A bike shop (whom I trust) replaced my tires with new 700X25c Pirelli P Zero Zello 4S front and rear, the rear tire did not clear the fork/frame for some reason, they switched the rear 700X25c with 700X23c. Now I have 700X25c on the front and 700X23c on the rear. It seems strange having a larger tire on the front and thinner tire on rear, as I have always and previously run 700X25c Continentals on both front and rear, although from an engineering point of view I have no substance to object, and they advised they do in fact run 700X25c front and 700X23c on new models of some of their Giant bikes. I have not ridden the tires enough yet to determine whether there is an issue, it just seems odd. Can someone who is technically endowed on this matter please advise me on whether this is appropriate.

  • Possible duplicates bicycles.stackexchange.com/questions/4555 and bicycles.stackexchange.com/questions/56429 Check them out and see how they relate to your situation.
    – Criggie
    Jun 6, 2021 at 22:01
  • 2
    2 mm difference is not worth getting your shorts in a twist about. The only odd thing is that the 25mm tires didn't fit, but the 23mm ones do, and (to the shop guys) appear to have enough clearance. Jun 6, 2021 at 22:17
  • Thank you for both responses, my bike is an older Raleigh aluminum w/carbon fiber forks, great for the city/road work, I've kept in perfect condition, been running Continentals for years (w/ Mavic Cosmic elite wheelset), but they didn't have them in stock, it is also odd there was no clearance for Pirelli 25mm as I've been running 25mm (Cont). The bike shop are good guys and made the genuine effort to do the right thing, so I don't want to be a pain.
    – T5P
    Jun 7, 2021 at 0:54
  • 1
    Maybe the 25mm Pirelli are slightly wider/taller than the Contis? Though in my experience Conti is pretty much spot on or even wider than advertised when installed on modern, wide rims. How much clearance do you have left now?
    – Michael
    Jun 7, 2021 at 6:06
  • 1
    @T5P Tyre size isn't always what the box says. Same as with shoes. Quite often it depends on the manufacturer.
    – Carel
    Jun 7, 2021 at 7:36


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