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Caster angle

eacook1

eacook1

Red Skull Member
ST4x4
Joined
Feb 25, 2021
Member Number
3550
Messages
212
Loc
Temecula, CA
I’m setting up a used diamond housing for my SAS. If I set my perches flat at zero my housing has about 2.5 degrees of caster which is about stock.

I am hoping to put this axle under my 4Runner as is without cutting the perches off and rotating them. Running 37s if that matters.

Would you roll with it?
 
You can run up to 7 degrees or so. Run it. If you rotate perches you have to turn the knuckle balls also.
 
Aisin said:
You can run up to 7 degrees or so. Run it. If you rotate perches you have to turn the knuckle balls also.
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I've ran 12* and it worked well. Most people are probably fine around 8*

Second part of your post is not true. You have no idea what the ratio between the pinion and knuckles are.
 
If I rotate the perches to get more caster why would I rotate the knuckle balls? Maybe I’m missing something.
 
So I guess I really need to get it under the vehicle before I make any final decisions.

I’m working on a frenched in pad for the short side of the housing to use bolts instead of a ubolt due to the interference of the center section. I need to make sure all the angles are good in case I need to move the perches because my pad angle would change.

Which angle do you give priority, pinion angle or caster? What’s the min caster you would run?
 
I always give priority to pinion angle. To much and your caster angle takes a dump. The crossover steering also hits the leafs. Hence a cut and turn of the ball.
 
eacook1 said:
Any idea what your pinion to knuckle angle is? That might give me an idea of where I’m at.
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No, it's a custom axle, how would I know.


Oddball said:
I always give priority to pinion angle. To much and your caster angle takes a dump. The crossover steering also hits the leafs. Hence a cut and turn of the ball.
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You're backwards there.
 
YotaAtieToo said:
You're backwards there.
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No, I'm not. Pinion up means less caster. When wheeling, pinion clearance and driveline angle are more important than caster. To little caster and the steering won't want to self center. It also might wander more. I usually throw in a 2.5° wedge to bring the pinion up.
 
Oddball said:
No, I'm not. Pinion up means less caster. When wheeling, pinion clearance and driveline angle are more important than caster. To little caster and the steering won't want to self center. It also might wander more. I usually throw in a 2.5° wedge to bring the pinion up.
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Well yes, if offroad is your main concern.

Imo, caster should be prioity if driving on the road.
 
This will be driven to every trail as I don't have a truck and trailer. This has to drive well.

So, 2.5 deg caster (stock) would be adequate but more might be better for the street and big tires.

Those on leafs, what is your approximate pinion angle in relation to the ground. This will give me a good starting point.
 
eacook1 said:
Those on leafs, what is your approximate pinion angle in relation to the ground. This will give me a good starting point.
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This is not how it works...

Just put the amount of caster needed, locking hubs and don't worry about pinion angle.

Pinion angle should be a way less important feature than caster at ride height.

If you want to make both perfect you'll have to set up pinion angle based off of the transfer case output location and cut and turn your Cs / balls on the housing.
 
As others have said, if your going to drive it on the street, your priority should be caster angle not pinion.

I like 6-8deg. 2.5 sounds way too low. Seems like newer vehicles are going with more caster these days 7-9deg. Honestly I'd put in as much caster as is reasonable and then make sure the pinion angle wasn't too bad. If the pinion angle is horrible then dial it back a bit.
 
Agree with Ghetto. I was going to suggest 5-7 degrees. I did a lot of reading on this when setting up my front end.
 
Points taken, before I do anything I will get it under the truck and look at all the angles, I was just trying to get the axle done before I cut the truck apart just due to work space in my garage.

Thanks!
 
Castor is your steering axis, more positive castor increases steering difficulty but makes the truck track better and return to center better. The 5-8* number is a good range for trail trucks that drive on the street. But you can't measure that relative to only the spring perches. The location of and on the springs will change the castor angles. So to do it right, it needs to be measured at ride height with a load (body, drivetrain, etc).

For pinion angle, that is also important, with standard u-joints on both ends of the drive shaft, the pinion flange and t-case output flange should be close to parallel. If you are running a CV joint on the t-case side, the pinion should point somewhat at the t-case output flange.
 
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What's your leaf spring, shackle, and perch setup? What truck?

On many SAS trucks, especially Tacomas, the shackle length plus frame drop results in the spring perches being angled at ride height. You need to get the weight of the truck on the actual springs to determine where everything is going to sit at ride height.

If the housing has 2.5° of Caster with the pinion angle at 0-2°, well that's what you're going to need to run for caster. Check what the caster is with the pinion at the required angle and see how the knuckle balls were welded on. Then see if you can make the perches work with your truck/suspension.
 
Its a 93 4runner V6, Skys 3F springs, hanger and shackle kit. Diamond housing and I assume their spring perches, bought used so I don't know for sure.

I will get weight on the springs before I make any decisions. Hopefully everything falls into place.
 
You might want to chop off the front of that shitty frame and build a new one.
 
Aisin said:
You might want to chop off the front of that shitty frame and build a new one.
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Maybe next go around if I 3link it. I got my hands full already. Trying to get this done for a late august Rubicon trip. My house and daughters Jeep have delayed this project as it is.
 
Just plan on your tie rod and drag link making love to your oil pan.
 
eacook1 said:
Its a 93 4runner V6, Skys 3F springs, hanger and shackle kit. Diamond housing and I assume their spring perches, bought used so I don't know for sure.

I will get weight on the springs before I make any decisions. Hopefully everything falls into place.
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Yeah, get the springs under the truck and see how it sits on the axle. It might work as-is, or might need an angle shim, or might need some chopping and welding.
 
Wait, go back to the beginning.

How are you measuring caster?

You need the axle under the truck, with wieght, and an angle finder in the highsteer arm. Guessing by setting the perch flat and checking the arm will not work.

I agree that 2.5* isn't enough. Not sure where you're saying that's stock. But IFS may be different, and it's not like old solid axle trucks drove all that great. Shoot for ~6-8*
 
V6 trucks have a very short front driveline. That, coupled with lift makes it impossible to run a double cardan. Your best bet is to get a 4cyl rear shaft and have it cut down with a long spline added. You will need to redrill the front output flange. Turning the pinion up will certainly help with driveshaft life. Or find a high pinion.

I daily'd my truck with 4° wedges in the front. But I also ground a bunch of meat off the crossover bar to prevent it from rubbing the leafs. Why? Because rock crawler. Road manners were acceptable, even on 38s. Perhaps ifs hubs and 1.25 spacers helped with returnability because of the larger steering radius.
 
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YotaAtieToo said:
How are you measuring caster?
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Setting a digital angle finder on top of the trunion race while the perches are set at 0 or parallel to the ground.
YotaAtieToo said:
I agree that 2.5* isn't enough. Not sure where you're saying that's stock.
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I read it somewhere. But also found it on 4crawler

80BD66C7-99CE-4CEC-A3F2-C05A680DD43F.jpeg
 
eacook1 said:
Setting a digital angle finder on top of the trunion race while the perches are set at 0 or parallel to the ground.


I read it somewhere. But also found it on 4crawler

80BD66C7-99CE-4CEC-A3F2-C05A680DD43F.jpeg
Click to expand...

Your info is right for stock suspension and stock tires. But with big tires and longer travel suspension, shoot for more as others have advised.

And the spring pad angle is irrelevant until you have the suspension under the truck and weighted. They may be at 0°, they may be at 10°.

Measure the caster in relation to the pinion angle, with the pinion set where you need it to be. Or if there's no diff installed, reference the mounting surface for the third member.

Edit: I say this because the caster/pinion relationship is more important. It's easy to cut/weld spring pads or shim them to change the relationship between the springs and axle, but changing the relationship between caster and pinion angles requires cutting off the knuckle balls.

Confirm your caster/pinion angles first. Then worry about the leaf spring angle second. This is a used axle that was assumedly built for a different rig so everything needs to be checked and measured to see what needs to change for your rig.
 
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Don't be scared of having to cut and turn the knuckle balls if you have to, it's stupid easy! It will only add a couple hours to the front axle build. Don't be like me and only focus on getting the castor right and forget about the pinion angle. It's technically right for a non CV shaft but it's the lowest hanging part of the front axle.

Also to echo the others, the stock suspension alignment measurements all go out the window except for toe.
 
No body complains of too much caster. In fact, about the only possible complaint is tire ware. The OEMs are having a tendency to go with less caster. (Like 2 degrees) It works for small tires and a perfect setup suspension. I did a lot of experiments and I wouldn’t consider anything less than 6. (12 is better)
 
I would be shocked if your pads were level with the axle installed. They will probably be laid back and your caster will be good.



WaterH said:
No body complains of too much caster. In fact, about the only possible complaint is tire ware. The OEMs are having a tendency to go with less caster. (Like 2 degrees) It works for small tires and a perfect setup suspension. I did a lot of experiments and I wouldn’t consider anything less than 6. (12 is better)
Click to expand...

Too much can get wierd also. I ran 12 and it worked, but I've read others that had not so great experience.
 
YotaAtieToo said:
I would be shocked if your pads were level with the axle installed. They will probably be laid back and your caster will be good.





Too much can get wierd also. I ran 12 and it worked, but I've read others that had not so great experience.
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I’ve heard of people running 20 without issue. Not sure why anybody would do that.
 
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