I have not written about Bino, my Dahon Vitesse folding bike, in a long, long time. He’s still with me, although I haven’t ridden him very often.
Recently, my wife thought of following in my pedal strokes in returning to indoor cycling of her own. I still have the Minoura LR340 magnetic turbo trainer, and that still has its small wheel adapter to work with Bino’s much smaller wheels. However, there are a few things that need to be done before this plan can take off in earnest.
The more immediate one concerns Bino’s tires. The Schwalbe Marathon Racer tires are not a good match for the LR340, with their heavily grooved and pattern-cut treads. Most wheel-on turbo trainers require a tire with smooth tread to work their best and last as long as possible, and a treaded tire will make a huge mess of rubber particles on the trainer as it heats up. In a rookie mistake realization, I’ve already gouged a bit of a groove on the LR340’s resistance roller as is, running it without cleaning the rear tire it contacts first.
Step one, then, is to get suitable tires…and really, only one model in the Schwalbe lineup fits the bill: the Kojak.
People one generation older than me will perhaps know of a TV crime show of the same name. That’s exactly why Schwalbe named this tire like it did – its lack of tread pattern matches Detective Kojak’s smooth, bald pate. Even looking at other 406 mm (20″) tire offerings from other tire makers, the Kojak is one of the few options that looks most like a shrunken-down, slick-tread road bike tire.
Another difference is the rated width. Unlike the 40 mm (1.5″) Marathon Racers, the Kojaks are slightly narrower at 35 mm (1.35″). With this change, the recommended pressure range increases accordingly, up to a rated 95 psi (6.5 bar) maximum. While the Kojak isn’t explicitly designed as an indoor training tire, the added air pressure and smooth tread should work well with the demands of that job.
I’d like to report that installing these tires was easy, but that would be a complete lie. Schwalbe’s 406 mm (20″) tire offerings almost universally have tight wire beads, and there’s something with the diameter and 14 mm width of Bino’s Newson Sportec rims that makes tire mounting disproportionately hard.
With the swap to the Kojaks, a third difficulty factor arose with the reuse of inner tubes…which were simply too wide for this application. On a road bike, there is little issue with using an inner tube meant for, say, 32-47 mm tires inside a 28 mm tire. On a small-wheeled folding bike, I found out the hard way that the size discrepancy between inner tube and tire width must be kept to a minimum. There just isn’t the same amount of room to stuff away excess inner tube material into the inside of the tire…without it folding in on itself so badly that it makes its own holes and punctures, or pinching between rim and tire bead (the inner tube will blow out explosively when inflated in this condition). My 47 mm (1.75″) inner tubes worked fine with the 40 mm (1.5″) Marathon Racers, but barely worked with the 35 mm (1.35″) Kojaks.
It took multiple dismounts and remounts to get this absolutely right, stuffing any exposed or pinched inner tube inside the tire bead. It got to the point where one of my burly Pedro’s tire levers had had enough and snapped at the final attempt. If a tire is tough enough to destroy a Pedro’s tire lever while mounting, your wheel and tire combination is no joke to fit. Such difficulty of turnaround is one reason why working on Bino’s tire punctures on the roadside frankly fills me with a bit of dread. On a particularly bad day with crap weather, I wouldn’t look past just folding the bike, hailing a cab, and going home that way. It is a boon, then, that the Kojak tires supposedly come with a measure of puncture protection built into their carcasses.
With the Kojaks mounted, Bino is a QR skewer swap away from being ready for trainer duty. The other half of the puzzle is modifying the LR340 itself, in a bid to replace its broken components with a field repair. That will be a tale for another time.