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I switched GP4000 tires to 25c and dropped about 15 psi in the front and 5-10 psi in the back. It's a smoother ride, and seems just as fast.

Now I have HED Ardennes Plus rims, 25 mm wide. The 23c tires are 26.6 mm wide on these rims, so I put the same pressures in that I did for my older rims with 25c.
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I posted this chart in another thread.

This chart compares GP4000 tires in different sizes. Is a lab test on rollers equivalent to riding on the road? And how does different pressures affect cornering? How much load on the tires?

Anyway, all sizes have lower rolling resistance as their pressure goes up. But 25c at 94 psi has the same resistance as the 23c at 123 psi.

Six jours

IMO a good rule of thumb is that the more charts and graphs a thread produces in an effort to show a difference, the less real-world difference there actually is.

But I think you and I are pretty much in agreement. I know I can talk myself into believing all sorts of things on the bike, especially WRT tire width. But in all honesty, I can't be sure of a difference with anything less than a five to seven millimeter change. Less than that, and I'm back to trying to talk myself into perceiving something that may or not be real.

chaadster

Haha! In fact...on all counts!

Doge

95/105

Doge

I have not seen any chart of 25s and 23s at the same deformation level (so different pressures) so I believe that. At the same pressure - yes. But when switching between them (for example tomorrow's race we are going 22 rear and 25 front)?

A 23(or 22) at 130 vs. a 25 at 105 roll about the same.

Doge

Shown below are some of the tires we have sitting behind me. My kid races and rides 10,000mi/year - all on Tubulars. We have sizes from 19mm to FMB silk 25mm and custom made 25mm - essentially a track tire and a bunch of Veloflex and other sizes. We have now - 19, 20, 22,23,24,25 and I road 28s for years and sometimes 200 miles/day.

If you don't race I'd go 25. If you do, it depends. Choose width based on road condition and type of ride/finish you plan.

25s are not lower rolling resistance in application because nobody inflates to the same pressure as a 22. The biggest determining factor for rolling is the case and tread and the glue job. Then you inflate appropriately. A test that inflates two totally different tires to the same pressure is a test report I don't read.

chaadster

From VeloNews, all Challenge tubulars:

K.Katso

I have Zipp 303 Firecrest tubulars. Actually they recommend 23 front and 25 rear for the best aero advantage. I typically run 23s on both, although I have experimented with the 25 rear. No way I would put a 25 on the front though.

DXchulo

I tried both of the same tire in 23 and 25 and really couldn't tell much difference. In theory I could lower the pressure on the 25s, but I just hated the feel of that. Most of the roads I usually ride aren't rough enough to justify running low pressure.

My main hope was that the 25s would be better on the descents, but that didn't really play out for me. YMMV

chaadster

Why is that?

I don't think I'd bother again, either I have some Michelin Pro Optimum 25c which I had on 19mm bsw Velocity Aeroheads that when mounted were very bulbous and poor at handling side loading. It seems that regardless of where I put the pressure, they'd shift under the rim when I was under the saddle. I don't recall the exact measurement, but they were in the 27mm actual width range measured with calipers.

I like my front wheel to be solid and responsive, so that's why I stick with 23s, but I imagine there are some 25s out there that are better than the POs were.

Six jours

JFWIW, it was Jan Heine/Bicycle Quarterly that got this ball rolling. His research showed pretty conclusively that narrower does not necessarily mean faster, and also that higher pressure does not necessarily mean faster either. A decade later, the mainstream bike press is catching on. Unfortunately, the main stream bike press is still using steel drums to calculate rolling resistance, which makes the data meaningless for anyone not riding on a steel drum.

At least part of the reason wider can be faster (or not slower, anyway) is that wider can be run at lower pressure. That seems counterintuitive (and don't forget that higher pressure can feel faster, because it gives the higher frequency vibrations that the rider equates with going fast) but the idea is to allow the tire to absorb shock, rather than transmitting it to the bike and rider. The human body can absorb a lot of wattage, depending upon the road surface. On anything less than perfectly surfaced road, a relatively wide, soft tire is not only more comfortable, but also rolls better - unless the rider has fouled things up by pumping it up too hard.

02Giant 

The wheels that came on my Orbea are 22mm wide, I have Conti GP 4000s II's in 23mm width (actual measure 24mm) mounted. I just bought a new aero wheelset that is 19mm wide, they have Conti GP 4000s II's in 25mm (actual measure 25mm) mounted, I don't expect any difference from the tires.

EvilWeasel

When i used to race motorcycles the fast guys would adjust Their tire pressure by 1/2 a lb or so depending on ambient track temperatures. Darned if my mid pack self could tell the difference.

Same concept here. Unless you are a dedicated, highly skilled racer... It's all just semantics.

FLvector

That's what I've been running for several months, 23mm front/25mm rear. 120psi front/110psi rear. My reason to do this was to see if I'd see a smoother ride and also thought it might provide additional miles for the rear tire. I go through at least 2 rear tires for every front, but now they appear to be wearing more evenly.

Zuzus pedals

I think 25s have a tad less rolling resistance and they're a bit more comfortable to ride on - a lot more so on chewed-up roads. If you are really concerned with riding a couple of seconds faster for every 10 miles, maybe put a 23 on the front so there's a (insert Emily Litella voice here) teensy weensy, itsy bitsy, tiny winy less aero drag where the front of the machine meets the air, and put a 25 on the rear for comfort and lower rolling resistance. Of course, if the road surface is gnarly, make sure you've got a toughened-up butt before going with 23s, especially on the rear wheel. Also make sure the air pressure is just right for the tire width and your weight.

chaadster

Meaningless, huh? You'd better tell that to the biggest players in the tire biz who've gone to Wheel Energy Lab for testing, because they think that steel drum has value.

Also, regarding the pressure thing, see the chart from post #32 ; higher pressure equals lower rolling resistance across the board, irrespective of casing size. And that's on the rough, diamond plate surface. Sure, there's a limit, like in MTB and CX, but for the road, it's a pretty safe bet that for most paved roads, higher pressures will roll better, even if they beat your a** doing it (and that's not just a wisecrack, it's something not to be ignored).

newbie101

I went from 25's to 23's and wound up with a wider tire. The advertised width is often inaccurate. Having said that the "23's" were wider, far more comfortable and simply superior all around.

Six jours

I didn't say there's no value in steel drum testing. Steel drum results sell tires, without a doubt, so there's plenty of value to the tire manufacturers.

The trouble is that there's no reality in steel drum testing. If there were, we'd all be riding steel tires, because they'd be the fastest on the steel drum.

chaadster

We have a situation over here; better this guy out!

biciklanto

I recently switched from 23mm to 28mm for Continental's Grand Prix 4000 S II. Riding everything from smooth pavement to muddy farm roads and gravel on my Domane meant that I wanted as much rubber under me as I could get.

I'm absolutely satisfied with my choice. I was running about 95/105PSI on the 23C tires and now run more like 75/85 on the 28C replacements, and have noticed a big difference in grip and smoothness with no perceptible speed tradeoff (according to Continental's graph above, my rolling resistance is still lower). The only downside I've felt at all is that my 5700-series 105 brakes are an awfully close fit with the tires, and if it's muddy or if there's a lot of straw on a farm road it'll collect and make some noise. I'll be swapping those soon, though.

My goal by this time next year is to be riding Zipp 303 tubulars with tires the same size that I've got on there now. That should really do it for me.

Tusky

The pros are using the 25's on the road and 28's on cobbled town circuits.

10 Wheels

I crashed using 23's. Hit a crack or something near the edge of the road.

Go with the wider tire for safety.

Shuffleman

I was riding 23's on my previous bike. On my new bike, I decided to go with 25's.
This is a little scientific but I do not seem to ride faster or have more endurance.
I did put some 23's on the new bike as the tires that I ordered took a few days longer to get here and I got antsy. I rode on the 23's a few times and then put on the new 25's. The tires were not the same brand but I kept them at the same psi levels. I am not sure that I noticed any difference.
I have an injury that I am fighting and went with the 25's to try to limit the vibrations as much as possible. People ask me about it all the time and I just tell them that the truth---I have no idea if it assists or not. I do not feel slower and if I am, it would be so negligible that it is not even funny.

hueyhoolihan

i like a light bike, so i go with the 23's. i don't care whether or not they are slower. i'm going for top honors in the superficial, coffee shop, informal, impromptu, "dead lift" competition.

Bob Ross

My wife switched from 23s to 25s earlier this year, and she offered an interesting observation, wonder if anyone else here has experienced this:

Irrespective of how they perform during normal day-to-day use (the jury's still out for her, though she's leaning towards the 25s as being more comfortable) she claims that when she gets a flat while riding the 23s are much more controllable. Since changing to the 25s she claims the bike is noticeably more unstable when a tire goes flat at speed.

Anyone else experience that...or have a suggestion why that might be the case?

(I'm no help, I've never used 25s.)