Thread: Caster angle

  1. #1
    Join Date
    Aug 2014
    Location
    United States
    Posts
    354

    Default Caster angle

    Does anyone know the factory setting for caster on your typical npr or fuso? My truck is obviously not factory but it's a start. It's currently about 2 degrees and anywhere up to around 10 degrees seems common. Just wondering what is typical on a truck like this and if I should try for more.

  2. #2
    Join Date
    Jul 2016
    Location
    Seattle, WA USA
    Posts
    46
    That range of adjustment sounds pretty massive even for caster. What is it you're trying to achieve? Are you mostly on road or off road? Trying to combat a road crown issue? I have a short wheel base fg140 and use it as a daily driver, 98% on road...I like my tight turning radius and my high speed manners are not twitchy or fatiguing...I just had my alignment done and though I used to sell alignment equipment, I didn't even think yet to specify my own angles like I do on my pickup or, frankly almost all my cars...so I assume the shop used published specs...and they seem fine. I did ask the shop one question: Do you compensate for road crown? I like all my rigs without that compensation cuz, if the road is bent, I wanna know it and have proper feedback on any off camber stuff. I think the only time I'd consider it is if I was driving the same, looooong highway each day. Normally, I simulate the anticipated load during the alignment, ( typically empty, half tank fuel, my fat butt and my dog, the way I travel 90% of the time)...but I omitted that on the FUSO alignment as well due to the heavy duty nature of the truck, with no apparent detrimental effect....I'm no good at posting pics/docs here, so I've sent caster specs to your Facebook page. The range is very much smaller than you describe, so I'd find a service manual for your specific rig or rely on the alignment shops specs..
    Last edited by skippythedog; 03-20-2017 at 12:04 AM.

  3. #3
    Join Date
    Aug 2014
    Location
    United States
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    354
    Thanks again!

  4. #4
    Join Date
    Mar 2010
    Location
    Jδmte i exil
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    126
    How does this truck adjust caster anyway ?
    Just curious really...
    Obvious is at its spring mounts. But does it otherwise have a caster adjustment via its kingpins for example ?

  5. #5
    Join Date
    Aug 2009
    Location
    Brisbane, Qld, Australia
    Posts
    504
    for FG front axle

    Toe-in 0 to 6 – Adjust
    Camber 1°00’ ± 30’ – Replace
    Caster 0°30’ ± 1°00’ – Replace
    Kingpin inclination angle 9°30’ ± 30’ – Replace

    Toe-in adjustment is turning the threaded bit of the long connection between the wheels.

    I have camber kits (eccentric kingpin bearing holders) that allow some adjustment of camber and castor.

    Once camber and castor are adjusted kingpin must have been taken care of .... unless there is something bent.

    Castor is what returns the steering wheel to centre when hands off.
    Its a rigid beam axle. Load is more important with independent suspension as the angles change a bit as springs compressed.

  6. #6
    Join Date
    Aug 2014
    Location
    United States
    Posts
    354
    My truck has a ball joint Dana 60 in the front. No adjustment there but I can shim the spring pads to rotate the axle backwards and increase caster or I can lengthen the spring shackles and achieve the same but it will change ride height and not change the caster much. I want a little more lift so I will probably start with the longer spring shackles and leave it alone until I drive it.

    Quote Originally Posted by skippythedog View Post
    That range of adjustment sounds pretty massive even for caster. What is it you're trying to achieve? Are you mostly on road or off road? Trying to combat a road crown issue? I have a short wheel base fg140 and use it as a daily driver, 98% on road...I like my tight turning radius and my high speed manners are not twitchy or fatiguing...I just had my alignment done and though I used to sell alignment equipment, I didn't even think yet to specify my own angles like I do on my pickup or, frankly almost all my cars...so I assume the shop used published specs...and they seem fine. I did ask the shop one question: Do you compensate for road crown? I like all my rigs without that compensation cuz, if the road is bent, I wanna know it and have proper feedback on any off camber stuff. I think the only time I'd consider it is if I was driving the same, looooong highway each day. Normally, I simulate the anticipated load during the alignment, ( typically empty, half tank fuel, my fat butt and my dog, the way I travel 90% of the time)...but I omitted that on the FUSO alignment as well due to the heavy duty nature of the truck, with no apparent detrimental effect....I'm no good at posting pics/docs here, so I've sent caster specs to your Facebook page. The range is very much smaller than you describe, so I'd find a service manual for your specific rig or rely on the alignment shops specs..
    I am shooting mainly for cruising well at 70mph but definitely want significant off road prowess. I know that some trucks can be picky about the caster angle due to potential death wobble like symptoms. I too don't like the alignment to compensate for anything. I am finding caster specs for the vehicle that my axle came from to be 2-5* positive. I will see what the spring shackle extension does and go from there.

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