Torana camber/caster adjustment.
This is something I have been meaning to post for a while but hang back till I had more feed back from customers. Fitting offset front suspension bushes. Its nothing new and has been done before. I'm a real fuss pot when it comes to wheel alignments, I have seen so many so called experts that reckon they know how to align everything from push bikes to road trains, but in reality I ask a couple of simple questions and quickly realize push bikes are probably beyond them.
I get quite a few call from customers in relation to the best camber and caster setting for their Torana. This of course is a double sided question. It depends on the intended driving conditions for example, circuit racing, Targa racing, drag racing, street cruising, outback touring, very high cambered roads and sloppy verses stiff suspension setup. The alignment should be tailored to suit the majority of the cars usage. I will concentrate on street as it would cover the majority of users on here.
Camber drivers side: zero -1/4 degree negative.
" pass " : 1/4 - 1/2 " "
Caster drivers side: 1- 5 degrees positive (even between sides)
Caster Pass " " " " " " "
Toe: at ride height 1.5mm to 3mm total toe in.
Thrust angle (diff thrust angle) zero thrust - 1mm per meter down hill (left)
Ok with my preferred setting out of the way the common question I get asked " is 3 or 4 degrees of negative camber ok". NO it will wear out the insides of both front tyres premature. This also reduces the tyre foot print on the road reducing traction in all but very high speed cornering and that is almost impossible on the street through every corner. So the wheel alignment guy putts way to much toe in to compensate for to much negative camber, then your car scrubs the tyres across the whole tread so it looks like they are wearing better, but you only get 5k - 10k out of the front tyres, twitchier steering and toe in on turns. Not good.
Its hard to get good caster and camber setting on the Torana at the best of times with the original setup and components. I have touched on the use of HQ stub axles a few times and the difference in king pin inclination causing excessive negative cambers. The KPI angle also effects the scrub radius which is not ideal. Over the past forty odd years many cars have been involved in accidents, driven over millions of large pot holes and probably the odd sheep dip, cattle grids and off road adventures. This can cause twisting, bending and cracking of the k-frames. I have seen my fair share of K-frames top towers that have come closer together and pulled the rails in with it, not easy to see by eye.
Fitting offset bushes to the lower front of front control arms can solve the majority of alignment problems.
Bush kit Whitline No: W52491
When fitting these bushes (one offset bush per side to the front of the front lower control arms) the camber and caster range can be greatly increased. I have been advised by customers that have fitted these bush kits they achieved a decrease of 3 degrees camber and at the same time increased caster between 4 1/2 - 6 degrees positive caster. Most of the camber/caster adjustment can be simply achieved by turning the eccentric bush bolt using a spanner. (much quicker and easier than top control arm shims). You also have further adjustment on the top control arms by using the original shims. I would recommend removing all the top control arms shims as this will reduce some of the negative camber first allowing for more positive caster which is a plus with power steering. Positive caster gives a more weighted feeling, generally better handling and improved camber gain in cornering. The bush offset in most cases will be offset towards the engine dragging the lower control arm ball joint position forward (more positive caster) and inward (reducing negative camber).
By adding more positive caster this causes a more forward lower ball joint position moving the tyre forward increasing the gap between the firewall and tyre, generally a plus for a Torana with bigger wheels and tyres. Although front flares to tyre gap will be reduced. Shimming the rear of the front top control arm mount will further increase positive caster so you can max out the adjustment of the bushes and trim up even caster between sides if necessary at the same time setting finer cambers if still required. It seam so far everyone has be able to achieve good alignment settings with these bushes and have commented how it improved the handling. The big benefit of power steering is the increased positive caster and still being able to steer it with ease. With a manual rack and 6 degrees of positive caster even with Popeye arms you would probably tear the steering column out quickly.
I hope this will help those with alignment issues. Just make sure your alignment guy is up to speed on basic alignment knowledge. I still get phone calls from alignment companies that can't work out why cars pull left or right and didn't know caster/camber or thrust angles effected pulls.