Every CB550 owner ends up at the same place eventually. New bike, tired old rubber, and a simple-sounding question: what tires should I buy? Type it into the SOHC/4 search box and you'll turn up a thread that started back in April 2007 and simply never stopped — the CB550 Tire Thread, north of thirty thousand reads and five pages deep. It opens, fittingly, with a member apologizing for asking a question he knows has been answered a hundred times before, and then a decade and a half of owners pile in anyway. That's what makes it an institution: tires are the one thing every single 550 needs, the choice is genuinely confusing, and the forum has been quietly converging on the same hard-won answers the whole time.
Here's what those answers are.
The trap everyone falls into first
The single most important lesson in the whole thread is also the most counterintuitive: the fat tire you want is probably the wrong one. A stock CB550 wears a 3.25-19 up front and a 3.75-18 out back, both on skinny 1.85-inch rims that Honda stamped right into the metal. Walk into a tire shop with those numbers and you'll almost always get talked into a metric "equivalent" — a 100/90 front, a 120/90 rear — because they look meatier and the shop makes more margin on them.
The forum's resident authority on this, a long-time member who goes by TwoTired, has explained the physics more times than he'd probably like to remember. The short version: those metric sizes aren't actually equivalent. They're wider and shorter than the old inch-size tires, and they're optimized for the wider rims that later bikes came with. Pinch a too-wide tire onto a narrow 1.85-inch 550 rim and the sidewalls get squeezed into a steeper angle with less support. To stiffen them back up you run more air pressure, which balloons the center of the tread — the "crown" — so the bike now rides on a narrow strip down the middle. That strip wears fast, the tire "squares off," and the handling gets worse the longer you ride it. As he put it, it's insidious: a squared-off tire feels fine when it's new and slowly turns your bike into a bar of soap.
You don't have to take one man's word for it, because the thread is full of owners who lived it. Rider after rider describes the same arc — a 120 rear that wore square in the center, a bike that had to be consciously "held" through corners and kept trying to stand up and run wide, and then the fix: drop back to proper sizes and the bike suddenly steers itself, holds a line, and feels neutral again. One owner summed up the transformation as no longer leaning off the bike to fight it through every bend. The consensus that emerges is remarkably consistent: a 90/90 (or 100 at most) front and a 110/90 (or a 120 at the absolute limit) rear is about as far as a stock rim should stretch, and going back to genuine inch sizes — a 3.25 front and a 4.00 rear — is what most veterans land on after they've experimented their way through the wide stuff.
The brand roll call
Once sizing is settled, the thread turns into a long, friendly argument about brands — and after fifteen years a rough hierarchy has shaken out. At the top for grip, the Avon names come up again and again: the AM26 Roadrider gets praised as a lot of tire for reasonable money, and the stickier Avon Venom earns near-reverent mentions from members who say old-Honda racers put them onto it. Right alongside sits the Bridgestone family — the budget-friendly Spitfire that keeps getting called the best bang for the buck, and the dual-compound BT45 that riders love for wet grip and slower wear. Metzeler earns a loyal following too, with the Lasertec and ME77 turning up as the value pick that grips well in the rain.
Then there's the classic-look camp. Dunlop's old K81/TT100 is the period-correct choice, the GT501 is the sportier option, and the Continental range — the RB2 and KB112, or the TK22/TK44 pairing one European member has run for two decades — scratches the vintage itch. The cautionary tales cluster at the bottom of the price sheet. The Dunlop D404 gets dinged as a Harley tire that's really only a small step up from the cheapest options, and the Cheng Shin budget tires draw the most colorful scorn in the whole thread — the general verdict being that with tires, you get exactly what you pay for, and skimping on the only two contact patches between you and the road is a strange place to save forty bucks.
The 16-inch rabbit hole
No CB550 tire discussion survives long before someone asks about swapping the rear to a fat 16-inch wheel for that stubby, tire-forward chopper stance. The thread does not disappoint. Members point out the geometry actually works out — a 130/90-16 comes out within a millimeter of the stock 18-inch rolling circumference, so you don't lower the bike or wreck the gearing — and the look is undeniably beefy. But the handling verdict is blunt. One veteran famously compared a 16-inch rim on a cafe bike to having a smoking-hot sister: great to look at, useless for the thing you actually want to do with it. The wide, flat car-like profile that makes those tires launch hard off the line is the same profile that makes them reluctant to tip into a corner. The takeaway the thread keeps circling back to: if you want wider and you're willing to lace a rim anyway, lace a wider 18 rather than dropping to a 16, unless the drag-strip look matters to you more than the twisties.
Gravel, mounting, and the soap debate
Two smaller but genuinely useful threads-within-the-thread are worth knowing about. If you're riding mixed pavement and gravel, owners point toward dual-sport options like the Avon Distanzia or Michelin Anakee — with the caveat that finding them in true 18/19-inch vintage sizes is the hard part, since most modern adventure rubber is built for 17-inch wheels. And on the eternal question of mounting your own, the thread is encouraging: plenty of members do it at home with a pair of 11-inch tire irons and patience, saving the roughly $35–$70 per wheel a shop charges. The one repeated warning is to skip the soap when seating the bead — Honda's own service manual advises against it — and to not over-obsess about balancing, since more than a few experienced hands report vintage tires rarely come out of the box meaningfully out of balance.
What it all adds up to
Strip fifteen years of back-and-forth down to its bones and the CB550 Tire Thread teaches one quietly radical idea: on a bike this light, the skinnier, taller, correctly-sized tire is the upgrade. The fat rear looks fast sitting still and feels slow everywhere else. Buy the size Honda specified, spend your money on a name that racers and rain-riders trust rather than the cheapest hoop that fits, and your fifty-year-old 550 will steer with a precision that shames bikes worth ten times as much. None of that is marketing — it's the accumulated experience of a few hundred owners who tried the wide stuff so you don't have to.
If you want the full, unvarnished version — complete with the arguments, the exceptions, and the occasional beautiful photo of a build gone sideways — the CB550 Tire Thread is right there, and the SOHC/4 Owners Club deserves the credit for keeping that kind of knowledge alive and searchable for free. Go read it, and buy the club a beer while you're at it.
Get the tires right and the 550 finally handles like it should — which is exactly when the rest of the build starts to matter. The Thirteen Motorcycles CB550/CB500 catalog is built for that next stage: an under-seat electronics tray and center-stand battery box to clean up the wiring and shift weight low and central, plus ignition and taillight mounts to finish the cafe look. Sort the rubber first — then make everything above it look as good as the bike now rides.
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