A 400x35A bike tyre is an older-size marking that can appear on junior, folding, utility or vintage bikes. The safe compatibility check is the ETRTO number: for this route, look for 37-340, meaning about 37 mm tyre width on a 340 mm rim.
Why ETRTO 37-340 matters
The words 400x35A are useful for searching, but the rim diameter decides whether the tyre will fit. A 37-340 tyre is not the same as a 355, 349, 451 or 440 tyre. If the old sidewall is worn, check both sides of the tyre, the old tube box, the rim label or the bike manual before ordering.
Tyre and tube route
The Hutchinson 400x35A rigid tyre ETRTO 37-340 is the key product route for this exact size. For tubes, compare printed ranges such as Schwalbe AV4 28/37-340/355 Schrader or Schwalbe SV4 28/37-340/355 Presta, then match the valve to the rim hole.
Common size traps
Small-wheel tyre labels overlap heavily. A 400x35A / 37-340 tyre sits near some 16 and 18 inch tube ranges, but it does not automatically replace another 16 inch tyre. If your sidewall says 18x1.25 / 32-355, use the 18x1.25 ETRTO 32-355 guide. If it says 500x28A / 28-440, use the 500x28A guide.
Before you buy
- Find the full old tyre marking and confirm 37-340.
- Check fork, frame, mudguard and brake clearance for a 35-37 mm tyre.
- Choose a tube range that includes 37-340 and the right valve type.
- Do not use a nearby 340/349/355/440/451 tyre without exact ETRTO confirmation.
Shop from the exact-size path
Start from the 400x35A product page when the sidewall confirms 37-340. If the old marking is incomplete, compare with the kids bike tyre category and the 16/18 inch tube categories, but let the ETRTO number make the final decision.
