The Mazda Cosmo Sport (L10A/L10B) ran from May 1967 to September 1972, hand-built at roughly one car a day for a total of 1,176 units — 343 Series I cars and 833 Series II. It was Mazda’s first production rotary car and one of the first production rotary cars from any manufacturer. Between the two series, Mazda changed more than the badge: the wheel diameter itself went from 14 inches to 15 inches, alongside a longer wheelbase, more power, and an extra gear.
OEM Wheel Specifications
| Spec | Series I (L10A, 1967-1968) | Series II (L10B, 1968-1972) | Confidence |
|---|---|---|---|
| Engine / output | 0810 twin-rotor, 982cc, approx. 110hp | 0813 twin-rotor, approx. 128hp / 103 lb-ft | Confirmed |
| Transmission | 4-speed manual | 5-speed manual, plus power brakes | Confirmed |
| Wheel diameter | 14 inches | 15 inches | Confirmed |
| Tire size | 6.15-14 (165R14 radial equivalent) | 155HR15 | Confirmed |
| Bolt pattern (PCD) | 120mm, 4-hole (4H120) | Reported (no manufacturer spec sheet found) | |
| Hub bore | Not independently confirmed | Unconfirmed | |
| Rim width / offset | Not independently confirmed | Unconfirmed | |
The wheelbase itself grew by 15cm for the Series II, giving the car more interior room and a steadier ride, and the extra inch of wheel diameter arrived alongside the bump from 110 to 128 horsepower and the switch to a 5-speed gearbox. So a 1967 Cosmo and a 1969 Cosmo can look nearly identical at a glance but be running two different wheel sizes underneath.
The 4-hole, 120mm bolt pattern is consistent across both series, and it isn’t unique to the Cosmo Sport within Mazda’s own lineup: a Japanese-language reference on bolt circle diameters groups the Cosmo Sport together with the second-generation Cosmo (CD, 1975-1981) and the first-generation Luce Rotary Coupe under the same 120mm PCD, and a separate owner discussion citing the same figure independently arrives at “PCD120, 4-hole.” Neither source is a manufacturer spec sheet, so we’re presenting this as reported and cross-referenced rather than factory-confirmed — we could not find an official Mazda document that states it directly.
What This Means for Aftermarket Fitment
A 4-hole, 120mm bolt pattern is unusual by modern standards — most current aftermarket wheels are drilled for 4×100 or 5×114.3 — so fitment on a genuine Cosmo Sport is really a period-correct-wheel question rather than a “browse any aftermarket catalog” question. Specialist reproduction wheel makers for Japanese classics, including RS Watanabe’s Eight Spoke line, list 120mm as one of the PCD options they produce, though we could not confirm from their published matching data that the Cosmo Sport specifically is listed as a compatible fitment — worth confirming your hub spec directly with the wheel maker before ordering.
Wheels Currently in Stock
Because the Cosmo Sport’s factory bolt pattern is an uncommon 4×120 rather than a bolt pattern shared with more common classics, we don’t carry a direct OEM-fit wheel for it. If you’re restoring a genuine L10A or L10B, check our current stock for period-style Japanese classic wheels and confirm bolt pattern and hub spec before buying, or message us with your car’s details and we’ll help source in Japan on request.
What We Could Not Verify
- Hub bore diameter for the factory wheel — no source we checked published this figure.
- Rim width and offset for either the Series I 14-inch wheel or the Series II 15-inch wheel.
- Whether all 833 Series II cars used an identical wheel spec throughout the four-year run, or whether any running changes occurred.
- The wheels on the car pictured in this article are painted steel wheels with trim rings/hubcaps, consistent with a period-correct restoration — we could not confirm from photos alone whether they are original Mazda-stamped wheels or correct-style reproduction parts.
Sources
- Mazda Cosmo – Wikipedia (English) https://en.wikipedia.org/wiki/Mazda_Cosmo
- ナット座ピッチ直径 – Wikipedia (Japanese, PCD reference table) https://ja.wikipedia.org/wiki/%E3%83%8A%E3%83%83%E3%83%88%E5%BA%A7%E3%83%94%E3%83%83%E3%83%81%E7%9B%B4%E5%BE%84
- Yahoo!知恵袋「コスモスポーツ（L10B）のホイールサイズPCD」 https://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q12195108412
- Blockley Tyres「Mazda Cosmo」(period tire size reference) https://www.blockleytyre.com/make/mazda/mazda-cosmo
- RS Watanabe「P.C.D.」ページ(対応PCD一覧) https://www.rs-watanabe.co.jp/products/wheel/p-c-d/