Caster thoughts?

[67Dart273]

Got the disk stuff under the car and on the road. Steering was hard enough (manual) and plans later are "back to the power." So I didn't want to go nuts on caster

But the "new" wheels are offset a bunch compared to the old steelies

Tires are a LOT fatter and shorter -- 215 60 x 14's
Old tires were 205 x 70 14's

It acts like it wants a lot more caster. I would think offset rims would need some less?

How do these short tires interact?

I don't want to do this too many times, because for me, it's a LOT of work.

 

[RustyRatRod]

I assume they are offset to the outside. You didn't say, so from here, I may be 180* off base. Offset wheels to the outside of the car effectively increase SAI. It really has zero effect on caster, although it can seem like the same thing. Since you're moving the centerline of the wheels inside and the rim and tire to the outside, you're increasing the amount of leverage it takes to steer the car, much the same as too much caster, but it's not quite the same. You've moved the center of the axle closer to the ground which increases the SAI arc travel, requiring more effort to steer. Reducing caster may help that, but it will probably give a bad road feel. You may not be 100% happy with it until you switch to power steering. Since SAI I a built in angle and non adjustable, there's nothing you can do except change wheels.

I would think the short tires would aggravate the problem, as they move the center of the wheel even closer to the ground effectively increasing SAI even further. I could be wrong.

All this is of course if the offset you mention moved the rim and tire to the outside of the car. Flush it all down the toilet if you went the other way.

 

[KitCarlson]

Del,

I found this article that explains caster relations in detail.http://www.motoiq.com/MagazineArtic...ur-Caster-King-Pin-Inclination-and-Scrub.aspx

It is necessary to down a few pages, then it gets to the scrub radius, wider, shorter tires increases, range of 3/4" to 3" may be acceptable.

For me it seem too much caster is hard to get, if you go to power steering, it will add some feedback. Other wise drive with a pinky finger.

 

[ir3333]

"it acts like it wants more caster"...how do you tell?
If it's hard to steer in the parking lot going real slow and your steering self centers at speed you're probably close for manual steering.

 

[67Dart273]

"it acts like it wants more caster"...how do you tell?
If it's hard to steer in the parking lot going real slow and your steering self centers at speed you're probably close for manual steering.

That's the problem, it DOES steer fairly hard going slow, but does NOT want to return around a corner

 

[67Dart273]

I assume they are offset to the outside. You didn't say, so from here, I may be 180* off base. Offset wheels to the outside of the car effectively increase SAI. It really has zero effect on caster, although it can seem like the same thing. Since you're moving the centerline of the wheels inside and the rim and tire to the outside, you're increasing the amount of leverage it takes to steer the car, much the same as too much caster, but it's not quite the same. You've moved the center of the axle closer to the ground which increases the SAI arc travel, requiring more effort to steer. Reducing caster may help that, but it will probably give a bad road feel. You may not be 100% happy with it until you switch to power steering. Since SAI I a built in angle and non adjustable, there's nothing you can do except change wheels.

I would think the short tires would aggravate the problem, as they move the center of the wheel even closer to the ground effectively increasing SAI even further. I could be wrong.

All this is of course if the offset you mention moved the rim and tire to the outside of the car. Flush it all down the toilet if you went the other way.

Yes, went from SBP factory steelies to outward offset ET that sorta match the Bullitt wheels, so a "bunch" outward offset.

My intuition and what you just said here pretty much agree. I'm about 2 1/2 caster right now, I may add some more. Or, LOL, try'n figure a way to get busy and get the PS back into the car

 

[67Dart273]

Del,

I found this article that explains caster relations in detail.http://www.motoiq.com/MagazineArtic...ur-Caster-King-Pin-Inclination-and-Scrub.aspx

It is necessary to down a few pages, then it gets to the scrub radius, wider, shorter tires increases, range of 3/4" to 3" may be acceptable.

For me it seem too much caster is hard to get, if you go to power steering, it will add some feedback. Other wise drive with a pinky finger.

Thanks, Dave, I'll go through that when I get time

 

[72bluNblu]

+2.5 for caster is already toward the high end for manual steering. As I'm sure you know, adding more caster will make the steering effort harder.

Power steering is a whole different story, I'm at +5 with my Challenger, no issues. The additional effort needed actually helps add some feel to the overboosted stock power steering.

This chart is posted all over the place, but its a good start for aligning these cars. I think that -.25 to -.5 degrees camber, +3 to +5 caster, and about 1/8" toe in is the way to go for most street rides. More negative camber helps handling, but much more than -1 degree starts to eat tires.

 

[67Dart273]

That chart is exactly what I used. Camber is about neg .25 or a smidge more. Caster is about 2.5. Toe is right at 1/8"