PAG 15 wheels!

[john]

So by doing that, does your king pin inclination point meet the tire centre at the ground?

That's an "ideal" situation tho', is it not?
Did original cars have zero scrub radius?

[Strat Fan]

That's an "ideal" situation tho', is it not?
Did original cars have zero scrub radius?

Subjective topic of course but I am led to believe that some scrub radius is better than none. I believe Lee Noble tried zero king pin offset on the Ascari & it did not work, very light steering yes but no feel/feedback.
The amount of offset used is dictated by many things but I would say that with the design of the original Stratos coffin spoke wheels (Front ET of 7mm I think) then there would always be some if not a lot of king pin offset present. I would hazard a guess that this is why the original cars uprights were modified to give 9 degrees (?) of king pin angle to help keep the offset to a minimum.
I have no knowledge of the Allora front suspension other than early cars ran Lada top wishbones but on the Corse the solution for the deepest dish wheel is simply to mount the brake disc as close as possible to the bottom ball joint (Whilst allowing for lock & travel), fit the slimmest brake caliper possible (If using a 4 pot dsisgn) & then have the wheel positioned so that is has the minimum necessary clearance from the caliper to the back of the spoke. Front Corse Rims are supposed to be ET38mm so the 15" Coffin spokes simply don't fit full stop.
On the contrary to all of this the Ultima has the worst scrub radius of any car I have ever worked on but doesn't seem to suffer any detremental effect.

[GrahamH]

You need some scrub radius present as mentioned above. This would have been different on the works cars than Hawk as they have a modified front upright giving more KPI giving better turn in on tight corners. As many have said above the best way to go about wheels and brakes is that its the wheel that drives what size brake you can fit. By that I mean you decide and rim dia and width and offsets based on your suspension geom, c of G, etc. not all 15" rims are the same so spoke clearance on the inside can catch you out with different wheels. Your brakes should also be sized front to rear for the C of G , master cyl sizes, car mass etc, and not just the largest you can fit inside the wheel. Not sure if we can get it organised, but a 2D template of the inside of the PAG15 and coffin spokes would be helpful to all. Could be avail to all and used for brake packaging and wheel choice. Also a worthy note the closer the caliper to the wheel rim the more likely you can get a stone stuck between the caliper and rim. On GT.race cars they often run stone scrapers, small kevlar blades attached to the caliper.

[GrahamH]

Thats great Jonathan, should help alot. Are the circuit/race versions just lightened road wheels as they dont need the long term fatigue factors and durabilty?