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  1. #1
    Senior Member bruce19's Avatar
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    Thinking of changing tire size...advice?

    I've always run 700X23's on my Masi Gran Criterium. Currently running Michelin Krylions and like them. Feels like they roll with little resistance. But, because I've heard good things about going up a size to 700X25 I was thinking about trying that out. Just wondering what the group wisdom is about the change and if there are preferred tires at that size.

  2. #2
    Let's do a Century jppe's Avatar
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    Curious-what are you looking to get out of the change? Speed increase, increased comfort, reduced flats, etc?
    Ride your Ride!!

  3. #3
    Senior Member kingfishr's Avatar
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    Switched to 25mm Continental 4000s and seems a bit more comfortable, in fact when I switched to another wheelset I couldn't for the life of me figure out why the ride felt harsher until I came home and realized that I was back on 23s.

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    Senior Member Gravity Aided's Avatar
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    I'm a clyde so 25's are my narrow .

  5. #5
    Have bike, will travel Barrettscv's Avatar
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    The larger tire will give you a little more air volume. You will be able to ride at a slightly reduced psi without any increased risk of pinch flats. The ride will be more supple and your speed on defective pavement will benefit by a small amount. You will have a slightly increased aero drag, but I would not expect any real negative impact on speed from this.

    However, the change will be very minor. There just is not that much of a size difference between 23 and 25. Other factors will count also. Are the two tires equal? A 700x25 Conti Grand Prix 4000S will provide greater overall speed than a 700x23 in a Conti Gatorhardshell.
    Last edited by Barrettscv; 12-02-12 at 03:56 PM.
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    Senior Member Gravity Aided's Avatar
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    That is my experience also

  7. #7
    Senior Member bruce19's Avatar
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    There was a previous thread with a reference to a site that said that 25s actually rolled better (less resistance) than 23s because rolling resistance was affected more by sidewall stiffness than tire width. I was trying to get a bit more speed while improving comfort a bit. But, let me be clear, I am not having any type of problem with my current set up. Just thought there might be a benefit to 25s based on that thread.

  8. #8
    Galveston County Texas 10 Wheels's Avatar
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    Put a 25 on the rear wheel for more comfort.
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  9. #9
    Senior Member bruce19's Avatar
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  10. #10
    Have bike, will travel Barrettscv's Avatar
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    Quote Originally Posted by bruce19 View Post
    There was a previous thread with a reference to a site that said that 25s actually rolled better (less resistance) than 23s because rolling resistance was affected more by sidewall stiffness than tire width. I was trying to get a bit more speed while improving comfort a bit. But, let me be clear, I am not having any type of problem with my current set up. Just thought there might be a benefit to 25s based on that thread.
    I agree that ride comfort can be improved by going from a size 23 to a size 25. I also agree that there is no loss in performance, a 25 can be more supple and there is a performance benefit from having the tire absorb the small impacts. On smooth pavement, the 23 sized tire at very high pressure has a small performance advantage over a larger tire at reduced pressure, mostly due to better aerodynamics. However, a 23 sized tire at very high pressure forces the bike and rider to move up and over small impacts, this reduces speed on bad pavement.

    I'm intensionally not trying to make an apples to apples comparison, a size 23 at 115psi will run faster than a size 25 at 95psi, if the pavement is perfectly smooth. Over damaged pavement, the size 25 at lower pressure becomes faster due to reduced suspension losses.

    This report discusses the energy consumed by suspension losses: http://janheine.wordpress.com/2010/1...-and-pressure/

    I use a 700x24 on my road bike and a variety of larger tires on my Cyclocross bike. I've seen a speed increase on the larger tires on sections of pavement that are damaged or defective. I see a loss of speed with larger tires on sections of pavement that are new and in perfect condition.

    If I was lucky enough to only ride on perfectly smooth pavement, I would always use a 700x23. However, my roads are often damaged: so I am faster and enjoying cycling more with the larger tires I use.
    Last edited by Barrettscv; 12-02-12 at 10:55 AM.
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  11. #11
    Banned. DnvrFox's Avatar
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    I find 25's better for that occasional light sand I seem to have to go through every now and then.

  12. #12
    Council of the Elders billydonn's Avatar
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    I don't even consider buying 23s anymore.

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  13. #13
    tsl
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    I've always run 25s on my roadies, with one exception.

    When I put the Crud RoadRacer fenders on the Litespeed for the winter, there isn't adequate clearance on the front for the 25. I put on a 23 of the same make and model, then adjust pressure accordingly. (See: PSI Rx)

    I've found there's a definite difference in both ride and handling between the 23 and the 25. I strongly prefer the 25.
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  14. #14
    Galveston County Texas 10 Wheels's Avatar
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    I got in 101 miles yesterday on 700 X 20 tires.

    Comfort is in the psi.

    Speed comes from your legs.
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  15. #15
    USMC Veteran qcpmsame's Avatar
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    I switched to a 700X25 in the Gatorskins in September because of the road conditions in some stretches I ride being really rough, like riding on cobbles. The 700X23 Schwalbe Lugano that were stock weren't really that tough, the rock aggregate in our roads cut them quickly and I had a blow out on a down hill from this. I cannot tell that there is anymore rolling resistance with the 25's than the 23's, it is only about a millimeter more in contact area between the two, it is the carcass and sidewall toughness I was looking for and the fact I am in at 238 lbs made me want the extra air volume to soften the blows form the aggregate's edges I cause, as others have said. The 25 gives me these factors very well.


    I still have two good 23's handy so I could go back if it seemed necessary. To get any aerodynamic advantage the rim would have to be a few mm wider so the side wall was straighter at the junction instead of having the pinched in profile with a 25, the aerodynamic losses from the 2mm extra width can barely be measured much less felt by a duffer like me.

    If money was no object I would go to tubular tyres, I ran them from the mid 70's to the mid 80's and the ride was exceptional, I had very few flats with them. Maybe I will get a wheelset for tubulars in the future when I need wheels.

    Bill
    Last edited by qcpmsame; 12-02-12 at 07:42 PM.
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  16. #16
    Senior Member GeorgeBMac's Avatar
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    Quote Originally Posted by qcpmsame View Post
    I switched to a 700X25 in the Gatorskins in September because of the road conditions in some stretches I ride being really rough, like riding on cobbles. The 700X23 Schwalbe Lugano that were stock weren't really that tough, the rock aggregate in our roads cut them quickly and I had a blow out on a down hill form this. I cannot that there is anymore rolling resistance with the 25's than the 23's, it is only about a millimeter more in contact area between the two, it is the carcass and sidewall toughness I was looking for and the fact I am in at 238 lbs made me want the extra air volume to soften the blows form the aggregate's edges I cause, as others have said. The 25 gives me these factors very well.


    I still have the 23's handy so I could go back if it seemed necessary. To get any aerodynamic advantage the rim would have to be a few mm wider so the side wall was straighter at the junction instead of having the pinched in profile with a 25, the aerodynamic losses from the 2mm extra width can barely be measured much less felt by a duffer like me.

    If money was no object I would go to tubular tyres, I ran them from the mid 70's to the mid 80's and the ride was exceptional, I had very few flats with them. Maybe I will get a wheelset for tubulars in the future when I need wheels.

    Bill
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  17. #17
    Senior Member kingfishr's Avatar
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    25mm tires contain about 20% more air than 23mm tires, that combined with the slightly lower tire pressure can make a noticable difference on poor roads.
    Last edited by kingfishr; 12-02-12 at 02:04 PM.

  18. #18
    don't try this at home. rm -rf's Avatar
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    I just did my first ride on 25c tires yesterday. Both the old 23c and the new 25c are Continental 4000S.

    I weigh about 170 lbs.

    The 23c tires were at 95 psi front, and 105-110 psi rear. That's my normal inflation.
    The 25c tires were at 90 psi front, and 102 psi rear. That seemed fine. I unscrewed the valve and "burped" maybe 5 psi out of the front during the ride, and it was still good.

    I'll have to experiment some more. Looking down, I saw no sidewall deflection on the front, and the normal amount on the rear. I'll probably try 85 psi front, and 100-105 psi rear--to avoid pinch flats.

    The old 23c GP4000s were very good on rougher roads. The new tires seemed to soak up the rough roads even better, but it's not a blind test, of course. I like them a lot, so far.

    Continental says the weights are: 23c 205 grams, 25c 230 grams.

    You have to look closely to see the tire size difference:


  19. #19
    don't try this at home. rm -rf's Avatar
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    Quote Originally Posted by 10 Wheels View Post
    Put a 25 on the rear wheel for more comfort.
    That's a good idea. There's a lot more weight on the rear wheel. But I move my front to the rear when the rear tire wears out. Otherwise, the front would stay on the bike for years, accumulating cuts and cracks in the rubber. The front barely has the center molding line worn off by the time the back is worn down.

  20. #20
    Senior Member GFish's Avatar
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    The only way to really know is try them. I think you'll be happy with 25's. And make sure you try different psi settings, lower pressure doesn't always make for a better ride.

  21. #21
    Senior Member Timtruro's Avatar
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    I ride 23's on one bike and 28's on two others. I ride 115 psi on the 23's and about 90 to 95 psi on the 28's. The 28's are more forgiving ride and to tell the truth I don't see much difference in performance. Psychologically I thing the 23's are a bit speedier and more nimble but not so much that it is a vast difference.
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  22. #22
    Slogging along rubic's Avatar
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    I really noticed a palpable improvement when I switched to 25's. Smoother ride and less flats.

  23. #23
    USMC Veteran qcpmsame's Avatar
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    Quote Originally Posted by GeorgeBMac View Post
    It's hard to worry about speed or comfort when you're laying wheels up on the side of the road...
    ???, I didn't crash, George, you got one over on me again, sorry.
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  24. #24
    Senior Member GeorgeBMac's Avatar
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    Quote Originally Posted by qcpmsame View Post
    ???, I didn't crash, George, you got one over on me again, sorry.
    Sorry: I meant that I find a blow out on a downhill kind of scary -- and I'm glad you didn't crash. But I'm also glad that you got rid of those tires that couldn't stand up to the conditions -- and that you are safe.

    So, please do all that you can to be careful! We need you around here and would miss you !
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  25. #25
    Elite Rider Hermes's Avatar
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    I tried the Continental GP 4000s 25mm on my Cervelo R5. I put 100 in the rear in 90 in the front. I liked the ride much better on the 25mm versus the GP 4000s 23 mm. I had a discussion with another BF member who uses the 24mm tubeless who likes that ride as well. We came to the conclusion that the performance is dependent on the wind conditions and the rim width. Some wheels have wider rims which result is better aero performance with wider tires. If you put a wider tire on a narrow rim, the aero performance may be reduced at some wind yaw angles. However, the lower rolling resistance of the wider tire may offset the loss in aero performance on some road surfaces. Whatever feels the best and allows one to meet riding goals is the way to go. I like the GP 4000s 23 mm and the GP 4000s 25 appears to have similar performance and a better ride. I weight 173 so rider weight is not a major consideration. YMMV.
    "Insanity: doing the same thing over and over again and expecting different results." Einstein

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