700x28 vs 32
 

I've been running 700x32s on my bike and thought have of going down to a 700x28 for daily riding. Am I going to notice much of a difference?

no.

If you're using an aero rim specifically designed for 28mm tires, like an ENVE 4.5 AR, then the change would allow the rim's aero design to function correctly, which could give you a small but perhaps measurable improvement.

Otherwise, not really. What mostly matters on the road is how a tire is made, not its dimensions, and a 14% width difference is pretty small in any case.

Everything thing else being the same, no, 28mm is not going to be much of a speed increase.

If you select a faster tire, like the 700c28 Vittoria Corsa, you will get less weight and lower rolling resistance along with slightly improved aerodynamic performance. The combined benefits you will notice. However, I wouldn't use this type of tire on gravel.

...a 14% change in width represents a 30% change in cross-sectional area and a similarly large difference in volume....not really small.


Either way, going to 28 over 32 really won't gain you anything. And will harm handling and looser-pack surfaces-should you encounter them. A no-win/lose scenario.

Yes, but I don't see how that's significant, outside of marketers trying to make the effects of increased tire width sound more significant than they are by expressing things in terms of some value that happens to grow quadratically.

Doubling the width gives you four times the volume, but for the most part, most of what appear to be the relevant consequences change by a factor of two. The amount of tire distortion for a given linear deflection is halved. The amount of travel you have before the tire bottoms out is halved. Once PSI is adjusted per width, the amount of air that goes into the tire is only roughly doubled. And so on.

What consequences quadruple as a result of the volume's quadrupling?

You might feel faster because of suspension losses. That's a fancy way of saying it feels faster to go the same speed when everything feels harsh and bumpy due to less cushion and a firmer tire casing at higher pressure.

Like on my road bike with 25mm tires. I feel like I'm going 21 mph - it feels like that speed to me. But then on my gravel bike with 42mm tires when I'm going 21 mph it feels slower, but I look down at my computer and am surprised at the speed.

Or you might not notice a difference at all.

I've gone the other direction on a bike, replacing 28s with 32s (both Conti GP 4 Seasons). I definitely noticed a difference. The bike was a lot more comfortable over rough pavement with the 32s. I didn't notice any speed differences.

I might switch over to a non knobby 32. I'm running Ritchey Crossmaxes right now but don't want to burn the knobs off and save them for more rough stuff.

What's been your experience switching from 32s to 28s or vice versa?

I went from 42s to 32s and then to 28s and was like whoa that's an over-correction so I went back to 32s. I was running Clement Strada LGGs and noticed a big difference in road feel/handling - mostly because I had to run significantly more pressure to maintain the same sag %. IIRC I was running 65-70psi in the 28s and was getting away with 40-45 in the 32s for about the same 15-17% sag.

Ya, you're most likely not going to be much faster but you will have to run higher pressures to get the same tire sag and as mentioned above you lose a lot of comfort and handling by going down to 28s.

If you're trying to be faster, work on riding in a more aero position and run higher pressures in your 32s.

ETA: Whoops - Missed you were running knobbies, ya go to a smooth tread 32 and you'll notice a huge improvement in speed on pavement.

Anyone able to run 32's with dual pivot calipers?

Depends on the rims in question and what calipers.

I could run 32mm (IRL measurement) slicks on my roadie with Campag skeleton calipers with HED Belgium+ and 28mm Schwalbe Pro Ones....so long as I didn't use the centering-adjustment on the caliper. At all. Using that centering-adjust lessened the tire clearance.

That my tire pressure had to scale close to linearly with width to maintain what seems like the right road feel. I switched my '83 Miyata 710 from 1 1/4 to 1 1/8 recently (mostly because the rims on that bike are narrow and it seemed weird to get more tires that inflated super bulbously), and found myself going (for rides on quality pavement) from 70-80 to 80-90.

Similarly, on smooth roads, I run the 53s on my gravel bike at 35-40; a bit below the linear scaling, but well above quadratic. According to the quadratic scaling, I'd be running them 25-30, which is pretty gooey and not something I do unless the ride includes considerable amounts of gravel.