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Wheel offset & suspension???

Discussion in 'The Hokey Ass Message Board' started by Tinbender, Sep 22, 2012.

  1. All I've ever heard was that too much positive offset was"hard on bearings". So whats the whole story. How much is too much? Is it worse for king pin, or ball joint suspension? What about handling and steering quality? Tell me what you know please. And yes I want to run big fat tires on my stude!
  2. It's not best but it's also not the end of the world either. You may need to inspect the bearings after about 50,000 miles or so. :rolleyes:

    With too much you may get a "death wobble".
  3. Halfdozen
    Joined: Mar 8, 2008
    Posts: 603


    As viewed from the front of the vehicle, the steering axis (line drawn through the king pin or ball joints) should fall within the tire contact patch, the closer to the centre the better. More wheel offset moves the centre of the tire outward away from the steering axis, steering becomes heavier at low speeds (especially with brakes applied), and the vehicle may be a bit twitchy when braking hard at higher speeds. If you go heavy on the positive offset, hitting a chuck hole or large bump in the road with one wheel may feel like it's trying to yank the steering wheel to that side. You may find it needs more toe in at alignment time, or it may be inclined to wander at speed. There are many other factors that will affect "how much is too much".
  4. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,583

    from Quincy, IL

    As I understand it, there are a few issues raised with wheel offset that is greater than what the front was designed for. For many decades, the standard front wheel set was the larger inner bearing and a smaller outer bearing. The larger of the two was, logically, intended to carry a greater portion of the load on that wheel/hub assembly.

    When a wheel is utilized that places the centerline of the tire significantly away from the place the original design intended, typically outboard, the load proportionately shifts toward the smaller outer bearing. Note, it is NOT wheel or tire WIDTH that changes this relationship, but wheel offset. So, it is entirely feasible to add wider wheels and tires and not induce this condition. But the smaller bearing can easily exceed it's 'design load' and fail prematurely.

    Another component(s) affected by wheel offset is the loading on the king pins/bushings or ball joints and, to some extent, control arms and bushings, spindles, and frame attach points. I am not saying they will catastrophically fail in short order, only that the geometry and physics involved does impose greater laods than the original design.

    Also, front end geometry is affected. The 'scrub radius' of the front tires is altered, and not usually for the better. The greater the (outboard) offset, the more the wheel and tire feed back into the steering system the road impacts and ridges and so forth in the pavement. Think of it like putting a lever on the front wheel, sticking straight out from the spindle. Now imagine grabbing that lever, first very close to the spindle and trying to turn (steer) the wheel......the closer to it the harder it will be to turn it, but the farther out you grasp it, the easier it is to steer the wheel with the lever.

    Now, the offset in the wheel is the same as the lever. This also applies to the aforementioned loading on the spindle, "A" arms, bushings etc.

    Do what you want, but one thing you can't do, is deny the effects. You can only choose to either consider them too small to worry about or accept the affects as the price of "style", physics be damned.


  5. i don't know how wide your thinking, but, years ago i had a 93 chevy truck. one of those cho cho customs sort of things. it had 15x10's all the way around with 295/50r15's. it drove like crap followed all the ruts in the road. in the rain it was almost undrivable. 2 years ago i bought a 72 c10. when i got it it had 15x10 boyd's with 275/60r15's all the way around it. drove like crap. i traded those for some weld wheels as quick as i could. guy thought he'd won the lottery. as far as wearing out parts i never had any problems with either.
  6. Thanks guy's! Exactly the info I'm looking for. I just tried a 8X15 with 2&1/2 back space. I would work just fine for fit. I'm not at ride height so SAI is a guess but it looks like it would be passable. These are not the wheels I'll be running, just tryin g to figure out what I need to find.
    Another question; Are spacers going to have the same effect as changing the off set? Seems to me It would. If I could safely run a 1" spacer then the 8&1/2" X15 with 4&1/2" back space that I already have would work. (effectively make them a 3&1/2" back space?) They match the rear 10X15. And I already have them!
  7. boooooob
    Joined: Sep 14, 2012
    Posts: 38



    I am boooooob I have no expertise in this area, but I have learned whatever your wheel width is, is usually about 1" less then the total outside rim . So an 8" wheel 0 offset is 4.5" (center), if you go + offset you will be putting the wheel closer inside to the vehicle, if you go - offset you will be going away from the vehicle, which would be much worse for bearings..... too much + offset will usually hit something on the inside (calipers, steering linkage) especially on older vehicles at least up front.:D

    But this is the weekend/alcohol so nothing can be held against me:D:D

  8. robyyo
    Joined: Sep 8, 2005
    Posts: 234

    from Orange CA

    What he said.
  9. Booooob, Offset is where the rim is in relation to the mounting surface. Back space is the distance from the inside of the rim to the mounting surface. I'm pretty sure I got the positive and negative right, (I'm in weekend mode myself :D )but these guys will let us know!:D Now get back to drinking!;)
  10. So would you guys consider an 8&1/2" wheel with 3&1/2 back space too much? What about 2&1/2" back space?
  11. A perfect example of "positive" offset is a FWD wheel.
    The same as increased back space.
  12. It is like putting a cheater bar on a wrench. The farther out from center that you get your wheel the more pressure it puts on the bearing.

    Its like waddyacare said, it is not normally a problem unless you go real extreme.
  13. Heo2
    Joined: Aug 9, 2011
    Posts: 661


    I had 6" crome reverse on the frontend inch with 1,5 backspace
    and i split the stearingbox in half when i hit a pothole and hit
    a tree on the side of the road lucky for me it hapened at
    low speed
  14. So what's extreme? Do the measurements I have look close to extreme? I know the fat tires will pull in ruts on the freeway. My "other " car has fat tires and I drive I 90! I can live with that. I'll run 8" wheels up front no matter what I do for suspension, to fill up the fat fenders, and go with the rear. I'm at a point where I'm not committed to this swap, but I'd really like to make it work. But I want to do this right. She's a keeper!
  15. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,480


    It largely depends on the overall strength of the components being used. Yes, less backspacing does indeed place more stress on the wheel bearings, and other adjacent suspension components.

    15"x8"s on a rear axle, with 2-1/2" backspacing will likely not cause so much extra wear that you'd ever notice it. On the front of a Model A, you bet it would.

    I run 15"x10"s, with 3-1/2" backspacing, spinning 36" x 12-1/2" tires on the front my OT/DD. They are, of course on a 3/4-ton spindle, on a solid axle, under a sub-1/2-ton truck. No wear issues. It is all application dependent.

    In short, inspect and grease you bearings joints, etc. at a regular interval. Properly torque them. Keep an eye on how much play, if any you can detect between inspection intervals. Replace as necessary. Bearings and seals (save for some rare cases) are not expensive.
  16. Thanks guys, I think I'm over thinking this:rolleyes:
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,480


    If you have to change your wheel bearings every 25,000 miles, instead of 50,000 miles, is that going to diminish the enjoyment of your vehicle?

    Wrench, drive, be happy, repeat as necessary.
  18. Not necessarily!

    Way too many guys just slap things together without thinking at all. At least you are aware for things, which is a good (smart) thing. :cool:
  19. my buddy had 15x10 wheels on a jeep and that was the only vehicle that i remember having to have the front wheel bearings repacked every 3-4 months compared to 1 time a year on anything i drove with maybe 7"rims. those 8" rims you mentioned should be fine so lets see some pic's!
  20. boooooob
    Joined: Sep 14, 2012
    Posts: 38


    You sure about too much positive back space:confused: Thats very negative and probably a reverse wheel, which is going to stick outward, 0 offset is 4.8" so you will be outward 1.3" or 2.3".......... Oh well back to drinking:D:D
    Have a good weekend:D


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