Building Rare 3-Piece Wheels - How to Get it Just Right (Custom halves, Offsets, and More)

“Where’s the Ferrari!?” - that’s a fair question. Hopefully anyone curious sees this comment.

The plan was to hit the dyno this past Wednesday, but I ran into issues when pressure testing my new intercooler. I had a pinhole leak between the water and air sides… so it’s a bit of a setback. Next week, fingers crossed!

Awesome explanations!

Work Equip Anhelos here🙋‍♂

That's how it is in the civilized world. In my country spacers are not allowed.

Mike, your text values for the back spacing and wheel center line are swapped in the measuring portion of the video. One half of width is 4.625" and back spacing is 5.625".

Also, why not use the overall width of the rim, 10.25", instead of the stated width, 9.25", for your measurements. I've always found it easier to deal with those values especially when measuring and calculating. Besides, it doesn't matter what the stated width is. If there's not enough room for the actual width of the rim, you're going to have a bad time.

Great video all the same and thank you for putting it together. I'm excited to see where you take this car. My preference is for a squared off tire not stretched. I'm sure it'll turn out great whatever direction you take. Good luck!

Could you make a vid explaining deep, shallow, and standard convex wheels?

There were only two different 3 piece Alpina wheels, which was a 13“ for the Alpina 2002 race cars and a 15“ which was 5x120.

Great video and likely most people would be able to understand the general idea of how to calculate it. However, and I hate to be pedantic but details matter, in your math part, you made a couple errors, but came out with the right number in the end.

You indicate the wheel centre line as 9.25 / 2 which is kinda correct, but the numbers you show are 9.25 / 2 = 5.626. I'm no math expert, but I'm pretty sure that number should actually be 4.625. You likely included the lip dimensions in that, but a few seconds later you account for that again, completely unnecessarily, which could skew the numbers to make them incorrect.

Then you get into factoring in the back space and subtracting it from the centreline to get the Delta. You list your backspace as 4.625. That is not correct, as you measured it as 5.625.

And the whole subtracting the lip width just confuses the issue but you had to do that to make your numbers work to get the correct final wheel offset number.

You ALREADY measured the offset from the outside of the lip so it isn't necessary to do that again.

Calculating the OFFSET doesn't require the inside lip wheel width. Use the outside lip wheel width for offset calculations, which on your wheel is 10.5". The lip could be an entire inch or a foot thick and if you're measuring the back space from the edge of that lip with a straight edge like you did, the outside lip wheel width should be used in the calcs.

For your wheel: 10.25 /2 = 5.125 ---> 5.125 - 5.625 (back space) = -0.5.  This number is the delta you mention. Or just call it 0.5 because we already know it's a positive offset wheel.

Delta just means difference. The offset of a wheel is just the difference, or delta, between the wheel centreline and the back pad or mounting face of the wheel. That's it. That's all it is. It's not rocket surgery. 

The delta is negative number because it's a positive offset wheel; the back pad sits outboard of the wheel centre line (the centre line subtracting a number larger than that distance will give a negative number). A positive number would equate to a negative offset. It seems counter intuitive, I know, but it is what it is.

The only way to get those math numbers to come out and correlate to the correct positive or negative offset is to measure backspacing from the front lip which is kinda dumb and difficult to do. And likely would be front spacing and not back spacing. Or you could just subtract the backspacing measurement from the entire wheel width and whatever is remaining is the front spacing.

The calcs for this wheel would be: 10.25/2=5.125 = Centreline. 10.25-5.625=4.625 = Front spacing. (10.25/2)-4.625= +0.5 = Back space. 

Outside Width (oW) / 2= Centre line (CL)
CL - Back space (bS) = Delta (D) 
(oW/2) - bS = D ---> Negative number is positive offset, positive number is negative offset.

or

oW-bS= Front spacing (fS)
Offset (OS) = (oW/2)-(oW-bS) = Offset with the correct negative or positive, in this case, that number is +0.5" = 13mm = ET13.
OS=(oW/2)-fS

Likely the easiest thing is if you can remember that a wheel with the mounting pad closer to back of the wheel, like a deep dish, will be a positive offset,. Then just do the half width and subtract the back space and ignore any mathematical positives or negatives and just think of it as the Delta. Deep dish wheel is positive offset while a flat outside face is a negative offset.

How to keep the positive and negative offsets strait in your head? For me, I like deep dish wheels (and pizza) so thats a positive for me. I'm not so much a fan of flat faced wheels so to me that's a negative.

I hope all that makes sense. If you can keep the positive vs negative offsets straight in your head, offset is just the distance between the wheel centre line and the mounting face of the wheel. That's it. Probably best to not make it more complex than it needs to be.

Rim is just slang. Y'all need to chill. People are triggered over the dumbest shit sometimes.

Let's see you make a three-piece wheel cut from, say, a stock Fuchs center? & show us how to cut the center from the wheel...eh?

Non native english speaker here.. but i always assumed tire is the rubber bit, rim is the metal bit and wheel is both together..

Call me crazy, but I think when you calculated your offset you used the wrong backspacing. You measured 5.625" but when calculating offset, you used 4.625"?. So your offset should have been -13mm? Maybe someone can correct me if I'm wrong.

I am so happy that I already have found the perfect spec for my next project car :)
Already got the ET and with :)
Good with forums and pictures :)

Epic video :D

These wheels are beautiful on this project! 👌

👍🤙🔥

You added 5mm to clear standard brakes, why not see about different rotors from other BMW parts bin ? Are you really going with stock Calipers? I feel like you'll have to do this all again if you upgrade the brakes that you made your wheels not fit for...

Little to no info about those "custom halves"... maybe include things like reverse lip vs step lip in terms of wheel diameter... kind of important aspect to building modular wheels.

Súper cool staff !! Thanks you 🔝💯😍

Thanks Mike!

Camber is really the key to fitting wheels that don't really fit. I have 18x9.5" wheels all around on my E34, and the wheels are ET35 so I'm running a 30mm spacer in the front. Without camber, they poke out, but with -2º of camber, they tuck into the fenders quite nicely.

sick RIMS, daddy

I used to sell truck/jeep wheels online and had to explain how wheel specs work to 60 year old men over the phone multiple times a day. it was miserable every time. I got pretty good at it tho lol

fitment is art

I use the word "rim" to refer to the wheel without a tire, and the term "wheel" to refer to a rim with a tire. Keep using rim :)

Great content, 💯 learned a lot in regards to fitment. This will definitely help a lot when ready to get mine done.

I see the caliper to back face clearance but I feel in my thoughts I'd give it a little more to compensate for pad wear and caliper movement

Wheel = rim + tyre, isn’t it?

No stretch, put some real tires on there!

Thanks for the best wheel size explanation I’ve seen!

Two sets ... Street and track!!!

I'd spend a few dollars on a large digital caliper for ordering expensive custom wheel parts. Even an inexpensive caliper will provide far more accurate and precise measurements than a tape measure. Don't want to spend on a large caliper? Use some metal blocks of known dimensions and do a little addition to subtract the cost of a specialized tool.

Are there no taller brake rotors available? More hat in the brake rotor pulls the rotor ring inwards permitting the use of those wheel centers without spacers. I suggest reviewing what brake options exist to make the wheels a more native fit.

Would love to see a walk around of your 6.0

Very instructive video, this has always interested me (and confused me). ;-)

Considering the point and meaning of the build. Bolt them and send it like Cory would.

Great content, thank you so much

100% smaller lip and meaty tire. Looks better and way more practical if you are going to rip on.

Ierland Engineerings wilwood big brake kit should gain you about 1/2" of caliper clearance.

Please for the love of all that is holy do not go with a stretched tire look.
In the late 80’s, while stationed in Germany I had a1987 VW scirocco with 16” 3 piece OZ rims (yes I said rims). I was erroneously talked into putting stretched tires on the rims with the impression that handling would be improved. The result was that with in two weeks all that I had accomplished was severe road rash to the outer edge of the rims. After replacing the outer halves I went with, as you stated a “chunky” tire fitment. The result was a more predictable handling on the B500 road and a much more pleasing look. Needless to say I did the same thing with my 1975 2002 BMW.
Great content, any chance you will eventually start on the 02 series I’ve seen in the back ground?

Amazing ! Wheels fitment is a confusing thing to me. This video explains a lot and i'm sure i'll go back to it several times ! I would love to learn more about it in a future video.

Definitely do a part 2 with a comparison. Us visual learners will appreciate seeing the original wheel setup and then the new arrangement 👌🏻

Sorry but you made a major mistake in your wheel offset data. 9.25 / 2 is 4.625 not 5.626. You swapped offset and backspace numbers.

I dislike BMW and Ferraris but this has become one of my favorite channels because of you. You explain things in a way that I don't feel stupid or like you think I'm 5 years old. Another of my favorites is m539 restoration with only BMW content 🤯

fkin send it

european here, rim is the metal part, tyre is the rubber part, wheel is the whole assembly !! no other calling is correct here