ford4v429

running 255 fronts again, 8000 miles again, getting slight cupping on the inside shoulder again... alignment still in spec (didnt save the numbers, but toe is at zero).

wondered thoughts on 1/16 toe in vs less negative camber to reduce cupping... in my thinking, negative camber would wear inside edge more, but seems like cupping would be more to a toe-out situation scrubbing the tread.

stock springs, 17x8 wheels, 5.5 backspace, tires are nitto 450 in 255-50-17 fronts (275-50-17 rears). funny, the offset isnt ideal, it pushes the wheel out about 3/8, increasing the scrub radius I thought was going to increase bumpsteer- but it completely eliminated it... with the stock wheels it would dance all over on our potholed roads, but with these you can drive hands off, tracks straight as an arrow...

just wondered other thoughts on adding some toe-in instead of taking some camber out...my thinking is the wider offset/increased scrub radius is causing some toe out during braking resulting in the cupping- appreciate any insight
tim

ford4v429

just tried something too- cut the wheels hard, drove fwd, took a pic. reversed without changing the wheel angle took a pic... driving forward, the tires tuck under hard, driving backwards they spread way out - as if when cut hard, they have a substantial toe in due to poor ackerman geometry... any way to correct this by shimming the rack, stiffer front lower arm bushings, or ?

my old F150 had this same issue- severely- even when new, my mark VII had it too, even after all new frontend- think maybe Ford just isnt real careful with Ackerman/rack width... at full turn, the tires just dont quite track with the wheelbase

Cavero

Could be something worn. Still the original control arms? That giant rubber bushing on the rear mount is probably the first place I'd check. Might not hurt to look at the ball joints too.

ford4v429

all original, I checked everything in the spring when the last tires were wearing, balljoints tight, bushings look good (all 3 of our cars show cracks in the rear bushings, but they are centered/tight if pried on)... gonna check again this weekend, probably have the alignment checked again- just thinking the wider tires might wear better with a little toe-in and maybe a little less camber- just the sawtooth cupping I would think is more from toe out/scrubbing than rolling on the inner edge from camber- but then too, both sets that started cupping had the curved tread blocks, they may tend to squirm more angled than a block tread...just still my gut feeling is a little toe-in should help even it out.

ford4v429

checked out the frontend, everythings still tight... went ahead and tried toeing it in (went 3/16 at the tread diameter), the slightly cupped tires were howling like crazy, almost quiet now... I flipped the tires from right to left (directional- have to remount) last time and they went totally quiet, no doubt that should help again, as they arent nearly as bad as last time, time will tell if the toe-in helps with the tire wear... if not will pull some camber out

shaunrc

Typically cupping is due to worn suspension parts. Visually the struts may look ok but they could be bad and a visual check will not always tell you what is wring. Jack up the front and manually turn your wheels side to side if you get play most likely inner or outer tie rod. Up and down play most commonly ball joint or control arm bushing and if your car is lowered it may feel like the struts are tight but they could be blown out