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  1. #1
    Senior Member MinnMan's Avatar
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    Minutia: 25 vs. 23 mm tires

    Like most folks riding performance road bikes, I ride with 23 mm tires. A friend swears that I'll be more comfortable and perhaps faster with a 25 mm tire in the back. Surely the difference would be small. But I'm wondering if any of you ride with 25 in the back and 23 in the front and if you think there's a noticeable improvement over two 23s?

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    Senior Member BikeArkansas's Avatar
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    I ride a 25 on the back with a 23 on the front. Have for a few years. Yes, it does ride easier. Sometimes I use a 25 on the front, but not often.
    I started riding my bike to get healthy. Now I try to stay healthy so I can ride my bike.

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    Squeaky Wheel woodway's Avatar
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    I've ridden both and the only difference I have noticed is I get fewer flats with the 25's (same brand of tire). I am sure racer types could tell the difference, but I am just a commuter hack and they feel the same to me.

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    I often ride with a 25 rear and a 23 front. I find a larger difference between different makes of tire than between different sizes. However, if I still lived where the roads are maintained I would likely go with 23 front and rear.

  5. #5
    Have bike, will travel Barrettscv's Avatar
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    I also ride 23s in the front & a 25 in the rear. I'm 210 lbs and rear wheel carries far more weight than the front. Also, the rear triangle cannot absorb much in the way of impact, while the fork is better able to flex. I can reduce my air pressure by 10 psi with a 25 sized tire without concern of pinch flatting. I prefer that the air in the tube absorb small impacts, rather than the wheel or rider.

  6. #6
    Council of the Elders billydonn's Avatar
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    Quote Originally Posted by Barrettscv View Post
    I also ride 23s in the front & a 25 in the rear. I'm 210 lbs and rear wheel carries far more weight than the front. Also, the rear triangle cannot absorb much in the way of impact, while the fork is better able to flex. I can reduce my air pressure by 10 psi with a 25 sized tire without concern of pinch flatting. I prefer that the air in the tube absorb small impacts, rather than the wheel or rider.
    Pretty much the same story here. Have taken to using 25s on both wheels lately and like it quite a lot.

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    Senior Member NOS88's Avatar
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    I typically ask for tires as birthday and other holiday gifts. My family knows the brand and model I like. Yet, they often get either 23s or 25s. When the rear tire wears enough, I replace it with the front one and put a new one on the front. I'm describing all of this because I often have a 23 - 25 mix on the bike. Frankly, I can't really discern the difference in ride. Too many other factors seem to be more relevant (e.g., wind, temp., my energy level on that day, etc.).
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  8. #8
    Senior Member Paul01's Avatar
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    I find 25s fore and aft more comfortable and no difference in speed.

  9. #9
    tsl
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    I started out with 25s at both ends, and run 25s on three of my bikes. The Portland gets 28s in the three-seasons.

    This past winter I outfitted the Litespeed with Crud Roadracer MkII fenders. The front tire rubbed. Reluctantly, I bought a 23mm tire, same make and model as my preferred tires--Conti 4-Season. All the bikes wear them. This fit with no rubbing. No matter what I did futzing with tire pressure, the bike rode harder. Handling seemed unaffected.

    In spring, as soon as the fenders came off, the 25 went back on the front. Ahhh.

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  10. #10
    Dan J chinarider's Avatar
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    I don't pretend to understand the physics, but from what I've been reading lately, 25s should be faster than 23s in addition to being more comfortable. The reasons people continue to use 23s and even 20s are tradition, snobbery and misconception. I'm not sure where the optimum for speed is. Assuming 25s are in fact faster than 23s, does that mean 28s should be even faster?

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  11. #11
    I need speed AzTallRider's Avatar
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    Quote Originally Posted by chinarider View Post
    I don't pretend to understand the physics, but from what I've been reading lately, 25s should be faster than 23s in addition to being more comfortable. The reasons people continue to use 23s and even 20s are tradition, snobbery and misconception. I'm not sure where the optimum for speed is. Assuming 25s are in fact faster than 23s, does that mean 28s should be even faster?

    Dan
    Do a bit more research, and look more closely at test results, and you will see that this is true only at relatively low inflation pressures, and only if you discount the affect of aerodynamics, which is generally greater than mechanical rolling resistance. I was using 25's for quite awhile, when I started riding at a weight of ~225, including in criteriums. There was noticeable improvement in speed and handling when I switched to 23's. When I have to change tires on my tubulars, I'll be going from 23 to 21. I inflate my clinchers to 120r/110f. That limits the sidewall flex that is the basis for a wider tire having less rolling resistance than a narrower tire. Every test I've read that claims wider tires are faster used sub 100psi pressures, and that is just not real world.

    Cycling is a sport where many decisions appear to be based on tradition, or to not have a scientific basis. But there are solid reasons behind most of those decisions, and ignoring them is usually a good way to find yourself off the back.

    Bottom line: 25's are more comfortable, but 23's are faster. Choose whichever you prefer.
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    I replaced my high mileage, cheap, original equipment 23’s with better quality 25’s about a month ago. I’m inflating them about 10 psi lower than the 23’s.
    I haven’t noticed any difference in either ride quality or speed.

  13. #13
    Time for a change. stapfam's Avatar
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    May depend on weight of the rider. A 200lbs rider may not have a comfortable ride on 23s inflated to 120psi.

    I am a lighweight and ride 23s and if pressure drops below 90psi I can feel the drag. When I was on 25s on my first bike- I could feel drag at any pressure below 100.
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  14. #14
    Senior Member ItsJustAHill's Avatar
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    I've switched to 25s on my bikes and find a noticeable difference in ride comfort. They may be slower, but the limiting factor's going to be the motor anyway.

  15. #15
    Have bike, will travel Barrettscv's Avatar
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    I think the user has to ask themselves what kind of riding they plan to enjoy.

    I've used 23s & 25 for faster group rides with 115 psi in the back & 100 psi in the front. I'm giving up a little ride quality for speed, but on a three hour, 20 to 22 mph ride, that's a good trade-off.

    For century rides, I like 25s & have used 28s with 105 psi in the back & 90 psi in the front. The ride comfort is better. I don't feel any loss in speed and may be faster if the improved ride helps me feel fresh after four hours. I'm not pushing as hard, with a speed between 16 and 19mph on these rides. Comfort can be king.

    I've also used 28s & 32s for riding on gravel and bad pavement with 95 psi in the back & 85 psi in the front. These tires do feel bulky on smooth pavement. However, these would clearly be faster than a narrow tire for a bigger rider like me once the surface goes to hell.

    Most performance road bikes with short reach brakes can only take a 25 or smaller tire. Many Randonneuring riders use bikes with long-reach brakes or Cantilever brakes so they can use larger sizes.
    Last edited by Barrettscv; 07-08-11 at 11:16 AM.

  16. #16
    Dan J chinarider's Avatar
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    Quote Originally Posted by AzTallRider View Post
    Every test I've read that claims wider tires are faster used sub 100psi pressures, and that is just not real world.
    don't know about that. I'm using 25s @ ~85f/95r (145 lbs). And even that is higher than what the deflection charts say.
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