Shavarsh
Shavarsh Reader
5/4/22 3:33 p.m.

Hello All,

Backstory:

I plan to build some control arms to replace my front pinto spindles with na miata spindles. If you aren't familiar with The Bean, it is my v8 pinto with an na miata rear subframe, control arms, and knuckles. I'd like to replace the front spindles with na/nb miata spindles to gain a slightly larger disc, more pad options, and a matching 4 lug bolt pattern. The spindles are remarkably similar and I'd like to maintain the front geometry I have with the current spindles. One difference is the miata spindle is slightly shorter than the pinto spindle (ball joint to ball joint). My solution at this point to this is to use a tall upper (or possibly lower, need to measure more accurately) ball joint.

 

The Question:

I will be using common circle track ball joints (at least for the upper) to ensure I can get cheap ball joints in a range of heights. The miata spindles will be reamed to match the selected ball joints My initial impressions after a bit of exploration points me toward using a 10 degree bolt in ball joint. So 2 questions: 

  • Does anyone have a preference for screw in type or 7 degree joints instead of bolt in/ 10 degree? Why? I do not plan to consider press ins at this time.
  • Does anyone have a 10 or 7 degree ball joint reamer that I can borrow (or buy from you)? The reamers are fairly expensive and I don't anticipate using it enough to buy new.

 

Any knowledge on the topic is appreciated. Here is an obligatory picture:

 

Driven5
Driven5 UberDork
5/4/22 4:27 p.m.

I'd be less concerned with taper angle than amount of material removal required. I believe that the Miata is a 7* taper. So depending on the diameters in question, sticking with the same taper *might* help in this regard.

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) PowerDork
5/4/22 6:00 p.m.

I've been a bit confused about this, and "just about" to do LCAs on a project of mine. I bought a 7 degree reamer that I'd be willing to lend you just to see your Pinto get a bit more awesome. I'm in East TN. You pay shipping both ways. 

Alternately, NOCONES set up his lathe to get the right taper. I don't suppose you could get access to one of those?

 

Shavarsh
Shavarsh Reader
5/4/22 6:53 p.m.
wheelsmithy (Joe-with-an-L) said:

I've been a bit confused about this, and "just about" to do LCAs on a project of mine. I bought a 7 degree reamer that I'd be willing to lend you just to see your Pinto get a bit more awesome. I'm in East TN. You pay shipping both ways. 

Alternately, NOCONES set up his lathe to get the right taper. I don't suppose you could get access to one of those?

 

That's a great offer wheelsmithy, thank you. It might be worth switching to a 7 degree taper to take you up on it. Let me nail down my plans before I ask you to ship anything.

The advantage I can see of the 10 degree is the smaller nut used (1/2 vs 9/16 for the 7 degree), and the cars that use 10 degree joints are newer (like the chevy s10) and might be more flaps available for emergency spares in the future.

I'm interested in the lathe setup suggestion. I do have access to a lathe but I'm not sure that I will be more accurate than a simple ream.

Shavarsh
Shavarsh Reader
5/5/22 5:09 p.m.

Can someone link me to NOCONES lathe solution? Or... does anyone have a 10 degree reamer?

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) PowerDork
5/5/22 6:07 p.m.

In reply to Shavarsh :

Cool, man. He didn't go into too much detail, but it is somewhere in his 2020 Challenge build. Maybe google setting up a lathe for a taper? Some have taper attachments. Unfortunately, I'm not good enough to give any advice. 

Shavarsh
Shavarsh Reader
5/5/22 11:44 p.m.

Wheelsmithy, you have mail. 

 

After thinking a bit more about it if I use a 7 degree taper I can match the taper of the miata ball joints, and the upper and lower pinto ball joints. While this may seem like an obvious choice it's taken me awhile to get here. The immediate benefit is being able to mount the miata spindles to the control arms already on the car. This should make it easier to determine if a different height ball joint is neccessary before needing to build control arms. There are enough 7 degree options that parts options/availability should not be a problem.

Shavarsh
Shavarsh Reader
5/23/22 4:29 p.m.

Hello All,

Here is some follow up information to complete this thread if someone needs it in the future. After deciding to use 7 degree ball joints I used the Howe site to cross reference pin heights/tapers/mounting style and standard "moog" part numbers. I came up with three main types I was interested in using for uppers:

From left to right: K5108, K772, K727

The K5108 is bolt in and uses a 1/2" thread, this was my first choice.

The K772 is thread in and uses a 9/16" thread.

The K727 is a thread in and uses a 11/16" thread. This ball joint is HUGE and will not work for my application.

 

Huge thanks to Wheelsmithy for lending me his 7 degree (1.5" over 12") reamer. Here are the results of reaming with a hand drill in the garage:

You can probably tell that the taper is far from straight. Unfortunately that meant I needed to straighten the taper necessitating the move to the larger K772 style joint.

This style joint is available from speedway in a few lengths for a reasonable price or from Howe/QA1/(I'm sure others) at many different lengths for more $$. For now this project will be shelved for a bit to focus on more pressing projects, but the information might be helpful to some of you. The most useful thing I found was the ability to cross reference between "moog" style ball joint pin heights using the Howe site. Thanks again to Wheelsmithy!

 

 

 

 

gumby
gumby Dork
5/23/22 5:14 p.m.

Saved for later, thanks for the follow up!

I played this game a little, with Toyota uprights and circle track arms/joints on my truck. If I need to revisit, the Howe info will be quite useful.

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