With boulderseal taking over so many of our Texas roads, I decided to try some wider tires for my randonneuring. Wider tires can improve handling and the ride on rough roads a lot. But, I spend so much randonneuring time trying to ride with riders who are faster than me that I didn't want to give up much speed with new tires.
I'm always surprised at how many people dispense tire width advice without even thinking about what kind of bike the target of the advice is riding. When it comes to tire width, all bikes are not created equal. Bikes that put the rider's profile completely above the tires are much more aerodynamically affected by wider tires than bikes that use small front tires and/or put the rider behind the front tire. A wider front tire may not slow down a low racer much, but it can certainly slow down a high racer. And even on my Stratus XP, which has a fairing and has me partially behind the front tire, I could see a very noticeable difference in speed when I ran wider tires. Of course, how much difference tire width makes is the subject of unending debate, and a very individual thing that depends on the rider and the roads ridden. You can do coast down comparisons, but rides are much more than just coasting down hills, so that doesn't really tell you much.
One of the things that finally jogged me into trying wider tires was the thinking held by some that aero wheels, especially wide aero wheels, can help with the aerodynamics of a wider tire, keeping you from losing much speed with them. I already had a set of aero wheels, which I rebuilt for this experiment. I documented rebuilding them in
this thread. Most riders don't use their expensive, delicate, low spoke aero wheels for randonneuring, but mine don't fit that description. They're old mtb wheels which have 32 spokes, so should be pretty strong, and even after rebuilding them, I don't have cubic dollars invested in them.
There are people who will tell you that aero wheels actually do better in the wind than regular wheels, but don't believe that for a minute. In a 50 mph crosswind, you'll like regular wheels much better than aero ones. With a 40 mph wind, aero wheels still aren't much fun. But with 30 mph or less winds, mine handle well. Since I rarely face winds harder than 30 mph on rides, that small problem isn't a deal breaker for me, so I decided to give these wheels a long run as my randonneuring wheels.
I had always run 559x25 Conti GP's on these wheels. These are fast tires. On my HED wheels, I didn't notice much difference in speed from my old 650c wheels and 23 tires, other than slightly better speed on fast descents. And even a tire that's only 2 mm wider than the 23's makes a difference in ride on rough roads. The GP 25's never handled any better than my 23's, though. I expect that's because a Conti GP just doesn't handle quite as well as a Michelin Pro Race, which is what I ran when I ran 23's.
But the experiment wouldn't be complete until I tried 28 mm tires on the HED wheels. I installed new Conti GP 28's last week, and Saturday's Peachy Keene was my first ride with them. I own this route and ride it often, so I figured it would be a good route for comparisons. The 559x28 GP's do look a bit silly on aero wheels, but I don't worry too much about making a fashion statement these days, anyway.
How much tire pressure to run is a debate, by itself. The GP 28's have a max of 116. I wanted to make sure to run enough pressure that I couldn't blame being slower on tire pressure, so Saturday, I inflated the rear to 108 and the front to 100 pounds. Peachy Keene has some rough county roads, but almost no boulderseal. Tire pressure experimentation will be necessary, and I'll likely end up running lower pressures than that on routes which are mostly boulderseal.
Before I get into the comparisons, let me remind once more that everyone is different. How valid my comparisons would be for anyone else is questionable. Also, I'm only an average speed rider. Since aerodynamics becomes a much bigger factor with speed, my findings especially wouldn't apply to a really fast rider. And Peachy Keene isn't the fastest of 200k routes. It is lots of very small county roads, with blind curves and stop signs, and lots of turns. My personal best time on this route is a 9:30, which I did two months ago. For comparison, My personal best time on any 200k is an 8:06 on Rio Vista Rumble. My best time on a 200k since losing half a lung to a surgeon is an 8:40, also on Rio Vista Rumble. It's plainly a faster route than Peachy Keene. Anyway, the bottom line is that if you're capable of a 7 hour 200k, my ramblings here certainly don't apply to you.
I rode with Steve and Peggy Saturday. One of the first things to do was compare coast downs with them. They are both light, strong riders who can drop me like a bad habit whenever they want. But, with my aerodynamic bike setup (I have a lot of seat recline, and with my long arms, have the handlebar low, out in front of my upper shins, much lower than where my knees are at their highest point), and gravity assist (I weigh 186 right now), on downhills, I out-coast almost everyone I ride with. With the 28's on Saturday, I still out-coasted Steve and Peggy. In the 20 to 25 mph range, my coasting advantage seemed pretty much the same as usual. At above 25 mph, I still out-coasted them, but not as much as usual. Not too much of a penalty, I figured, since I don't spend too many miles above 25 mph on these long rides.
A comparison between Saturday's ride and my ride on Peachy Keene two months ago seems like a natural. Conditions were very similar. On both rides, things started with a tailwind, but quickly changed. Two months ago, it was a hard southeast wind that showed up after a couple of hours. Saturday, it was a straight east wind. Temperatures were almost the same for both rides. I would normally expect to be a bit stronger for a May ride than a March one, but I hadn't ridden 200k or more in a month, because of the shingles I've had for the last three weeks. My strength for the two rides is probably very similar. My effort for both rides was, too. On both rides, I rode a brisk (for me) pace.
I did the March ride mostly by myself. As often happens when I do that, my stops were very short. Saturday, chatting non-stop with Steve and Peggy, my stops were a bit longer. Here are the stats:
Overall time On the bike time heart rate average
March 14th 9:30 8:33 139
May 8th 9:52 8:21 142
On March 14th, I spent less than an hour off the bike, pretty good for me for a 200k. The bottom line is that I put out a slightly harder effort Saturday, and had a slightly better time. I'm thinking that, just as it felt, the speed of these 28's is really close to that of the 25's, and to that of the 650C x 23's before them. And the ride of the 28's is pretty unbelieveable, comparison-wise. I quickly got very confident on the roughest parts of the road, and handling was easily the best I've ever seen on the Corsa.
I bought these 559x28 Conti GP's knowing that if I didn't like them for randonneuring on the Corsa, they'd work well as commuting tires on the Stratus XP. As well as they performed on Saturday, there's going to be a lot more randonneuring miles on them before I try anything else.
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The Great Wider Tire Rando Experiment (Read 5667 times)
