HQ Stub axle

[merce36]

I have a FC Wagon with HR front end and I would like to put HQ stud pattern. What exactly do I need to do? Any help would be appreciated. Diff is not an issue.
Cheers
John

[FC427]

Just bolt them on  ......FC427....

[FCRB26]

That just about sums it up whole stub axle brakes the lot bolt on and run your original steering arms if you want.

[NosFEratu]

The 14" spindles (hk to wb) are different in two aspects to the 13" spindles (hd hr).  The axle and steering arm location are moved up 20mm on the spindle.  This in effect provides a factory 20mm dropped spindle.

Much more importantly if you just swap over the hr steering arm on to the later spindle the tie rod is moved up 20mm as well.  This could lead to significant bump steer to say the least so be careful. 

Alfred

[FCRB26]

I dont think 20mm is going to make much difference especially when just about everyone with a modified fe fc  has lowered it at least 2 inches plus doesnt that do the same thing?

My FC was lowered at least 50mm and i didnt notice a difference?

[NosFEratu]

Sorry but I may not have made it clear in my post.  I was not referring to lowering the car as this is a very common and generally safe practice.  My concern is about bolting on standard hr steering arms on 14" spindles. 

Steering geometry is particularly sensitive to the height misalignment of the tie rod ends which can occur either through changing steering arm location or drag link/rack height.  Even a 5mm change can make a huge difference in bump steer so 20mm will definitely change bump steer.

Before I put the rack and pinion on our van it already used 14" spindles but it used hk steering arms which make up for the change steering arm location.  This combination seemed to work well although I didnt check it with a bump steer gauge.

As an example of bump steer there is a "kit" (tie rod end taper sleeves) available to fit xb falcon spindles to a xm xp falcons.  The only problem is the steering arm height is 20mm different between the two models.  While it looks wonderful bolted on they are unsafe to drive.

One of these conversions was my first real experience in bump steer 25 years ago. Took a mates V8 fishop falcon for a drive and nearly killed myself.  I hit a pot hole with the right hand wheel and the whole car lurched toward oncoming traffic.  Nearly shat myself.  Couple of minutes later the same thing happened on the other side.  I slowly took the car home and kindly told him what I thought.

When I started building/modifying front ends and steering I built a bump steer checker.  In the last couple of years I have built a laser bump steer gauge at a huge cost of about $10 (depends on how cheap you can buy the laser key ring). This is the same design as the ART Laser Bump steer gauge which is about $300.  Just do a google on that it will come up.

I am not saying we should not modify things (I am all for it) just that we have to be careful when we do.

regards

The Butler
     

   

[jasonr70002]

So are you saying to fit HK,T,G steering arms or HQ etc to rectify this problem so we can avoid this issue. I for one would like to know as I was going to do the same brakes.

[NosFEratu]

I wouldn't fit HQ steering arms as they are completely different. 

I recommend the use of HK/T/G steering arms to minimise bump steer issues - they can be used with HQ brakes.   

Regards

The Butler

[jasonr70002]

How can the issue be eliminated rather than minimized or is it impossible to do so.

Jason

[NosFEratu]

I am not sure how much bump steer exists in standard fe/fc but most cars have some from the factory.  The worst Australian car from the factory I know of was the VB to VK Commodores.  Their bump steer is around 25mm over the entire suspension movement.  Similarly 65/66 Mustangs had about the same.  In SA the Transport authority uses the Commodore as worse case scenarios for people building kit care or doing left to rights 

Ideally bump steer should be zero but this is rarely the case.  Even changing the static wheel alignment can have an impact.  EG changing caster will alter the height of the steering arm and therefore the outer tie rod end.  Even lowering the car can have an impact as that may put the normal range of suspension movement into the range the manufacturer didnt care about.

As an example we bought a beautiful 65 Mustang Fastback converted to rhd.  When I tested the bump steer it had 75mm change in toe over the complete range.  In examination I found the guys who assembled it had used those taper adapters between the tie rod and steering arm.  Funny thing this car had no need for them but what they did do was change the tie rod height by about 5mm.

After I removed them the bump steer came down to about 30mm which is getting close to original lhd.  From the bump  steer pattern on my graph I new I need to get the out tie rod end down a few more mm.  So I increased the positive caster from 1 - 4 degrees.  This moved the tie rod enough to end up with about 4mm change in toe with most of that happening on full droop.  After that it drove fantastically.

It is easy to measure bump steer. There is plenty of info on google or in books.   The biggest issue is removing the spring and shocker and making or buying a gauge.  Put aside an afternoon and you will be fine.  Dont expect perfection on street car but remember many mods can make it worse.

regards

John   

[NosFEratu]

Just got out my trusty genuine holden manuals for HR and HK and had a look at the steering arm drawings for both models.  The drawings show the hk steering arm tie rod location is 0.8" lower to the ground than an hr which is about 20mm.   This makes up for he raised streering arm location on the hk-wb 14" spindle.

This indicates the hk-hg steering arm on the 14" spindle emulates the steering geometry of a standard hr.  Hope this is of some help.

regards


John   

[jarred]

this has been so useful to me,have had massive problems trying to get a hold of hr disc brake stub axles at a reasonable price so hq is by next best option,knowing this has prepared me for finding the hk steering arms... thank you kind sir!