Measuring Castor

[Engineer]

Need help bad!
How?! What is the best most accurate way to measure castor?
and
what sorta pinion angle is good? ive got 7deg that any good?


Thanks for any info!!!
Ryan

[Jafa]

Point the wheels straight ahead, chuck an angle finder on top of the knuckle, parallel with the long axis of your truck as much as possible. If ya knuckle is not there, then on top of the kingpin bearing cup works. Dont forget this is only really measures it at ride height, it changes as soon as the suspension moves.

[Engineer]

i was thinking gettng abit of bar and putting it through the kingpin holes and measuring the angle using trig.. is that the best way? basically i f**kd up a measurement of where the radius arm mounts go and got carried away with the welder and times against me now with trying to fix it before the workshop gets leased out!!ive got new diff mounts drawn up but i cant guarantee theyre right cos i dont know the best way to measure castor but they do give me pinion angle of 7deg. i dont stress about much but it starting to get to me now. i just need pointed in right direction.

where the chassis mounts are will be a right ass to remove, but if i have to i will get the plasma and big fuk off grinder out and fab up new mounts.
ive got bundera front end which mean the arm sit inside the chassis unlike prado arms that sit under it! if it was prado arms then itd be way easier.....ohhh the stress.
right well thats my rant over.

thanks ryan

[Engineer]

Point the wheels straight ahead, chuck an angle finder on top of the knuckle, parallel with the long axis of your truck as much as possible. If ya knuckle is not there, then on top of the kingpin bearing cup works. Dont forget this is only really measures it at ride height, it changes as soon as the suspension moves.

i thought of angle finder but i dont have one!

[Bulletproof]

Need help bad!
How?! What is the best most accurate way to measure castor?
and
what sorta pinion angle is good? ive got 7deg that any good?


Thanks for any info!!!
Ryan

The Angle of the pinion needs to point toward the gearbox so the universals are not stressed. If you have a high pinion diff it doesnt pay to have too much angle because lubrication to the front pinion bearing relys on gravity feed from oil thrown up by the crown wheel.

If you dont have an angle finder the castor can be done with a straight edge on the ground and a builders 600mm Square.
With a rod throght the king pins the lean back for positive caster is 10.47 mm for 1 degree over the 600mms of the square. Therefore 2 degrees =20.95mm and 3 =31.44mm with the truck sitting in normal position

Cheers Richard

[mud_slinger]

to change the castor you can bang in a wedge between the bottom of the diff housin and the leafs thats if its leaf

[Engineer]

just found a angle finder here at work, its bloody good so this weekend i'll have a measure up of pinion and castor, be good to find the relation between the two. thinking i might go custom arms etc now...hmm

[NJV6]

Double triangluated 4 link for the front.......

[Bulletproof]

just found a angle finder here at work, its bloody good so this weekend i'll have a measure up of pinion and castor, be good to find the relation between the two. thinking i might go custom arms etc now...hmm

There doesn't have to be any relation between Wheel castor and pinion angle.

If a truck is not lifted they remain as standard. With a lift the angle of the pinion generally needs to be tilted up but at the same time the wheel castor needs to be leaned back to make it positive so the only way to do this is to cut the swivel hubs off and rotate them backwards to achieve the right castor.
That what I did.

Cheers Richard

[Engineer]

but its easier to measure and set up pinion angle than it is castor so if i find the relation of the two then i can set the pinion up to a certain degree and know the castor will be right for the std vehicle.

[Bulletproof]

but its easier to measure and set up pinion angle than it is castor so if i find the relation of the two then i can set the pinion up to a certain degree and know the castor will be right for the std vehicle.

I think you are missing the whole point and putting the cart before the horse.
Castor angle has to be within 1-3 degrees positive, where as pinion angle can be miles out and can be done from eyesight.

Cheer Richard

[hosehustler]

All I did was a bit of reading and chat to couple of friends (bulletproof and Rick), all I ended up doing was clamping a spirit level that also has a digital readout of degrees, between the centre point of top and bottom king pins.
Had the truck body/chassis set at ride height on axle stands, and had the front axle on stands set at ride height.........
i.e the vehicle and axle are both sitting as they would be cruising down the road.
Then I rotated the housing to be at 5 degrees castor, and made front and rear mounts to suit, that gives me allowance to run 35's in the future ( further 2 inch spring lift)
Once castor was set I welded spring towers in at the point that matched what I'd set the body as ride height.
pinion angle then takes care of itself, castor is more important for a vehicle that needs a WOF

[Engineer]

thanks guys i realise castor is more important, its hard to describe what i mean...
it is easier to set pinion angle up than castor so..i find the relation between the pinion angle and castor. i can work out what angle the pinion has to be at for the castor to be say 3deg.
for example if the relation is when the castor is at 3deg and the pinion is at 7
so if i set the pinion at 8 deg the castor will be at 4 etc etc

so when im lying under the the truck by myself i can put my square onto the pinion and set it up at 7deg and then i know the castor is at 3..
does that make sense?

[Engineer]

All I did was a bit of reading and chat to couple of friends (bulletproof and Rick), all I ended up doing was clamping a spirit level that also has a digital readout of degrees, between the centre point of top and bottom king pins.
Had the truck body/chassis set at ride height on axle stands, and had the front axle on stands set at ride height.........
i.e the vehicle and axle are both sitting as they would be cruising down the road.
Then I rotated the housing to be at 5 degrees castor, and made front and rear mounts to suit, that gives me allowance to run 35's in the future ( further 2 inch spring lift)
Once castor was set I welded spring towers in at the point that matched what I'd set the body as ride height.
pinion angle then takes care of itself, castor is more important for a vehicle that needs a WOF

thats what im gunna do now as i did manage to get a digi smart level.
thanks

[Bulletproof]

I know Tim has said he set his at 5 degrees because he intends to put a 2inch lift in. I think until he does that he may get wheel shake . Time will tell . Mine is 3.4 and I still get some wheel shake on the simex tyres even though it is fine on the BFG radials.

The standard on a hilux is nearer 1 degree and a nissan safari has 2.6 ? and I would err in that direction. The main reason for positive castor is so a truck self centres when you let go of the steering wheel.

What causes the wheel shake with too much castor is the 9 degee king pin angle which lowers the wheel as you turn on lock. If you have a lot of positive castor the wheels drops too much as it moves back and rises as it goes forward. one wheel fights the other and pushes on the power steering valves and there is no way you can hold the steering wheel.

cheers Richard