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7* caster debate

Discussion in 'The Hokey Ass Message Board' started by hillbilly4008, Apr 1, 2013.

  1. exactly 7 degrees

    13 vote(s)
  2. somewhere ballpark

    114 vote(s)
  1. Jamoke
    Joined: Sep 1, 2011
    Posts: 686


    If your going fenderless I would increase the wheel base also I use ( 124" ) As much + Caster as possible with in reason 7-10 , the Hot Rod will go down the highway like its on a string
    scrap metal 48 likes this.
  2. NortonG
    Joined: Dec 26, 2003
    Posts: 2,117

    Member Emeritus

    Now that is a HotRodders answer to this problem!
  3. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    Member Emeritus

  4. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    from Texas

    This is a debate, but I would always recommend following a good builders advice as he know's the tires, rake, offset, KPI, weight on the front axle etc.

    Being from a racing background I think of Caster more in terms of Camber gain and weight jacking and have always preferred as much as feasible.

    I would like to say that of the rods I have seen and one evil one I drove (my dads) wheel offset and KPI and the resultant scrub radius would be as much or more on my mind and I would try to have a scrub radius of 1 - 2 inches. Also Scrub Radius (a little will do) helps a bit on parking.

  5. sedanbob
    Joined: Apr 19, 2011
    Posts: 110


    I have a '33 sedan with MII IFS with coilovers. I set it up level while building the car, with the caster set around 1* - 1.5*(according to the chassis builder). As I continued building, and adding weight to the car, it settled some which I did not notice. I drove it very little before heading to the alignment shop, but it was very skittish - it definitely demanded both your hands on the wheel and your full attention keeping it between the lines.
    At the alignment shop, the first thing they noticed was the settling, so we adjusted it back up to where the lower arms were level, like they should have been. That settling in the front also reduced the caster. We didn't measure the caster it before leveling it, but it was down at least an inch.
    With it leveled they proceeded to set the caster, camber, and toe-in. I now have 5* caster, and it is a joy to drive on the highway, but still not a major chore to park.
    Thankfully, with the IFS, making those adjustments was easy.
  6. TERPU
    Joined: Jan 2, 2004
    Posts: 2,230


    Glad you are happy with where you set it. You asked for opinions so I gave one. See you on the Highway. I'll be in the '33 Sedan with an early Cadillac

  7. F&J
    Joined: Apr 5, 2007
    Posts: 13,217


    I didn't say I was happy with where I set it ;).. I needed a baseline to go with that quick box. I've grown fond of quick steer on 2 dailys in the last 10 years, and that's why I wanted to try this box.

    No idea on if I will need to change the caster, but I do have a 10 minute way to add 2* more caster to help test it, while on the road. I'll put up a pic later. This thread had me second guessing again, as when I went to do some blocksanding this morning, I tugged on the steering wheel again..:D.. it still feels good.
  8. FritzTownFord
    Joined: Apr 7, 2007
    Posts: 1,020


    Stupid questions part 2 -
    Where do I take the "toe" measurements? I read 1/8" - at what point?
    Front of the tires, out in front somewhere?

    I'm running 6.00/16 Firestone fronts - 7.50/16 rears. And 5 degrees caster.
  9. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    from Texas

    Tire tread is close enough
  10. ESGEE
    Joined: Feb 25, 2013
    Posts: 606

    from Sweden

    The debate is intressting...
  11. I was always taught to measure from the tire treads as close to the height of the wheel bearings as possible.

    It has served me well, but can be a chore with a fully assembled vehicle. ;)
  12. Are the various years spindles manufactured the same with regard to the kingpin C/L and spindle C/L ?

    A little offset there will have a pretty big impact on trail
  13. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    from MI

    The effect of caster varies with king pin(steering axis) inclination. General rule; 4 degrees or more.
  14. Plumb Bob is the ticket for me. No balky tool to store. The Bob and String stores well. Easy one man operation, just mark the floor then measure. The tape measure doesn't need a second hand either that way.
  15. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    from Texas

    Later model suspensions like Mustangs run about an inch of offset to reduce trail. If the Spindle is fore/aft then mechanical trail will be added or reduced.

    We used this in karting and race spindles.

    This is a FSAE spindle set to reduce trail.


    Last edited: Apr 4, 2013
  16. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,061

    Ned Ludd

    It's a thought I had. The one thing all our solid axle front ends have that ifs doesn't is the structurally extremely slender tie rod, which the scrub offsets put in compression during normal use. If that were to oscillate harmonically in a deflection like that of an English longbow, something like the shimmy described is likely to result.

    The fixes this would suggest are either to hang a weight on the tie rod, to change its natural frequency - though as hoop says to move the problem to another speed - or to divide the tie rod into several less-slender rods with one or more idler arms to the axle; or to use a chunkier tie rod; or to run the tie rod ahead of the axle, where it is normally in tension. I wonder: is anyone getting a wobble with a front-tie-rod set-up?

    Just a thought.

    One advantage I see to a multi-piece tie rod with idlers is that it offers more options for locating drag-link steering, which may in some cases make it easier to design out bump steer.
  17. ago
    Joined: Oct 12, 2005
    Posts: 2,199

    from pgh. pa.

    What do think would happen if you put an idler in the tie rod the same length as the panhard or drag link? I use heavy wall tubing for my tie rods.

  18. MR K.
    Joined: Aug 20, 2009
    Posts: 594

    MR K.

    Hi everyone. Look at caster angle for my roadster AV8 build. So looking through threads. I have 4 degrees of caster with motor and trans installed. Body is not on yet. Might make new brackets to give me 5 or 6 after all the reading. My reading on my angle finder is off the center of the axle. Is this the right spot or should I really be checking on the king pin.

    Sent from my SM-N960U using The H.A.M.B. mobile app

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