# are 25cc much better than 23cc



## inspectormorse (Nov 30, 2013)

For gran fondos and long distance race, what do you prefer 23 or 25s?

which ones and why? pros and cons?

thanks.


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## NJBiker72 (Jul 9, 2011)

Whatever you are comfortable with. I use 23s mostly. But have ridden 75+ miles on 25s, 28s, and 32s.


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## tihsepa (Nov 27, 2008)

25's. They are better for me. Seeing as only me can fit on my bike thats all that matters. 
I weigh 190 and run 80 up front 90 in the back. Very comfortable and reliable. 
I break all the cycling rules though. Big tires, 32 spokes, wide rims, carbon frame with the proper fit for my riding style ect............


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## FuelForThought (May 13, 2012)

How much do you weigh? 23 inflated to 85psi would be fine for a 140lb rider doing long distance. Harder to make them comfy for a 200lb rider


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## Drew Eckhardt (Nov 11, 2009)

inspectormorse said:


> For gran fondos and long distance race, what do you prefer 23 or 25s?
> 
> which ones and why? pros and cons?
> 
> thanks.


It depends how much you weigh. At 145-150 pounds 23mm are really pleasant at 90psi.

Passing 200 pounds, 90-95 front and 100-105 psi rear are viable starting points for a week of riding on 25mm tires without pinch flats.


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## inspectormorse (Nov 30, 2013)

Drew Eckhardt said:


> It depends how much you weigh. At 145-150 pounds 23mm are really pleasant at 90psi.
> 
> Passing 200 pounds, 90-95 front and 100-105 psi rear are viable starting points for a week of riding on 25mm tires without pinch flats.


I'm 148 lbs so 23s are good for 100 mile gran fondos?


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## NJBiker72 (Jul 9, 2011)

inspectormorse said:


> I'm 148 lbs so 23s are good for 100 mile gran fondos?


I am 170 and they are fine for me. So yes.


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## inspectormorse (Nov 30, 2013)

Thanks NJBiker72 . . . I should have asked this question earlier it would have saved me from experiencing tire rub from 25cc and tire flex on sweeping turns on inside chainstays that took off the paint (just cosmetic damage) from my carbon bike. I guess better to know it now then to get a nastier surprise after clocking more miles.

How about configuring front wheel with 25cc and 23cc. Will I gain any advantage if using 25cc on front wheel?


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## NJBiker72 (Jul 9, 2011)

inspectormorse said:


> Thanks NJBiker72 . . . I should have asked this question earlier it would have saved me from experiencing tire rub from 25cc and tire flex on sweeping turns on inside chainstays that took off the paint (just cosmetic damage) from my carbon bike. I guess better to know it now then to get a nastier surprise after clocking more miles.
> 
> How about configuring front wheel with 25cc and 23cc. Will I gain any advantage if using 25cc on front wheel?


I don't see why you would in particular. If anything I would think you would get more benefit from a 25c on the rear where most of your weight is. I guess it could help comfort for a bump you hit with your front tire. Maybe help handling on bad surfaces and gravel??

I am taking it fits on the front but not the rear??


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## inspectormorse (Nov 30, 2013)

it fits on both front and rear wheels. The problem is when cornering on high speeds, the tires rubbed against insides of the chainstays. I only found about this problem recently and I've put some vinyl 3m stickers on areas affected. I've supertightened the quick release now as well.

The tires literally took off the paint leaving surface powder coated (no carbon is exposed so thankfully). I should have never used 25ccs. Well at least, it's just cosmetic damage.


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## Jay Strongbow (May 8, 2010)

inspectormorse said:


> it fits on both front and rear wheels. The problem is when cornering on high speeds, the tires rubbed against insides of the chainstays. I only found about this problem recently and I've put some vinyl 3m stickers on areas affected. *I've supertightened the quick release now as well*.
> 
> The tires literally took off the paint leaving surface powder coated (no carbon is exposed so thankfully). I should have never used 25ccs. Well at least, it's just cosmetic damage.


I'd stop doing that if I were you. Your quick realease only needs to be "tight enough". Any tighter will not help with wheel flex. But more importantly you might be cooking your hub bearings with too much QR pressure.


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## inspectormorse (Nov 30, 2013)

jay, so do you just suggest to just be tight enough based on manual . . . right turn bolt with finger tight, then QR level push in enough to make imprint on hand?

also do you suggest just going back to 23ss.

I'm [email protected] off that the 25ccs did that on my new carbon bike on internal side chainstays both sides (wheelside).


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## JCavilia (Sep 12, 2005)

BTW, it's not "25cc" -- it's 25mm (millimeters), the approximate width of the inflated tire. The "C" doesn't mean "centimeters," it means -- well, it doesn't mean anything anymore; it's a weird historical relic of a old size-designation system. When the tire says "700-25C" it means a 25mm width tire for a 700C rim (which in the modern system is more properly designated as a rim with a 622mm bead seat diameter).


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## aclinjury (Sep 12, 2011)

I'm a little curious as to what kind of frame, tires, and wheels do you have? You must have really flexy wheels, or narrow frame, or really wide "25c" tires, to have the combo rub your chainstays. Some 25c tires (like those from Hutchinson) measured less than 23mm! But some 25c tires measure up to like 26mm. So tire sizes have no stringent standards at all.

As for the difference between 23c and 25c, I've found the 25c to be a tad sluggish, and slower turning around corners. A 25c does not enable you any more corner grip compared to a 23c. What a 25c might do is enable you to lower the psi by about 5, and if you can tell the difference by lowering 5 psi, then you have a really sensitive butt or the placebo effect is working well.

In order to feel a real difference in ride quality (suppleness), one would need to go from a 23c to 28c. IMO 25c tires are a little gimmicky. And oh don't get me started on the whole "aero-ness" of a 25c tire on a wide rim; one of the most ridiculously hyped up concept in the bicycle tire and wheel market.


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## inspectormorse (Nov 30, 2013)

Hey there
they are hi quality japanese tires, the wheels are hi quality carbon wide rims, and the bike is a hi quality carbon bike from a tier one company.

There was clearance on both sides, but didn't know high speed turns would make tires dig(flex?) into the paint.


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## willembad (Jun 26, 2013)

inspectormorse said:


> ...but didn't know high speed turns would make tires dig(flex?) into the paint.


You do realize that if a tire deforms at the contact patch (at the road surface) for whatever reason that the rest of the tire is still the same shape it was before you got on the bike, right? IMHO it sounds more like you had a wheel flex issue to cause the tire to rub the chainstays.


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## JCavilia (Sep 12, 2005)

inspectormorse said:


> Hey there
> they are hi quality japanese tires, the wheels are hi quality carbon wide rims, and the bike is a hi quality carbon bike from a tier one company.
> 
> There was clearance on both sides, but didn't know high speed turns would make tires dig(flex?) into the paint.


I'm curious why the apparent reluctance to reveal the specific brands and models of your "hi quality" stuff. You'll get more useful advice if you give more specific information.

Your wheels in particular may be a big part of the issue. If there's flex happening, it's happening in the wheels, not the tire. And the wheel's susceptibility to that is mainly a function of build, not the rim quality. Who built the wheels? if they're machine-built, have you had the spoke tension checked by a good wheel builder? Retensioning the spokes may solve your problem.

On the other hand, your frame just may not have enough clearance for that tire/rim combination. You say there "was clearance," but how much? 3mm? 1mm? Less? All wheels flex some. You need some extra room for that.


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## ziscwg (Apr 19, 2010)

They still make 23 mm tires??
Well, OK, I will never buy one.


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## aclinjury (Sep 12, 2011)

How wide is your rim? 23mm? 25mm? If you put a 25c tire on a 25mm rim, the tire may ballon out to 26mm. Having said that, I have run 28mm tire (which actually measures out to 27.5mm) on my frame and I'm guessing there is about 3-4mm of clearance on each sde of the chainstays, and so far I have not experience frame rubbing. But I'm only 120-122 lbs.

and JCavilla is right, better if you give the specific brands. Saying high quality so and so don't mean much.


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## JCavilia (Sep 12, 2005)

ziscwg said:


> They still make 23 mm tires??
> Well, OK, I will never buy one.


There are still some 20 mm tires.


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## dcgriz (Feb 13, 2011)

JCavilia said:


> There are still some 20 mm tires.


they will be the hot item with the unobtainium rims on 36 spoke wheels come 2030


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## Gregory Taylor (Mar 29, 2002)

Agree 100%. And even "high quality" frames and parts can have issues, like soft spoke tension (as suggested above) or a loose wheel bearing (which will allow the wheel to wander on the axle). Or a "high quality" Japanese tire can be too big for the frame. It happens.


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## SystemShock (Jun 14, 2008)

aclinjury said:


> What a 25c might do is enable you to lower the psi by about 5, and if you can tell the difference by lowering 5 psi, then you have a really sensitive butt or the placebo effect is working well.


All else being equal, and assuming that a '23mm tire' actually DOES measure a true 23mm, and that a '25mm tire' actually DOES measure a true 25mm (many don't, as you note)... the 25mm tire will have 18% percent more air volume than the 23mm, at identical pressures.

So, that would seem to give you the leeway to lower the pressure on the 25mm a lot more than "5 psi". More like 10-15psi, at least. 

For instance, I used to run 25mm tires at 105 psi or so, but now I run 27-28mm at 90 psi (I'm a heavy guy). Never got pinch flats with either, but the ride quality @90psi is so very much better. :yesnod: 

Nor do I feel any slower... maybe a little faster actually, because rough roads make me 'bounce' less/seem to rob my momentum less. 

_To the OP:_ It really sucks/is scandalous that your bike can't even take 25mm tires without scraping paint. It does seem that finicky designs like that with super-limited tire clearances are slowly-but-surely becoming less popular... and good riddance to 'em. 

There are 24mm tires out there (Vittoria and Continental make some), you could possibly try one of those. Also measure your current tires to see if they really are a true 25mm, that'll give you a sounder basis to operate from (for instance, I have some Michelin Pro Races that are listed at 25mm, but actually run 27mm, and this isn't that uncommon).


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## Dunbar (Aug 8, 2010)

^I agree, going from 23 to 25mm tires should allow you to safely run 10psi less pressure which I can definitely notice.

AFAIK, many race oriented road bikes still do not officially support 25mm tires although that has been changing in recent years. I know that Cervelo just started advertising that their 2014 S and R series have clearance for 25mm tires.

It would helpful if the OP would post a picture of the rear wheel/tire clearance at the chain stays. Just because it fits doesn't necessarily mean there's enough clearance to avoid rubbing.


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## powbob (Jun 10, 2008)

I recently went from 23 to 25 conti 4000S and I love the difference. I weigh 220 lbs which is probably a big part of this. But, even the pro's are going to 25's now though and they are built like twigs.


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## AndrwSwitch (May 28, 2009)

23mm for me. I weigh 155 right now and am working my way back to 140-145. So I can ride at 80 and 95 psi as it is. And I like the way my 23s handle.


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## SpeedNeeder (Aug 19, 2013)

I've only ridden the 23's that came with my bike. 
I have noticed much better bump handling with lower pressures (90) but I'm afraid of getting a pinch flat so u stay at 100-110 typically. 
Im 6'1 170


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## tihsepa (Nov 27, 2008)

Is "High Quality" with no brand another term for "cheap chinese crap"?


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## AndrwSwitch (May 28, 2009)

tihsepa said:


> Is "High Quality" with no brand another term for "cheap chinese crap"?


Oh, snap!

But I'm curious too.


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## aclinjury (Sep 12, 2011)

Here is a nice little article concerning tire sizes, written in layman's terms.

Friction (and contact patch size)

Here's what I got from it.

- wider tires do not give you better friction or "sticking power" if the rubber is the same.

- The "contact patch" of the tire does not depend on the size of the tire, but rather it depends on the force pushing on the tire (in this case, it's the weight of the rider). Tire air pressure (within reasonable operationg range) does not affect the size of contact patch either.

- Wider tire has more bulk, and because of this extra bulk, it will manage heat better than a skinnier tire. And also because of the extra bulk, it will not tend to rip and shear under forces (and this can become an issue if the rider is heavy, and taking a hard corner)

All of the above points assume that everything else is equal, meaning the tire profile, tire rubber are the same between a wide and skinny tire.

However, a skinny tire if contructed of a different rubber and has a different profile, can still certainly outperform a wider tire any day. For example, let's compare a racing motorcyle tire versus one of those fatass tire on a Harley. The racing motorcycle tire is usually around 180/190 wide, which is in fact much narrower than some of these fatass tires you'll see on custom cruisers. The racing motorcyle tire also has a more toroidal shape with a higher sidewall, and this shape (profile) allows the rider to corner the bike much more aggressively than otherwise. The fat cruiser tire will never be able to afford the rider this.

So back to bicycle. Simply going to a wider tire does not necessarily mean "better performance". Performance really depends on many many factors, eg., choice of rubber, profile of the tire. Also if you're a lighter rider, you *WILL* most definitely want some *heat* into a tire during aggressive cornering or aggressive braking. Reason is because heat usually turns the rubber stickier (ie, heat changes the friction character of rubber). Well guess what, if you're skinny 120, 130-lb dude, and you're riding a wide tire, you ain't (due to lack o weight) gonna be able to put in the same amount of heat into that wider tire compared to a bigger 200-lb dude. In this instance, your performance can actually suffer.

Now if you're 200-lb goliath, then you'd want to go wider tire. Wider tire has more bulk, which can manage heat better (as heavier riders put more heat into a tire), and also more bulk means the tire will resist shearing better than a skinner tire. Umm but guess what, if you go too low of a pressure (because you want a comfy ride), then well you sort of negate the benefit of running a wide tire. Lower pressure will definitely cause the tire to wear out faster, and lower pressure will also cause the tire to deform in ways that the manufacturer did not intend it to. 

Question:

Has there been *even* any sort of informal tests by anyone? or any manufacturer?... regarding the effects of changing to a wider tire? Like everything else in science, there must is an "optimal" point. I would be interested to know the "optimal" point when all these parameters are put together: rider's weight, longetivity of tire, cornering ability (can be measured with force sensors on tire), braking ability (can also be measured).

And on top of tire sizes, there's also an issue of the *rim.* Simply put, a tire of a given size will carry a little different profile when fitted on rims of different width. A 25c (or 23c, etc) tire will not carry the same profile, and will behave differently when fitted on a 19mm wide rim versus when fitted on a 23mm rim versus a 25mm wide rim, and I'll bet somewhere along the line of rim width, there is an "optimal" width which the rim should be. I'm no expert, but I would think that one would only want to use a wider tire given that rim width also increase. Putting a 25c tire on a 19mm wide rim will give you a "Monster Truck" wheel, or at the very least "beach cruiser" wheel, not necessarily "better".

But so far, we've only read personal anedoctes stories of guys saying wider is better, with their personal experience (mostly in terms of comfort feeling). Guys will say this a lot "they feel more confidence in corners, more stability in corners". Not that I doubt their feeling, but feeling can be very subjective (even resulting from a placebo effect), and without scientific data,.. well then it's a subjective thing.

Now I suppose if all one wants to do is mainly ride the flat roads, but roads with lots of bumps and potholes, then going wider with lower pressure will help. But this doesn't mean you'll get better performance on a mountain descent.

Another thing I'm ever so wondering about is this claim. Guys say they'll drop the PSI by 10 by going from 100 to 90, and now suddenly he's riding on a magic carpet (as far as comfort goes)? Come again homie? Now I've run mtb bikes with both clinchers and tubeless setup ranging from 25-35 psi, and on my road bikes I've experiment with 80 psi (tubeless), to 90 (on clinchers) to 100 to 110. And for the life of my butt, I can't honestly feel any difference in comfort between say 90 and 100. Now between 80 and 110 (on clinchers), I do feel that 80 is a tad more comfy, but at 80, it's pinch flat galore for me if i'm on clinchers. I'm 120 lbs.


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## ziscwg (Apr 19, 2010)

ziscwg said:


> They still make 23 mm tires??
> Well, OK, I will never buy one.





JCavilia said:


> There are still some 20 mm tires.


Wow, those are from like the stone age....


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## ziscwg (Apr 19, 2010)

SystemShock said:


> There are 24mm tires out there (Vittoria and Continental make some), you could possibly try one of those. Also measure your current tires to see if they really are a true 25mm, that'll give you a sounder basis to operate from (for instance, I have some Michelin Pro Races that are listed at 25mm, but actually run 27mm, and this isn't that uncommon).


The Vittoria 24 mm tire (the Open Pave) is a 25mm. Mine measures 25 on my 19 mm rim. Now, the Vittoria Diamonte Pro 25mm runs small. It was a real 24 on my rim. I was not a big fan of this tire. I'd rather run an Open Corsa 23 mm.


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## ziscwg (Apr 19, 2010)

ziscwg said:


> They still make 23 mm tires??
> Well, OK, I will never buy one.





JCavilia said:


> There are still some 20 mm tires.





aclinjury said:


> Here is a nice little article concerning tire sizes, written in layman's terms.
> 
> Friction (and contact patch size)
> 
> ...



Wow, that was a lot.
Personally, the only valid comparison would be using a 23 and 25 mm tire of the same model. For example, Vittoria Open Corsa 23 and 25 mm. It would be hard to compare a 23 mm Open Corsa to a 25 mm Conit 4000s.


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## danl1 (Jul 23, 2005)

aclinjury said:


> Here is a nice little article concerning tire sizes, written in layman's terms.
> 
> Friction (and contact patch size)
> 
> ...


Roughly true, but that's about 'traction', not rolling resistance, so there's more to the story. 

The size of the patch won't change much with tire size (assuming the same pressure), but the shape will. The larger tire will have a 'rounder' contact patch (or IOW, the skinny tire will have a longer patch.) Effectively, the tire wider will deflect less as the tire rotates into the patch, and that lower deflection will absorb less energy, so mean less rolling resistance. 

Another way of looking at it: The wider tire has greater surface area (to contain the air), so at the same internal pressures, the larger tire has a higher tension. And if you think of it sort of like a trampoline, it's obvious that higher tension will deflect less to a given pressure.

That reveals another little-recognized factor: At the same pressures, a wider tire will 'feel' harder in terms of ride comfort. You need to drop pressure on the wider tire to get to the same basis, in terms of how much deflection will occur at a given load. 

So there's no free lunch. You can have more efficiency out of a wider tire, but it will be rougher riding. If the pressure is dropped so the (vertical) deflection is the same, you still get some advantage to the shape of the deflection, but not as much as one might hope. But you do get more pinch-flat protection, because there's more 'headroom.' The outcome is that you can run the larger tires lower still, and still be safe from pinch-flats but get more comfort. 

And more than just comfort, because efficiency is about more than tire deflection. While that's a source of friction, it also saves energy, by reducing the amount that you and the bike bounce up and down - which is another energy cost. And that can make a lot of difference.

And I won't agree that pressure does not change contact patch size. It's not exactly correct, but it's roughly true that the size of the contact patch will be the weight carried / psi. So, if a wheel was carrying 100 lbs and had 100psi pressure, the contact patch would be 1 sq. in, more or less. But it is true that the size of that patch does not impact 'traction' very much. THat is, if you cut the pressure to double the contact patch, the tractional friction would change almost-not-at-all.

Although, this is a place where bikes are somewhat different creatures than larger vehicles. Any patch of rubber (for any vehicle) will have some contact points, and some areas that don't contact due to the road surface roughness. But because we're so light, our patches are small. So the size of the aggregate in the tarmac can impact the percentage of the patch that is in contact - larger aggregate being relatively less area. So a somewhat larger patch can improve traction in our cases. On larger tires from motos and cars, the percent change is negligible. Similarly, this effect disappears if we're comparing bicycle tires on a smooth surface. 

Some folks argue that a wider, softer tire doesn't corner as well. I will certainly agree that it doesn't feel as confident as the tire 'squirms', but I have no way to know if it's actually less grippy in real-world bicycle scenarios. I suspect there's a small difference.

I feel like I have to talk about wide rims. First note: They were initially designed to be used with 23's. The idea is that they increase the circumference under pressure, so give many of the advantages of a wider tire, but without creating the 'lightbulb' shape of a wider tire, and in fact decreasing that from even a 23 on a standard rim. So you gain the rolling resistance and pinch-flat advantages and improve handling, while not adding rubber. Sure, you can then put wider tires on those, which is great for really rough (e.g. gravel) surfaces or high rider weights, but is not really optimizing the designed advantages. At least that's the argument given.

So what's best? Depends on rider, road, intent, and conditions. At 185, I prefer 23's on wide rims to 25's on narrow for most of my riding, though I'll put 25's on the wides if I'm headed into some of the rougher routes. But the differences are narrow, and 'preference' is the key word. There's little right or wrong, and even better and worse are pretty speculative. Part of the fun of our lifestyle is trying different combinations and learning what suits you.

Some extra reading material, which many will have already seen:
Bicycle Quarterly: Performance of Tires | Off The Beaten Path

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


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## JCavilia (Sep 12, 2005)

ziscwg said:


> Wow, those are from like the stone age....


Well, no. They're not really obsolete -- it's just that their use is now wisely limited (mostly - I'm sure there are some weight weenie guys out there who ride them more) to situations where they might make sense, like short time trials on very good roads.


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## JCavilia (Sep 12, 2005)

tihsepa said:


> Is "High Quality" with no brand another term for "cheap chinese crap"?


Not sure, but "Hi quality" may be.


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## easyridernyc (Jan 10, 2008)

*can of worms*



inspectormorse said:


> For gran fondos and long distance race, what do you prefer 23 or 25s?
> 
> which ones and why? pros and cons?
> 
> thanks.


you're opening up a can of worms here, bro. 

my two cents is 23's have less material. less material, less resistance. less resistance, more speed. 

25's are not that much more different, but you can feel the difference in material and resistance. not a ton, but its there. if you're going for comfort 25's at 100 psi will get you there, comfortable. ftw? probably 23's at 120, depending on the wheelset and tires....


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## AndrwSwitch (May 28, 2009)

I'm glad someone else noticed wider tires riding harsher at equal pressure. I'd wondered if I was making it up. 

acl, I notice that that article is from a motorcycle site. Relative to motorcycles, I think that cyclists change tire pressure by a proportionally much larger amount, and vary force applied to the tire somewhat less. We also don't kick out the kind of Watts to heat up the tread.

Schwalbe puts out white papers on some of this stuff from time to time.

FWIW, when I started experimenting, I dropped my tire pressure from 120 to 95. I think a 10 psi difference is more in the "it's subtle but it's there" range - I think I could tell riding two otherwise equal setups back-to-back. But I doubt I'd notice if I rode one one day and the other on the following day. I do suspect that there's some non-linear stuff happening around there, but I dunno.


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## ziscwg (Apr 19, 2010)

AndrwSwitch said:


> I'm glad someone else noticed wider tires riding harsher at equal pressure. I'd wondered if I was making it up.
> 
> .



Yeah, you have to lower the pressure with the wider tires if you want to compare the same models. That's the key. Don't go too low or the sidewalls get weird.


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## Dunbar (Aug 8, 2010)

AndrwSwitch said:


> FWIW, when I started experimenting, I dropped my tire pressure from 120 to 95. I think a 10 psi difference is more in the "it's subtle but it's there" range - I think I could tell riding two otherwise equal setups back-to-back. But I doubt I'd notice if I rode one one day and the other on the following day.


I think it depends on the suppleness of the tire. IME a 10psi drop in pressure is more noticeable on something like a GP4000s or PR4 than a Gatorskin or Durano Plus. We're still riding narrow tires at fairly high PSI so you can't expect your bike to transform into a beach cruiser just by removing 10psi from the tires.

Frame stiffness is another factor that can affect ride quality as well IME. A really stiff and unforgiving frame won't benefit much from dropping 10-15psi in the tires because the frame is sending way more harshness up to the rider than the tires are.


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## Kerry Irons (Feb 25, 2002)

aclinjury said:


> - The "contact patch" of the tire does not depend on the size of the tire, but rather it depends on the force pushing on the tire (in this case, it's the weight of the rider). Tire air pressure (within reasonable operationg range) does not affect the size of contact patch either.


Half right. The size of the contact patch is essentially the force applied divided by the tire pressure. 100 lb. weight on the tire at 100 psi = 1 square inch contact patch. If you pump the tire to 120 psi the contact patch shrinks to 0.83 sq. in. If you drop the pressure to 80 psi the contact patch grows to 1.25 sq. in. If you think that 50% difference in the size of the contact patch is "zero difference" then you have an interesting definition of "not affected by tire pressure."



aclinjury said:


> - Wider tire has more bulk, and because of this extra bulk, it will manage heat better than a skinnier tire. And also because of the extra bulk, it will not tend to rip and shear under forces (and this can become an issue if the rider is heavy, and taking a hard corner).


Heat management? Where is all this heat coming from? The tire is moving through the air at 20 mph or so. The small amount of heat generated from the rubber scrubbing against the pavement is dissipated easily. Heat from rim braking goes directly into the tire/tube and establishes an equilibrium temperature which would only be lower in the larger tire because it has a bit more surface area. The "ripping and shearing" is occurring in the tread rubber, and that is not any different as a function of tire size (assuming we're talking the same brand/model of tire).

Your source seems pretty confused about the real world.


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## SpeedNeeder (Aug 19, 2013)

danl1 said:


> Roughly true, but that's about 'traction', not rolling resistance, so there's more to the story.
> 
> The size of the patch won't change much with tire size (assuming the same pressure), but the shape will. The larger tire will have a 'rounder' contact patch (or IOW, the skinny tire will have a longer patch.) Effectively, the tire wider will deflect less as the tire rotates into the patch, and that lower deflection will absorb less energy, so mean less rolling resistance.
> 
> ...


What? Wider tires are faster? Maybe at 5 mph, but at 20?


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## Dunbar (Aug 8, 2010)

SpeedNeeder said:


> What? Wider tires are faster? Maybe at 5 mph, but at 20?


Actually what I've seen from the wind tunnel tests is going from 23 to a 25mm tire causes 20-100g of extra aero drag at 30mph. It depends on what size tire the wheel was designed for. 30mph for most of us roadies is going to require 500-600 watts on flat ground with no wind. I'm not sure most of us would notice a few extra watts of drag at those power levels. At 20mph you're not going fast enough to notice the difference.


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