A Body or B Body spindles for front brakes?

[PeteBratt]

Well I have all the parts for the disc brake swap for my '69 Charger.  I have a set of B Body spindles and A Body spindles and can't decide which is a better choice.  Both spindles are from '73's.  This is what I have learned so far:

A Body:

Puts the caliper in the front (oppose to original, towards the rear)
Keep geometry the same

Question:  Can the opposite side spindle be used to change the caliper location: e.g. put the drivers side spindle on the pass and vice versa?
Will this affect suspension geometry at all?  It appears that the bolt and mounting locations are symmetrical for each side.

B Body:

Correct caliper location
'Can' lead to 'bump steer' (what is that exactly?)

I have heard from the local mopar guys, who have said to due about a dozen of these swaps that they will work just fine.
Question: is that so?

I have a set of both spindles all sandblasted and ready to be powder coated as soon as I can make up my mind which I should use.

Any help appreciated.
Pete

[rt green]

bump steer  is when you hit a bump and the steering wheel will dart to the left or right harshly. this  is easy to remedy. what you have to do is correct the height difference on the center link by making sure the center link is exaclty horazontal.  why they say that the brake calipers on the wrong side causes this is beyond me which ever spindles you do not use, i would be interested in them.    bruce

[PeteBratt]

Well I just found a large link regarding this debate, seems I am not the only one who is curious on this issue.  What actualy happens is the B Body spindle is 3/8" taller and increases the 'toe in' which, under large suspension travel, produces bump steer. 

I would like to talk to someone who has done the  A body swap and the B Body swap....

Does anyone notice your calipers in the front?  Does the caliper hit the sway bar or steering knuckle (w/e it is)?

[andyf]

Either knuckle will work and you can mount the caliper to the rear or to the front with either knuckle.  Rear hanging the caliper makes the brake hose routing a little tricky so you'll most likely need custom hoses.  But custom hoses are really no big deal if you have a local supplier who can make them for you.

The taller knuckles change the camber gain on the suspension and raise the roll center.  Both of those changes are probably a positive but it all kind of depends on your ride height. 

I recommend the taller knuckles for my 13 inch brake kits and we rear hang the calipers.  I recommend the use of Firm Feel upper control arms when using the taller knuckles.

[is_it_EVER_done?]

Personally, I only use the taller spindles, and recommend them to anyone that asks. they allow a bit more adjustment than the "correct" units, and allow you to achieve more positive caster without sacrificing camber adjustment, which translates to a handling improvement that you can feel.

The missinformation on the differences is ridiculous. The M.A. article is good for providing pictures, and other factual information on specific components, but unfortunately Ehrenberg made some extreme statements in his original article (which you WON'T find on the MA website), and rather than admit that he was wrong, he continues to make claims that have been proven incorrect by engineres, user testing, and many millions of miles of flawless use by hundreds of thousands of users. On the plus side, he softens his claims with every article revision so more and more people are making the change (and enjoying the benefits), but you still get the people that (since they read it once) will continue to state on all the Mopar boards that it is dangerous or even lethal, even though they have zero experience or testing with the conversion.

I have been doing the "tall spindle" single piston upgrade since the spindles/brakes first came out, and have done the conversion a couple of dozen times. In addition, I have done the A body spindle changeover roughly 8 times over the years, and have also done several SSBC, Master Power, and Scarebird changeovers for others. Keep in mind that I don't just bolt everything together and say "Done", I do test through the full range of suspension travel (even more so, as I check with the suspension bumpers removed).

Some things I can state as fact are, #1.  the upper ball joints cannot reach their travel limit with the tall spindles and no stops installed (I have only tested this with Moog as they're the only one I will use, or allow others to use if they want my help, so I cannot guarantee this with cheepy replacements), #2. I have never seen any change in "bump steer" between the two spindles as measured by "tire store" alignment equipment. -- If there is a change that can be measured by lazer equipment, it is meaningless. -- In other words, if you don't have any bump steer now, you won't with a spindle swap to the taller units. #3. There is no good reason to forward mount the calipers .  Rear mounting them allows you to eliminate sway bar interference problems., Use the 73 Charger brake hoses for a perfect fit, plus you shift over 25 pounds of unsprung weight further back. -- I personally have never seen the statement that rear mounting calipers will increase bump steer, but I guarantee you it's wrong if it has been said as posted earlier. In addition, forward mounting extends the length of the brake hose, and the fact that it must pass through the suspension, puts it at for more risk of abrasion/failure than rear mounting.

The point of all this is simply, -- use whichever spindles you want. -- The taller ones allow more adjustment for dialing in your suspension for todays tires, shocks, and road surfaces, but if you have any concerns, the shorter ones will be fine. I've been thrashing these cars for over 35 years, and am one of the last people that daily drive these cars (25,000 + per year), I put myself, family, extended family (grandson), and dog in the cars with the tall spindles/ FMJ brakes, and can assure you that I leave nothing to chance or untested. I would not make the suggestion otherwise.

You can sell the A-body spindles for enough to make all the other upgrades free. Plus you can feel good about it by knowing that you are not putting the buyer in danger. Of course if you decide to use the A-body units, you can sell the B units, and  still know you are not putting anyone in harms way.


Off subject. ANDYF, You state that the tall spindle has handling improvements, but recommend the aftermarket upper controll arms with it. I have never used the aftermarket upper arms, but I would appreciate it if you would explain how these are an improvement. From looking at the FF website, I am left with the impression that it is designed to "eliminate" the pluses of the tall spindle by re-creating the the stock geometry, which I assume eliminates the camber improvement with it's related potential improvement in caster. Can you explane further? Thanks.

[Lightning]

AndyF: on that Coronet y'all did with the Viper brakes, is it possible to use a 11" rotor instead of the 13" one?  Also, would one have to use the 12" rotors to fit the Viper's rear brakes?

[bull]

I went by this: http://www.moparaction.com/Tech/archive/disc-main.html but I've heard so many people say they haven't had problems with the '73-up B-, R-, F-, J-, and M-body spindles that I wouldn't worry about the spindle center height. The article I linked warns against using anything but the '73- '76 disc-equipped A-body cars and it also warns against swapping the spindles side to side, but I ignored that one and obeyed the first.

[andyf]

The tubular upper control arms give you the improved camber gain of the taller knuckles but keep the upper ball joint more centered in its travel.  Also, it is nice to have new clean a arms rather than rebuilding old rusty stuff with stripped out threads.  Plus you get the increased caster.  I'm not sure if the aftermarket arms are lighter or stronger than the originals but the other reasons are enough for me.

Lightning - We do make a kit for putting early viper calipers onto the 11.75 rotors but you can't fit them on anything smaller than that.  I don't make a rear brake kit so I can't help you with your other question.

[Steve P.]

Andy, is that pic. of a 65' Coronet??

[andyf]

yes, the car with the viper brakes is my '65 Coronet 500.

[Steve P.]

Pics. man pics. 

[andyf]

You want pics of a Coronet on a Charger site?

There are a few pics of my car on my website in the gallery section.  www.arengineering.com

[Steve P.]

It's a MOPAR isn't it??

Look to the left..

[andyf]

Here she is on the chassis dyno.  474 rwhp thru the exhaust manifolds with an Edelbrock carb.

[Shakey]

Here she is on the chassis dyno.  474 rwhp thru the exhaust manifolds with an Edelbrock carb.

474 rwhp - That all!  Sounds like you better spend some time tuning it properly!   

Does your insurance cover "repaving" costs for the streets in your town?

[andyf]

Steve,  I'll answer your PM here since others also asked the Coronet.  Rear wheels are 17x10, fronts are 17x8.  Rear tires are 315/45-17 tires off of a McLaren street car.  Fronts in this picture were 235/45-17 but I've since changed to 235/55-17 since the 45 series tires were a little too small. 
Wheels are custom Fikse three piece.  The rears have about 7 inches of backspacing, the fronts are 5.72 BS which is a standard Mustang setup.  Rear is mini-tubbed with the springs moved into the frame. 
Front suspension is the tall FMJ knuckles with Porsche calipers and Mercedes 13 inch rotors.  Tubular upper control arms from Firm Feel with a custom tubular anti-sway bar and boxed lower arms.  Rear end is a stock B body Dana out of a '68 or '69 Charger hung on 3800 lb Super Stock springs.

[Steve P.]

Thanks Andy. I can't wait to see the car all done..    I'm lovin' it.....

[andyf]

Hi Steve, well I'm not sure it will ever be all done.  Mostly I just use it to test new parts so it isn't really a project car.  It is more like a test vehicle or an R&D mule.  If I put a $10,000 paint job on it then I'd probably be unwilling to thrash it so hard.

Here is a picture of it at the dragstrip.  I'd like to get it out to a road race track this year and thrash it around some corners.

[Steve P.]

Hi Steve, well I'm not sure it will ever be all done.  Mostly I just use it to test new parts so it isn't really a project car.  It is more like a test vehicle or an R&D mule.  If I put a $10,000 paint job on it then I'd probably be unwilling to thrash it so hard.

Here is a picture of it at the dragstrip.  I'd like to get it out to a road race track this year and thrash it around some corners.

Sounds good to me. Can I go with ya??

[andyf]

Sure but that is going to be a long tow from FL to Oregon.  I usually test parts at Portland International since it is a fairly fast track that is hard on brakes.

[Steve P.]

Andy, is the top center section of your core support removable?? I was looking at pics. on your site and it looks like it's got some sort of attaching bracket  one side..

[andyf]

Yes, I modified the core support so I can unbolt it when pulling the engine.  Makes it easier to drag the engine straight out the front of the car.