Why This Page Exists
Across more than a hundred fitment guides we have now written, one field comes back empty more than any other. Not the bolt pattern — that is almost always published. The hub bore.
The Japanese factory databases print it as 調査中 — literally “under investigation” — on dozens of vehicles. That is not a blank cell; it is the compiler saying the figure has not been researched. On some cars nobody publishes it at all.
This page explains what the number is, why it matters more than people think, how to measure it yourself, and which cars we have found it missing on.
What the Hub Bore Actually Does
The hub bore is the diameter of the hole in the middle of the wheel, and the register it seats on is the machined circular step at the centre of the hub.
There are two ways a wheel can be located on a car:
- Hub-centric. The wheel sits on the register, which centres it and carries the vehicle’s weight in shear. The studs clamp the wheel against the hub face. This is how almost every modern car works.
- Nut-centric. The wheel is centred by the tapered seats of the lug nuts pulling it true. The bore only has to clear the hub. This is how a lot of 1960s and 1970s fitments work — and it is why, as we argue in our Hakosuka guide, the classic wheel makers do not publish a bore for those cars.
On a hub-centric car, running a wheel whose bore is too large means the studs are carrying load they were not designed for. It will feel fine at first. On a heavy vehicle it is not fine.
The Asymmetry Nobody Warns You About
Getting the bore wrong is not symmetrical.
Too large is a problem you can fix. A wheel bored 73 mm on a 60 mm hub takes a 60 mm hub-centric ring, costs a few pounds, and is completely normal — almost every aftermarket wheel is bored large deliberately so one wheel fits many cars.
Too small is not a problem you can fix. A wheel bored 66 mm will not go onto a 67 mm hub at all. It is an interference, not a loose fit, and no ring helps. We hit this exact case on the Mitsubishi GTO at 67 mm, shopping in a market full of 66 mm Nissan wheels.
So when you are buying, the wheel’s bore is your floor, not your target.
How to Measure It
- Take a wheel off. You need to see the hub.
- Find the machined circular step the wheel seats on — the raised boss at the centre. This is not the outer edge of the hub flange, and it is not the brake disc’s centre.
- Measure its diameter with a caliper, across the widest point.
- Measure again at ninety degrees and take the larger of the two figures. Fifty-year-old hubs are not always perfectly round.
- Do the rear as well as the front if the car has independent rear suspension or a live axle. They are not always the same — see below.
Send us the number with your chassis code and we will match wheels to it, and publish it here with credit.
Front and Rear Are Not Always the Same
This catches people, and two cars we have covered demonstrate it clearly.
On the Datsun 240Z, careful owner measurements give roughly 72.7 to 72.9 mm at the front hub and 67.9 to 68.1 mm at the rear stub axle. The car has independent rear suspension and the two ends are simply different parts. There is no single “S30 hub bore”.
On the Sunny and Sunny Truck, RS Watanabe publishes the figure as フロントノミφ73 — “front only, 73” — and declines to give a rear figure at all, because the rear is a live axle.
And the Honda NSX is printed in the Japanese database as 70/64 mm, a pair rather than a single number, on a mid-engined car with different front and rear hubs.
So: do not buy four identical hub rings on the strength of one published figure.
Where the Number Is Missing
Cars we have covered where the Japanese factory database explicitly says the hub bore has not been researched:
- The entire Toyota X platform — GX81, JZX90, JZX100 Chaser, Mark II and Cresta. Only the JZX110 Verossa has a figure, at 60 mm.
- Nissan Stagea, every grade including the 260RS.
- Nissan Fuga Y50 — while the Y51 and every other FM-platform car reads 66 mm.
- Bluebird U12, U13 and U14, while the Sylphy successor reads 66 mm.
- FTO and Galant VR-4, while the Legnum reads 67 mm.
- Kei sports cars — the Beat, the Cappuccino, the AZ-1.
- Pulsar GTI-R, where no hub-ring maker lists a product either.
- Hilux 2WD petrol grades and the Crown S130 wagon.
And cars where no source publishes it at all, including the Isuzu Bighorn, the VehiCROSS, the R30 and R31 Skyline and the S12 Silvia.
The Common Japanese Figures
For orientation. These are the registers we have confirmed most often across our guides:
| Bore | Typically |
|---|---|
| 54 mm | Toyota and Daihatsu small cars, kei cars, Celica and Caldina turbo |
| 56 mm | Subaru, Honda Life, ordinary Honda Civic and Integra |
| 60 mm | Toyota rear-drive and luxury — Crown, Celsior, Soarer, Supra, Altezza, Estima, Harrier |
| 64 mm | Honda performance — Type R, Accord Euro R, S2000, Honda Z |
| 66 mm | Nissan generally — Silvia, Skyline, Z, Fuga, Laurel |
| 67 mm | Mitsubishi and Mazda — Evo, GTO, Diamante, MX-6, Bongo, MX-5 NC |
| 106 mm | Japanese light trucks — Hilux Surf, Prado, Land Cruiser 80 |
| 110 mm | Land Cruiser 100 and the post-1999 70 series |
Use that table to sanity-check a figure, never to replace one.