Upgrading Dawes Kingpin 500A Wheels: Finding Modern Alternatives

ByThe Answerlode Editorial Team

Understanding the 500A Problem

You’ve stumbled onto one of the trickier issues facing Dawes Kingpin owners: the 500A wheel size. This isn’t a marketing designation—it’s an ISO 37-440 wheel, named after its 440mm bead seat diameter. The 500A was a French standard used primarily for European juvenile and folding bicycles, and outside the Kingpin, it barely exists in the modern cycling world.

The real challenge isn’t that 500A wheels themselves are rare (many Kingpins are still on their original wheels). The problem is finding replacement tires. Manufacturers stopped making 500A tires years ago. A quick search online returns almost nothing. This leaves owners with three practical options: keep and maintain existing wheels, have wheels rebuilt with modern spokes, or switch to a compatible modern size entirely.

Why 500A Disappeared

The 500A size was never popular outside the Kingpin’s specific niche. By the time folding bicycles became mainstream again in the 21st century, manufacturers had standardized around two main 20-inch wheel sizes: ISO 406mm and ISO 451mm. These are far more common and have much wider tire selection. The 500A died not from technical failure, but from market consolidation—there simply wasn’t enough demand to justify production.

The 451mm Option: The Easiest Path

If you want to go the new-wheels route, upgrading to 451mm (ISO 407, sometimes marked “20 x 1 3/8”) is the most practical choice. Many Kingpin owners have successfully done this. It gives you access to dozens of modern tire options from mainstream manufacturers, and 451mm wheels are widely available.

The catch: you’ll need new rims and hubs, not just tires. The bead seat diameters (440mm vs. 451mm) are incompatible—a 451mm tire will not fit a 440mm rim, and trying to force it risks rim damage and tire failure. You’re looking at a full wheelset replacement, which typically costs £150–400 depending on quality and components you choose.

Before you buy, confirm that a 451mm wheelset will fit your Kingpin’s brakes and frame. Most Kingpins accommodate the upgrade without issue, but it’s worth checking your specific model.

Rebuilding Your Existing Wheels

If you prefer to keep your original wheels and rims, rebuilding them is technically possible. A skilled wheel builder can replace broken or tired spokes with new ones, respoke the wheel, and true it again. This preserves the original 500A rim and hub.

The complications: spoke availability for 500A wheels is limited, and you’ll need to find a builder familiar with older, non-standard sizes. A local independent bike shop may be willing to help, or you might contact specialist vintage-bike mechanics. Expect to pay £60–150 per wheel for a full respoke and rebuild. It’s less expensive than replacing the whole wheelset but requires finding someone with the skill and willingness.

Once rebuilt, you still face the original tire problem. You won’t be able to replace the tires with new stock—but if your current tires are serviceable, you can continue riding on them while looking for suitable used replacements, ideally acquiring a few spares while they’re still available secondhand.

Finding Spare 500A Tires While You Can

If you go the rebuilding route, your best strategy is to scour eBay, Gumtree, Facebook marketplace, and vintage cycling forums for unused or lightly used 500A tires now. Keep them stored in a cool, dry place. They may last decades unused, and having spares in your garage is insurance against being stuck with an unrideable bike in five years.

Making Your Decision

Keep the wheels if: You want to preserve originality, you can find usable spare tires, or the wheels are in good condition and your current tires are still serviceable. This works if you’re not commuting long distances and can accept limited tire choices forever.

Rebuild the wheels if: The rims are good but spokes are broken, and you have access to a skilled builder. This is a middle path: your investment is smaller than a new wheelset, and you maintain originality.

Replace with 451mm if: You want modern tire options and will actually use the bike regularly. The cost is higher upfront, but you’ll never worry about parts availability again. Many Kingpin enthusiasts consider this the practical long-term choice.

A Final Thought on Spoke Count

Incidentally, earlier Kingpins came with 36-spoke wheels, while some later models have 28-spoke rims. If you’re rebuilding, try to source 36-spoke versions if available—they’re more durable under load and less prone to spoke breakage than 28-spoke designs.

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