rim offset and adapters....

[Zed]

I've update the illustration per request to reflect identical wheels with different offsets.

IMHO FWD offsets look fine on a Z.

[pparaska]

Dan, I was thinking of the effect of a longer arm to the vertical load on the bearing farthest from the center of the contact patch. The closest bearing. Vertical forces are all that matters, but a moment equalibrium and vertical force equilibrium eqs. are needed to solve them. Preaching to your choir, I know.

Anyway, if the center of the contact patch is a distance D laterally from the inboard bearing, and the outboard bearing is a lateral distance d from the inboard bearing, the relationship for the vertical forces on the bearings are:

F(outer) = Center of Force * D/d (downward)

F(inner) = Center of Force * (D/d - 1) (upward)

The only thing that matters here is the center of the contact patch (assuming all weight acts there).

If you add a spacer to a given wheel/tire combo, then D gets larger. As you can see both loads go up. But if you add a spacer to a same width tire wheel that has more positive offset (hub face close to pretty side of wheel), so that the center of force is still acting the same lateral distance from the bearings, all the forces on the bearings, spindle, etc. are the same.

Rick, I used that catch all phrase "all else being equal", saving myself from having to discuss the loads due to wider tires :devious: That phrase always gets you out of trouble, huh? Thanks for that explaination though! Yes, wider tires do add to the loads - in several ways.

[VRJoe]

Ok, I'll jump in here for a moment. Using Petes' diagram above I'll try to explain it this way:

The bearings are designed for a LOAD of X with a FORCE CENTER at D.

If the load (X) is the same and D remains the same it makes no difference if D includes a spacer. The forces on the bearings are the same. If the design for D is 3" it doesn't matter if 2" is from the rim and 1" is from a spacer or if 3" is from the rim, the bearings see the same force.

If D changes (+ or -) then the force exerted on the bearings changes and does nasty things to the bearings.

If load (X) changes we get the same effect, changes to the forces exerted on the bearings. Load (X) is effected by almost everything if you really get into it, but it does not have the same impact as the moment arm (D). Things get interesting from the load aspect when you take suspension into account .

Think of it like a lever if that helps.

Spacers may have some issues, but they shouldn't fry bearings if they're used correctly.

-VRJoe

[240znz]

I'm glad I didn't take physics at uni...gezzz...my head hurts trying to figure this out...ouch:ermm:

[mike240]

i agree with both dan and pete.

dan, i also think that the 'flat face' look of fwd offset wheels don't look as aggressive as slightly deeper dish wheels and that spacers can cause problems in the sense that if they aren't perfectly round and flat (i.e. not warped). to me, it's an extra piece in there. i'd much rather have my wheel bolted directly to the hub.

pete, you are correct in the sense of the center of the track line. yeah, the spacers push the wheel out more but the + offset of the wheel brings the center of the track line back in. it's good to get a spacer where the width is EXACTLY the same as the offset of the wheel.

they may work well for some people and more power to them but they just aren't my cup of tea.

IMHO, if wheel companies would stop being little bitches and make it where you can specify the backspacing and offset of the wheels when you order them...W/O having to give up your firstborn to pay for them. the last time i checked, they were here for us, not the other way around. too bad we can't boycott them.