I have trek 3700 with 26X2 knobbytires on them. I do not intend to ever go off road again. What is the thinnest size tire I can put on. I don't know what size my rims are but everything is standard on the bike.

Thank you, Chris

  • 3
    As always, refer to Sheldon Brown. Measure you rim internal width, and use his chart for a guide. If anything, go up a size from the minimum, as (despite much misinformation) width and rolling resistance are not significantly related (unless you are a tour rider where seconds/hour are important).
    – mattnz
    Commented Jul 4, 2015 at 6:20
  • 2
    Bigger tires are nicer in that they are often more comfortable. I'd go for a 26x1.75 probably.
    – Batman
    Commented Jul 4, 2015 at 11:14
  • Of course, you can get relatively smooth tires in pretty much any width (except perhaps the 4-inch size). But without knowing your rim width, 1.75 is probably a safe width, as Batman suggests. (But note that if you want to reduce rolling resistance you should run a relatively high pressure -- probably 50-75psi on a 1.75, and proportionally higher as you go narrower.) Commented Jul 4, 2015 at 12:28

1 Answer 1


Am assuming you have the Bontrager AT-650? That is the current wheel set from what I can see. You should theoretically be able to go down all the way to 23mm on those, as from what I've been able to see the rim width should be ~19mm.

If you would want to is a different matter. Super skinny tires on a hybrid/mountain bike just seems off to me. When I converted my MTB to a more roadworthy bike I put 28mm slicks on and these were a good mix of comfort and speed IMO.

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