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Changed Tires From 700x23 to 700x25

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Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Changed Tires From 700x23 to 700x25

Old 09-07-15, 01:20 AM
  #51  
mawashi
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Originally Posted by chasm54 View Post
Answer provided two hours before you posted...
I wait with baited breath on his savant response...
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Old 09-07-15, 01:58 AM
  #52  
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I like 25's. I haven't had the time or energy to overthink this one.

Hit it a pine cone in a sharp corner on a steep descent today, going 20+ mph when I hit it. Wasn't left wishing for a narrower tire at higher pressure........
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Old 09-07-15, 03:57 AM
  #53  
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Originally Posted by nastystang View Post
Since tire contact patch is as you say difficult to calculate and area is of no use without hard numbers from rider weight,bike wieght and tire pressure what does that have to do with the width of the tire. I got your math and without any hard numbers the only thing for sure is width and its only 8%. Given the fact that I am just slightly heavier lets say 2% I have never seen a three minute advantage from 25 over a 23 or vice versa. Its all good I see what you are saying but simply put its not going to have an impact on the average joe. Different tires might, but not dramatically.
25mm tires are also aerodynamically inferior and weigh more than 23's. There is a reason why 23's have been the sweet spot for decades...they strike a good balance for a performance oriented road bike. The top racers in the world in the TdF this year were riding 28-30mm width tires on the cobble stages FWIW at pretty obscenely low air pressures as they were riding tubulars without tubes and so no worry about pinch flatting. On common rougher surfaces among heavier average riders, 25's make a lot of sense. Honestly I ride each on different bikes and the biggest difference is what I feel...the 25's running 5 psi or so lower pressure have a more muted ride because of greater air volume. Also my 23mm tire bike is faster as well on the same route...but this maybe more about the bike than the tire diff.
Also tire construction matter when it comes to speed as well. Have to compare apples to apples like TPI when comparing tire widths relative to speed and even ride quality. Higher TPI tires tend to be faster and ride better and of course cost more.

Last edited by Campag4life; 09-07-15 at 04:04 AM.
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Old 09-09-15, 10:32 PM
  #54  
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I've had 25s on my bike for almost a week now. (I've kept the tire pressure at 80/85.) I have covered several different "go to" routes between 15-20 miles during this time, and in each case I have shaved 2-3 minutes over previous times for those same routes. I don't believe my cycling skills have improved dramatically this past week, or that I have had a favourable tail wind each time. For me, shifting from 23s to 25s appears to have increased my overall average speed and ride comfort. I'm a happy camper.

Last edited by Catinella; 09-09-15 at 10:49 PM.
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Old 09-12-15, 06:29 PM
  #55  
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I've read so much information on the web and this forum about tires that it's making my head spin (almost as fast as my wheels!). Today I rode a favourite 33 mile route for the third time since changing from 23s to 25s. In each case I completed the route about 5 minutes faster than before the tire change. I think the general consensus is that the thinner tires should be faster, but that is not what I have experienced. That being the case, I am thinking that my increase is speed might be attributed to the quality of the rubber on the tires. The older 23s felt hard and dried out. If I ran my hand over the tread, there seemed to be no friction. The rubber on the new 25s seems more supple, and there is definitely some grip/friction when I run my hand over the tread.

I bet that if I were able to compare two sets of identical (brand & size) tires, but one set was several years old and seen a lot of UV, that the newer tires would be faster.
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Old 09-12-15, 07:49 PM
  #56  
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That's what BT said in post #4: "new tires are new.old tires are old tires."

(but for the record, most pro teams now believe 25 is now the sweet spot. Faster than 23s, but not too wide to be non-aero.)
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Old 09-12-15, 09:36 PM
  #57  
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Originally Posted by pacificaslim View Post
That's what BT said in post #4: "new tires are new.old tires are old tires."

(but for the record, most pro teams now believe 25 is now the sweet spot. Faster than 23s, but not too wide to be non-aero.)
Re aero, it depends on the wheel/tire combination. The better the rim matches the tire, the more aero it will be. From what I read, pro teams without wide rims are staying at 23.

My wheels are 19mm. That's why I'm hesitant about going from 23's to 25's.

Will the added comfort from slightly lower pressure and/or lower rolling resistance of 25's make up for a less aero setup with a 19mm rim? What's the right combination of comfort/rolling resistance/aero for a 1 hour training ride vs a seven hour century? Will the difference even be noticeable?

My tires are on sale right now so I might just try both sizes.


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Last edited by TimothyH; 09-12-15 at 09:39 PM.
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Old 09-13-15, 03:54 AM
  #58  
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Originally Posted by pacificaslim View Post
That's what BT said in post #4: "new tires are new.old tires are old tires."

(but for the record, most pro teams now believe 25 is now the sweet spot. Faster than 23s, but not too wide to be non-aero.)
Thinking about this.. wondering if for the rear tube, if a 25 could actually be more aero than a 23, since a 25 more likely matches the width of the seat tube that it sits behind?
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Old 09-13-15, 09:03 AM
  #59  
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Originally Posted by Sy Reene View Post
Thinking about this.. wondering if for the rear tube, if a 25 could actually be more aero than a 23, since a 25 more likely matches the width of the seat tube that it sits behind?
matching the rim is important for aero.
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Old 09-14-15, 10:58 AM
  #60  
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Originally Posted by rpenmanparker View Post
Why do the English quote weight in 14 lb increments? And why is it not stones instead of stone for more than one? Inquiring minds want to know. I mean stone is a perfectly fine unit of measure, but only if taken to two decimal places. If I could ignore the difference between 154 and 168 lbs (11 and 12 stone), my life would surely be a hell of a lot simpler. One stone represents the entire range of weight I have experienced through my entire adult life. Does that range not need to be broken down a little bit more precisely?
Originally Posted by f4rrest View Post
No, my conclusion was that in the apples-to-apples comparison (where contact patch area is the same) that the wider tire is faster. But the reason it's nonsense is because nobody runs the larger tires with the same pressure, even though they insist on saying "larger tires are faster." No, not necessarily, if you deflate them.

Even Continental adds the footnote to that effect. See "Assumption: inflation pressures and tire loads are equal." below.

Too confusing.... This has facts in it.

There is a really good article on this in Lava Magazine...the issue with Gwen Jorgenson on the cover. 25's are faster. But if you are not already pretty fast don't worry about it.
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Old 09-14-15, 11:28 AM
  #61  
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I have no idea if they are faster and don't care, but 25's are more comfortable so I run them. 32's are even more comfortable but I used my set up and had the 25's in the house. I'll probably go back to 32's when I need to buy tires.

The road surfaces I ride aren't velodrome track smooth, so the less air pressure I run is of importance to me.
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Old 09-14-15, 11:48 AM
  #62  
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Originally Posted by Catinella View Post
...make that much difference?
No. Enjoy the ride!
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