Time for Front end work?

[capriceforever]

My 1979 caprice has P225/75R15 tires on it, when it should have P205/75R15. I've put the wider tires on because it handles better and I like the more aggressive look to it.

However my front tires both wear a bit prematurely on the outsides of the tires, rounding off the outside edges of the tire. Probably shortens the tire life 20 or 25%.

Can this be attributed to putting too wide a tire on the car? Or is this indicative of a need for front end work? Car does have >300K with no front end work yet.

Thanks

[capriceowns]

My 87 has the same tires. They were on it when I bought it and theres no wear like that.

Might just be time for an alignment?

[GreyGoose006]

mine does that and i've had it aligned twice. it has to do with the way the steeing geometry turns the wheels when you make sharp turns. if you do a lot of sharp turns and manuvering, then the outer edges will get a little worn. just rotate the tires more often and it should be ok.
you could have under inflated tires too.

[silicon212]

That's a caster setting. Have the alignment checked.

[GreyGoose006]

me? i've gotten two alignments. guess i'll go somewhere else then.

[PeteA216]

I have the same problem even after a proper alignment and a new center link (Aligned after center link installation). Should I do like Grey Goose and get it done elsewhere? They gave me a computer printout of all the specs before and after. I didn't think you could get much better than that.

[GreyGoose006]

agreed.

when i got the print out, everything looked pretty kosher.
i think maybe in these cars, due to their front heaviness, a tidbit of camber wouldnt be a bad thing. not a lot. maybe 1-2*

[silicon212]

What you want is caster. A little more positive caster can help it turn better. The caster is the angle in the vertical plane between the upper and lower ball joints as viewed from the side of the car. If the upper ball joint is ahead of the lower ball joint, the car is said to have positive caster. Behind and it's negative caster. Or something like that.

By playing with the caster, you can adjust the angle of 'tilt' that the wheels have in a turn, in order to get the tires to have as much contact as possible throughout the turn, without messing with the camber - which would adjust the angle of the 'tilt' of the wheel when you're in a straight line (the tractor look). Messing with the camber or toe can get the car to pull to one side, caster generally won't do that (but it does affect steering). Remember that the published specifications pertaining to caster, camber and toe for a particular car are a compromise so that it's driveable to someone who appreciates a decent handling car, as well as for Grandma who takes her car to the store and church and that's it. The numbers can be played with to tailor the car's handling capability to your specific needs. What prevents tire wear on Grandma's car can actually contribute to increased tire wear on a car driven in a slalom course.

I'd stick to the book for the numbers on camber and toe, but caster is one of those things that you can do to get the car to handle BETTER than decent. Of course, you need an alignment rack to do this ...

[GreyGoose006]

i'm a little confused.
basically, caster is the axis of rotation in respect to steering the wheels?
how could it be adjusted to minimize tire wear during normal driving with a bit of hard cornering?
since most of the wear on my tires is on the outer edge, it is almost as if the wheel is "folding under" during turns.
its like the camber goes from dead on while going straight, to POSITIVE while steering.

another thing i have noticed is that the wheels "fight" each other during a turn.
it seems as if the inner wheel is turning more than the outer wheel. it is very noticable when turning sharply on gravel... the turning radius on gravel seems to be noticably sharper on gravel than regular asphalt.

[GreyGoose006]

if you are in a parking garage and the slick concrete floors are wet, when i turn the wheel close to or as far as it will go, there is a squealing sound of the tires fighting each other. i know it's not the rear tires because i have an open diff.

[silicon212]

Caster affects the tires in a turn the same way camber affects them going straight. When you turn the wheels, depending on the caster setting, the tires can be making full contact with the road, -or- the camber on them will change - one tire goes positive in relation to straight-ahead, while the other goes negative. This isn't always a bad thing - in fact, properly adjusted, caster can make the car easier to steer resulting in better cornering.

Caster and camber are somewhat dependent - you change the camber setting on these cars by subtracting or adding shims to both sides of each control arm. You adjust caster by removing shims from one side (say the front) and adding to the other side (say the back) on one arm.

[GreyGoose006]

so by my underrstanding, i have negative caster. if the outer front wheel is 'folding under' when turning, and causing excess wear, then it is negative caster.

[silicon212]

Originally Posted by GreyGoose006

so by my underrstanding, i have negative caster. if the outer front wheel is 'folding under' when turning, and causing excess wear, then it is negative caster.

The caster on these cars is negative by design - the upper ball joint sits behind the lower ball joint when viewed from below. The settings are either a little more or a little less negative (aka 'positive').

I'm discovering that there is a bit of voodoo in finding a good alignment that works. My use of games such as NASCAR Racing and whatnot have helped me to understand how the relationship of caster and camber work as these are numbers you play with on your race car's setup in the game, to get it to turn around the track at certain speeds. In the game, as in life, one particular setup might get you around the track quite well at 150MPH, but driving the car at lower speeds can be hell unleashed - one of my setups in the game helped me win against the game's strongest AI, but the car always wanted to spin around on caution laps!

[GreyGoose006]

ok, then i mean that my caster is too positive. (the upper is ahead of the lower)

racing games arent exactly good to use for predicting car setups.
in Live for speed, the best setup for any car is to use the greatest spring travel (no lowering) and the weakest springs that will keep the car about 1-2 inches above stock height. then crank the anti roll bars (stonger in the front for RWD, stronger in the rear for FWD) and set the shocks so that the bound strength is just strong enough to keep the car from bottoming out when you press DROP (a button that drops the car from a set height) and the rebound as high as it will go. take the tire pressure as low as it will go, and you have a winner.

not excactly realistic.

in GT3 you simply set spring strength to max and lower the car as far as it will go and you are good.

[silicon212]

I'm talking about NASCAR Racing, from Sierra Games. This was a true simulator and used real-world physics and not arcade physics such as most other games. Crew members of actual Winston Cup teams were using this 'game' to practice setups that translated to real-world gains - i.e. what worked in the game also worked on the real car.

In it, you had adjustments such as camber, caster, toe, cross-weight, front-to-back weight, wedge, height, springs and tire pressures and compounds.

You could tweak caster and camber by measuring the temperature of the tires on three points - inside, center and outside - just as in the real world.