# Dura-Ace C24s... 23mm or 25mm?



## OldZaskar (Jul 1, 2009)

I'm currently running 23mm (Continental Grand Prix 4000S II 700x23) tires, and it's almost time for new tires. I'm assuming the 25mm version would not be ideal for the 21.8mm rim? 

What say the gurus (or those who've tried both)?

Thanks!


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## Mcfarton (May 23, 2014)

why would they not be ideal? how much do you weigh?


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## OldZaskar (Jul 1, 2009)

About 185lbs. I usually run 110/105 psi.

See there's that "assuming" thing gone wrong. I figured since the tire was wider than the rim, it'd be more susceptible to squirming, folding, etc. in turns?


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## Blue CheeseHead (Jul 14, 2008)

I run 25's on my DA wheels. As a rim gets wider it is less necessary to run a wider tire. On my HED + wheels I run 23mm tires. Installed width of 25mm tires on the DA and 23mm tires on the HED are both 25+mm.


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## tvad (Aug 31, 2003)

23mm is as large as I go on my DA C24.


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## JSWhaler (Nov 25, 2009)

I run 23 mm on mine


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## Oxtox (Aug 16, 2006)

23 mm on mine.


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## spdntrxi (Jul 25, 2013)

I run the S-works turbo 24's on mine.. seem fine.


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## Jay Strongbow (May 8, 2010)

OldZaskar said:


> About *185lbs.* I usually run 110/105 psi.
> 
> See there's that "assuming" thing gone wrong. I figured *since the tire *was wider than the rim, it'd be more susceptible to squirming, folding, etc. in turns?


25, no question. Less PSI too.

23, and 25 for that matter, is wider than 19 and people were and are still just fine using them without folding and squishing ect. I like the wider rims myself but most of the marketing and internet groupthink about the evils of lighbulb effect is unwarrented. You'll be fine with any size and I think you'll find what's most comfortable for your weight without giving up any speed (possibly gaining it) is 25mm.
25 rear and 23 front is another option. That's what I use at my weight of 145ish. Although I'm fairly light the roads really suck around here so 25mm are much better for me.


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## rruff (Feb 28, 2006)

OldZaskar said:


> See there's that "assuming" thing gone wrong. I figured since the tire was wider than the rim, it'd be more susceptible to squirming, folding, etc. in turns?


The hype is out of control!

For some reason I never noticed my 23mm tires on 18mm rims squirming or folding when racing down switchback descents. Don't worry about it. 

But also don't go to 25mm for fashion. If you prefer more comfort, then go ahead, but if speed what you are trying to optimize then 23s are probably a hair faster but not much.


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## Blue CheeseHead (Jul 14, 2008)

rruff said:


> ...23s are probably a hair faster but not much.


On what basis do you make that conclusion? Plenty has been published on benefits, including speed, of wider tires. Pro teams are now starting to ride 25s as well.

Is it hype or enlightenment?

For someone 185#s, 25 are certainly the better option.


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## Jay Strongbow (May 8, 2010)

Blue CheeseHead said:


> *On what basis do you make that conclusion? *Plenty has been published on benefits, including speed, of wider tires. Pro teams are now starting to ride 25s as well.
> 
> Is it hype or enlightenment?
> 
> For someone 185#s, 25 are certainly the better option.


I'm not trying to speak for him but I'd guess it's on the basis of a 140ish pound rider on smooth rollers in a wind tunnel or data aquired in a similar controlled and best case scenario environment. Unlikely that 23s are actually faster for a 185 pounder on real world roads.


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## rruff (Feb 28, 2006)

Blue CheeseHead said:


> Plenty has been published on benefits, including speed, of wider tires. Pro teams are now starting to ride 25s as well.


Pro teams are riding 25mm *tubulars* on wide rims. A 25mm tubular is like a 23mm clincher. 

Aero performance is better with small tires, enough to outweigh the difference in rolling resistance, usually.


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## dcgriz (Feb 13, 2011)

rruff said:


> Pro teams are riding 25mm *tubulars* on wide rims. A 25mm tubular is like a 23mm clincher.
> 
> Aero performance is better with small tires, enough to outweigh the difference in rolling resistance, usually.


IMO, tire width increase is not a solution that fits all. It's got trade-offs like everything else related to cycling.

Pro teams are mostly concerned with aero performance because of the speeds they are attaining. Creating a rim-tire profile that is conducive to aero performance seems to be the quest on that. At those speeds aero eclipses rolling resistance by far.

Recreational riders, traveling at non-aero range speeds, are mostly concerned with rolling resistance and possibly comfort. Thus wider tires at lower pressures.

Furthermore, the roughness of the tarmac also affects tire performance. A narrower tire at higher pressure will travel faster on a smooth pavement that a wider tire at less pressure. When the road surface becomes rougher, the opposite tends to be happening because of the "bouncing" of the tire over the road imperfections.

Bottom line, IMO, there is no one solution that fits all. It's best to pick the tire (and/or wheel) that best suits the task at hand or if equipment choices are not available, what fits what you do most of the times.


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## Blue CheeseHead (Jul 14, 2008)

rruff said:


> Pro teams are riding 25mm *tubulars* on wide rims. A 25mm tubular is like a 23mm clincher.
> 
> Aero performance is better with small tires, enough to outweigh the difference in rolling resistance, usually.


Poor argument. If 23mm clincher is faster than 25mm, then it would hold that a 23mm tubular would be faster than 25mm due to similar claimed aero benefit.

Hey, ride what you like, but for a 185# rider 23's on the rims in question are not the best choice.


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## rruff (Feb 28, 2006)

Blue CheeseHead said:


> Poor argument. If 23mm clincher is faster than 25mm, then it would hold that a 23mm tubular would be faster than 25mm due to similar claimed aero benefit.


A 25mm tubular on a wide rim is 25mm wide. A 23mm clincher on a wide rim is 25mm wide. 

23 mm (and even smaller) tubulars are faster on the wide rims, but in road races on poor pavement, there are other considerations.

EDIT: If the road is poor, small tires usually aren't faster.


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## tvad (Aug 31, 2003)

Much ado about nothing. 

23...25...use what you like. The discussion has no real meaning other than people showcasing debating skills.


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## Oxtox (Aug 16, 2006)

tvad said:


> Much ado about nothing. 23...25...use what you like. The discussion has no real meaning other than debating skills.


no shitt.

really tired of hearing about the magical qualities of 25s...


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## cxwrench (Nov 9, 2004)

rruff said:


> Pro teams are riding 25mm *tubulars* on wide rims. A *25mm tubular is like a 23mm clincher.
> *
> Aero performance is better with small tires, enough to outweigh the difference in rolling resistance, usually.


Huh? What are you trying to say here? We've got 24mm tubulars on the race wheels. Guess how wide they are? 24mm. Given that tubulars are so much harder to pinch, you could argue that a smaller tubular actually can be ridden at slightly lower pressure and feel like a larger clincher. 

I'd agree the difference in rolling resistance is minuscule, the aero is very small, the comfort/traction benefits are larger.


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## robt57 (Jul 23, 2011)

Oxtox said:


> no shitt.
> 
> really tired of hearing about the magical qualities of 25s...


I confess to some fanboying myself. Still run 23s, mostly front with a 25 rear. But recently put 23/23 back on my Addict. I think it is still a good direction and I have retired [so to speak] nearly all my narrow rims as well. I think it is girth proportional in term of 'need' so to speak. Clydes benefiting most ? [I am 210-15, is that clyde?]


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## Trek_5200 (Apr 21, 2013)

23's are fine for most road bike circumstances. The skeptic in me believes 25's their popularity in part because bike manufacturers are making their bikes too stiff/harsh, however there are roads where 23's just don't cut it, such as the ride i did yesterday out to Montauk. Toward's the end we were on a road that was just short of bombed out condition and in desperate need of repaving. Wished I was on 25's for that road, but on most rides 23's work great.


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## cxwrench (Nov 9, 2004)

Trek_5200 said:


> 23's are fine for most road bike circumstances. The skeptic in me believes 25's their popularity in part because bike manufacturers are making their bikes too stiff/harsh, however there are roads where 23's just don't cut it, such as the ride i did yesterday out to Montauk. Toward's the end we were on a road that was just short of bombed out condition and in desperate need of repaving. Wished I was on 25's for that road, but on most rides 23's work great.


It's not that '23's are fine for most people/roads' it's that the tire size should be related to ride weight and road conditions. If you're small, ride 23's. If you're small or medium size and ride sorta crappy roads, try 25. If you're big, at least 25, maybe 28. As people say...it all depends.


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## ziscwg (Apr 19, 2010)

Trek_5200 said:


> *23's are fine for most road bike circumstances. *The skeptic in me believes 25's their popularity in part because bike manufacturers are making their bikes too stiff/harsh, however there are roads where 23's just don't cut it, such as the ride i did yesterday out to Montauk. Toward's the end we were on a road that was just short of bombed out condition and in desperate need of repaving. Wished I was on 25's for that road, but on most rides 23's work great.


Let me help you..............
"*23's are fine for SMOOTH road bike circumstances."

*In the normal world of less than ideally maintained roads, the 25s are great and make a huge difference in ride quality. (adjusted to the appropriate pressure differential)

Take a 23 mm 4000s and ride it. Then put on a 25mm 4000s and ride it with (estimating) 5-8 psi less pressure, and you will wonder why you waited so long. Or, your area just has the smoothest roads on God's green earth and we are then super jealous .


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## Trek_5200 (Apr 21, 2013)

ziscwg said:


> Let me help you..............
> "*23's are fine for SMOOTH road bike circumstances."
> 
> *In the normal world of less than ideally maintained roads, the 25s are great and make a huge difference in ride quality. (adjusted to the appropriate pressure differential)
> ...


Agree, and if the roads are that bad, a gravel bike with 28's might even be appropriate and called for. I'm fortunate in that where i ride 23's are a good solution vast majority of the time. Winter is another matter.


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## deviousalex (Aug 18, 2010)

OldZaskar said:


> I'm assuming the 25mm version would not be ideal for the 21.8mm rim?


By that logic, how did cyclocross tires ever work?


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## OldZaskar (Jul 1, 2009)

deviousalex said:


> By that logic, how did cyclocross tires ever work?


by "ever work", I guess you're referring to "ability to install". Yeah, I know 25s will fit. 

I'm not interested in the off-road (cyclocross) angle here... In fact, that's specifically what I'm asking about - to avoid, e.g. the "lightbulb" profile.


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## cxwrench (Nov 9, 2004)

OldZaskar said:


> by "ever work", I guess you're referring to "ability to install". Yeah, I know 25s will fit.
> 
> I'm not interested in the off-road (cyclocross) angle here... In fact, that's specifically what I'm asking about - to avoid, e.g. the "lightbulb" profile.


That's what he's talking about. Even at low pressure the cx tires stayed on and function. Of course you can mount them on the rims, they're 700c. Hell, you could mount 29er tires on road rims and they'd be rideable.


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## bleckb (Jun 13, 2005)

Jan Heine of Bicycle Quarterly has done what many see as the best testing of this issue. Here's a link to one of his blog posts: https://janheine.wordpress.com/2014/01/01/tires-how-wide-is-too-wide/ which also has links to more and more and more and more.


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## mfdemicco (Nov 8, 2002)

On these wheels, 23s measure 25, and 25s measure 27.5 mm.


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## ziscwg (Apr 19, 2010)

mfdemicco said:


> On these wheels, 23s measure 25, and 25s measure 27.5 mm.


as long as the tires clear the frame and fork, you are good to go and riding smooth.


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## TiCoyote (Jun 28, 2005)

Here's my take: 
23s are more aero. 25s have lower rolling resistance. The majority of resistance you must overcome when riding is wind/air resistance. This can be as much as 90% (not sure where I read this stat, maybe in another thread?). Therefore, an aero tire should be faster (or at least require less wattage) than one that rolls more smoothly (not to mention the fact that the 23mm will be slightly lighter, giving it a 1-2 punch). 

HOWEVER, I put 25mm tires on my bike when I did a tour, and I've never looked back. Although a 23 may be faster on a perfectly smooth road, having the extra comfort means I'm faster for the long haul on an endurance ride, because the bumps don't beat me up too much. 

Meanwhile, the Dealer's Manual for the DA C24s states that 23-28mm is the appropriate tire size, so a 25 certainly won't be too big for that rim.


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## deviousalex (Aug 18, 2010)

TiCoyote said:


> 23s are more aero.


Not necessarily true. Some manufacturers are recommending 25s as more aero for these wider rims because it smoothes out the rim to tire transition and creates less drag. Maybe in a dead on headwind 23s would be more aero but I doubt in any sort of cross wind.


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## cxwrench (Nov 9, 2004)

The 'aero' difference between 23 and 25? For a normal guy that isn't paid to pin a number on? Get real. As Ti and alex posted there are much more important things to worry about than a possible minute aero advantage some of the time. Having good ride quality and cornering traction is much more important for 99.999% of the time.


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## Blue CheeseHead (Jul 14, 2008)

deviousalex said:


> Not necessarily true. Some manufacturers are recommending 25s as more aero for these wider rims because it smoothes out the rim to tire transition and creates less drag. Maybe in a dead on headwind 23s would be more aero but I doubt in any sort of cross wind.


I am not sure who recommends 25's based on aero considerations. HED designed their 25mm wide Plus rims around a 23 based on the aero benefits you state. 

There seems to be a false assumption by many that wide rims mean that wide tires need to be used. A wider rim increases the installed cross section of any clincher, reducing the need to run a wider tire. I generally run a tire that measures 25mm installed. It could be a 25mm Conti installed on a 19 or 20mm wide rim or a 23mm Fusion III on my 25mm Ardennes Plus.


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