Any drawback to keeping the drum spindles on my 66 Valiant?

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Super Sleeper

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I will definitely be upgrading my front 10" drum brakes to disk in the future. It seems to me like the options for disk brake conversion seem to fall either into changing out the spindles to later model disk brake spindles or keeping the drum brake spindles with a conversion bracket to the caliper (Leed or Wilwood). BTW, I do plan to go with 4.5" bolt circle and 15" rims when I do the conversion. The thing I wonder about is the small upper ball joint used on the 66 and the larger upper ball joint used on later models.
I saw one manufacturer of tubular upper control arms that suggested that their big ball joint UCA can be adapted to the early drum brake spindle by reaming out the spindle (MagnumForce). Is this a legit, viable solution? Is there really any drawback to keeping the small upper ball joint? I'm not really stuck on the idea of tubular UCAs but just the question of any limitations of staying with the drum brake spindles and the small ball joint.

Thanks - Jim
 
Whichever way you want to go. The OE spindles are good.
 
I had my OEM spindles reamed. Bill over at RMS didn't seem to think that was any kind of an issue and he certainly knows his stuff.
 
Good words, thanks. Also for the referral to RMS. Always looking for more input and better questions to ask. I am so new to Mopar that sometimes I don't know what to ask!
 
Good words, thanks. Also for the referral to RMS. Always looking for more input and better questions to ask. I am so new to Mopar that sometimes I don't know what to ask!


I should clarify that bill himself reamed the spindles and powdercoated them for me.
 
Later model disc spindles and rotors will get you the larger bolt pattern and 1/2" right hand threads both sides. Aftermarket has a tapped bushing to fit your smaller ball joint to this larger spindle hole. Factory engineers determined the smaller ball joint to be adequate, so it was years into 2nd generation A-bodies before they were replaced by the larger ball joint in all builds.
 
You can ream the small ball joint spindle to fit the larger ball joint and fit BBP brakes / brake kits.
 
I never had a problem with the small ball joint A arms or the spindles.Maybe if you were Autocross racing.As said above, Chrysler had used that design for years.
 
I will definitely be upgrading my front 10" drum brakes to disk in the future. It seems to me like the options for disk brake conversion seem to fall either into changing out the spindles to later model disk brake spindles or keeping the drum brake spindles with a conversion bracket to the caliper (Leed or Wilwood). BTW, I do plan to go with 4.5" bolt circle and 15" rims when I do the conversion.

Thanks - Jim

When I did my conversion (15 + years ago ) to Disk Brakes ... the SSBC kit "required" the 10 inch spindles !!!! And the SSBC Rotors have Both Bolt patterns for the wheels... 5 on 4 & 5 on 4.5... and came with Both sets of wheel Studs ( 7/16 & 1/2 )
Since my 65 'cuda was a Formula S, it already had the 10 inch spindles... I did the install and have been totally happy with the SSBC disks... and NEVER a problem all these years !!!
SSB10.jpg


SSB23.jpg
 
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That SSBC set-up looks sharp, nice photos too. I hope they get their business straightened out. They've been a major supplier in the muscle car world for quite a long time.
 
Clifcuda65’s pictures tell a good story. Whatever brake setup you go with, mount the calipers on the rear so you have clearance for a front sway bar. The only drawback that I’ve experienced with the 73-76 LBP discs on an early a-body is the 5/8” increase in track width on each side. Dr. Diff has a really good deal on complete 73-76 disk conversions for about $450. Another option is Scarebird that uses your existing spindles while mixing readily available components from newer cars.
 
I have 9" drums on my Valiant. Been looking at the Scarebird kits for mine. I like how they use readily available late model parts.
 
I prefer the later 73+ spindles for the strength, they have more meat on them. I’m sure the early spindles hold up just fine as most of you have said. I guess the bigger bearings make me feel better, along with the large ball joint and having the easy parts availability at common stores
 
Thanks for all the replies. It seems that I have a lot of good choices. Good tips about overall track and sway bar clearance.
 
Dr Diff sells the ball joint that screws into the earlier UCA and has the larger stem of the 73 and later ball joint.
 
I've got the original set-up (drums) on my 66 Valiant. I mean I went thru and replaced everything, brake lines included front to back, but its still just the stock set-up and it stops great! I live in Minneapolis and routinely travel 35W and it stops no problem from 70mph. In fact it stops better than my Dodge Ram.
Why the need to change? Unless you're racing it?
 
I wouldn't use 9" drum spindles for anything. The small diameter lower ball joint bolts have been known to shear off, even Ma Mopar got rid of them well before getting rid of front drum brakes. The 10" drum spindles used different lower ball joints with larger ball joint to spindle bolts.

That being said- the later disk spindles use larger wheel bearings, which not only increases the strength of the spindle but increases the bearing surface as well, both are nice improvements. The larger upper ball joint is also a strength improvement. I haven't heard of a small upper ball joint failing though, so the added strength there really isn't a safety issue. Another thing to consider is that all of the factory engineering was done for bias ply tires. By the time the factory swapped over to using radials, they had already implemented the larger upper ball joints, thicker spindles, larger bearings, and larger bolt pattern with larger diameter studs. So while there are plenty of folks running converted drum spindles with disks without any issues, if you're going to say "they came from the factory that way" then you should consider the factory probably wouldn't have made them that way if they were going to have radials. Just food for thought.

As for the SSBC kit, I've never understood it. They're mostly just OE '60's Mustang parts, there's really nothing fancy about them. You can use the '73+ Mopar disk conversion just as easily and for a similar price, and all your parts are off the shelf. With SSBC out of business, there are some parts you either can't get or need to have modified to work.
 
I wouldn't use 9" drum spindles for anything. The small diameter lower ball joint bolts have been known to shear off, even Ma Mopar got rid of them well before getting rid of front drum brakes. The 10" drum spindles used different lower ball joints with larger ball joint to spindle bolts.

That being said- the later disk spindles use larger wheel bearings, which not only increases the strength of the spindle but increases the bearing surface as well, both are nice improvements. The larger upper ball joint is also a strength improvement. I haven't heard of a small upper ball joint failing though, so the added strength there really isn't a safety issue. Another thing to consider is that all of the factory engineering was done for bias ply tires. By the time the factory swapped over to using radials, they had already implemented the larger upper ball joints, thicker spindles, larger bearings, and larger bolt pattern with larger diameter studs. So while there are plenty of folks running converted drum spindles with disks without any issues, if you're going to say "they came from the factory that way" then you should consider the factory probably wouldn't have made them that way if they were going to have radials. Just food for thought.

As for the SSBC kit, I've never understood it. They're mostly just OE '60's Mustang parts, there's really nothing fancy about them. You can use the '73+ Mopar disk conversion just as easily and for a similar price, and all your parts are off the shelf. With SSBC out of business, there are some parts you either can't get or need to have modified to work.
That's pretty much why I asked - because of the tradeoffs you mentioned. This forum has a large number of people with the various disk brake upgrades running around putting miles on them, racing them, etc. I'd guess most are running radials and many with 15" (and larger) wheels and larger tires. So all the input is good!
 
That's pretty much why I asked - because of the tradeoffs you mentioned. This forum has a large number of people with the various disk brake upgrades running around putting miles on them, racing them, etc. I'd guess most are running radials and many with 15" (and larger) wheels and larger tires. So all the input is good!

Yeah the only ones I would absolutely avoid are the 9” drum spindles, but there are definitely people that are still using them.

I run 275/35/18’s, 13” disks and 1.12” torsion bars on the front of my car, so for my piece of mind I like having the 73+ spindles with the larger wheel bearings and ball joints.

If you’re already going to the 5x4.5” pattern, and you’re looking at going to tubular UCA’s, then the disk spindles are only going to add about $150 to your upgrade. No reaming drum spindles, bigger wheel bearings, all the goodies. And there are disk kits for those spindles. If you’re going to run 15” wheels, you could also consider using the 11.75” disk set up that came on the later B/R bodies. I ran those disks on my Challenger when I was using it as my daily, and even with 275/40/17’s those brakes could really haul that thing to a stop. DoctorDiff sells them as his “stage 2” kit.

Are tubular UCA’s totally necessary? No, you can get by with a set of the offset upper control arm bushings in the stock UCA’s. But that will limit the amount of positive caster you can get, which may be significant depending on your cars set up. The other thing is that you can still get the QA1 UCA’s with a small ball joint, part #52303. So you can go tubular and keep the small ball joint if you want.

For me I just don’t see spending all that money and not upgrading to the larger ball joints and spindles. Also, do look at whether those brake kits are compatible with your wheels. The Wilwoods in particular now have a very large hub, and require the wheel to have a 3.050” hub bore. Not that many wheels actually meet that spec, it limits your choices significantly.
 
For me I just don’t see spending all that money and not upgrading to the larger ball joints and spindles. Also, do look at whether those brake kits are compatible with your wheels. The Wilwoods in particular now have a very large hub, and require the wheel to have a 3.050” hub bore. Not that many wheels actually meet that spec, it limits your choices significantly.
I had not realized that! Kind of defeats the purpose of having drillings for both 4.0 and 4.5 BC doesn't it? I was looking to use the Wheel Vintiques 69 series Police wheels but also capable of fitting the my Formula S 14" OEM wheels (for shows). I am not looking to build a g-machine but maybe have a little time doing open-track. But in any case I was going to stay around 11" rotors. I like the 4-piston calipers and have a pair of K-H calipers in the box. That's why I was also looking at Leed. I ran K-H on my Boss 302 when I was open tracking it.

Do all the later disk spindles add the same amount of track width to the front end versus the earlier 10" drum spindles?

Thanks again - Jim This is what I have now:
49172894221_348599d553_n.jpg

49172413238_1012b3992e_n.jpg
Valiant 96_2 by Jim Harris, on Flickr
 
Yeah the Wilwoods won’t work with any of the original SBP wheels. Or even those police wheels.

I think Leeds picked up where SSBC left off, that would be an option. Obviously the drawback there is the company went out of business once already. But most of the wearing parts are just mustang parts. The rotors are modified but with the number of miles most people drive these cars one set of rotors might be all you need anyway. Maybe two?

All the 73+ mopar disks widen the track the same amount, the 10.95’s and 11.75’s are the same there. Both would make them wider than it is now with the 10” drum spindles. But the hub on those would be too big for your original wheels. They would work fine with the police wheels though.

You could also look at scarebird, they have kits for the 10” drum spindles. I don’t know a ton about those conversions other than they use Toyota rotors but I know some of the earlier rims fit. You’d have to have the SBP drilled into the hub though.

There’s also the MBM kit, it’s just a 73+ mopar disk set up but they turn down the hub some so the earlier mopar disk wheels fit (not enough meat to take out for the drum wheels) and have the rotor blank drilled for SBP. You could have those mods done at you your local machine shop. I thought DoctorDiff mentioned somewhere about doing something similar, maybe that was a rear disk set up.
 
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