Why is my caster angle negative?? And other caster and lift quesrions

[cog97]

Evening Folks,

After reading up on the importance of dialing in caster I’ve come to notice that my new to me FZJ80 already has a ‘negative’ caster on stock springs and shocks... when I say negative, I mean the axle is rotated like this: \ when looking in from the front left tire.

why is this the case? If I lift my cruiser 2-2.25 inches, could I get away with running Delta VS’s 4 inch caster arms on my 2-2.25 inch lift? My noob logic thinks that the 4 inch caster arms will account for the lift and the fact that my caster angle is already negative!

I’m very surprised since I’ve not noticed any terrible steering, I’ve gotten used to it tbh...

Here to absorb any knowledge i can.

thanks!

V/r

Luke

 

[Irish Reiver]

Have you had the caster measured at a shop?

 

[cog97]

Have you had the caster measured at a shop?

Not yet. Should I? It’s pretty apparent it’s negative (though i admit it’s only slightly negative)

 

[Irish Reiver]

I think i recall the spec is 2°- 4°. I think that would be hard to spot with the naked eye (mine anyway). What are the bushing in the control arm like?

 

[Grandlooser]

Your steering pivots are not inline with the tilt of the axle housing. What you are seeing is just the housing tilt, not the caster angle.

 

[cog97]

I think i recall the spec is 2°- 4°. I think that would be hard to spot with the naked eye (mine anyway). What are the bushing in the control arm like?

The bushings seem fine, I honestly haven’t noticed any “squirrelly” steering or what not. They do just fine going 75 on the highway.
Do you think an alignment shop would be able to give a yes no on my caster arm question? From What I’ve read and heard the caster arms are the best way to go, but I don’t wanna have to buy a 2 inch arm set only to then go with a 4 inch arm set later down the line.

caster plates are good and all but the thought of altering the axle is not too pleasant.

 

[Irish Reiver]

I would get it measured so you at least have a baseline.

 

[COYS]

You won't know what you're missing until you drive a properly sorted rig. As they say, ignorance is bliss.

Not sure what lift you're getting, but the most common sit at around 2.5-3" as in my case. Get the 4" Delta arms and dial it all in at a reputable alignment shop. If you haven't already, refresh every bit of the suspension rubber with fresh OEM parts at ~$1200 + labor. This combo will net any owner a lot of smiles. At least it did for me.

Good luck, bud.

 

[Grandlooser]

Is nobody else going to acknowledge that op is basing his caster on observing the housing tilt? All our axles look like that when stock to point the pinion up a bit.

 

[leonard_nemoy]

Like grandlooser said, you can't judge caster by looking at the housing. Caster is the angle of the steering pivot. You need to take it to an alignment shop so you know what your caster is.

Do you feel safe driving it on the interstate? If your caster was -2, I highly doubt you would dare drive it at highway speeds.

Take it to a alignment shop, you cannot judge caster by looking at the axle.

 

[cog97]

Like grandlooser said, you can't judge caster by looking at the housing. Caster is the angle of the steering pivot. You need to take it to an alignment shop so you know what your caster is.

Do you feel safe driving it on the interstate? If your caster was -2, I highly doubt you would dare drive it at highway speeds.

Take it to a alignment shop, you cannot judge caster by looking at the axle.

Will do,

I’m realizing that caster angle for vibe free driving after lifting is one of those topics that vary from truck to truck and it’s not as straight forward as one would think..

Thanks..

edit: yes It drives fine

 

[cog97]

You won't know what you're missing until you drive a properly sorted rig. As they say, ignorance is bliss.

Not sure what lift you're getting, but the most common sit at around 2.5-3" as in my case. Get the 4" Delta arms and dial it all in at a reputable alignment shop. If you haven't already, refresh every bit of the suspension rubber with fresh OEM parts at ~$1200 + labor. This combo will net any owner a lot of smiles. At least it did for me.

Good luck, bud.

Are you having any issues with your DS angle? I want to use 4 inch caster arms for a 2.5/3 inch lift but not sure how that’d impact the geometry.

 

[leonard_nemoy]

Don't forget about eimkeiths weld in radius arm drop bracket mounts(RAM). I just installed a set and they are a great option at a great price.

Radius Arm Mounts - https://eimkeith.com/ram/

Here is my write up on the install if your interested in them.

*UPDATED* Eimkeith RAM (radius arm mount) install - https://forum.ih8mud.com/threads/updated-eimkeith-ram-radius-arm-mount-install.1241709/page-2

 

[cog97]

Don't forget about eimkeiths weld in radius arm drop bracket mounts(RAM). I just installed a set and they are a great option at a great price.

Radius Arm Mounts - https://eimkeith.com/ram/

Here is my write up on the install if your interested in them.

*UPDATED* Eimkeith RAM (radius arm mount) install - https://forum.ih8mud.com/threads/updated-eimkeith-ram-radius-arm-mount-install.1241709/page-2

Any issues with ground clearance when wheeling?

 

[leonard_nemoy]

Any issues with ground clearance when wheeling?

Not for my style of wheeling, as long as your not building a dedicated rock crawler they shouldn't be an issue. Plus if you look at the shape of them, I think it would be pretty hard to get them hung up and stuck on a rock. They are nice and round so I would imagine that they would just slide over anything. They are made of 1/4" plate so they can also take a beating.

If you lift one of these 80's and run aftermarket tires that give you 2" of additional ground clearance and install these than your radius arms would still be the same height as stock. But everything else would be higher.

 

[cog97]

Not for my style of wheeling, as long as your not building a dedicated rock crawler they shouldn't be an issue. Plus if you look at the shape of them, I think it would be pretty hard to get them hung up and stuck on a rock. They are nice and round so I would imagine that they would just slide over anything. They are made of 1/4" plate so they can also take a beating.

If you lift one of these 80's and run aftermarket tires that give you 2" of additional ground clearance and install these than your radius arms would still be the same height as stock. But everything else would be higher.

Arent you running a 2 inch lift with 30 mm spacers? Wouldn’t that place you closer to 3 inches? How’s your caster angle with these 50mm caster bracket drops?

 

[baldilocks]

Will do,

I’m realizing that caster angle for vibe free driving after lifting is one of those topics that vary from truck to truck and it’s not as straight forward as one would think..

Thanks..

edit: yes It drives fine

Castor angle has nothing to do with vibe free driving. Pinion flange angle relative to transfer case output flange angle has everything to do with a vibe free driveline. Castor angle correction and a vibe free driveline are separate concerns. The pinion angle can be your point of focus or good road manners via plenty of castor angle can be your focus.

The good news is that if you actually keep your lift at 2.5-3” max, it’s possible to satisfy both concerns and end up with in spec castor angle and also satisfy the pinion angle necessary to run a DC front shaft. However, you won’t achieve this by running Delta 4” arms on a 2.5-3” lift. The arms will provide 4+ degrees of castor but the pinion will be rotated down too low to make either type of driveline happy. This is why my 80 has been converted to part time.

There is a relatively small window for lift vs castor spec plus a happy driveline. I’m on 5” of lift running Delta 6” arms. Castor is about 5* as measure by me with a digital angle finder. On 37” tires, it drives much better now than it did with stock arms plus Slee 4” castor plates which produced a smooth running DC shaft but only 0.5* positive castor. Once the Delta arms dialed in the castor to where it drives well, the pinion is lower and now the DC shaft gets unhappy at about 45mph if I leave the hubs locked. The standard shaft is worse.

Study up on the spring choices out there because it’s very possible to get 4” lift from a 2.5-3” spring unless your rig is very heavy. Opening Pandora’s box is an easy thing to do.

 

[cog97]

Castor angle has nothing to do with vibe free driving. Pinion flange angle relative to transfer case output flange angle has everything to do with a vibe free driveline. Castor angle correction and a vibe free driveline are separate concerns. The pinion angle can be your point of focus or good road manners via plenty of castor angle can be your focus.

The good news is that if you actually keep your lift at 2.5-3” max, it’s possible to satisfy both concerns and end up with in spec castor angle and also satisfy the pinion angle necessary to run a DC front shaft. However, you won’t achieve this by running Delta 4” arms on a 2.5-3” lift. The arms will provide 4+ degrees of castor but the pinion will be rotated down too low to make either type of driveline happy. This is why my 80 has been converted to part time.

There is a relatively small window for lift vs castor spec plus a happy driveline. I’m on 5” of lift running Delta 6” arms. Castor is about 5* as measure by me with a digital angle finder. On 37” tires, it drives much better now than it did with stock arms plus Slee 4” castor plates which produced a smooth running DC shaft but only 0.5* positive castor. Once the Delta arms dialed in the castor to where it drives well, the pinion is lower and now the DC shaft gets unhappy at about 45mph if I leave the hubs locked. The standard shaft is worse.

Study up on the spring choices out there because it’s very possible to get 4” lift from a 2.5-3” spring unless your rig is very heavy. Opening Pandora’s box is an easy thing to do.

Well, it’s clear that I’ll have to do some more reading on this. I may or may not come back with more questions once I process that and think about my options... FWIW I’m looking at a dobinsons lift that, after reading up, turns out about 2.25 of lift in The front and 2.5 in the rear so whatever correction method I use will have to be for a 2.25/2 inch lift...

thanks sir!

V/r

Luke

 

[leonard_nemoy]

Arent you running a 2 inch lift with 30 mm spacers? Wouldn’t that place you closer to 3 inches? How’s your caster angle with these 50mm caster bracket drops?

Yes, I have about 3" of lift in the front. My caster is sitting at 4 degrees + caster.

 

[mudgudgeon]

Caster is the line drawn between the centre of the top and bottom trunion bearings. They are also known as king pin bearings. Easier to picture them as connected by an invisible pin.

Diagram on the top left shows a vertical line (left) then the caster line through the trunions (right). The angle that the trunions lean backward at the top is the caster angle.
If it's leaning back (correct), it's positive. Caster positively returns steering to centre, and keeps a truck tracking straight.

If the caster angle leans forward, it's negative and the truck will wander along an uneven road, and can duck and weave under brakes.