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I went from a 23mm to 25mm tires on my '07 Tarmac Expert. The change was a blessing as I was able to do everything with more confidence. A part of it was for going from Gatorskins to Grand Prix 4000s II. Now that my Grand Prix are about to be worn out, I'm considering to going to 28mm versions. I know that my frame and brake callipers can clear the tire, however I'm not sure if I will gain any major benefits. I do a lot of climbin and try to stay off the flats.

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    Tire width is a trade-off between weight, traction, handling on soft/loose surfaces, shock-absorption, and several other factors. But for the most part tire width is less important than tire pressure, tread characteristics, puncture resistance, etc. – Daniel R Hicks Jan 4 '17 at 3:51
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Here are some benefits:

  • less chance of snakebite flats
  • increased ride comfort on rough terrain
  • less frequent tire inflation to maintain pressure (because of greater volume of air)
  • ability to carry greater weight
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  • Why would you have less chance of snakebite flats? And why would you have to inflate tyre any less? - Tyre pressure is related to the weight of the rider and load. – OraNob Jan 4 '17 at 9:14
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    @OraNob Larger tyres are run at lower pressures. Since pressure drop is related to the fractional loss of air from a tyre, they lose pressure much more slowly than a low-volume tyre. Also, the rate of air loss is lower when the pressure is lower. – Will Vousden Jan 4 '17 at 11:08
  • @Will Vousden - then the correct answer is due to lower pressure and not greater volume? – OraNob Jan 4 '17 at 12:31
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    @OraNob Not quite. If you have a 25 mm tyre and a 28 mm tyre, both at 100 psi (for example), and you let a fixed volume of air out of both tyres, the pressure in the 25 mm tyre will drop more than that in the 28 mm tyre. – Will Vousden Jan 4 '17 at 13:02
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    @OraNob And there's a second consideration, which is that the 25 mm tyre should actually be run at a higher pressure than the 28 mm tyre. In this case, if you press the valve on both tyres (or otherwise allow air to escape through an orifice of a fixed size), the 25 mm tyre will lose a greater volume of air in a given time because the pressure pushing the air out is higher. So there are actually two separate effects at play here, both in favour of a larger tyre. – Will Vousden Jan 4 '17 at 13:06
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If you're climbing a lot than the other consideration is weight of tyre and tube. The 28mm tyres take a larger inner-tube and the tyres are heavier than their 25mm equivalent. Benefit you would gain from 28mm - would be grip and comfort due to a wider contact patch and larger volume.

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    Of course, the additional weight is equivalent to a few gulps of water. – Daniel R Hicks Jan 4 '17 at 13:07
  • @Daniel R Hicks - when you are a honed athlete (like me) where every second counts - a few gulps is the difference between 100th and 101st place at Bognor Regis Sportive. I would also wish to point out the other misnomers of cycling regarding rotational weight vs static weight and Y grammes off my wheels is like Y x 10 grammes off total weight. – OraNob Jan 4 '17 at 15:28
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    Y grams on the wheels is like 2*Y grams on the frame, and only with regard to acceleration. The 10x thing is pure bunk. – Daniel R Hicks Jan 4 '17 at 18:38
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I use 28mm in the winter when the roads around here in New England get bad. The roads are sometimes a combination of wet, sandy, and some patches of ice. The wider tires seem to help. I have more contact with the road I feel. The wider softer tires help with shock absorption with the holes that start to form in the road. I recall hearing during the TdF commentary a few years back that on raining days the riders lessen their tire pressure in order to increase the contact area between the road and tire. I figure that a 28mm does that for me all the time.

A couple of drawbacks of 28mm are the rolling resistance is a little more and I can't get the tire on the frame fully inflated. The 28mm are so wide that they will not fit through my brakes if the tires is fully inflated.

Someone asked above why one would need to inflate 28mm tires any less. I find this is the case for me. I attribute it to the tube containing more air so any air I do loose overnight is less noticeable. Essentially I get away with topping off my tires less often.

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  • Downvoted as it contains inaccurate information. Wider tyres actually give less rolling resistance not more. – Andy P Jan 4 '17 at 11:34
  • @AndyP - This is a long-standing subject of debate, and tests have shown both results. A lot depends on the conditions of use. – Daniel R Hicks Jan 4 '17 at 13:06
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    @DanielRHicks That debate is more or less over. The vast majority of recent test data shows wide tyres are faster, bike and wheel manufacturers are designing around wider tyres, and even pro teams are opting to run wider (not just for the classics) despite the weight and aerodynamic penalty. See: schwalbetires.com/tech_info/rolling_resistance and: bicyclerollingresistance.com/specials/conti-gp4000s-ii-23-25-28 – Andy P Jan 4 '17 at 14:04
  • Is it not the case wider tires are only effective on wider rims? The contact patch remains the same size but the shape of the contact patch changes significant with wider rims which affects rolling resistance - hence the increased popularity of wider rims. – OraNob Jan 4 '17 at 14:31
  • At the same pressure 28mm have lower resistance than 23mm but I don't ride those two tires at the same pressure. I always ride the 28mm about 15psi lower than the 23mm. I guess I do this because that is what the sidewall says. – LDinCT Jan 4 '17 at 21:40

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