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I have a Schwinn Sporterra 2011. It has a 622x20 rim and the default tires are 700x38C. I'm thinking of "upgrading" to thinner tires.

Now, my local cycle shop has Specialized tires that are 32C. They can also get me Schwalbe 28C tires, but in 2-3 weeks time. What I'm trying to understand is, coming from 38C tires, how much of a difference will 28C or 32C make -- Difference to things like speed and handling? Will 28C be much "faster" and worth the long wait time?

(I'm actually thinking of switching to a road bike in 6 months but till the time I save up for that, I want to get thinner tires on the current bike. I was told they'll make quite a difference. Thoughts?)

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Tire pressure and tread pattern are what make the difference, not width. –  Daniel R Hicks Oct 10 '13 at 20:33
    
@DanielRHicks. I have noticed (in changing last two sets of tires on my cycle)that as the tire width reduces the air pressure increases. Is this not generally the case? –  Akshay Oct 10 '13 at 20:50
    
@Akshay - The max "sidewall" pressure, for a given tire design, will generally go down as width increases. But few people run their tires at the max sidewall pressure. There are 38C tires rated at 80-90 pounds, but few people will run them over 50. –  Daniel R Hicks Oct 10 '13 at 23:22
    
I think it makes very little difference. I broke a spoke on my "regular" wheel with 32c tire and swapped it out with a spare front wheel with a 28c tire. I noticed no difference at all in ride quality or rolling resistance and my commute speed stayed exactly the same - I was going to swap the tires to put the 32c on that wheel, but never bothered because it feels the same. The only difference I notice is that the 28c seems to need air more often than the 32c, but I don't know if that has to do with the volume of air in the tires, or if I have a slow leak. –  Johnny Oct 14 '13 at 20:11
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3 Answers

They will make a significant difference, but the size of the tire alone won't make much of a difference to your speed. If your current tires have a substantial amount of tread on them, you may notice a speed difference since smaller tires tend to have less tread on average. It's probably not going to be a substantial difference though, even if you have the knobbiest 38's on the market. Your biggest speed limitation is wind resistance, and while the narrower profile of the tires will knock that down a little, it's a small portion of the overall wind resistance that you experience.

Where you'll notice the biggest difference will be in how much harsher the ride will feel with skinnier tires. They run at higher pressures so you end up feeling every bump in the road more.

You'll also notice that the steering feels more nimble due to the lighter weight of the skinnier tires.

You'll also be more prone to pinch flats with skinnier tires. To what extent will depend on the tire pressure that you've been running and the tire pressure you're going to run.

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Another answer noted that tread pattern and tire pressure make a larger difference than the width. If you have a smooth tread pattern at high pressure, you will roll more easily and the tire won't "squirm" going around corners. Tire compound can also affect handling. The worst tires I ever rode on were a cheap narrow-ish (maybe 28c) set with raised tread made of a harder rubber compound. The traction was terrible: I could lock the rear tire even under fairly light breaking.

There is a connection between width and tire pressure. Generally narrower tires support higher pressures, and also require higher pressures to support the same weight on a smaller volume of air. Up to a point, running higher pressure will reduce rolling resistance. If you run the pressure too high it may actually slow you down as small bumps will jostle you more. You can try running wider tires at their max pressure to reduce rolling resistance and see how they feel, but it will likely give you a rough ride and have fairly poor contact with the road surface, compared with a narrower tire at the same pressure.

The 32C tires will likely give a noticeable difference: the ride may be a little rougher but rolling resistance should be reduced, and you'll probably feel a little more certain on corners. Contrary to the other poster, rolling resistance is less than air resistance, but is a significant factor at moderate speed: if you're riding at 25MPH, air resistance totally dominates, but at 15MPH, rolling resistance is non-negligible.

I would say just get the 32C tires and start riding on them: it's probably not worth the wait. There's also a good chance that 28C might be too much of a good thing.

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I have tested everything from 35 to 32, 28, 24 and finally to 23 from different brands. The overall experience depends on several factors, most notably the kind of riding you do, your weight, frame design and material etc. For the same tire type (ie a decent road tire) a 32 tire will give good comfort for a heavy rider and is excellent for everyday use. I chose 28 (Continental 4 seasons) for my city/commute bike and I am quite happy but the ride is definitely harder, especially with my aluminium frame. Tires below 28 are only for road bike use, ideally with a carbon frame.

In conclusion, if you are heavy or ride bad roads, get the 32. If you are skinny or ride good quality tarmac, you can consider 28. Invest in good quality, things like tpi (threads per inch) are very important. Make sure you use the correct pressure.

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