Old 10-17-17, 06:47 AM
multimodal commuter
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Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...

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Originally Posted by WillBradley1 View Post
Hey there,

I've had a problem with some old straight edge 26" 1 3/8 wheels on a 1960 DBS damecykel... Even riding on super low pressure and carefully centred, the bead of the tyre pops out regularly. It doesnt seem dangerous, I dont notice until I inspect it, but finally it ripped the bead of my rear (very cheap) tyre and its toast.

I know Im stupid riding on these ancient rims for my 25min commute everyday... But its my temporary bike while I restore my main road bike (and ideally until after winter)... Its not meant to be high performance bike... I fancy just keeping the original rims and I cant afford any major changes right now anyway so I was thinking whether just buying 26" 1 1/2 tyres could be a solution?

According to sheldon brown my 26 1 3/8 rims have a 590 mm, 26 1 1/2 tyres are 584 mm. I feel a 6mm tight fit could be perfect to keep them seated?

Anyone have any experience with interchanging tyre sizes? I used to have some road bike tyres that were there right size but near impossible to get on, Im almost feeling 6mm isnt much and I could get away with more? But really I have no idea!

No, you probably cannot get a 650b tire on a 650a rim. That 6 mm is too tight. If you do manage to get the tire on, you will never get it off. This has been tried many times and no, sorry, it is not the solution.

I wonder if you have the right tire now. Schwinn made an EA1 size rim and tire (597 mm) that for unclear reasons they labeled as if it were an EA3 or 650a rim and tire (590 mm). Perhaps you have a Schwinn size tire now? If so, then a proper 650a tire will solve your problem.

Alas it is also possible that the bead of your rim is damaged, in which case you will have no luck mounting tires safely.

Good luck!
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