R107 gen 2 upper ball joint compatibility - PeachParts Mercedes-Benz Forum

rwd4evr · #1 05-02-2022, 02:42 AM

I'm getting near time to rebuild/modify/improve the frontend in my 450slc drift car. I'm going with 560sl spindles and lower control arms for a few reasons.
1. The brakes are in the rear of the axle and I'll have more clearance with the front of the upper control arm.
2. The bigger r129 brakes I'm using push the caliper further away from axle center line for additional clearance at full lock
3. The brakes are pushed further out from the vehicle center line which is another win for clearance for increased steering angle.
4. The lower ball joint is a straight shank with clamp in the spindle so I can use a custom stud and mono ball lower ball joint with spacers to adjust the roll center without having to cut a taper and threads on it.

I'm extending the control arms 40-50mm per side for more inner fender/frame/subframe/swaybar clearance. I have the parts here but I have not dragged the donor 560 SL into the shop to pull it apart yet and I'm wondering if the upper ball joint stud is interchangeable between the Gen 1 and the Gen 2 spindles. Meaning can I use a bolt on gen 1 upper ball joint in the Gen 2 upper ball joint hole in the spindle? This will save me a bunch of trouble since I can just build a completely fabricated upper control arm using the correct bolt on Mercedes ball joint rather than cutting and extending the forged gen 2 upper control arm which is a non replaceable ball joint.

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Roncallo · #2 05-02-2022, 05:27 PM

I would be interested to know this as well. since 560SL upper arms are very expensive and have been in and out of the NLA list for some time now. Pretty easy to make your own control arms if you can get a compatible ball joint.

rwd4evr · #3 05-02-2022, 11:55 PM

Damn I was hoping you had the answer

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rwd4evr · #4 05-03-2022, 12:06 AM

Quote:

Originally Posted by Roncallo

I would be interested to know this as well. since 560SL upper arms are very expensive and have been in and out of the NLA list for some time now. Pretty easy to make your own control arms if you can get a compatible ball joint.

Do you have one off of a car to measure? I've got a bunch of gen 1. I measure this.

16mm = Top of taper in spindle hole

14.4mm = small end of ball joint shaft taper

14mm~ from small end to 16mm diameter up the shaft

Hope that makes sense.

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Roncallo · #5 05-03-2022, 01:03 AM

Quote:

Originally Posted by rwd4evr

Do you have one off of a car to measure? I've got a bunch of gen 1. I measure this.

16mm = Top of taper in spindle hole

14.4mm = small end of ball joint shaft taper

14mm~ from small end to 16mm diameter up the shaft

Hope that makes sense.

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I might have one off the car I will check tomorrow, which is later today. But it might be buried.

rwd4evr · #6 05-03-2022, 01:36 AM

Cool, that will be helpfull. I was just looking at some parts and I never realized how much longer the Gen 2 control arms are to the ball joint pivot point. I only have a r129 spindle to compare but it's the same as the lower half of the gen2 107. I knew the brakes were pushed out considerably but never realized the kingpin axis was moved so far. It's gotta be 35-40mm. **** I really need to get that gen 2 subframe on the table to figure out what I'm doing.

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rwd4evr · #7 05-03-2022, 07:38 PM

Damn. Just looked at the 560sl. The upper arms are about the same length but the lower arms are considerably longer. So the kingpin inclination is drastically increased in the Gen 2. Unfortunately that is the opposite of what you want in a drift car. The higher the KPI the more positive camber at full lock

guess I'm just extending the arms and using the Gen 1 stuff for now at least.

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eduardop · #8 07-18-2022, 08:14 PM

Very nice, so I can just build a completely fabricated upper control arm using the correct bolt on Mercedes ball joint rather than cutting and extending the forged gen 2 upper control

rwd4evr · #9 03-10-2023, 04:27 AM

Quote:

Originally Posted by eduardop

Very nice, so I can just build a completely fabricated upper control arm using the correct bolt on Mercedes ball joint rather than cutting and extending the forged gen 2 upper control

No. Unfortunately the upper ball joint is completely different on the gen 2. Tapered on a gen 1. You could find an upper bolt on ball joint from something else that has the same size straight shank as the gen 2 107 I would think.

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