Roger440

Errr, i'm not sure that helped a great deal!!!!!!! Im still trying to get clear in my head how mounting the (mechanical-ish) equipment on a smaller rim alters the castor reading i obtain from the 20degree swing. I tried it with 2 different wheels on the same car and got the same result! That said, only an inch difference in rim diameter, same overall wheel diameter. If i could put, say, a 10 inch wheel on it as well, maybe i would grasp it. Sadly i cant do that ! In really simplistic terms the castor angle is what it is surely, regardless of wheel size. Is it not a function of the suspension design? Yes i have re-read the castor page! The method would we use to read it is done because it is far easier to achive in the real world on a car. In reality could you not measure the angle off a suitable part of the strut (if fitted) with a gauge? As i say not very practical but is this right.? Can you simplyify the reply a bit?

OK, so im still not sure i understand. At the risk of going off at a tangent, the porsche factory equipment mounts in the centre of the wheel so how does that affect it? Bear with me hear, Im sure you are right that rim diameter is critical, but im trying to understand exactly why rather than just take it as a given.

Interesting. We had this on a Porsche 944 S2 a few weeks ago. A customer supplied his own lowering springs he bought from a guy i know well. We fitted them, did all the usual, then looked up to find the top 5 coils virtually touching each other. Hadn't even left the workshop!! Anyway, much fooling around later, lots of phone calls etc, supplier sourced some more lowering springs from a different manufacturer. Duly fitted only to find exactly the same problem. It just so happened, that afternoon, a guy from a damper rebuild place who has been doing suspension for many years called round. Took one look, grunted, and said it was no surprise! Seems that a lot of the manufacturers just copy each others product without ever seeing the car. Neither set was from any of the real serious players in the spring market. Sadly they don't do them for this car. We too scratched our heads for some time trying to work out if we had missed something. My vote on the calibra is that the springs are simply not man enough, or have used incorrect materials, probably the latter as it took time to occur.

Can you clarify the "wheel diameter" Do you mean the overall wheel diameter including the tyre, or the actual rim diameter. If you mean wheel diameter, then yes i follow you. If rim diameter, then no - im still not clear. Fortunately, the castor angle was the same both sides and within spec and is non-adjustable on this car, so at least i'm semi in the clear on that measurement. Might have to continue this tommorow as i need some shut eye. Very interesting though.

20 degrees

Vauxhall Monaros! They all wear the front inner edges of the tyres. Not really got to the bottom of it yet though. They normally check out OK but still wear the tyres. My current thereoy is that there is more movement in the suspension than Holden/vauxhall allowed for in the toe set up. Interestingly, the VXR models which feature firmer suspension seem to suffer less? On mine i rather unscientifically increased toe in slightly and that seemed to sort it. Really ought to get to the bottom of it though, well at least when i have been fully educated!

I think i follow that. Firstly though, surely it is the overall wheel diameter that is critical, or is it the diameter at which the equipment is mounted? I don't know how important this is but i am not using electronic machine. Camber and caster checks done with a seperate gauge and toe done with some old but quite accurate optical gear. Yeah, i know, takes forever, but it is all we have

The wheels were the same offset, but were 1 inch smaller in diameter. Could you explain where/what the difference would be? Im not quite sure how that would be. Yes, that is a holden SS ute (sadly not a maloo) with 5.7 V8 - oh and a turbo on it too! OOps, sorry tony, was writing my post at same time as you did. Yes yes yes, please explain. Not sure i entirely follow your first stab at an explanation either.

Recently did some adjustments on a Porsche 996 after the customer had changed the suspension and lowered it a touch. Camber and toe front and back was wrong. Said customer had some Very nice expensive wheels, and as our equipment is of the rim clamp variety -(is that the right description?) i elected to change the wheels for some "less good" ones we have lying around to avoid any possilbility of marking them. The customer posted on a forum saying how happy he was only for someone to come along and say that his garage must be daft changing the wheels as the alignment would then be wrong. Having thought about it at some length, i am still of the opinion this is nonsense. Am i missing something. Yes, i did check the run out when i mounted the equipment, and yes the wheels fit correctly (they are off another porsche) Any views?

In my experience, i have found poly bushes to be excellent when used in a compressive application, ie drag strut. ALL the problems i have ever had are where it is experiencing radial movement, ie a wisbone pivot. It is these applications where the squeaking occurs, usually because the outside of the bush is rotating within the housing. Greasing or lubricating is hardly the solution -it shouldn't be moving! The bush should absorb the movement. I do currently have some in this application on my ute rear trailing arms. I bought these because they are adjustable (camber/toe). Rubber variants are not available. That said, no squeaks. I suspect that this is partly because they have a seperate inner sleeve, which means no assembly lube required and the bolts were tightened with the cars weight in place.