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  1. #1
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    Any reason not to go with 28mm tires over 25mm?

    So I picked up a 2016 Evo Hi-MOD (Ksyrium Elite wheelset) this winter and I'm looking to get a pair of Vittoria Corsa G+ tires to replace my aging 25mm GP4000S II.

    There seems to be plenty of clearance with my 25mm Conti's (which measure ~27.5mm on the Ksyriums) at the fork/seatstays/chainstays/brakes and Cannondale says the frame fits 28mm tires.

    Would there be any reason (besides a small weight penalty) to get the 25mm tires vs 28mm? Seems like 28s would be faster at the same pressure I run now, or just as fast and more comfortable if I run them at a slightly lower pressure.

    Thanks!

  2. #2
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    If they fit, no reason at all IMO. I'm not sure what the Vittorias actually measure compared to stated dimensions. Most of the 28's I've run stretch out to between 29-30 eventually, gaining a mm or two from where they were when new, so if you have the clearance, go for it. The only 28's I've run that were undersized were conti 4seasons, and just barely.

  3. #3
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    i guess its all personal preference. i have bikes with 25s, 28s, and 32s. i dont feel a massive difference in comfort but i do like the feel of a high psi 25c best. it feels fast and agile to me.
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  4. #4
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    Bike handling will be a little slower. Whether you call that 'less twitchy' and like it or 'sluggish' and don't I can't say.

  5. #5
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    THe 28 Vittoria Corsa G is a bit smaller than the Conti 4000s 28. THey are nice tires. I'm guessing they will be around 30ish on your rims

  6. #6
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    Quote Originally Posted by Jay Strongbow View Post
    Bike handling will be a little slower. Whether you call that 'less twitchy' and like it or 'sluggish' and don't I can't say.
    Have you compared the different tires on the same bike and wheels? And is it something that you could feel, or were you able to measure the differences with a power meter, clock and multiple runs?
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  7. #7
    Matnlely Dregaend
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    Quote Originally Posted by velodog View Post
    Have you compared the different tires on the same bike and wheels? And is it something that you could feel, or were you able to measure the differences with a power meter, clock and multiple runs?
    Not commenting on the premise, but having run 23, 25, and 28mm Rubino Pros on the same bike and wheels, I settled on 25s. It feels more like a race tire and it's comfortable. In full disclosure it is on a single speed road bike that I ride during shoulder season (ie gravel, sand, dirt, and garbage on the roads).
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  8. #8
    'brifter' is a lame word.
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    I'm all about wider tires but those Mavic rims are pretty narrow so you really won't be able to take full advantage of the wider tires. Get some nice wide rim wheels while you're at it.
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  9. #9
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    A little slower and heavier
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  10. #10
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    Quote Originally Posted by Srode View Post
    A little slower and heavier
    How much slower?
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  11. #11
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    I went from 25s to 28s and I'll never go back. Much nicer ride since you can run lower pressure and no noticeable difference in speed - they did not feel slower or heavier to me. IMO, as long as they will fit in your frame, it's a no-brainer.
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  12. #12
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    Quote Originally Posted by velodog View Post
    How much slower?
    Depends.....

    Check out some the rolling resistance tests to see the watt difference
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  13. #13
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    Quote Originally Posted by Srode View Post
    Depends.....

    Check out some the rolling resistance tests to see the watt difference
    This test sez the bigger the tire the lower the rolling resistance, so how does that make you slower?

    Continental Grand Prix 4000S II 23 25 28 mm Comparison
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  14. #14
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    Oh Gawd, not another narrow/wide tire debate.

    Sure, look at the difference in watts. Can anybody tell me with a straight face that they can feel the difference of 5 watts?
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  15. #15
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    Quote Originally Posted by Lombard View Post
    Oh Gawd, not another narrow/wide tire debate.

    Sure, look at the difference in watts. Can anybody tell me with a straight face that they can feel the difference of 5 watts?
    I can positively say that I can not feel it.

    On another note, someone in one of these replies said that the handling will change, said the larger tires will be less twitchy or sluggish, whatever you'd want to call it. Now I can't compare apples to apples because they are 2 different bikes with different wheel sizes, but I can say that there is nothing sluggish about the handling of the bike with the 650b\42mm wheel tire combo.

    And on the 700c bike, when I went from 23mm to 25mm, same tire, the handling didn't get sluggish. If anything a larger tire having a larger foot print should have the handling improve, allowing faster cornering and more lean angle before losing traction.
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  16. #16
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    Quote Originally Posted by cxwrench View Post
    I'm all about wider tires
    There's got to be a point where it's no longer a benefit beyond...

  17. #17
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    Quote Originally Posted by bvber View Post
    There's got to be a point where it's no longer a benefit beyond...
    I'd say it's no longer a benefit here.....in rolling resistance that is.
    Attached Thumbnails Attached Thumbnails Any reason not to go with 28mm tires over 25mm?-fat-tire.jpg  
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  18. #18
    'brifter' is a lame word.
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    Quote Originally Posted by Jay Strongbow View Post
    Bike handling will be a little slower. Whether you call that 'less twitchy' and like it or 'sluggish' and don't I can't say.
    The way the bike handles can't change. That's all based on the geometry of the bike, which won't change if you change both tires. The weight of the wider tire is slightly higher, which will very very very very very slightly increase the amount of weight you're actually 'steering'. I don't think most people would be able to feel it. Some might, and that might lead to a feeling of slightly more stability w/ a heavier tire(greater moment of inertia), but it won't change the way the bike actually steers. Not possible.
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  19. #19
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    Quote Originally Posted by cxwrench View Post
    The way the bike handles can't change. That's all based on the geometry of the bike, which won't change if you change both tires. The weight of the wider tire is slightly higher, which will very very very very very slightly increase the amount of weight you're actually 'steering'. I don't think most people would be able to feel it. Some might, and that might lead to a feeling of slightly more stability w/ a heavier tire(greater moment of inertia), but it won't change the way the bike actually steers. Not possible.
    Actually, trail does change when you change tire sizes/overall wheel diameter which affects handling, although the difference between a 25mm and a 28 is negligible, so I'd say it's a wash. I never noticed a difference between 25/28. I did convert a 26" mtb to 700c x 42mm tires and that was beyond negligible. It took a while to get it dialed.

    You can test it here: Bicycle Trail Calculator | yojimg.net

  20. #20
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    Quote Originally Posted by cxwrench View Post
    The way the bike handles can't change. That's all based on the geometry of the bike, which won't change if you change both tires. The weight of the wider tire is slightly higher, which will very very very very very slightly increase the amount of weight you're actually 'steering'. I don't think most people would be able to feel it. Some might, and that might lead to a feeling of slightly more stability w/ a heavier tire(greater moment of inertia), but it won't change the way the bike actually steers. Not possible.
    Interesting. So the feeling of better stability when I went to wider tires was due to more front weight and not because of a greater contact patch?

    I could have sworn my bike felt more stable and better going around corners when I went from 15mm rims to 17mm rims - effectively widening my tires with no added weight. Placebo effect?
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  21. #21
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    Tire size will also affect bottom bracket height which will change handling. But as harryman said the difference between 25 and 28 mm is very small as far as those changes go.

  22. #22
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    Quote Originally Posted by Lombard View Post
    Interesting. So the feeling of better stability when I went to wider tires was due to more front weight and not because of a greater contact patch?

    I could have sworn my bike felt more stable and better going around corners when I went from 15mm rims to 17mm rims - effectively widening my tires with no added weight. Placebo effect?
    No, that may make a change that is noticeable...changing the shape of the contact patch might make it feel a bit different.
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  23. #23
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    Quote Originally Posted by cxwrench View Post
    No, that may make a change that is noticeable...changing the shape of the contact patch might make it feel a bit different.
    Ahh, OK, thanks CX. Interestingly, when I went from a 14mm to a 15mm rim, I could feel it. When I went from a 15mm to 17mm rim, I could feel it.

    But.....when I went from 17mm to 18mm, no difference in feel.

    I'm guessing the law of diminishing returns applies here.
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  24. #24
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    Quote Originally Posted by cxwrench View Post
    The way the bike handles can't change. That's all based on the geometry of the bike, which won't change if you change both tires. The weight of the wider tire is slightly higher, which will very very very very very slightly increase the amount of weight you're actually 'steering'. I don't think most people would be able to feel it. Some might, and that might lead to a feeling of slightly more stability w/ a heavier tire(greater moment of inertia), but it won't change the way the bike actually steers. Not possible.
    There is this thing called pneumatic trail. Jan Heine of Bicycle Quarterly has discussed it at length. Changing tire sizes changes pneumatic trail.

  25. #25
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    Quote Originally Posted by velodog View Post
    Have you compared the different tires on the same bike and wheels? And is it something that you could feel, or were you able to measure the differences with a power meter, clock and multiple runs?
    Yes
    Yes
    No

    How to heck do you figure someone could measure handling with a powermeter or clock?

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