25 versus 23

I have decided to take a leap into the Great Unknown.  Well, unknown for me at least.  I recently ordered new tires and eschewed the 700×23 tires I have used for well over a decade for the wider 700×25.

Exciting, isn’t it?  Let me tell you all about it.

For decades, conventional wisdom held that the narrower the tire, the faster the ride.  Professionals rode on ridiculously thin tires, some as narrow as 19mm.  And folks won races with those tires, so there was plenty of evidence suggesting people had things figured out.  Of course, if almost all the pros are using 19mm tires then almost all the professional races will be won with those tires.  It became a self-fulfilling prophecy.

Nevertheless, the notion that thinner tires were faster became conventional wisdom.  This wisdom was handed down to the more casual riders.  Despite being less comfortable, amateurs (including Your Humble Author) were more than willing to endure increased vibrations of narrower tires if it meant shaving a few seconds per mile.

This is how the world worked for many years until scientists got involved.  Using fancy graphs and important-sounding words like “rolling resistance,” the scientists proved that wider tires were actually a little bit faster than the narrow ones.  It certainly was counter-intuitive.  Not only were the tires wider, but that extra rubber adds weight and is slightly less aerodynamic.  Still, there was no refuting the test data and the professional ranks slowly changed their ways.  By 2015, 700×25 tires were making inroads into the casual riding class.  Everything was better – the bikes were faster and the rides were more comfortable with the wider tires.

That it took me five more years to make the switch myself should surprise no one.


My 700×23 tires were getting threadbare so I decided to make the leap to 700×25.  I stuck with the same tire – Continental Four Seasons – for the sake of the experiment and because I’ve grown to like these tires a lot.  When they came in the mail, I hit my first snag.  I couldn’t put the stupid things on my wheel!  This was more than a little embarrassing, but I simply couldn’t force the tire onto the rim.  It’s not like I hadn’t changed my tires 5,000 times before (or so it feels like).

I swallowed my pride and sheepishly handed my bike over to my local bicycle shop.  Imagine how happy I was when they had a hard time with it as well!  It took two mechanics and a special tool to get the first tire on the rim.  My self-confidence restored, I waited with interest to see how the second tire went on.  Incredibly, the second tire went on with very little effort.

“Now explain that!” I said to the head mechanic. “Either the people at Continental or the people at Bontrager (my wheel company) aren’t very exacting in their standards.  Which is it?”

“Hard to say,” said the mechanic.  I didn’t find that answer very helpful, so I pressed further.  It turns out the industry doesn’t have precise standards so this sort of thing happens from time to time.  The mechanic said he’s seen certain tire companies that simply won’t fit on certain wheel sets, although they should.  His advice when this happens?  “Buy a tire from a different company.”

I suppose some things are best left at that level of detail.

2020 a
Bike Repair During A Pandemic:  The mechanic is wearing a mask, as is Your Humble Author (on the opposite side of the camera lens).  I was also one of two customers allowed in the shop at the same time.


2020 d
I’ve learned that taking interesting pictures of tires isn’t easy.  Hopefully this demonstrates how little difference in appearance the two sizes are.



So after all this fuss and bother, I’ve gone a few rides with my new tires.  Here’s what I think:

  • Visibly, it’s hard to tell the difference between the two sizes.  If someone snuck into my house and swapped out my tires, I probably wouldn’t have noticed  based on a visual inspection.  Upon close scrutiny, the 25s are clearly larger.  It’s just not obvious to the casual observer is what I’m trying to say.


  • The ride is definitely more comfortable.  I noticed the difference in the first 100 yards when I crossed over a gutter in the road.  Compared to my old 23s, the new tires were definitely “cushy.”  I can see how this would be a big advantage on a long ride – far less vibration would make for a more comfortable ride.


  • As for the speed, it’s hard to say.  If there is an improvement, it would be measured in a few seconds/mile.  I’d need to take my bike onto a course I have done several times to see what results I get.  I certainly doesn’t feel faster (or slower for that matter) but I wouldn’t have expected it to.


So there you have it.  As expected, the wider tires are more comfortable and not noticeably slower/faster.  They also look very similar to my old 23mm tires.  I now have the perplexing issue of tires not fitting on wheels when they should.  There’s definitely more research necessary in this field.  I’ll let you know when I have figured it out.








12 thoughts on “25 versus 23

  1. After reading this, I was confused so I went out and looked at the tires on my bike. They are 700 x 38 c (so they are wider than either of yours), which is logical since I have a city bike which I in fact use mainly within the city of Frankfurt, plus an occasional excursion to Bad Vilbel or Bad Homburg. I never measure any times in seconds, but I have noticed that with each passing year it takes me about one minute longer to get from home to the opera house. (Probably two minutes longer on the way back, which is slightly uphill.)

    1. I, too, have noticed that my times to various destinations increase slightly with each passing year. I suspect this has very little to do with my bicycle, however!

  2. Good read. You definitely don’t lose speed with 25’s, but you will if you jump up to 28’s. On the fit issue, rubber is not an exacting material. Same thing happens with car tires, but they have machines to get the tire on the rim.
    Keep it up, I love your articles.

    1. The mechanic and I looked at the thin amount of space between my 25s and the front fork and concluded that I’d reached my limit on this bike. My hybrid has 35s, but that is a completely different machine. Thanks for your kind words!

  3. The increase in comfort transfers to your ability to push harder on your pedals. It’s the same principle that’ll make you 2 to 3-mph slower on crappy roads vs. baby bottom smooth asphalt. The constant jarring wears you down. I ride Specialized Turbo Pro 26’s and they’re fantastic. I also agree with ridingmilford… 28’s are a bit too much.

    1. I wonder if I could squeeze another mm in my fork and go to 26? The Contis work very well for me. I haven’t used anything else in 8 years, but I’m willing to take a look in a few thousand miles when I need a new tire.

      1. I still have to give the 26’s a look-see on my Trek. That bike is notoriously unforgiving in room. With a 23-mm rim I can fit a 25, but with a standard 19.5-mm allow rim, I can’t (the light bulb effect). I’ll check that this weekend – if I can fit my 50’s with 26-mm tires on that bike, it’ll be a safe bet you’ll be okay. I’ve been meaning to check that for a while now.

  4. I might have missed this, but did you decrease tire pressure when you ‘moved up’? I’m not sure what those scientists say, but I do around 10 psi less on the 25s than on my 23s (I have both) to increase the cushy factor by a tad.

    1. Initially, I kept the pressure the same (one less variable) but lately I’ve been taking 5-10 PSI out of them like you do. The scientists say this defeats the small improvement in speed afforded by the wider tires. Speed is less important to me as time goes by, so I’m okay with that!

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