Link pin shims with angled bushings

[sabre1]

One point I don't think has been raised yet about the entire front suspension is that all the pieces need to be assembled so there is no free play - as that will allow movement that will contribute to camber change; the link pins are only one aspect of achieving and maintaining the desired camber. Looseness in the kingpins, play between the control arms and the beam bearings/bushings, wheel bearing play in the drum - it all adds up!

-Jim

[FV80]

And I'm pretty sure there's some measurable WHEEL FLEX in there as well. These (mostly) *REALLY OLD* wheels are not quite as stout as new alloy wide wheels.
Steve, FV80

[sabre1]

Steve,

I think EVERYTHING is bending! If you look at the ratio of wheel centerline to the ground (say 11" for a 22" tire) and the spacing between the two link pins (~5.25" then divide by two [2.625] to get the ratio) you are looking at a multiplying factor of 4.19 to 1! So 100 pounds lateral cornering force will give you ~419 pounds pushing inward on the bottom link pin (assuming outside wheel). Cornering at 1 G is going to raise this number significantly.

Also, let us not forget that it isn't just the lower arm that being affected: the lower arm is in compression, but the upper arm is in tension - so it (and associated pieces) are stretching!

-Jim

[cendiv37]

Steve,

I think EVERYTHING is bending!

-Jim

No truer words were ever spoken both from the theoretical (everything does bend/move some when loaded) to the practical (it all adds up) yielding a huge loss in camber "control".

But amazingly is seldom breaks, except for the spindles... And we have an app for that.

[hardingfv32-1]

I would say that it is wrong to state we have lost camber control. We have a system that bends in a very consistent and predictable manner. I don't think anyone can say that their car balance changes from lap to lap with a normal functioning front end setup. We do have a system that is side load dependent when it comes to where you are on the camber curve. This would seem to operate in a manner opposite to the jacking effect in the rear. Maybe this exasperates handling problems when the track conditions are less than ideal.

I would challenge the wheel bending thesis. I had an occasion to use less than .015" clearance between my DA wheel magnet and the sensor while trouble shooting a problem. The magnet did not seem to contact the sensor.

Brian

[FV80]

...I would challenge the wheel bending thesis. I had an occasion to use less than .015" clearance between my DA wheel magnet and the sensor while trouble shooting a problem. The magnet did not seem to contact the sensor.
Brian

Don't know what you did different than me, but *I* otoh, have lost several magnets (and sensors) until I finally came up with one that would work with about 1/4 inch of clearance. Now, all seems to work reliably from event to event. (and this is JUST outside the drum outer diameter!) .. Maybe I'm running too much slop in the wheel bearings ??

Steve, FV80

[jpetillo]

Steve,

I think EVERYTHING is bending! If you look at the ratio of wheel centerline to the ground (say 11" for a 22" tire) and the spacing between the two link pins (~5.25" then divide by two [2.625] to get the ratio) you are looking at a multiplying factor of 4.19 to 1! So 100 pounds lateral cornering force will give you ~419 pounds pushing inward on the bottom link pin (assuming outside wheel). Cornering at 1 G is going to raise this number significantly.

Also, let us not forget that it isn't just the lower arm that being affected: the lower arm is in compression, but the upper arm is in tension - so it (and associated pieces) are stretching!

-Jim

Jim,
Your numbers seem a bit high for 100 lbs of lateral force. The upper link pin is 13" from the ground and the lower is 7.75" (5.25" between). That gives a lever ratio of 2.48:1 from the bottom of the tire to the lower link pin. So 100 lbs at the base of the tire is 248 lbs at the bottom link pin. The difference gives the outward force on the top pin - so 148 lbs out.

But, like you said at 1 G, it raises the number significantly. It's closer to 275-300 lbs of lateral cornering force. Using 300 lbs, you get around 750 lbs in at the lower link and and 450 lbs out on top.

I think that's right - let me know if you think I messed up.
John