One trick to prevent tyres blowing off rims is to use a thicker rim tape or sometimes two rim tapes - this prevents the tyre beads from sliding down into the well at one side and then allowing the tyre beads at the other side of the rim from popping over the top of the rim's side wall. The Weinmann Alesa rims I have for sale are identical to Raoul's and I have regularly used good fitting tyres up to 110 psi without resorting to two rim tapes.
It's important to remember that both both rims and tyres are built to certain tolerances - so it is quite possible to have a slightly undersize rim and a slightly oversize tyre that will blow off at the slightest provocation - that is where the trick of the double rim tapes comes in handy.
Also when mounting the tyre it is very important to make certain that the moulding mark near the tyre's bead is even amount away from the rim - tyres often have to be forced slightly to get them to sit on the rim properly. This applies just as much to modern kevlar beaded tyres with hook edge rims as it does to the older tyres and rims. The older Michelin kevlar beaded tyres and quite a few of the Hutchinsons were often prone to blowing off the rim.
Hilary Stone, Bristol, England
Raoul Delmare wrote:
>
> The rims were ( & still are ) the correct original Weinmanns . Are
> these the same as the "Alesa" model rims that Hilary Stone is selling
> right now ?
>
> These rims are easy to identify at a glance . When looking at them with
> tires mounted & ready to ride , the exterior of the rim , toward the
> spokes ( the inner part of the exterior , if you know what I mean ) , has
> a bump at each spoke nipple , and what I'll call very small shoulders where
> the sidewalls of the rim begin . Some people would say that these rims have
> dimples & shoulders . Actually I think that they are quite elegant looking
> , once you get used to them .
>
> The point - These rims are NOT "hook bead" rims . These rims are
> NOT "straight side" rims . These rims actually flair-out just a little
> bit ! They allow the tire to slip off rather easily .
>
> I played with my new bicycle all evening , and well into the night . By
> the time I got around to putting air into the tires , I'd forgotten what I
> knew about those rims . The cheap tires had something surprisingly large
> written on their sidewalls , like maybe 105 p.s.i . I can't remember
> what I put in them , but I had sense enough to check that the beads were
> evenly seated , before I put 5 more p.s.i. into the rear than into the
> front . I hopped on , to ride around in the basement . I was just
> checking saddle height . There was the strangest creaking noise , like the
> tightening of old ropes on an old sailing vessel . Hmmmmm . . . What
> was that interesting sound ? BOOM!!!!
>
> I knew better , and yet I still did it .
>
> Some while later , I fitted that bicycle with wonderful new Panaracer
> Pasela 27-inch x 32mm tires , & new top-quality rim strips , and new
> inner tubes ( o.k. , so the new tubes were still cheap ones ) . I took it
> along on a long automobile trip , which included a lovely group bicycle
> ride , in the hills East of Dallas , Texas . Everything was great ,
> until I arrived home again , days later . I arrived late at night , and
> only pulled a few essentials out of the car . The next day the bicycle sat
> in the parked car , on a mild and comfortable Summer day , with the
> windows closed , in the sun . That evening , I unpacked everything
> including the bicycle .
>
> I had put something like 85 p.s.i. into the front , and 90 p.s.i.
> into the rear . In the oven-heat from the sunshine , the rear had blown
> off .
>
> I always knew that you were not supposed to put more than about 85 p.s.i.
> into anything mounted on those rims .
>
> They are wide rims , with slightly flared sidewalls , that don't hold
> all that much pressure . So , buy wide tires . My 32mm Paselas are
> top-quality , with Kevlar beads , and no belts . So , these tires are
> wide , light-weight , and flexible . And yes , as I've mentioned before
> , in a group of well equipped tourists , I was out-coasting everybody
> else - very much ! ( Love those 1973 Campy Record hubs too ! )
>
> Those rims are just like those wonderful & inexpensive ( "cheap &
> cheerful" ) 1977 Hutchinson SuperSprint sew-up tires that I loved .
>
> They work perfectly at 80 to 85 p.s.i .
>
Steve Maas wrote:
>
>
>> Yes, I confess, it was my Carlton that blew a tire right outside the
>> parking lot at the beginning of the ride.
.........
>>
>> On the way out with my "new" Olmo, I noticed that Chuck had quite a nice
>> selection of 27" tires, so I bought a new pair of Continentals to
>> replace the cheapo tires on the Carlton. The old rims on the Carlton do
>> not hook the bead, like modern ones, so the tire can slip off the rim,
>> causing a blowout. Perhaps the better tires, with stronger bead wires,
>> will help. (Anyone have another suggestion?)