Interesting. What’s the math behind it all?
It’s a tradeoff between comfort, weight and air resistance.
Contrary to popular belief, narrower tires don’t have lower rolling resistance. Racers use narrower tires because they are more aerodynamic, but that only matters at high speeds (>20 mph, roughly). They are also lighter, so they feel more nimble (i.e. accelerates better).
But for commuting or touring at moderate speeds, you’re better off with a wider tire. I recently switched from 25 to 28 on my “road bike” (cyclocross bike set up as a sort of touring bike) and noticed much better comfort, with no measurable loss in average speed.
I would add though, that not all 32 (or 28) tires are made equal. I run my 700x28 tires at 100 psi; not all tires are rated to that pressure.
In view of the last few posts, maybe not so “nuts” after all.
There is a flat contact patch between the tire and the road. As the tire rolls, the tread and casing of the tire deforms as the contact patch moves (relatively speaking) around the perimeter of the tire. With a high pressure narrow tire, the contact patch is long and skinny. With a lower pressure wider tire, the contact patch is short and wide. This requires less of the sidewall to flex and deform, thus less wasted energy to do that, and thus less rolling resistance.
I’ll admit that narrow high pressure tires “feel” fast. But some of that is actually vibration from the tire as it bounces/skips across the roughness of road surface. Yes, track riders pump their tires to 160psi, but they’re riding on a perfectly smooth surface. Everyday road riders may find it faster and much more comfortable to drop a few psi. Here’s another article from Bicycles Quarterly Optimizing Your Tire Pressure for Your Weight (pdf) you may find useful.
It was only this year that I read in one of Lennard Zinn’s Velonews columns that suggested lower tire pressure yeilded lower rolling resistance. When I searched for information to corroberate, I found the BQ articles. Before then, on my road bike I ran 700x23’s at 120psi. I dropped that to about 100psi, am going just as fast if not faster and the ride is much more comfortable. When I wear out this set of tires, I’ll be going to x25’s, at least in the rear.
I managed to miss that you had already purchased new tires.
GP 4000’s and GP 4000S’s are great tires. Gatorskins are too, but remember what I mentioned wider tires having lower rolling resistance than narrow tires of the same general construction? The Gatorskin tires tougher, more durable tread and sidewalls take much more energy to deform, and are noticeably slower.
Don’t blindly pump up those GP’s to 120psi. Read the BQ article I linked to determine the optimum pressure for you and you should be very happy with them. Ride a lot, have fun, and when you’ve worn them out, consider replacing them with a high performance x28 or x32 tire.
Thanks for that info and the article! If I understand the graph right:
- I weigh 180 lbs with a bike that’s most like a “racing bike” and it has 700c x 23 tires
- The bike weighs about 25 lbs, bringing the total up to 205 lbs
- That means 40% or 82 lbs go to the front and 60% or 123 lbs to the rear
- Which means, according to that article, optimal would 80 psi (?!) for the front and 130 psi (?) for the rear?
I wish I had waited a day or two more. I bought the tires in a hurry because I wanted them by a trip on Monday.
If the Gatorskin’s sidewalls take more energy to deform, wouldn’t they be faster and not slower – according to the whole rolling resistance thing?
In half an hour or riding the new tires, my initial experience is that they definitely feel rougher (meaning vibrations and such are transmitted much more thoroughly, which I kind of like) but they don’t feel noticeably faster or easier to climb with. But I’m reserving subjective judgment until I get more mileage in them.
While we’re all here, I have a couple of bicycle tire-related questions. Hope the OP doesn’t mind:
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When the instructions for changing a flat say to put the tire back on without using the levers, they’re kidding, right? The last thing I want to do is put a hole in a brand new tube, but there’s no way on God’s green earth that bead is going back on without some leverage behind it. Hell, sometimes I can barely get the tire back on even with the levers.
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Does anybody make a bicycle pump (especially a floor pump) that will seal on the stem the first time without letting all the air out of the tire first?
Why yes, I did discover a flat tire when I was hoping to go for a ride today.
Yes, that’s what the article suggests should get you in the ballpark for the 15% tire drop. But I believe your700x23c GP4000S has a max pressure of 120psi, so keep that in mind. For what it’s worth, I’m about 195, and my Trek Madone is 18 pounds. I run 700x23 GP4000’s on that bike, and I keep my front inflated to 90-95psi, right in line with the graph. But I keep my rear at 110-115psi, substantially less. This might not be “optimum”, but it works well enough for me.
No, the tire needs to deform to create the long skinny contact patch. More pliable tires, like your GP4000S’s, do this more easily than Gatorskins. The energy used to deform the tires is energy that isn’t propelling you forward down the road.
It depends on the rim and tire combination. Some set ups can really be a bitch to remount the tire on, especially when the tire is new. Others can be mounted by only using your fingers (well, mostly thumbs).
Folding tires with kevlar beads are usually easier to mount. Wider rims help too.
I have some mountain bike tires that literally fall onto the rim.
I’ve encountered some combinations that had me swearing for an hour (I’m looking at you, Continental tires and Campy rims)
All pumps can do that. You can’t. It’s technique.
Are you using presta (bike) or schrader (car-style) valves?
With schrader, as the pump connection goes on, you lose air. You just have to be quick.
With presta, no air comes out of the tube at all if you are doing it right. The valve stays closed even as the pump goes on, and only opens to let air in as you pump. It can sound like air is escaping as you take the pump off but this is actually air escaping from the pump tube not the tyre
Go for it, Robot Arm, though you might get more answers if you start a separate thread.
Heh, another day, another crash. I’ve bled more in the last three days than I had in the past three years combined 
The whole “rotate heel out” maneuver is just not something that comes reflexively when I’m bracing a fall… I can barely do it right when I’m standing still and in perfect control, much less when I’m about panicking about a sudden car / stop sign / pedestrian / bump. To make things worse, the pedal provides no clear audible or tactile feedback when it clips or unclips. This time I was changing gears going uphill (bad idea to begin with) and the chain came loose and apparently my foot wasn’t far enough back on the pedal and it had clipped itself in without me noticing. Splat.
Sooo… got any tips?
Or are there any pedal designs that do utilize more of a sideways kick instead of a twist? I ride pretty much perpendicular to the ground and don’t move my feet side-to-side much unless I’m about to stop.
Eh? Are we reading the same thread? Let me recap the last few posts:
I didn’t intend to imply anything about speed or efficiency as the differences there are almost completely irrelevant to the average newbie cyclist. My point was that you’d have to be nearly numb to not notice a difference in feel between a 32 and 23c tire, and I think that opinion has been corroborated by many other posters above.
I’ve got a pair of the same pedals on my mtb, and though the movement is completely involuntary to me now and hard to recall, IIRC twisting alone is not very effective.
Try rolling your foot slightly downward (that is, roll your ankle to the outside) rather than just pushing your heel out horizontally.
I think, in context, it’s safe to assume that he was talking about speed. I definitely notice an increase in road feel – and I think I like that so far – but not much difference in speed, which was his original point.
I’ll try that next time I’m on. Thank you.
The sidewall itself doesn’t have any appreciable amount of mechanical strength; it doesn’t resist the deformation of the tire. That’s what the air is for. The amount of deformation of the tire is primarily a function of air pressure.
However, air itself is almost perfectly elastic, so there’s no energy lost to compressing the air. The energy loss (rolling resistance) comes from the energy required to deform the tire as each part of the tire comes into contact with the ground, and then bounce back as it leaves the ground. A very elastic and supple tire absorbs very little energy, and therefore has very good rolling resistance. A stiff, thick tire takes a lot of energy to deform, which means it’s robbing a lot of energy from motion. I.e. it has high rolling resistance.
Then stand still and practice until it becomes second nature. When I got my first pair of clipless pedals, I spent about one hour on my bike, stationary (supporting myself by holding on to a handrail), and practicing clipping in and out. I haven’t had a single fall caused by pedals since then.
Throw your levers away and get yourself one of these* Every time I help someone that has never seen one of these change a tire, the response is “Damn that is neat, where can I get one?” The speed lever works like a tire machine for a car tire.
Anyway when you go to put the new tube in, put some air in it so it is unfolded, this will make it easier to install without pinching.
Use the speed lever to reinstall the tire on the wheel, it will take no more than 15 seconds.
*If Crank Bros makes anything that is not first rate, I have never used it. Best stuff out there IMHO.
The Speedlever’s not bad, but I prefer the Quik Stick