My two cents: You can exceed the ideal handling of a bike with a tire size. Just because it can be done doesn't mean you should or that goodness will follow the intention.
I do not limit my observation to the analysis of head tube angle, fork offset, and wheel size. You can easily (sort of) diagram how all of that will play out in the alteration of the bike's trail dimension when shod with the objective tire. Many influences make a frame and a complete bike handle as they were designed. I have had an up-sizing and a down-sizing experience, illustrating the importance of the design of the bike. My down-sizing lesson was on my 1989 StumpJumper that was optimized for 1.95" tires. I mounted some 1.5" Ritchey Tom's Slicks for my weekday commuting, believing I'd gain a magical reduction of rolling resistance and cornering grip. The roll was much easier, but the awkwardness was introduced to the front geometry by the downsized tire converted the smooth handling bike into an awkward one with abrupt transitions at unexpected moments due to the angle of steering, angle of lean, and speed. The gain of rolling efficiency only seemed to bring me to the unpredictable edge of handling that would require countering in some manner. My up-sizing was on my Rambouillet, which I had been riding with 28 to 32mm tires. I wanted more cushion for smoothness when riding on unpaved surfaces and tried some 38s with the fenders off. Wow, not ideal. At all. The subtle coordination of a well-provided design, its dimensions, geometry, and tube selection in my size became obvious. That bike is designed around the 32mm tire. Under the sag under my weight and intended loads, all of my bike's details come together for a seamless riding experience, not counting the low-speed seated pedaling zig-zagging from flop that several others have noted over the years. I also put 2.2" HardPack II tires on my '86 RockHopper, eagerly anticipating riding the trails up to and down the Continental Divide in the area around Spar City and Creede in Mineral County, CO. Also not ideal. Floppy sidewalls were overcome by lazy steering and long stays, initiating several oversteering wipeouts as the sidewalls collapsed under load. Not a problem of underinflation, the point of the tire was being able to ride on paths best described as paved with baby head-sized stones. Those separated sharp edges required pretty robust inflation to avoid pinch flats. The bike design just transmitted loads abruptly to the tires by steering input and pedaling when turning because of the longer (pre-NORBA geo) stays and slack steering. Lots of individual conversations will ensue about how the rest of the bike and its tendencies can have effect on steering and handling. Andy Cheatham Pittsburgh On Sunday, August 31, 2025 at 12:46:53 AM UTC-4 Patrick Moore wrote: > The pavement wheelset for the 2016 Matthews road bike for dirt is shod > with 51 mm actual on 27 mm IW rims/48 labeled Soma Supple Vitesse SLs, 360 > digital grams, and tomato skin thin. You’d think they’d roll like butter on > ice. > > But compared to the former 61 mm 450 gram ultralight 700C Big Ones, they > “feel” as if they require extra effort to keep moving; this consistently > over ~18 months in identical conditions. (I jettisoned the Big Ones > because, while Schwalbe called them their *fastest rolling tire, bar none* > when > they came out ~10 years ago, and IME they lived up to this description, > they made the bike wallow in turns. The Somas make the bike handle as I > asked Chauncey to make it handle, like my Riv Roads; at least, as close as > 29” fat tires at 17 to 23 psi can do that. > > I chose the Somas as allrounder tires that would ride well on pavement but > be fat and soft enough to handle at least shallower sand. They handle very > well on pavement, roll somewhat sluggishly on pavement, but their rounded > profile ploughs in sand; not good. > > So, since I do have a second, Thunder Burt wheelset for off road, I don’t > need 50 mm tires on pavement; thus the questions: > > 1. Would I gain any advantage in handling, or even rolling resistance, do > you think, by swapping them for narrower road tires; say 44 mm Snoqualmie > extralights (I’d use tubes)? The Rims — Velocity Blunt SS — are 27 mm wide > inside. Extrapolating from the information on the SP web page I’d guess > these would measure 45-6 on the Blunt SS rims. > > 2. The bike was designed for 700C tires between 50 and 60 mm (with > fenders) and 650Bs up to 75 or 80 mm wide, tho’ ‘ve never used the latter. > I realize that this is a very general qeustion, but is there a rule of > thumb for how narrow you can go on a given frame designed for wider tires > without degrading handling? > > Note: if you don’t have statistics, anecdotes welcome! > > Anecdotal case in point for degraded handling: on NORBA-type rigid > mountain bikes, designed for 50s, 35 street tires felt OK tho’ handling > wasn’t sparkling. With 23 mm tires (26X1” Turbos) it was bad indeed (oddly, > degraded both straight line stability and cornering stability), tho’ they > made the bike fast in a straight line. OTOH, with 60 mm actual Big Apples > my old Diamond Back handled superbly on pavement, if a bit staidly. > > Any thoughts? > > Thanks, Patrick > > > -- > > Patrick Moore > Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum > > ------------------------------------------------------------------------------------------------------- > > Executive resumes, LinkedIn profiles, bios, letters, and other writing > services > > > ------------------------------------------------------------------------------------------------------- > > *When thou didst not, savage, k**now thine own meaning,* > > *But wouldst gabble like a** thing most brutish,* > > *I endowed thy purposes w**ith words that made them known.* > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/1a650123-9c45-47d7-8bb3-dd106b20df4en%40googlegroups.com.
