Harrison wheel alignment

[Krait]

Originally Posted by sambo

Geoff, are those adjustable radius rods available off the shelf? I'm toying with the idea of adjustable top arms from Summit. The strut would need to be modified for a different ball joint so it's not a simple bolt in replacement.

Paul, Yep they are, Whiteline sell them for Commodores. They could only fix part of the problem on my car as the wheels ended up too far off centre in the wheel arch hence why the new top arms were required as well.

[sambo]

Same here Geoff, my wheels are a bit forward of centre in the wheel arches.

Craig, what do you mean by shock mounting alignment? I'm guessing you mean perpendicular to the mounting bolt when viewed from the side?

[muzzza]

Treeve,

Bump steer is physically designed into the system based on the location of the suspension pivot points and the rack. Lowering a car without physically changing these does not cause bump steer.

Technically you are of course 100% correct. Point taken. Lowering the entire subframe does not cause bump steer......... but in most cases it will exacerbate any bump steer characteristics, more to do with compromised pivot point arcs and resultant camber changes than anything else.

[400TT]

Originally Posted by sambo

Craig, what do you mean by shock mounting alignment? I'm guessing you mean perpendicular to the mounting bolt when viewed from the side?

Yes, that is it. Sorry mate if I wasn't clear. Cheers.

[sambo]

I got hold of some perspex and made the turn plates today. I was pretty happy when the caster measurement came up very close to the readings from the suspension place - see passenger side below.



Then I fitted the longer bolt to the front of the cross pin on the passenger side (see below) and managed to get about 4 degrees of caster but couldn't go any further as the shorter bolt was starting to bend.

I don't like the idea of tightening everything up at such an angle so I'm going to buy some adjustable top A-arms from summit and do away with the shims. Requires a new strut to accommodate a different top ball joint but it makes the whole thing a lot easier to adjust.

If you're wondering why on earth I'm going to so much trouble to achieve some fairly standard suspension settings - SO AM I!!

[Gav]

Hooly Dooly that is a lot of shims in there Sambo.
I wound up having to machine down the 'link' for the upper arms on mine to get some decent front camber. Worked really well, but shouldn't have required milling down parts I'd have thought!
The aftermarket Summit/FFR upper arms are very popular with the earlier CR guys too.

[Krait]

Paul, Be sure the Summit A arms can't hit the spring when you're attempting to get the castor right. Look at the ones I had made with one side curved to avoid the spring.

[sambo]

Thanks Geoff, that could be a problem with the straight arms. Might have to look at something like this http://www.summitracing.com/parts/sps-94800.

[Chris L]

G'day Sambo;
This may not be to relevant for you, but I'll throw it in anyway. I have a Python kit with the Jag rear (single shocks) and adjustable upper/lower front end front.
The car was all over the place alignment wise, particularly under acceleration, it wanted to throw you off the road between gears when you really got up it. I stuffed around with tyre pressures but it made no discernible difference.
I basically needed to start again and get a professional opinion to diagnose the problem. Shelbyfest was coming and I had no desire to go there the way the car was.
I went to Centreline Suspension (Chris & Glenn) in Thomastown on a recommendation from friends at FPR. The cars front rubber bushes were flogged out and the big problem was a rear half shaft bent about 4mm. This was supposedly modified and re welded in a jig when it was produced !!, so how it ended up out that far has me buggered. They fixed that, put Teflon heim joints all through the front and set the car at the following settings.

Camber- front negative 1.5 degrees per side/Rear negative .25 degrees per side
Castor -front positive 2.5 degrees
Toe - negative 1mm per side front and rear

It totally changed the car and I just could not believe the difference. The guys have their own track weapon and were extremely reasonable to me and I would recommend them for an honest diagnosis any day. They made suggestions for shock settings, spring rates, tyre pressures relevant to the car and they even set brake bias for me. Was the best money I spent full stop. They will do as little or as much as you wish, but are real helpful with there info and experience. Definitely worth a visit if frustration and results are lacking.

Apologies for the length of the post, but if there is any misalignment in the car, it can be bloody hard to find by yourself and you will never get the best from the car until that is all good.
All the best.
Chris L

[sambo]

Thanks for the info Chris, I might take the car there when it's ready for a final setup. Your settings are very similar to mine.

My Cobra is no longer all over the place, it's actually really solid now with a couple of "minor" issues - the wheels don't self-centre out of corners and in a straight line it darts around with the slightest turn of the wheel. I put this down to lack of caster (hopefully).

Those issues aside, I pushed the car through a few sweepers on the weekend and the cornering grip is phenomenal, body roll almost non existent. Can't wait to get out on the track.

[Gav]

Are you going to the nationals Sambo?

[sambo]

Unfortunately not Gav, I'll be Tassie during the first week of October.

[Gav]

What a bugger.

[sambo]

Gav, it gives you some time to get used to all that extra torque!

Following Krait's info on spring clearances I ordered these curved, adjustable top arms from Summit today.



Also heard through the grapevine that shortening the bottom control arm by 5-10mm improves the situation.

While we're at it, a couple of photos of a Skyline rear end with adjustable arms.

[Gav]

That's a nifty bit of gear Sambo.
Lots of adjustment there!

How is the top coming along?

[sambo]

The hardtop is on the list Gav. Probably won't happen before the interior is done - hard decisions to be made on colours first.

[400TT]

Sambo, just wondering why you haven't painted your diff centre. Just in case you haven't looked into it, have you thought about painting your diff centre in some black POR15. It sticks best to rusty, rough services like your diff centre and flows really well even when brushed. Basically it will give you diff centre that black powder coated look.

[sambo]

Hi Craig. With POR there's minimal prep but repairs are difficult. With black chassis paint you'd just blend it back in but the POR forms a kind of skin. I have the POR wheel kit but I'm worried what will happen if I get a few chips.

[400TT]

Sambo, I assumed the cradle was powder coated. We limit the use of POR15 to diff centres etc. as POR15 works best where the surface has plenty of bite, sorry really rough and rusty is the go.

Powder coating has the same problem with being able to repair.

Haven't used the wheel stuff.