OnkelUdo wrote: billy bee wrote:
Another option is to run a 20mm wheel spacer and use 3-series wheels with a 40mm offset, but we are concerned that puts too much leverage (?) on the hub/bearing.
This is a popular misconception but if you think it through, you are not changing the stresses on the bearings or hub if the net offset difference is 0. That said, finding quality bolt on spacers in 20mm is slightly harder than 25mm.
Now lets think outside the box. if you are going bolt-on spacers, why not change to one of the most common bolt circles around and ditch the early BMW lug bolts, odd center bore size and less common bolt circle. I would vote 5 x 4.5" but others will have other opinions. This process costs a lot more in the converters (25mm adapters instead of spacers) as an upfront cost but WILL save heartache and likely money long term.
Not entirely true. While you can have a wheel that sits in the same spot edge of barrel wise, you do change the bearing stress anytime you add a spacer. When you draw out the force diagram on the hub/bearing, you have the weight of the car pushing down, the reactive force from the wheel supporting it, but you also have a torque because those two are not directly in line with each other. Torque in the direction of camber adjustment for lack of a better way to describe it.
As you move the mounting surface of the wheel outward, that torque load rises, even if the barrel edge of the wheel doesn't move. Think about it with an extremely unrealistic example, if you have a wheel that has an extremely convex face, something that moves the mounting surface out past the lip of the wheel. Then you add spacers to keep the barrel of the wheel in the same place it was before. There is now a very large upward torque on the hub. The normal force hasn't changed, there is still the same amount of weight sitting there, but because you've moved that mounting face, the torque has grown quite a lot.
Now, is it something to worry about with something like a 25mm spacer? probably not. But any spacer does increase that bearing wear by some amount.
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