Deciphering front end analysis

[ScottBarnes]

I’m trying to figure out why my Stroppe seems to be wandering more than it should, so I took it down to make sure toe in was perfect. They gave me this analysis sheet that I’m trying to figure out. It “looks” like I’ve got negative caster? Is that a correct read?

[phyler]

You need to talk to Digger. He'll explain so those numbers and then some.

That said, I believe you have positive caster on each side but it's the cross caster that is negative. Cross caster is how far off the sides are from each other. What that value really means though, Digger would need to explain.



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[horseplay]

hey Scott you need to increase your positive caster by a couple of deg. when you don't have all the positive caster that you need the vehicle can feel unstable and when you side to side caster is doesn't match it can feel funny when you brake and on road that have a lot of road crown. C bushings and radius arm bushings.

[crawlercreations]

Your caster is at 2.3* POSITIVE on the driver's side and 2.6* POSITIVE on the passenger side. As has been said you need to swap out your radius arm bushings for some with more caster designed in. The negative value you are seeing is the cross caster. Not a big enough difference for you to notice. Cross caster helps with keeping you going straight on a crowned road, ideally. That small of a difference would not be noticeable, in these old broncos, realistically.

I like 7*-8* of positive caster myself but that would kill your driveshaft angle. I would shoot for 4*-5* if you can get there with the available bushings for your lift height and driveshaft angle. You'll have to find out what bushings you have currently installed before you can figure out what bushings you need.

[ScottBarnes]

Thx - I’m assuming the only way to determine existing caster in bushings is to yank them off? Are they stamped?

[crawlercreations]

Thx - I’m assuming the only way to determine existing caster in bushings is to yank them off? Are they stamped?

Most are stamped nowadays but older ones are a crap shoot. Some are marked outside of the clamp zone but not many. Most likely need to tear it apart to figure it out.

How much lift is on it?

[ScottBarnes]

3.5” lift -


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[Digger]

Your Caster is +2.3° Drivers / +2.6° Passenger. The report shows RED because it is out of spec.(Low) . I like to be on the high end of that with 3-5°, similar to other modern power steering equipped vehicles.

Camber looks OK for a Bronco. Factory was 1.5°. The truck will pull to the side with higher positive camber. Right in your case. However the lower caster on the driver's side will counter the camber pull on the passenger side.

Toe is fine number-wise. However, if you have heavily offset wheels or tires that stick out a ways, the truck can dynamically toe-out due to the drag of the tires while driving. The drag tends to stretch/straighten the tierod, load the tie-rod ends, etc resulting is loss of toe-in, which can make the trunk wander as toe approaches zero.

I would start with fixing the Caster. Yes, you will have to pull radius arm bushings. If that doesn't completely fix it, bump the toe up to .37°, but no more than .50° (total toe) Between these two angles, it should noticeably improve any wandering issues.



One other factor might be tire pressure. It's routine for alignment shops to check tire pressure before alignment. If they set your pressure at 32psi, that is likely too high for big tires. The bigger the tire, the less pressure needed to support the truck. Too high and its like driving on ice skates, the truck will wander from riding on only the center of the tire patch. My 37's are down to 26psi on the street to get full contact. Higher than 28psi and Im all over the lane at interstate speeds.

[crawlercreations]

3.5” lift -


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As long as your driveshaft can handle it I'd go with 7* bushings. That should get you closer.

[ScottBarnes]

Your Caster is +2.3° Drivers / +2.6° Passenger. The report shows RED because it is out of spec.(Low) . I like to be on the high end of that with 3-5°, similar to other modern power steering equipped vehicles.

Camber looks OK for a Bronco. Factory was 1.5°. The truck will pull to the side with higher positive camber. Right in your case. However the lower caster on the driver's side will counter the camber pull on the passenger side.

Toe is fine number-wise. However, if you have heavily offset wheels or tires that stick out a ways, the truck can dynamically toe-out due to the drag of the tires while driving. The drag tends to stretch/straighten the tierod, load the tie-rod ends, etc resulting is loss of toe-in, which can make the trunk wander as toe approaches zero.

I would start with fixing the Caster. Yes, you will have to pull radius arm bushings. If that doesn't completely fix it, bump the toe up to .37°, but no more than .50° (total toe) Between these two angles, it should noticeably improve any wandering issues.



One other factor might be tire pressure. It's routine for alignment shops to check tire pressure before alignment. If they set your pressure at 32psi, that is likely too high for big tires. The bigger the tire, the less pressure needed to support the truck. Too high and its like driving on ice skates, the truck will wander from riding on only the center of the tire patch. My 37's are down to 26psi on the street to get full contact. Higher than 28psi and Im all over the lane at interstate speeds.

Thanks fellas -- So if I have 2 degree bushings now (just hypothetical), and I replace with 7 degree bushings, I should end up with a 5+ positive caster, correct?

Problem is that I'm leaving for MX Thurs a.m. and don't have a bunch of time to order/received bushings -- But I do know where I can put my hands on some 7 degree right now.

[crawlercreations]

Your Caster is +2.3° Drivers / +2.6° Passenger. The report shows RED because it is out of spec.(Low) . I like to be on the high end of that with 3-5°, similar to other modern power steering equipped vehicles.

Camber looks OK for a Bronco. Factory was 1.5°. The truck will pull to the side with higher positive camber. Right in your case. However the lower caster on the driver's side will counter the camber pull on the passenger side.

Toe is fine number-wise. However, if you have heavily offset wheels or tires that stick out a ways, the truck can dynamically toe-out due to the drag of the tires while driving. The drag tends to stretch/straighten the tierod, load the tie-rod ends, etc resulting is loss of toe-in, which can make the trunk wander as toe approaches zero.

I would start with fixing the Caster. Yes, you will have to pull radius arm bushings. If that doesn't completely fix it, bump the toe up to .37°, but no more than .50° (total toe) Between these two angles, it should noticeably improve any wandering issues.



One other factor might be tire pressure. It's routine for alignment shops to check tire pressure before alignment. If they set your pressure at 32psi, that is likely too high for big tires. The bigger the tire, the less pressure needed to support the truck. Too high and its like driving on ice skates, the truck will wander from riding on only the center of the tire patch. My 37's are down to 26psi on the street to get full contact. Higher than 28psi and Im all over the lane at interstate speeds.

Thanks fellas -- So if I have 2 degree bushings now (just hypothetical), and I replace with 7 degree bushings, I should end up with a 5+ positive caster, correct?

Problem is that I'm leaving for MX Thurs a.m. and don't have a bunch of time to order/received bushings -- But I do know where I can put my hands on some 7 degree right now.

Most 3.5" kits I've seen come with 4* so you would gain 3* from where you are now. That would put you closer to 5.5*. If you only have 2* right now you would gain 5* and put you at about 7.5*. I doubt you have 2* though.

[ScottBarnes]

Looks like Those bushings are a 2 person job especially without s lift. Any shops in town that we trust to do that work?

[Viperwolf1]

I think you may be out of time for a bushing swap. It would be a most of the day swap if you had new ones. The old ones could even be 7 degree already.

Too many people trying to get too many things done at the very last minute right now.

[ScottBarnes]

I think you may be out of time for a bushing swap. It would be a most of the day swap if you had new ones. The old ones could even be 7 degree already.

Too many people trying to get too many things done at the very last minute right now.

LOL -- Pot calling the kettle black right there!!

I've swapped them before, and it did take the better part of a day with a helping hand. That's the problem - no helping hands. I'm sitting here now trying to decide if I want to do it our not. I've got new bushings in hand. It's not a terrifying drive the way it is..

[Viperwolf1]

Jeff says to bring your bushings, Bronco and his aluminum jack stands over to his place tomorrow and we will make it happen.

[ScottBarnes]

Jeff says to bring your bushings, Bronco and his aluminum jack stands over to his place tomorrow and we will make it happen.

LOL -- he can borrow those jack stands anytime, as long as they don't leave my garage!!

I think I've convinced myself (with your scolding) to wait until we return to fine tune this thing. But I'm going to make you drive it on those narrow highways if it starts getting stupid on me!

See ya next week!

[Digger]

Phil, I think I saw you headed south on I25 around noon today near Longmont

[Viperwolf1]

Phil, I think I saw you headed south on I25 around noon today near Longmont

Yep. Going to bajaproof a couple Broncos.

[ScottBarnes]

Phil, I think I saw you headed south on I25 around noon today near Longmont

Yep. Going to bajaproof a couple Broncos.

that’s right! Get on me because I’m gonna swap some rubber bushings and you’re probably off swapping rear ends and transfer cases! [emoji23][emoji23]


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[Viperwolf1]

Just installed a new set of heads last night. Might be rebuilding a transmission tomorrow.