Cycling and Picking the Proper Width Tires to Match Your Bike (and Wheels). All Angles Considered (Or Maybe “A Lot” of Angles).
One of my favorite characteristics of cycling centers around the toys. I loved toys as a kid and now that I make my own money, I haven’t changed a bit, my toys have just gotten more expensive. If you ask me, this is exactly as it should be.
In road cycling, much has changed over the last few years as wider tires and have become all the rage. Rim width has changed to accommodate the wider tires while maintaining aerodynamics in roughly the same way the old 19 to 20 mm rims were compatible with 23 mm tires. Today, rims come in widths ranging from the old alloy standard of 19 mm and run all the way up to 25 and even 29 mm. This can present interesting problems when it comes to restoring old frames such as my Trek 5200, but also a solution…
The reason for the explosion in popularity of wider tires is sound – wider tires, within reason, improve comfortability enough that they can more than make up for issues in rolling resistance. In simple terms, you lose watts with wider tires but gain more watts with a smoother ride. Back just seven or eight years ago, everyone rode 23’s. Today, 28’s on road bikes are quite popular, while 25’s and 26’s are vastly more prevalent that the old 23’s. I’ve got about 60,000 miles on 23 mm tires and about 14,000 on 25’s and 26’s and I can tell you without hesitation, I won’t be going back to 23’s. 25’s and 26’s are the cats pajamas, comparatively.
Where this really gets interesting (and incredibly geeky) is with increased rim widths.
As wider tires grew in popularity, rims followed suit. As it turns out, if you simply put a 25 or 28 mm tire on a rim that’s 19 mm wide, you end up with a lightbulb effect where the profile of the tire and rim ends up looking like a lightbulb, or for a 28 mm tire, an ice cream cone. If, however, you make the rim wider, the lightbulb effect is diminished and your wheel/tire combination start resembling the old 19/23 mm combination of old. In fact, modern testing has shown that, for the pro sprinters, they want their rim to be 1 mm wider that the tire. So, if I’m running a 25 mm tire, I want the rim to be 26 mm wide. If I’m a seasoned pro and my sprint top speed is north of 45-mph (72 km/h). I most definitely am not and I need a good 6% hill to get up to that kind of speed. I roll a 25 mm tire on 23 mm wheels for my Trek, and 26 mm tires on 25 mm wheels for my Specialized and those are plenty fine.
Here’s where this gets geeky – and incredibly awesome for anyone with an older bike/frame. See, up until about eight years ago (it’s 2021 now), road bikes were built for 20 to 23 mm tires exclusively. Everyone knew thin tires were obviously faster, so why build a fast bike to use slow tires? Well, now that the real world trumped the lab experiment (as it so often does), we know that wider tires, up to 28 mm for a road bike are superior to the old 23’s. This presents clearance issues on older bikes at the chainstays. On my 1999 Trek 5200, with 19 mm wide rims, I couldn’t fit more than a 24 mm tire. The lightbulb effect would cause a 25 mm tire to rub the chainstays when I climbed a hill out of the saddle. However, when I jumped to the 23 mm wide Ican wheelset, the lightbulb/ice cream cone effect is lessened as the rim width increased by 4 mm… so I can easily fit a 25 mm tire without fear of rubbing. In fact, I’ve been running 25’s for coming up on two seasons on that bike without a single issue. Without getting lost in the weeds (which is definitely possible), the wider rim meant I could fit a wider, more comfortable tire on the bike. This has its limits, of course; a 26 mm tire on a 25 mm wide rim is a bridge too far for my Trek. The tire will rub the chainstays out of the saddle – to check, simply install the tire and wheel and try to push the tire into the chainstay. If you can touch tire to chainstay by pushing the tire toward the chainstay with your finger, the tire wall likely rub the chainstay when you’re climbing out of the saddle (btw, you’re not looking to ram the tire over, simply apply some side pressure to the tire to see if you can hit the chainstay).
And that brings me to the Venge. In the comparison photo above, I’ve got the Venge with the 23 mm wide x 38 mm deep standard Ican wheelset on the left and the upgraded Fast & Light 25 w x 50 d upgraded wheelset on the right. The photo on the left has my Venge shod with a 25 mm tire, the right with a 26. As I said a paragraph ago, the 25 mm rim/26 mm tire combo doesn’t work on the Trek. It’s wonderful on the fourteen year newer Specialized. Now, a friend has a Venge as well, and he did get a 28 mm tire to fit but the clearance betwixt the tire and seat post was tight. The chainstays had enough clearance, though he said for the future he’d be sticking with a 25 or 26 rather than risk a pebble or dirt/mud getting stuck between the seatstay and tire, ruining his frame.
So let’s look at this in terms of real clearance. I’ve got both bikes:
The first two images are from my Trek 5200, the third is of my Venge. So, we’ve got a few millimeters either side on the Trek for clearance. This is just enough to keep the wheels from flexing under load to a point where the tire could hit the chainstay. I’ve got another millimeter for the Venge. Again, enough so the wheel can’t flex enough under load to make the tire rub the chainstay.
Again, with the Trek, the tire clearance only works because the rim width is 23 mm. If I had a 19 or 20 mm (or likely, anything wider) rim, I wouldn’t be able to fit anything more than a 24 mm tire. I’ve tried 25’s with a 19 mm rim and ended up having to touch up the paint on the inside of the chainstays.
One final note. Another friend with a 5200 tried a 25 mm tire on a 29 mm wide rim. That didn’t work, either. The rim was too wide.