So I’m looking at some Conti GP 4000s II’s in 25mm…..

I’ve got 23mm tyres on at the moment, and 28mm on another bike. The 28mm tyres feel really slugglish in comparison to the 23mm’s so I can’t believe all the chat about 25mm having less rolling resistance than 23mm. However the tyres are a different brand.

Has anyone tried the same brand in different widths?

They will be used for crits/road races so I’m not bothered about comfort. But I’d like a bit more grip in the wet and on rough surfaces. And like the moon on a stick, I don’t want to be able to feel any extra rolling resistance….

Whats the verdict?

I have the GPs in 25. They look and feel a lot bigger and a little sluggish compared to my 23mm Mitch pros.

Difrent tyre, different bike, possible ly different pressure, that’s why they feel different.

You’ll have less rolling resistance with 25s at the same pressure, more grip at lower pressure.

I switched from 23mm to 25mm Vittoria Open Corsa’s. Can’t say I noticed any difference to be honest, except that I’m yet to puncture on the 25mm’s (that would normally be the kiss of death, but as I’m currently not riding due to injury thanks some silly bint driving into me I doubt I’ll puncture them for a while yet).
They certainly don’t feel any slower/more sluggish than the 23mm Vittoria’s.

I will only use 25mm from now on.

I went from 23 to 25 GP4000s on a stiff aluminium frame

Noticeably more comfortable and grippier (was 10psi lower pressure) but if anything slightly faster average speeds, probably helped by our awful roads.

Part worn 23s for sale, I’m converted.

Got 23s on the winter hack and 25s on the proper bike. Changing to 25s from 23s on the proper bike I noticed an improvement in comfort , for the margins I work in speed was essentially the same.

Can’t comment on the racier tyres, but 25s feel a bit comfier and no slower than 23s, and 28s no comfier than 25s but quite a bit slower. All Gatorskin folders. Might need to take a few pounds out of the 28s to get the comfort benefit, but I suspect that’d make them a tad slower still. All on the same bike, a Cross-Check.

Both the 23’s and 28’s are run at the same pressure (110psi) but yeah the bike that has the 28’s is a bit heavier and chunkier any way.

I might give the 25’s a go. My thought was primarily to get a bit more grip in the wet, but as it’ll be Giant P-SL tyres (which were somewhat slidey last time in the wet) versus Conti black chilli, there will probably be a benefit from the compound for starters.

If you want grip then 110 is a daft pressure unless you are really heavy. Look at the 15% rule.

Both the 23’s and 28’s are run at the same pressure (110psi)

This suggests that if 110psi is correct for 23s then the 28s should be around 80psi (all else being equal).

http://www.bikequarterly.com/images/TireDrop.pdf

And unless your weight is really far forward giving 50:50 distribution then the front should be lower than the back.

I run Mavic Yksions, 23mm on one wheelset, 25mm on the other. I certainly don’t notice any difference at all, and my Strava times seem to back this up, I get an equal number of PBs, KOMs, Top 10s, whatevers on both sets of tyres.

25s sound good as grip has to mean quicker cornering etc. which is going to save time.
More generally rolling can def be lower with wider tyres. But there is also aero component which can easily counter any gains from decreased rolling, depending on the wheel. So keep something narrow for time trials especially if you run narrower deep wheels as they can still be overall faster.

I would expect to notice the differences in speed under normal conditions. The total difference is going to be masked by the wind, effects from traffic or which clothing you are wearing. I am having a really hard time working out whether my 404 with a 20mm veloflex is faster than my 808 with a 22 Bonty.

Always used to run 23’s, but switched to 25’s last year. Same model (Continental Competition tubulars).

The 25’s are more comfortable, offer more grip, and roll just as fast.

I recently built up a wet weather bike with 30’s, and these have been a total revelation. Despite the extra width theoretically increasing rolling resistance, they are so comfortable that I am able to go faster, and run lower pressures that absorb bumps and keep traction going when narrower tires run at higher pressures would just bounce around. The contact patch of even the widest road tire is ever so small in reality.

My advice would be go as wide as your frame will allow, and consider 27’s as a good compromise.

The differences in rolling resistance & aerodynamics are so small youre not going to be able to work them out with strava etc (and certainly not feel).

Its about comfort (and some say grip, no one has convincingly explained how they know this).

Despite the extra width theoretically increasing rolling resistance

No, a wider tyre profile has less rolling resistance.

All other factors being equal, Greater contact patch = More friction = Higher resistance.

It’s all here:

http://www.schwalbetires.com/tech_info/rolling_resistance#why

and here:

http://www.bikeradar.com/gear/article/bicycle-tires-puncturing-the-myths-29245/

and here:

Tire Rolling Resistance

Narrow tires run at higher pressures have a lower rolling resistance than wider tires run at lower pressures.

It is just that the sum of the improved traction, and the ability to maintain contact with the road due to lower pressures more than compensate to make a fatter tire ultimately a faster tire.

At the end of the day, it is a cumulative effect of many factors. For me, I can conclude that I am faster and fresher for longer due to the extra comfort afforded by 30’s. We seem to both agree that up to a certain threshold (fat bikes need not apply!), fatter is faster.

No (you didn’t mention greater contact patch/lower pressure first).

At the same pressure the rolling resistance is lower.

There will be a lower pressure at which RR is the same.

Below that the RR will be greater.

I have just gone from the same 23c Giant tyres to 25c GP4000s. They look huge on the bike in comparison, not ridden it yet. I ran the 23’s at 110psi and have put the 25’s at 100.

I have the GPs in 25. They look and feel a lot bigger and a little sluggish compared to my 23mm Mitch pros.

this is exactly the change I have just made. first thing is that on my aksiums the tyres look higher rather than wider than my son’s conti 23s (also on aksiums)

and after a highly scientific 15 mile first ride I thought the contis felt draggier. but it was hot and windy and i am old and fat.

hoping that I will end up liking them due to increased cornering confidence, better comfort and lower rolling resistance – just not sure about the rolling resistance right now…

Cynic-al – what is the 15% rule?

I run 110psi out of habit, always seemed a fairly good pressure to reliably avoid punctures on the commute. I’m about 11stone.

Ok, so 23’s at 110psi, what pressure for 25’s???

Its in irc’s link.

EDIT nice edit solarider

So, for 70kg worth of rider, that bikequarterly article suggests ~55 psi front and ~85psi rear for a 25mm tyre?

Seems really quite low especially at the front???

Lower overall rolling resistance overall in a bigger tyre on a road that’s anything but perfect tarmac comes from being able to use less pressure so the tyre can deform to the ground. If every ~3mm bump in the road, every few cm, has to lift the bike against your weight because your 23C tyre is at a rock-hard 120PSI, that’s momentum lost. A 28C tyre at lower pressure will allow the tyre to deform more, bumping you around less and maintaining momentum better. It’s a tiny difference per bump but it adds up fast. Called ‘suspension losses’ apparently and Bicycle Quarterly have written some interesting stuff on it. I think I agree with it from personal experience. Comfort advantage really adds up after a number of hours too.

Narrow tires run at higher pressures have a lower rolling resistance than wider tires run at lower pressures.

Only on perfectly smooth surfaces, ie a track or rollers where these differences were probably measured. On a track boards, the lower-pressure tyre will be slower as there’s energy going into flexing the casing. Last time I looked, UK roads were such a state that there’s a balance to be had and I’m all for 25-32C these days.

I have run both Mavik Yksion Pro and Schwalbe Ones in 23 and 25c. Normally run at similar pressures, within 5-10psi of 115psi. Comfort is a little better on 25c, particularly on typical roads. Cornering on the limit is much improved due to the tyre profile.

The Ones are a nicer tyre, but the Yksions are much better than many people give them credit for.

^^^ 25mm are noticeably more comfortable if run at appropriate pressures. Try dropping the pressure to around 90 psi and feel the improvement.

I’ve used GP4000Ss in 23 and 25 on a handful of bikes now for about 3 years solid.

For my money: If your road surfaces are rubbish then the 25 is likely to be favoured more, unsurprisingly. But, subjectively or otherwise, I find the 23s a little nicer at speed because they’re more stable in corners on a normal narrow rim, thanks to the narrower profile and higher pressure. So they play a bit to your inner animal, whereas 25s just kind of take the edge off. YMMV, natch. But I’d say that for the most part there’s little in it other than what sort of feel you want: are you out to cane it, or out to eat miles? The GP4000S is a cracking tyre in any width.

(If it matters, I’m knocking on 14st and run 23s at 100-110, 25s at roughly 90. Going lower adds comfort; adds speed on rough surfaces to a point, when it then becomes slower; and reduces stability in corners. IME, YMMV, all that jazz.)

I’ve bought the 25mm’s. Looks like virtually naff all difference to the 23mm Giants that came off or the 23mm GP4S on my other bike.

Not bothered about comfort, just hoping they’ll be a bit better in the wet due to the compound and/or running at lower pressures.

Cornering on the limit is much improved due to the tyre profile.

As before, how does the profile matter when the tyre deforms to the road surface irrespective of its profile?

“just hoping they’ll be a bit better in the wet due to the compound“

I won’t claim to have experience with vast numbers of tyres by any means, but of those I’ve used, the Black Chili is certainly the best in the wet.

That’ll do for me Bez! 🙂

second 15 mile ride tonight at around 85psi front and 90psi rear – again highly scientific (not!), but starting to think that once I get the pressures sorted and get used to the different approach to riding rough surfaces I will be faster overall

btw I used a proper pressure gauge tonight rather than rely on the track pump gauge which apparently over reads by quite a bit…

http://www.conti-tyres.co.uk/conticycle/road_tyres/GP4000sII/WideRaceTyreTest_TOUR_Magazine_2014.pdf

I just don’t get why wider tyres feel so much slower yet the tests say they’re faster.

I’m looking for a flaw in the testing mechanism. Could be that there’s some difference between power as measured on the rolling road, and power on a ride ? The rolling road is constant, the actual ride is lots of constant accelerations and decelerations with each pedal stroke ? Don’t know why, but my legs tell me that narrower is faster, and I’ve tried 28 /25 /23.

25’s

got 23s and 25s on road bikes

got 32s on my cross bike

i am a normal rider and there is **** all difference in average speed between them all on my 30km commute

i am a normal rider and there is **** all difference in average speed between them all on my 30km commute

And for most people that is all that really matters, we are talking little bits of time that only matters in races, and even then only sometimes. Wearing tighter lycra will make a lot more difference. A more aero position will make a much much bigger difference.

The peace of mind you get from a bit more rubber on the road is worth more most of the time.

Even wide rims like zipp firecrests are fastest with 23mm tyres though. Its just they used to be best with 19 or 20mm. You are still going to give up a tiny bit with 25s on most wheels.
Put latex tubes in if you can be arsed, (and are careful)they will make a bigger difference if your tyre is decent.

You can over think this stuff. I did 70 miles yesterday with a 20mm tyre, as I am using it up. I forgot I was on a narrow tyre and it was not a harsh ride. My speed was a healthy 21.5mph. (If it had been wet I may have ended up in the hedge though)

flap_jack – Member
I just don’t get why wider tyres feel so much slower yet the tests say they’re faster.

Narrower is lighter, and you tend to inflate them higher, which makes them harsher, which feels faster

What difference do latex tubes make? And what are the downsides? Are they the ones that lose air over a few days?

Downsides are as you mentioned you have to inflate them regularly. They tend to be a bit more expensive. When you fit them you just have to be sure they are not twisted or pinched. They are a lot less forgiving than normal tubes. Do not get oil or grease near them, it weakens them. If you get a small hole in your tyre- all the way through, then when you come to fit another tube, use a normal one. The latex tube can find its way through holes, bulge and fail.

That sounds bad doesn’t it? But I run them in the summer no worries.

The difference is that they roll faster and feel nicer when combined with a supple tyre. It makes enough difference that I would never dream of doing a TT with butyl tubes.

Tests (as linked further back) don’t say wider is faster, but that it has lower rolling resistance.
Faster you ride,the more effect comes from aero, so faster riders are faster on narrow tyres, slower riders faster on wider.
This of course ignores any fatigue effects from harsh hard narrow tyres, so a fast strong rider chooses narrow tyres, everone else probably faster on wider tyres.
Or something….

I could barely tell the difference comparing the 23mm and 25mm size wise so I doubt I’ll be able to tell the difference performance wise!