Machining Wheel Hubs

[tnord]

This isn't directly related to my M3, but rather my F30 340 daily. However, I have what is perhaps an unreasonable aversion to wheel spacers, so I'm curious if this could also be a solution to finding wheels that could work for my M3.

I got a deal on some bimmerworld ta5r on BF a couple years ago, and have never been 100% satisfied with the fit. The rear wheels poke ever so slightly (though I haven't had any rubbing), and I like the marginally less aggressive setup of my OE winter wheels with spacers better (405M 8'' +34 with 12mm). On Apex's fitment guide for the F30, it gives two options for their "aggressive street" setups, a 9.5'' width with either an ET33 or ET35. I got the ET35, but it still looks like the tire (275 PS4S) look like it'll contact the fender under compression, but the camber curve under compression must tuck it just enough.

By my math the current setup with the winter wheels is

(8'' width / 2) = 4'' or 101.6mm
101.6mm - ET34 = 67.6mm
67.6mm + 12mm = 79.6mm from hub

the ta5r setup is
(9.5'' width / 2) = 120.65mm
120.65 - ET35 = 85.65mm from hub

so to make the ta5r the same as the winter setup, I'd need to remove 6mm of material from the hub and make it an ET41. I don't think that much is necessary, or maybe even safe. the ta5r is offered up to an ET44, so depending how things are manufactured there might be enough material at the center to still be fine.

curious if people have ever removed hub facing material for the wheel to obtain a proper fit rather than buy higher offset wheels and add spacers? thoughts?

[Nate047]

You say you are averse to running a wheel spacer... But you are considering cutting off part of the wheel? Not sure this is the right approach here.

Just because the TA5R is offered in higher offsets does not necessarily mean the mounting area is the same on the lower offsets and can just be cut down to size.

Off the top of my head I would say try a 265 or 255 tire, add a little bit of camber, and/or get a different set of wheels.

[tnord]

I don't know that it's the right approach either, that's why I'm asking if anyone else has done it, or knows of a reason it's a bad idea.

When you get a new wheel, the mounting face looks like a machined surface doesn't it? From a manufacturing efficiency perspective, I could certainly envision multiple wheels being cast with a minimum offset, then the hub facing material is machined down to the desired offset. In which case what I'm considering isn't any different.

But there's probably a minimum material depth that you need at the hub, and minimum depth of material for the wheel bolts. My inclination is that the 2-5mm I'd consider removing isn't going to be a big deal, but I don't know. Somewhere in all of this is a consideration for maximum depth also because you need a minimum amount of thread engagement of the wheel bolt.

[George Hill]

To double check your math and fitment also considering how the tire affects the setup I'd recommend punching your numbers into willtheyfit.com as a sanity check.

I don't know if you can chop up the hub face but I would look and see how "deep" the hub bore is. If its only 7mm then I don't think you can take 6mm off even if there is enough meat.