KCnoobie

I have a Trek 7.3fx that currently has 32c tires. I am wondering what size tires will fit on those rims. I am wanting to know if I can mount smaller width road tires (slicks) on these rims for less rolling resistance such as a 25c or a 23c tire? If so any suggestions on which tires would be the best? Also what are the advantages and disadvantages to running smaller width tires?

jsdavis

If anything, narrower tires have more rolling resistance.

To answer your question though, according to Sheldon Brown's site, your 15mm rims can handle 23-32mm tires.
https://sheldonbrown.com/tire-sizing.html#width

KCnoobie

Narrower tires will have more rolling resistance? That puzzles me. My thinking is the less tire surface touching the pavement the less resistance. Am I thinking incorrectly?

Scooby214

Does your bike have the Bontrager Race All Weather Hardcase tires? There are other tires that may roll better for you in a 700x32 or 700x28 size. The Bontragers have 60tpi casings. Many tires with higher threads per inch, such as 120 or 150tpi, will have lower rolling resistance than tires with lower thread count casings. I haven't used the bontragers mentioned above, so I can't tell you if putting narrower tires on your bike will give you less rolling resistance than your current tires.

Narrower tires can have more rolling resistance at the same pressure as wider tires, but narrower tires can be inflated higher to offset this. The tradeoff is that the narrow tire may have a harsher ride at the high pressure and won't conform to rough riding surfaces as well as a wider tire at a lower pressure. A good quality 700x32 tire can have very low rolling resistance without having the harsh riding characteristics of a narrow tire, like a 700x23. Be sure to read the Sheldon Brown link above, as it can better explain things than I can.

My road bike has 700x23 Vittoria Rubino Pro III tires. My hybrid has 26x1.5" (38mm) Vittoria Randonneur Pro tires. My 3 speed commuter has 700x32 Vittoria Randonneur Pro tires. Of the three bikes, I find the 700x32 tires are the best compromise for me. They roll very well, are light enough to accelerate quickly, and are big enough to smooth out the rough roads found on my commute.

Bill Kapaun

That's why they use those "fatties" on the Tour d' France etc.

To the OP-
You can pretty much use as skinny as you want. (20c)
I use 26C's on a 20mm rim with absolutely no problem.

prathmann

It's clear that wider tires have more air resistance and, if the construction is at all similar, they also weigh more. Both would dictate against their use for racing. Rolling resistance is less clear and will depend partly on the quality of the road surface and details of the tire construction.

Bike tire widths are measured in mm - what's the purpose of the 'c' you keep appending to the size?

Bill Kapaun

Well, IF you read the original post, you'd see the OP refers to tires by the "c" designation, so they know what I mean!
I guess you need to study Sheldon or somebody??
https://sheldonbrown.com/harris/tires/622.html

You pick & choose your tire constraints that support your arguments and dismiss the ones that don't support them, even if they are more meaningful.
A "skinnier" tire might have more rolling resistance if you operate it at "fat" tire pressures, but only an idiot would do that.
Enough feeding the troll!

KCnoobie

Ok as everyone can see my screen name includes the word noobie. So obviously I'm pretty much very new to the whole cycling thing. Prathmann the "c" I keep referring to is on my tire and on all the web sites I've been looking at. I really have no idea what it really means. I have read Sheldon's link and will reread it several more times until it all sinks in my head. If I were to change to a narrower tire I would run it at very close to the max psi stated on the sidewall. I see no reason to run tires at a lower pressure simply for a smoother ride. After all it's a bicycle not a luxury sedan. I very well may just leave the existing tires on the bike for now and just work on loosing some of my gut. I just have an addictive personality and like to tinker with things sometimes more than I should...lol... So far I enjoy riding very much and hope the enjoyment continues.

Bill Kapaun

One advantage not really touched on was weight-
I went from 35's to 26's on my hybrid and the difference in acceleration was remarkable due to the lighter tires.
This isn't as important if your riding tends to be "cruising" long distances, but if you are riding around town where you constantly have to slow down/speed up because of traffic lights/busy intersections etc., light is GOOD. Ditto for hills.

prathmann

I think I touched on it just above in post #6 where I already mentioned that both lighter weight and less air resistance are clear advantages of narrower tires.

As to the 'c' I note that Sheldon always correctly used mm when referring specifically to the width of a tire - i.e. on the page to which you referred he listed various tire widths and has 'mm' after each of them. The 'c' is only used when the wheel size is included, such as a 700c size wheel. So it's ok to say the tire is a 700x32c size, but not correct to say you have a 32c width tire.

The 'c' in the wheel size is for historical reasons - at one time there were various different wheel sizes all with an overall outer tire diameter of about 700mm but intended for tires of different widths - A, B, C, etc. So they had 700a, 700b, 700c rims, and only the 700c size is around anymore. And now that 700c rim diameter wheel is used for a great variety of tire widths - most of which aren't anywhere close to what a 'c' width tire was originally.

Sounds like a good plan. The bike I rode on today's club ride has 38 mm tires while the one I rode on yesterday's ride with the same club has 23 mm tires. The one with the narrower (and lighter) tires does feel a little more responsive when starting from a stop, but my overall speed is not very different on the two bikes.
Unless you're racing where a difference of a few seconds might be critical, you may as well wear out your current tires first and then decide what size you'd like to use when getting replacements.

Bill Kapaun

On a whim today, I mounted a 23c tire on a 20MM wide rim. (19.5MM inside the flanges with a caliper, measuring "bump" to "bump")
I'd have absolutely no fear about the tire coming off the rim, even though the braking surfaces of the rim are about .5MM wider than the max width of the tire.