The *official* HR disc brake conversion thread

Brakes discussion.

Re: The *official* HR disc brake conversion thread

by Tuf064 » Tue Jun 09, 2009 6:53 pm

well i can get hold of some HR rear drums for $44 each for second hand ones. were the drums themselves all the same or were they different whether disc or drum front? the guy who has these drums says they are all the same.. cylinders and shoes are fine, have both of those at work :)

just need the confirmation before i go ahead and buy the drums.
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Re: The *official* HR disc brake conversion thread

by utility8 » Thu Dec 10, 2009 5:02 pm

For those that are interested in the theory of Front Rack versus Rear Rack on HR Front End conversions.

I have added this information about The Ackerman Principle to allow quick & easy searching.

Read on, it is well worth it.

If you follow how it works, then consider using a front rack on a frontend designed for a rear link assembly, such as a HR unit.

The outer tie rod ends will need to be where the front tyres are. Can that be done?

No, it can't.

Images 3 & 4 are typical of the problems created by a rack mounted to the front of a HR front crossmember.

Image 3 is what you have with a front mount rack.

Image 4 is what you get when trying to steer.

Image 5 is what you are unable to achieve as the front tyres are in the way.

As I said in my previous post, I have a HR cross member in an EH with a front rack. 23 years of it. It is a compromise at best. The geometry is not right & really, with what I now know, should this design of steering modification be able to be legally registered?

This information below was sourced from the following link.


Maybe this will help some of you guys to understand the Ackerman principle and how it affects T-Buckets. The basic theory is that the front wheels of a 2 wheel steer vehicle with the steering on the front should remain tangent to the turning circles of each individual wheel. It is theorized that the center point of these circles falls on a line that is the same as the centerline of the rear axle housing projected out into space. The center of the both arcs is at the same point on the rear axle centerline. That centerpoint slides along that line as the amount of steering input is changed. In other words, on a small amount of turn the centerpoint is way out there, in a hard turn the center is closer to the car. In the straight-ahead position the centerpoint is at infinity. That's way, way, way out there! It's time for a little drawing to keep from confusing you with this attempt at an explanation.

As you can see, the left wheel turns on a shorter radius circle and needs to turn sharper than the right wheel to remain tangent to its turning circle. Why do these wheels need to stay tangent? That places the least amount of side loading on the tires and suspension components. In other words tire and parts wear is going to be minimized. How do we get the geometry such that this desired effect is achieved? Fortunately Mr. Ackerman came along and figured out that if he arranged the mechanical parts of the steering system so that the pivot points of the linkage (tie rod) that connected the two front wheels were closer than the pivot points for the front wheel mounting assembly (spindles with their kingpins), it would affect how the wheels reacted when turning was occurring. He apparently noticed that if he made these points such that if you drew a line from the center of the kingpin to the center of the rear axle housing and placed the tie rod ends center on that line, it would give the desired change in the angles that the two wheels turned. Old Mr. Ackerman found that he had a principle that applied universally. I bet he was pretty proud!

Time for another illustration. O.K., automobiles steered fine and everyone was happy. And along comes Joe Hot Rod and he decides that his heap needs to be nice and low. Hey, no problem. Let's move the spring back behind the axle and down nice and low. Looks great, in da weeds! Oops, small problem, no place for the tie rod to run back there. Imagine that you can see a "great idea" light bulb over Joe's head. Hey that's easy, just swap the spindles side for side and put the tie rod on the front. Look, the wheels still are connected and turn when you give the steering wheel a twist. That will cure all of my problems.

Well not quite Joe. You have just wiped out Mr. Ackerman's principle. Your tie rod attachment points (tie rod end or heim joint) no longer fall on that imaginary line. So what happens now? Well, either the inside wheel does what it is supposed to do, or the outside wheel behaves correctly, but not both at the same time. So now old Joe has that nice set of new high dollar tires grinding themselves up on the local asphalt every time he goes around a corner. The car also has a tendency to get a little quirky because the wheels can't make up their minds which one is going to be in charge of where they are going to point.

Is old Joe just screwed on this deal now, stuck with this problem? Nope! He just needs to get those pesky attachment points back over on Mr. Ackerman's imaginary line. It works just as well on a front mounted tie rod as a rear mounted one. Remember, Mr. Ackerman found out that it was universal. It depends on what he has for front-end hardware as to what he can do to correct this situation. Early Ford spindles with the built on steering arms can be heated and bent to get back out there where they should be. Just be darn careful doing it; if you don't know what you're doing find someone who does and have them do it. The aftermarket offers some parts that can take care of this problem. Sometimes special design parts will need to be made. A lot depends on the individual situation. Brake configurations (calipers and rotors mostly) can create some interesting obstacles. If you can't get out there where Mr. Ackerman says you should be, at least get as close as you can.

Lo and behold, old Joe made the changes and guess what? His lo and in da weeds bucket is cruising along life's highway is fine style. Tire life is improved, steering is less quirky (still needs a little work on the bumpsteer deal) and he is all smiles.

Well, old Joe is not alone on this deal, he's got lots of buddies with the same problem and they haven't done a thing about it. So what happens? Well they just go cruising alongof course they stop by the tire store a little more often than Joe and leave some of their hard earned. And they have to pay a little closer attention to where their missile is headed when all of the guys are out for a cruise and find that great little road with all of the curves that just beg for a guy to open it up just a tad.a tad? Yah right!

By George Barnes.
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Re: The *official* HR disc brake conversion thread

by driftdaddy [old] » Thu Dec 08, 2011 7:41 am

Hi Guys,
Please excuse my ignorance, but I am a complete novice when it comes to old Holdens. I have just rebuilt and installed a HR front end on my EH wagon, with LC rotors and calipers. I have just ordered the inner/outer tie rods, and drag link for the HR steering. My question is does the steering bolt up to the column the same way as the standard EH steering? I'm nowhere near the car and I only get to work on it on the weekends, so ducking out to the shed to look isn't an option. Any help would be appreciated.

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Re: The *official* HR disc brake conversion thread

by stork [old] » Thu Dec 08, 2011 8:28 am

You will ned to get a HR type drop arm to fit to the box,as EH EJ are dirrerent.The rest sounds correct mate.
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Re: The *official* HR disc brake conversion thread

by stitch [old] » Tue Apr 10, 2012 10:31 pm

Can anyone tell me what offset wheels I can use with a HR frontend
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Re: The *official* HR disc brake conversion thread

by dave63 [old] » Thu Aug 22, 2013 8:07 pm

Have a look at Hopper Stoppers website , they have good info on what fits what on early holdens
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