I have an old mountainbike with a 2.1 inch tire fitted on it. My inner tubes are rated for 1.75" to 2.5". I went ahead and purchased a 1.75 inch Schwalbe Cruiser Plus.

What are the respective dangers when fitting a too narrow or a too wide tire on a rim?

  • 1
    Related to bicycles.stackexchange.com/questions/52587/… but this is a subtly-different question.
    – Criggie
    Commented Oct 11, 2023 at 18:30
  • 3
    I understand the question (last paragraph) but the previous information does not relate. Are you using the inner tube size as a guide to pick tire size? That does not make much sense. Tire and rim should fit, then make sure the inner tube is matching the chosen tire size. The inner width of the rim determines what tire width is considered acceptable.
    – WornChain
    Commented Oct 11, 2023 at 19:57

1 Answer 1

  • Too wide tire (relative to the inside rim width): handling will be become "vague", as the tire will move more laterally than it should, especially at low pressure (which is recommended for wider tires). With some rim brakes: impossibility to remove the wheel without deflating the tires.
  • Too narrow tire: impossibility to mount the tire, risk of exposing the rim too much if a "sharp object" is encountered (kerb, stone, root,...).

It should be noted that: what defines "too wide" and "too narrow" is not linked to the tube, but to the inside width of the rim, as explained in this answer.

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