I had a flat tire in my rear wheel, so I took my road bike to the repair shop. They had to replace both the inner tube and the tire. After using it for 2-3 times. (mostly just going in to the gym or running errands) It became flat again and I can't inflate it, also the valve cap is not closing just going around.

I checked my front wheel and it is a 700-25, so I am not sure if the problem is that they put a 700-20 on my rear wheel or it got damaged again.

Should I just replace it myself from now on, or go back to the shop?

  • I do not really understand what exact types of wheels and tyres you are referring to. With wheels you usually write about the inner rim width. With tyres you write about the nominal diameter. Putting a 20 mm tyre (or oven 25) on a 25 mm rim should not be possible at all. It just wouldn't stay well. Can you tell us what exactly is written on those rims and tyres or can you measure for us? Commented Apr 22 at 8:41
  • 1
    I have checked the side, and it says 28-622 700x28C which makes me wander why it doesn’t fit? ( also measured it and it’s 20 mm, but it’s flat so maybe that’s why it’s smaller?)
    – hboogie
    Commented Apr 22 at 9:43
  • 3
    @hboogie the new tyre is 28 mm wide based on the ETRTO number you gave. Not sure where you're getting the number "20" from ?
    – Criggie
    Commented Apr 22 at 10:07
  • @ Criggie measured with tape the width of the tire first, as it seemed to be fitting funny on the rim. Also the wheel is totally flat, so that could be something why I only got that number. (sorry I don't know how to add pictures yet)
    – hboogie
    Commented Apr 22 at 11:29

1 Answer 1


Road bikes often have Presta valves. These have an "acorn nut" on top which needs to be loosened to allow the stem in the middle to push into the valve under finger or air pressure from the pump.

The plastic/metal cap that comes off completely is a valve cap but its only job is to keep grit and water out of the valve. It does not need to seal, and many riders choose to discard them and ride without.

The valve and valve type will have no bearing at all on the width of your tyre.

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