same wheels waiting to get repainted, stored in the shed. My set is going to be mounted on one of my 500E's.

If I have time tonight I'll measure the shank length for you as well, lets see if we come up with the same number, (still guess that 39-40mm shank length is correct).

But you have to measure, or you may end up with damaged emergency brakes as described in a earlier post.
The front wheel hubs are more forgiving, too long bolts on the fronts don't generally harm anything, it's only the rear hubs that are critical.

So less than 17mm is not good for safely attaching the wheel to the hub, and over 20mm may be in conflict with the rear hub emergency brakes.

So these are "12M x 1.5 R12 ??mm" (?? shank length), and will be easy to get lug bolts.

I'll post back tonight...
 

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My favorite all time wheels.. big thumbs up.... 👍
 

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Discussion Starter #11
Funny you should mention Aero 1 regarding back hubs and getting the correct length, as my mechanic who services my cars said the exact same thing about the emergency brake system.
I found the wheels in ebay here in the UK, been looking for a set of originals of these type for a while
now. When they were delivered and i opened the boxes they were perfect condition, i knew they
were good from the pics on ebay, but seeing was believing, however they'll look better on the car rather than in the boxes, lol. many thanks for your time and effort for your advice and info regarding the bolts.
 

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OK, I wasn't able to find my precision mm scale, and I couldn't find a spare lug bolt laying around, it's freaking cold out, and my furnace kicked off tonight, what a pain. Regardless I did find a small scale not exactly suited for this type of measurement, and I pulled off one of the lugs on our 94 E420 to use as a test bolt. The test bolt is 40mm shank length.

I measured both a front wheel and a rear wheel in the back of the shed with not a lot of light and was surprised to find the 40mm bolt too long. I measured several times with a scale that doesn't have the edge as the beginning and it appears that the gap from the edge to where the scale begins is about 1.5 mm roughly. My precision scale is metal, the edge is the beginning of measuring, and it has a sliding T that allows for real accurate measurements.

So all that being said, I do recall now that the lug bolts on some of the 129 wheels are shorter, haven't fooled with them in a long time. I found an old receipt for the custom bolts I bought to mount the R230 wheels on my SL, and they were 23mm, very short lug bolts.

But here is what I see at first glance. A 40mm shank lug bolt sticks out the back side approximately 28-29mm's, which is way too long. Again it was not ideal conditions to measure, and I was using a crude scale, but I'm fairly sure you could use 29mm or 30mm as the measurement, to be on the safe side.

So, the rule is to have 20mm max sticking out the back side, but it can be as low as 17mm. Using my measurements and simple math comes up with a shank length needed of 27mm to 30mm. The 40mm shank gives us a 30mm measurement, so 30mm shank should give us a 20mm shank measurement length we're looking for.

Looking on the Otisincla.com web site, they have two sizes that would work, based upon these preliminary measurements,. 28mm or 30mm


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I'll try to find my precision scale over the week-end, and measure outside in the daylight, even so I'd go for the 28mm bolts, puts you in the range comfortably.

This is great exercise for me as well, I'll need to buy new bolts when I go to mount my set of BBS's.

I'll follow up on Saturday with exact measurement, but I don't think it will change.

Later.. Aero_I
 

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I just took good measurements with a precision scale and in daylight, using the same 40mm test bolt. Both front and rear wheel measurements come out the same as they should, and the exact measurement is 28mm of shank sticking out the back side of the wheels.

So a 32mm shank length bolt would result in 20mm sticking out the back side of the wheel, a 29mm shank would give 17mm for a measurement, and a 30mm shank length bolt will give you an 18mm measurement.

Use either of these lengths you can find, 29mm, 30mm, 31mm, or 32mm, where 30mm may be more common, and the easiest to find.

So, look for "12M x 1.5 R12 30mm" bolts. Good luck, look forward to seeing some pictures of the wheels mounted.. Cheers..
 
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