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Discussion Starter · #1 ·
So a while back I ordered and installed this roll center adjustment kit, with a set of uprated ball joints: Link
I recently took my car to get an alignment, only to be told it could not be done because the ball joints were not seated correctly. Now, there are two different options for ball joints, and I'm wondering if I have the wrong set...

The site says to check the last 6 digits of the VIN to determine which ones are needed. My VIN is YV1MK672682047114. Unless I'm reading something wrong, that places me into the 18mm ball joint group, which is what I believe I ordered (no longer have the receipt, it's been over a year since I bought them).

This brings me to my current dilemma... not only am I now unsure of which ones I actually need (I'm assuming I probably need the 21mm, despite the VIN check saying otherwise), but I also cannot find any of these uprated ball joints that are available. Any advice on how to know for sure which ones I need, or where I might be able to buy some?

Thanks in advance 馃檹
 

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2007 S40 2.4i / 2007 C70 T5
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Your car is a 2008, I'm pretty sure it has the 21mm design. As far as I know, the ball joint that volvo calls "18mm" was used until around 2005/2006 model year vehicles (S40/V50 and the first year C70). The first C30's were launched in 2007. And for example, I have a S40 and C70, both 2007 model year and both have the 21mm design.

For some reason, volvo and aftermarket companies call the same ball joint with different sizes. Some aftermarket companies use the top of the cone to measure the size, whereas volvo uses the base of the cone to do so.

Here's a picture where I described the size differences:
(BTW, TRW JBJ740 is a volvo "21mm" ball joint.)

 

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Discussion Starter · #4 ·
You know... it didn't even occur to me to rip one of them out and break out the calipers to take some measurements. If the weather allows it, I'll do so tomorrow.

It's pretty aggravating that ALG suggests the wrong size... oh well, that's life I suppose.
Thanks for the TRW part number. I'm gonna call Hardrace tomorrow and see how long it'd take to get another set from them (they are supposedly stronger than OEM), but if it's gonna be a while I'll grab the TRWs 馃檹
 

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Here are more part numbers for 21mm ball joints:

  • FoMoCo 3M51-3395-BC (Genuine, but AFAIK, is not sold separately. And, it's a TRW ball joint)
  • TRW JBJ740 (OEM - Same as genuine)
  • Lemforder 31350 01
  • Febi Bilstein 30380
  • Meyle 716 010 0017 / MBJ0291
  • Delphi TC1971
  • Import Direct BJ14057 (O'reilly's)
  • MAS BJ45235
 

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Discussion Starter · #6 ·
Welp... woke up to an inch of snow on the ground, so I'm not going out to take any measurements today, haha.

Called Hardrace... they said they'd have to order some from Taiwan and it'd be a 4-5 week minimum. So I ordered a set of Delphis on Amazon, and they should be here within a week (and it should be easy to return them if needed). Will update when they're here and on the car. Thanks for all the part numbers Facusan, major major help, and likely saved me from buying a new set of swing arms馃檹
 

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I hate to be the bubble burster, I wanted a solution like this as well, but ball joint spacers like that don't actually impact roll center. Roll center is based on the pivot point, which those do not move.

 

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Welp... woke up to an inch of snow on the ground, so I'm not going out to take any measurements today, haha.

Called Hardrace... they said they'd have to order some from Taiwan and it'd be a 4-5 week minimum. So I ordered a set of Delphis on Amazon, and they should be here within a week (and it should be easy to return them if needed). Will update when they're here and on the car. Thanks for all the part numbers Facusan, major major help, and likely saved me from buying a new set of swing arms馃檹
Facusan is good people.....
 

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I hate to be the bubble burster, I wanted a solution like this as well, but ball joint spacers like that don't actually impact roll center. Roll center is based on the pivot point, which those do not move.

geometry.......suspension geometry.........suspension geometry based on what you want out of the car........educate yourself you must
 

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Discussion Starter · #10 ·
I hate to be the bubble burster, I wanted a solution like this as well, but ball joint spacers like that don't actually impact roll center. Roll center is based on the pivot point, which those do not move.

Well... that's simply not true.

Slope Triangle Parallel Font Diagram


To find the roll center, you first need to find the instantaneous center, which in this image is the intersection between the two dashed lines. The top line is drawn at a 90 degree angle from the centerline of the strut starting at the top mounting point, and the bottom line is drawn through the angle of the control arm. It is true that changing the pivot point of the control arm will move that line, but so does moving the other end. Lowering a vehicle will raise the non-pivoting end of the control arm, using a spacer helps push it back down closer to the stock height/angle.
 

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But both ends of the arm are a pivot point, no? I'm far from an expert, but Google around some, I'm not seeing any evidence that supports what you're saying.

Think about it, if it wasn't about the pivot point, what would happen if your control arm was shaped like a piece of macaroni? "~" The line they're drawing in that diagram is along the arm because the pivot points happen to be at both ends of the arm.
 

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So a while back I ordered and installed this roll center adjustment kit, with a set of uprated ball joints: Link
I recently took my car to get an alignment, only to be told it could not be done because the ball joints were not seated correctly. Now, there are two different options for ball joints, and I'm wondering if I have the wrong set...

The site says to check the last 6 digits of the VIN to determine which ones are needed. My VIN is YV1MK672682047114. Unless I'm reading something wrong, that places me into the 18mm ball joint group, which is what I believe I ordered (no longer have the receipt, it's been over a year since I bought them).

This brings me to my current dilemma... not only am I now unsure of which ones I actually need (I'm assuming I probably need the 21mm, despite the VIN check saying otherwise), but I also cannot find any of these uprated ball joints that are available. Any advice on how to know for sure which ones I need, or where I might be able to buy some?

Thanks in advance 馃檹
Erpese? Cryptorchidism?
 
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