Here's the thing: tire size and pressure does more to change (negatively or positively) the "comfort" of your bicycle than your Cervelo R5 vs. S5 choice (or most other similar-ish framed carbon bicycles).
There's been plenty of reading to be had about this subject, but it does not honestly seem like the average customer is aware of such things. Bike shops do very little to help explain this as well (unless you're at Inside Out Sports, obviously).
Without going into too much detail and while still providing you with an engaging user experience, if you would like to discover this in more detail for yourself, here are some links:
http://www.slowtwitch.com/Tech/Thoughts_on_science_perception_4571.html
https://silca.cc/blogs/journal/118397252-tire-size-pressure-aero-comfort-rolling-resistance-and-more-part-1-how-we-got-to-now
https://silca.cc/blogs/journal/118616068-part-2-tire-stiffness-wider-is-stiffer-harsher
https://silca.cc/blogs/journal/part-3-tire-pressure-and-comfort
https://silca.cc/blogs/journal/part-3b-faq-and-putting-it-together-so-far
https://silca.cc/blogs/journal/part-4a-rolling-resistance-the-history-and-previous-works
https://silca.cc/blogs/journal/part-4b-rolling-resistance-and-impedance.
https://silca.cc/blogs/journal/part-5-tire-pressure-and-aerodynamics
So you're welcome to simply take my word for it, which I guess most will do given the volume of data and science that is presented above me...or you can go read all of those.
Here are some handy quotes, for those that wish for an expedited experience:
"Carbon Vs Steel Similar Geometry Custom Frames: 4psi"
What the above is saying that you can account for the different in comfort/compliance between those two things listed (carbon frame vs. steel frame, similar geometry) by changing tire pressure by as little as 4psi.
4psi!! That's huge! Or, maybe huge isn't the right word. That's "incredible" seems to flow better with the tone that this has in my head.
"No other single component affects the comfort, handling and efficiency of a bicycle like the tires. Tires are the sole connection to the ground, they are the sole transmitter of drive force to propel the cyclist forward, and they are the sole means of gripping the road during cornering. They are the most dominant spring in the bike/rider system which means that more than anything else, they control comfort. They are the sole component which will (ideally) ever have to resist the abrasive contact of asphalt, concrete or gravel with minimal damage."
I think that puts it pretty succinctly.
"The initial design of this test was to show that larger diameter tires are actually Stiffer/Less Comfortable when inflated to the same pressure."
i.e. don't pump those b***** up so high!
"What we can say is that all those people who feel their larger tires are more comfortable, you may be correct for bumps smaller than 8mm radius...we could not measure that, so it is hard to know, but for larger radii, you are best to lower your air pressure a bit to truly take advantage of the larger tire widths.
The most exciting aspect of this study is that it has begun to point us in the direction of how much pressure we need to lose with tire width increases, and even better it hints that while that lower pressure will provide similar ride comfort on most surfaces, it will likely improve comfort on small bumps.
Our recommendation is that you decrease tire pressure by 3-4% for each millimeter of tire width increase. This will ensure similar compliance over most surfaces while providing improved compliance over small bumps and edges."
Pretty self explanatory, again. The bold typeface was not mine, instead the author (Josh Poertner) recognized its importance and emboldened it for us!
"Our recommendation is to begin keeping a log of your air pressures. Start where you are today and reduce pressure by 5psi or 0.5Bar and ride it for a few days, then reduce it a bit more, etc. We have worked with hundreds of athletes, both professional and amateur and find that just a few weeks of keeping a pressure log will begin to completely change the way you think about your pressures and tires. In many cases, we find athletes deciding that they can race their aero road bike on that course they were planning to buy a more comfortable bike for. Triathletes, some of whom are now racing at pressures 2Bar (30psi) lower than before, are telling us that they are running better off the bike as they are less fatigued from vibration, and better still, they aren't riding any slower!"
Ok, now I added the bold part. I'm beginning to quote too much of this, so I'll stop at this point and summarize by saying:
Wider rims (bead width and overall width) allow for wider tires to be run at lower pressures and increased compliance while still maintaining (or improving) rolling resistance and aerodynamics, and combined with tire and tube choice can maintain or improve flat protection.
You would probably be amazed if you experimented with this yourself (if you haven't already). So all of THAT is why I wanted some wider rims on my S5. Tucson roads are harsh and demanding (lots of cracked pavement and sealing) and frequently have run off in the roads (from flash flooding and such) containing gravel and sand.
BUT, now that I don't work at IOS, I have to be stingy. I have to be a demanding consumer who gets the most out of my money! So I was scouring the internet for good options. One that kept coming up was the Flo Cycling 30 alloy wheelset. I liked this option for a variety of reasons: cost, aerodynamics, weight, and rim specifications, among others. I disliked it for some reasons: hub type (meh hubs), shipping time, brake surface wears off (the black coloring does anyway). I was very close to pulling the trigger on this a few times.
Luckily for me, however, I discovered that a local bike "shop" sells custom built pre spec'd wheelsets for extremely reasonable prices. They have - among many others - a "Phalanx" wheelset that comes with:
- Kinlin XR-31t rim (31 being it's depth in mm, and "t" denoting that it is tubeless ready)
- Sapim Laser spokes (20/28, a reasonable combination for an all around wheelset)
- DT Swiss 350 hubs (DT hubs are fantastic, and these are their entry level hubs but the mechanicals are similar or the same as their much more expensive hubs)
All of this comes in a a relatively lightweight 1600ish grams (a bit more, but not much) and a very paltry $450 (plus shipping or tax). Considering I live here now, I opted for local pickup, obviously.
I took them home and got to work installing them on my bicycle. I combined these wheels with some Specialized S-Works Turbo Cotton 700x24 tires that I have had for a while but never used. These tires are definitely race-oriented, but they are the nicest "wide" tires I have just sitting around. Interestingly, Continental tires typically measure MUCH wider on wide rims (a 23mm Conti tire might actually measure 25mm+ on these rims), whereas Specialized SW TC tend to measure close to what they are actually stated as being (a 24mm tire is typically only a bit over 24mm on a wider rim).
So my preference would honestly be for a 25mm GP4000s II tire, but I don't feel like spending $150 ish on two tires right now. Maybe once these are worn out (which could be next year sometime, honestly).
I combined both of those with Vittoria Latex tubes into which I installed sealant. At IOS we've done this quite a few times for customer in their race wheels (usually using Orange Seal sealant) and is something I've traditionally done in my own race wheels, but I figured now would be a good time to start using sealant in all of my cycling applications. It's a very easy process that only takes a few seconds and detracts nothing from the performance of the tire/tube/wheel. The goal - for those unfamiliar - is to have sealant rolling around in the tube and when a puncture happens the sealant rushes to the hole and plugs the hole, essentially. This can prevent psi loss and let you keep rolling, sometimes unaware that the sealant has even done anything! Think of the sealant as platelets in your blood.
I wrapped everything up and was very pleased with the result, aesthetically speaking:
I rode the bike around the block a bit after tuning it up and discovered that some of the spokes still needed to be stress relieved (if you ever get new wheels or a new bike and notice "pings" that can be somewhat loud especially when you tilt your bike to one side or the other your wheels/spokes were not stress relieved; essentially what happens during a wheel build is the spokes, hub and rim are all hooked up and dished and trued but sometimes when truing a wheel/tightening a spoke the spoke turns as the nipple turns, which sort of deforms the spoke and then as you tilt the bike to one side or the other you are relieving the stress on the opposite side you lean and the spoke sort of "frees" itself...make sense?) but other than that the difference between these wheels (with tires inflated to 85psi) and my old wheels (with tires inflated to 100psi) was pretty huge. MUCH, much smoother.
There are a few things confounding that perception, however:
- Nicer tires (MUCH nicer tires) that are more supple and essentially have zero puncture resistance
- Nicer tubes; latex tubes can actually - according to some - make a perceivable difference in ride quality
- Perception bias: I WANT these wheels to feel better, so - naturally - they do!
- Pump inaccuracy: I always use the same pump, but most pumps actually have a pretty huge error margin. Mine is pretty nice (Lezyne Digital Drive and it gives me an actual digital PSI reading, which is nice) but I have no idea if it's accurate or not as I haven't ponied up for a tire pressure gauge.
Update on 2/22/2017
I've now had these wheels for quite some time now. Since July of 2016 I have put a few thousand miles on these wheels and only recently swapped tires for some 700x25 GP4000s II's. I never got a single flat (ok that's not true, I got one flat but it was because I slammed into a pothole and my tube got pinched), it was just time to replace the tires, especially the rear one, as the cuts had started accumulating beyond an "I'm comfortable with those for 100+ mile rides" measurement.
I have to say that I remain very impressed. Such a low-cost wheelset remaining true and bombroof even hitting some pretty crazy potholes and cracks is quite an achievement.
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