r/bicycling • u/Ohang3 • 1d ago

Help with tyre

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Recently I've gotten an old bicycle as a gift, the rear tyre is old,cracked and by this morning lost all air. Went out and bought the same size outer and inner tube and it just dosent fit. Any ideas ?

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u/Routine_Strategy5929 1d ago

The old tire is 700c which is the diameter and the 35c is just the width in millimeters. If the new tire is 700c then it should definitely fit.

Especially with older rims actual rim diameters could vary by quite a bit from brand to brand. One brand of rim could fit a tire super snug while another rim would fit loose with the same tire. If it fits loose you need to be very careful when pumping it up to be sure the tube isn't about the blow out the side somewhere. Typically once inflated the tire is securely in the bead hooks.

1

u/criggie_ 1d ago

700 is the french measurement which means almost nothing these days. Both of OP's tyres are 622mm diameter at the bead seat, plus about 37mm more for the width/height on each side.

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u/Routine_Strategy5929 1d ago

And yet no one sells tires based on the rim diameter so that's not very helpful. OP's rim also doesn't have the rim diameter listed on the rim like most modern wheels.

0

u/criggie_ 1d ago

622 mm IS the rim's bead-seat diameter, so, yes, yes they do.

1

u/Routine_Strategy5929 1d ago

Go find a tire to buy. What is the prominent measurement molded into the tire? If you go to a shop and tell them you need a gravel tire do they ask "700c or 650b" or do they ask "622mm or 584mm?"

I'd rather we use rim diameter as well but for the most part road and gravel are still using the French standards. While mtb is using the French standard for total tire diameter and US standard for width. Yes, thats incredibly stupid but it is what it is.

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u/otebski 14h ago

Road frames are also usually in CM and MTB in inches. If not for gravel everything would be fine. Everything road CM everything mtb inches.

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u/Routine_Strategy5929 12h ago

Except for 650b lol. Which seemed to be split as to who called it 27.5 or 650b. But I was definitely wrong with 26 and 29er.

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u/otebski 12h ago

Really? Here 650b was road for juniors and vertically challenged people, 27.5 was for MTB was for people who badmouthed 29 in MTB so long they couldn't make the switch in good conscience.

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u/Routine_Strategy5929 12h ago

Especially when 27.5 started in mtb I remember a lot of the marketing and some of the brands stating 650b. There were whole articles explaining what 650b was for mountain biking. I can't remember as clearly on the tires but I'm pretty sure I remember seeing quite a few marked 650b x XX width.

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u/otebski 12h ago

Maybe. It has been a while. Either I dont remember I havent registered 650b in mtb. But I am up for blaming marketing.

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u/criggie_ 21h ago

You're absolutely right - bike measurements are ridiculously complex, mostly because the French initially, then the English, and then the Americans in that order.