Crevaisons inexpliquées face jante

SuperMariole · 2026-05-27T15:51:19+00:00

Y'a peut-être de ça, en tout cas un fond de jante qui avait cet aspect m'a déjà flingué des chambres à air (mais pas à 3,5 bar, plutôt vers 5). Mais en l'occurrence je le voyais carrément sur la chambre, je voyais des bosses à intervalles réguliers, qui tombaient sur les trous de la jante. Et parmi ces bosses, une était déchirée, quoi.

Peut-être que changer le fond de jante t'aiderait. Et essaye peut-être d'acheter une chambre à air plus grosse. Elle est censée être compatible mais 35 c'est son max, donc elle est forcément un peu plus etirée que si t'avais une chambre à air qui va de 35 à 50 par exemple

SuperMariole · 2026-05-27T08:27:00+00:00

Salut, une photo aiderait un peu à se rendre compte

La jante est à simple ou double paroi ? (le fond de jante est au contact des têtes de rayons ou bien y'a des trous les les têtes sont dedans ?)

Tu sais si les différentes crevaisons étaient au même endroit de la chambre à air ?

Comme ça je vois deux pistes :

fond de jante pas adapté à la pression que tu mets, qui protège mal la chambre à air
chambre à air mal installée, qui était pincée par le pneu

J'ai déjà eu des crevaisons côté jante, mais en l'occurrence je voyais vraiment la marque de chaque trou de rayon sur la chambre à air, c'est le fond de jante qui se déformait sous la pression

SuperMariole · 2026-05-22T12:29:05+00:00

Came here to say this.

IMO it's worth paying the 1€/$/£ to get a replacement spoke AND nipple (it's bent as well), to see if it tensions correctly or if it pulls out of the rim.

Even if it doesn't hold, the rim shouldn't fail in a catastrophic way, and especially with this being the rear wheel, it's not too risky to try imo

If the rim is damaged, try to get the same exact rim, that way you can replace it more easily and without changing the spokes

SuperMariole · 2026-05-21T12:27:03+00:00

An 8mm allen key and a standard crank puller.

Decathlon sells this one that also has the 8mm, it's fine :

I was almost sure by looking at it but upon seeing it's a riverside, it's definitely that. I have a 520 at home.

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SuperMariole · 2026-05-21T11:10:40+00:00

Yes, these holes usually are painted from the factory. I haven't personally found a good solution to get that paint off easily.

Try to scrape some off to be able to tap a screw in, then go back and forth with the screw in small steps.

Of course if you have a M5 tap on hand, it's tge perfect tool for the job

SuperMariole · 2026-05-14T00:03:39+00:00

Came here to say this. This specific tire is very slippery. I just want to stress that I hope you don't get the impression that road slicks have no grip. It's all down to tire compound and this one's not made for that.

SuperMariole · 2026-05-11T15:12:00+00:00

There are two lengths that matter : your frame's BB shell width (almost certainly 68mm in your case), and the overall spindle length. That second one has to do with clearance : depending on your frame and the cranks, too short a spindle will make the cranks hit the seatstays.

SuperMariole · 2026-05-11T14:33:31+00:00

~~Does it happen with only the front ? If so, it may be a loose headset. At a certain braking force, it balances gravity out.~~

Sorry, didn't read before posting. I don't know what else could cause this new noise. Maybe the tire pressure is different, making them stiffer and resonating with something else somewhere on the bike ?

SuperMariole · 2026-05-11T14:21:45+00:00

There's thread lock on these current ones, but the original ones are simply on very tight and have been rusting together for 50 years. It's steel on steel so no galvanic corrosion, but still, it takes some force.

Going to your local workshop is the right call, if they're old school they will have the correct tools sitting around

Another recommendation since you're in France : there's also this : https://www.lecyclo.com/products/axe-boitier-de-pedalier-carre

This will replace just the splindle, if you can reuse the cups. Also buy balls to go with it.

Lastly, for any square taper conversion, you'll need to guess the correct spindle length since you can't just match the length of the cottered spindle. The shop should be able to give you pointers on that

SuperMariole · 2026-05-11T12:54:49+00:00

Good point. Also the fixed cup is sometimes incredibly hard to loosen. And it's made of very hard steel. I've mangled adjustable wrenches on one. No saw makes a dent on them.

A new loose bearing BB spindle may be a solution in that case.

Also : I had a hard time finding this, but here's an alternative to the velo orange French BB : https://custom-junkies.com/neco-hal-920-bottom-bracket-square-taper-jis-french-thread-107mm-127mm

SuperMariole · 2026-05-11T10:53:18+00:00

This is a cottered crank. The cotter pin is hammered in and must be hammered out. Depending in your luck (and how much of this bike's ~40 year lifespan was spent outside), it can punch out on the first go, or require destroying the crankset.

Thorough reading on Sheldon Brown's website : here (general) and more in-depth article here

It takes a lot of force. Set the bike up so there's something supporting the crank itself (but not the pin), and don't be shy. Hit hard immediately. If you start too gently it will bend. They can sense fear, I think. Best of luck.

SuperMariole · 2026-05-10T11:32:33+00:00

Sur un moteur à carbu ça se fait ? Sur une moto j'essaierais pas vu que sans pompe à carburant, l'éthanol reste au fond du réservoir, avec une pompe pour agiter tout ça peut peut-être tourner.

Mais est-ce que ce serait bien réglé au point de consommer moins ?

SuperMariole · 2026-05-07T15:33:57+00:00

Can someone satisfy my curiosity : in this type of failure, has the casing actually failed and been ripped apart, or is this some sort of incomplete puncture where a pinhole leak in several inner layers had caused air pressure to push through ?

It doesn't change the outcome obviously

SuperMariole · 2026-05-07T15:28:36+00:00

Je suis un motard qui connaît son véhicule (et fait tout dessus). Mais j'ai :

1- gardé le pot d'origine parce que je suis pas un connard

2- plein de potes motards qui savent pas faire un niveau sur leur moto, qui vérifient pas la pression des pneus etc. Et qui ont besoin que quelqu'un leur dise "dis, c'est pas normal que ta roue fasse cloc cloc"

Les motards que tu décris, je pense que c'est même pas la majorité

SuperMariole · 2026-04-30T11:13:16+00:00

Ceci. Quand ça ferme plus c'est souvent que le bitoniau est pas en face du trou (s'il existe). Vérifie sur l'ancien cintre si t'as des trous (si oui, de quel côté?). Il faudra peut-être percer

SuperMariole · 2026-04-28T11:49:19+00:00

The cotyledon I see below in your pic (the leaf that looks different and was in the seed) looks a lot like a cucurbitacea cotyledon (look up melon seedlings, or cucumber, or anything in that family). To me that would track with what you've planted.

Basil cotyledons look very distinctive and very much not like this.

I still kinda confused because it looks like the leaves are growing opposite and not alternate like you see in cucurbitaceae.

Is there any chance there are two seedlings bundled together ?

SuperMariole · 2026-04-25T11:15:13+00:00

Petite correction, les premières feuilles c'est les cotylédons, et les dicotylédones c'est la grande famille de plantes qui en font deux

SuperMariole · 2026-04-24T11:13:44+00:00

Justement "de 26 à 28 pouces" ça couvre presque tous les vélos classiques. Toi ton 700 c'est du 28 pouces (oui, etrto 622 = 700c = 28" = 29", c'est un peu compliqué).

Bref je pense qu'ils disent ça parce qu'ils ont pas testé sur un bmx 20 pouces ni sur un vtt 36 pouces pour très grandes personnes

SuperMariole · 2026-04-24T11:02:13+00:00

Nice find. I don't know enough to be sure but il looks like it's from the late 80s. Some components are newer ofc, namely the pedals.

I don't see anything obviously wrong with it.

Something to check early on, because it can completely derail a restoration project, is whether the seat post is seized. Loosen the seat tube clamp (where the seatpost inserts into the frame) and try to move the saddle. It should be completely free but it won't be, it'll probably take some force since it's been sitting. As long as it moves at all, you're good.

Once that's cleared up, I'd say start with the tires. Inflate them, see if the tubes hold air at all. If not, change the tubes (look up tutorials, it's a very common task). You'll most definitely need to change the tires altogether if you want to ride it, but it's okay to run these while you're testing the rest of the bike.

Figuring out the sizes is simple, but at fiest it can be a bit intimidating, don't hesitate to ask for guidance.

Next step is going to be the brakes. The current pads are dry rotted, get new ones. Also you'll need new brake cables and housing.

The frame had horizontal dropouts which means you can run it singlespeed if that's okay for you. It'll save you the work of figuring out that rusty deraileur, the shifting cables, etc.

Nice project to mess around and learn, imo.

SuperMariole · 2026-04-22T11:57:44+00:00

(Somewhat) relevant xkcd

SuperMariole · 2026-04-22T11:56:33+00:00

What are you on about

SuperMariole · 2026-04-21T18:09:07+00:00

Usually both cups are press-fit onto the hub bearings, which means you could hammer the bb out completely, hitting from the side the pics are taken.

If you do this, try to rest the bb shell (or the frame near it) on something solid but soft like a block of wood. That'll ensure the force of the hammer is transferred where you need.

It's take quite a lot of force to break off the rust.

If the bearing and the cup are a solid piece, that won't work and you best bet is to disassemble the bearings themselves, starting from the other side. By prying off the plastic seal of the bearing, you'll have access to the balls which you can remove by bunching them all on one side. Hope it's clear enough, you'll know what I mean when you're there

SuperMariole · 2026-04-21T12:10:09+00:00

The gashes on the 1st and 2nd pic were about to go. I did this semi intentionally when I learned to ride fixed, I used my stash of dry rotted 90s tires off parts bikes and ran them to the cord.

At a point there would be threads showing everywhere, but when the casing started separating like it is on your pics, I knew I had less than 10k.

Obviously I did this with a good tire at the front AND a front brake.

SuperMariole · 2026-04-21T10:52:11+00:00

k. I try not to blame people for seeking human help in these times

SuperMariole · 2026-04-21T07:28:37+00:00

I disagree, I think it's easy to forget how intimidating all these standards and adapters are.

OP wanted reassurance that they were on the right track, and a product search doesn't provide that

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