Is it time to replace your race suit? Let’s get you track-ready. Customer Question: Fitting A Personal Wheel To A BMW M3, And When You Actually Need A Spacer
Customer question, steering wheel bosses and PCD
This came in this week and it is a good one, because the answer is not the same for every M3. The question was simple enough: a Personal wheel, an M3, and does he need a 6 x 74mm boss or a spacer.
Short version. If it is an F80 M3, buy the B-G boss and you are done, because every B-G hub is drilled for both patterns. If it is an E30, E36, E46 or E90, we do not list a B-G boss for those and everything else on the shelf is 6 x 70mm only, so yes, you need the spacer. And there is one thing about the spacer that catches people out, which is the rest of this page.
- Personal and Nardi wheels are 6 x 74mm PCD. MOMO, Sparco, OMP and Mountney are 6 x 70mm
- Every B-G Racing hub we sell is dual drilled for both patterns
- Every MOMO, OMP and Sparco hub we sell is 6 x 70mm only
- The B-G 6 bolt spacer converts one pattern to the other from 40mm upward
- The 10mm and 20mm spacers do NOT convert, they need the boss and wheel to match already
The two numbers, and who uses which
Almost every aftermarket wheel made in the last forty years uses one of two bolt circles, six bolts on either a 70mm or a 74mm circle. Written down it is 6 x 70mm PCD or 6 x 74mm PCD, and PCD just means the diameter of the circle the bolts sit on.
Your Personal is 6 x 74mm. So is Nardi and so is Raid. Everything else we sell in volume, MOMO, Sparco, OMP, Simoni Racing and the Mountney M-Range, is 6 x 70mm. The wheel and the boss have to agree, and a 4mm difference across the circle is enough that the bolts simply will not line up.
6 x 70mm
MOMO, Sparco, OMP, Simoni Racing, Mountney M-Range and Reverie. This is the common one, and it is what every MOMO, OMP and Sparco boss kit on this site is drilled for.
6 x 74mm
Nardi, Personal and Raid. Fewer wheels, but they are the ones people buy when they want something classic looking, which is why this question comes up as often as it does.
Which M3 have you got?
This is the bit that decides your answer, because we list a B-G hub for one generation of 3 Series and not the others.
| Your M3 | Boss we list | Drilled for | Spacer needed for a Personal? |
|---|---|---|---|
| F80 M3, 2014 to 2018 | B-G Hub BMW 3 Series 2011-2019, £109.99 | 6 x 70 and 6 x 74 | No, bolts straight on |
| E90 and E92 M3, 2007 to 2013 | MOMO or OMP | 6 x 70 only | Yes |
| E46 M3, 2000 to 2006 | MOMO or OMP | 6 x 70 only | Yes |
| E36 M3, 1992 to 1999 | MOMO, with and without airbag | 6 x 70 only | Yes |
| E30 M3, 1986 to 1991 | MOMO | 6 x 70 only | Yes |
Prices include VAT and are correct on 16 August 2026. We checked all 62 BMW boss kits on the site for this: every B-G one is dual drilled, and every MOMO, OMP and Sparco one is 6 x 70mm. If your M3 is not standard, or the column has been changed at some point, ring us before ordering either part.
The spacer that converts one pattern to the other
B-G make an alloy spacer that is dual drilled the same way their hubs are, 6 x 70mm on one face and 6 x 74mm on the other. It bolts to your 6 x 70mm boss on one side and your Personal wheel bolts to it on the other, and it comes with the bolts. £33.60 including VAT.
It is sold in seven depths: 10mm, 20mm, 40mm, 60mm, 80mm, 100mm and 120mm.
What that does to your driving position
Worth being straight about. Because only the 40mm and up depths are dual drilled, converting the pattern also brings the wheel at least 40mm closer to your chest. There is no way to convert the PCD without moving the wheel, and anyone who tells you otherwise is selling you the wrong part.
On some cars that is exactly what people want. Plenty of drivers fit a spacer on purpose to bring the wheel to them, and 40mm is not far off what a lot of people choose anyway. On a car where you already sit close to the wheel it is worth measuring before you order, because 40mm is more than it sounds when your arms are already bent.
If you want the position adjustable instead of fixed, B-G do an adjustable alloy spacer at £118.80 that moves between 40mm and 70mm and is dual drilled the same way. It is the dearer answer but you only set it up once.
What it costs either way
| Route | Parts | Total |
|---|---|---|
| F80 M3, direct | B-G dual drilled boss | £109.99 |
| E30 to E90, with the spacer | MOMO or OMP boss, plus B-G 6 bolt spacer 40mm or more at £33.60 | Boss price plus £33.60 |
| E30 to E90, adjustable | MOMO or OMP boss, plus B-G adjustable spacer | Boss price plus £118.80 |
All prices include VAT and are correct on 16 August 2026. Boss prices vary by generation, so the card for your car below carries the real figure. The spacer comes with its own bolts.
Those two things settle the whole order. Give Cameron the registration and he will confirm the boss, whether you need the spacer at all, and which depth suits how you like to sit, before you spend anything on either part.
Common questions on this
Can I just drill my existing boss to 74mm?
We would not, and we would not sell you a boss on that basis. The boss is the thing holding the wheel to the column and the bolt holes are not far apart, so opening them up puts the new holes into the edge of the old ones. Buy the spacer, it is £33.60.
Is a 6 x 70mm wheel on a 6 x 74mm boss the same problem in reverse?
Yes, and the same spacer solves it. It is dual drilled both faces, so it works in either direction. Same rule applies: 40mm or more, the 10mm and 20mm will not do it.
Does the spacer weaken anything?
It is machined alloy and it comes with the correct bolts, and it is a normal part to run. What it does change is leverage, because the wheel is further from the column, so torque the bolts properly and check them again after the first drive. If you are not confident doing that, we would rather you brought the car to us.
Will a Personal wheel fit any of your other cars the same way?
The logic is identical on every car we do a hub for. If there is a B-G hub, it is dual drilled and your Personal bolts straight on. If there is only a MOMO, OMP or Sparco hub, it is 6 x 70mm and you need the 40mm or larger spacer. Ask us and we will check your car in a minute.
Do I need anything else to finish the job?
The boss comes with its fixings and the spacer comes with its own bolts, so between them you have what you need. Check the horn wire reaches once the wheel sits further out, because on a spacer that is the one thing that occasionally comes up short.
Where to go next
We have written up the whole B-G and MOMO boss kit range by make, so if you want the full list for your car there is a guide for it. Every one of them carries the same pattern logic as this page.
Ring 0115 9893488 with the year of the car and whether it has an airbag, and Cameron will confirm the boss, the spacer and the depth in one go. It is a five minute conversation and it is a lot cheaper than a 20mm spacer that turns out to be the wrong part.
Garreth and Cameron have been supplying steering wheels, bosses and spacers since 2003. Tell us the car and whether it has an airbag and we will confirm the whole order before you buy any of it.
