Disk brake parts swap
- Thread starter Dart fan
- Start date
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goldduster318
Overzealous Car Modifier
Knuckles and brakes, yes, control arms no. You need either the ball joint adapters from Dr Diff or some 73-76 style upper control arms.
You would also want to use 73-76 A-body lower ball joints.
You would also want to use 73-76 A-body lower ball joints.
doogievlg
Well-Known Member
I just did this swap and this is 100% correct. My dart is a 73 so I used the same control arms and used the spindles and brakes off a 1980 volare. I had a major head ache dealing with this but inspect the spindles closely! One of mine was bent so after it was done and went to an alignment I found out it couldn’t get better than -2 degrees camber. Had to pay for extra spindles and then have the shop swap them.
doogievlg
Well-Known Member
Spindles and knuckles are the same thing.
Jarlaxle
Well-Known Member
They physically fit, but can screw up the geometry. The RIGHT knuckles/spindles are 73-4 E body and 73-6 disc brake A body.
They don’t “screw up” the geometry. This is BS that Ehrenberger threw into his “disco-tech” article a million years ago with no numbers or evidence to back it up.
Using the FMJ or B body spindles primarily does two things, it slightly increases bump steer, but also improves camber gain. More significantly than it increases bump steer.
You can actually see all that plotted out in this article Swapping Disc-Brake Spindles - Mopar Muscle Magazine
Because I run wide front tires (275/35/18’s) I actually prefer to use the FMJ spindles. The camber gain with wider tires is more useful than the small change in bump steer is detrimental.
Like everything in suspension, there are trade offs and how you use the car is important. But the FMJ and B/R body spindles don’t “screw up” the geometry. The change they do make is small, to the point that most probably wouldn’t even notice.
And if anyone agrees with Ehrenberger, I’ve got a set of 73+ A-body disk spindles I’d happily trade for a set of FMJ’s straight across.
I see your retaliatory red X with no supporting evidence and raise you a "Red Brick", which has done 160 mph down the back straight at Willow Springs with FMJ spindles. mopar handling
Do FMJ spindles change the geometry? Yes, absolutely. Do they "screw up" the geometry? No, they do not. The numbers do not lie, you can see exactly what they do for/to the geometry in the article I posted. A small increase in bump steer for a better camber gain curve, the latter of which is more noticeable with wider, grippier front tires than the small change in bump steer (which can be corrected out if you like). Like I said, it's a trade off. Suspension geometry is ALWAYS a trade off. But I'm keeping the FMJ spindles on my Duster, and the "over-angling" of the ball joints is straight BS.
The "right" spindles are the ones that work best with your set up. If you're lowered and running wide, modern compound tires, the evidence shows the FMJ's are the right choice. If you're running at stock height with skinny little BFG's, it's not gonna matter at all either way.
Do FMJ spindles change the geometry? Yes, absolutely. Do they "screw up" the geometry? No, they do not. The numbers do not lie, you can see exactly what they do for/to the geometry in the article I posted. A small increase in bump steer for a better camber gain curve, the latter of which is more noticeable with wider, grippier front tires than the small change in bump steer (which can be corrected out if you like). Like I said, it's a trade off. Suspension geometry is ALWAYS a trade off. But I'm keeping the FMJ spindles on my Duster, and the "over-angling" of the ball joints is straight BS.
The "right" spindles are the ones that work best with your set up. If you're lowered and running wide, modern compound tires, the evidence shows the FMJ's are the right choice. If you're running at stock height with skinny little BFG's, it's not gonna matter at all either way.
Dave999
Well-Known Member
Are the FMJ spindles taller?
i could see some benfit there... kinda like lowering your car without lowering it in rspect to the roll centre change you get. I think..... i may be wrong.
i could see some benfit there... kinda like lowering your car without lowering it in rspect to the roll centre change you get. I think..... i may be wrong.
Yes, the FMJ spindles are slightly taller. You can see that in the pictures from the article I linked
The article, which was written by Bill Reilly, does a great job at looking at the differences in geometry and breaking down the changes that occur because of that. Ultimately, the changes are VERY minor. Like the vast majority of people will never be able to tell the difference the way these cars are usually driven.
For most builds there is no reason to seek out, or avoid, FMJ spindles. At this point even the FMJ cars are not that easy to find in junk yards anymore, so a big part of the utility is gone. But I’m sure a lot of people missed out on a cheap disk brake upgrade because they bought into Ehrenberger’s BS.
I have the FMJ spindles on both my Challenger and my Duster, but part of that was that I was able to pull them from the local yard for cheap. I do run the wide, sticky tires that make their improvement in camber gain more relevant, so I will absolutely be keeping them for that reason. But if I had 73+ A/E spindles I wouldn’t go out of my way to convert to FMJ’s either.
Dave999
Well-Known Member
many thanks, i have now gone to the article.... can't get there from work PC due to some kind of dislike of my UK based address.... but i can from home.
@Old man ray ray. Maybe this thread will help.
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