Tubeless jinx continues - losing air when cornering/ on cambers

Posted by: 13thfloormonk

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it's clearly from the tyre flexing and pulling the bead enough for air to seep out.

Are you getting sealant leakage showing this to be the case? 

Yep, can see the wee lines of dried sealant on the sidewalls. At slightly lower pressures I can actually recreate it with my hands, e.g. flex the tyre sideways and can see/hear the air and sealant hissing out from the bead.

I'll take it all apart and add a layer of tape, see if that works...

What pressures are you running? If you can flex the tyre with your hands enough to make the bead leak, I would try bumping up the tyre pressure.

Flexing with my hands was after it leaked i.e. low pressures. However it lost pressure over a 3 hour ride starting from 40psi.

I'm suspecting the tape, I've got a DCR rim which has been a total pain in the bollocks to tape from day 1, the well is just too deep so the tape can't stretch or flex enough and ends up sort of suspended slightly off the floor of the rim. I just peeled all the tape off and there was a suspicious amount of sealant UNDER the tape.

I also noticed the tape was no longer adhered to the rim so maybe the tape was shifting about or allowing the tyre to shift about or something 🙄

I'll have it all figured out by winter at which point the rim will be worn out anyway. Come back Kinlin, all is forgiven!

I was going to post this earlier, but some of the symptoms, tyre flexing on rim ... though at 40psi!!

Dont think another wrap of tape will help with the tyre flexing off the rim 🤔
My recent problems on the Camino,where i need a higher pressure, 45psi, when loaded for cycle touring, have both been due to tape issues which I identified by sticking the rear wheel in a water trough and eventually finding a tiny amount of air leaking from where the valve goes into the rim and a hint of sealant in the water. 

The first was the yellow OEM tape which somehow I must have damaged changing the tyre 🤷‍♂️ Never had that issue on a mtb wheel.

The second was replacing the OEM tape with Peatys rim tape and finding a couple of days later it had started coming undone, despite being overlapped by 5-6 spoke holes. Re-did it and went round the rim twice and used a bit of Duct tape to keep the cut end fixed. The Peatys rim tape didn't come with any 'fixing' tape, so I didn't think I needed any or I put to much tension on the tape when applying. The Peatys tape is much less sticky than Vittoria tape.
 

Posted by: 13thfloormonk

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However it lost pressure over a 3 hour ride starting from 40psi.

If it's losing that much air that fast, it should be easy to find the leak just by pumping it up and spraying it with with soapy water.

I know where the leaks are, they're between the bead and the rim, I could see where the sealant had leaked out. For whatever reason the bead is clearly lifting off the rim when I corner hard or hit an off-camber. It isn't a a steady/gradual leak.

Am trying to find a set of those Caffelatex rim strips to see if they work better with the awkward rim shape...

Some Rim/Tyre combos just don’t work, especially once the tyre slackens off a bit unfortunately. I’ve got a set of wheels that either need an insert or something like a Super Gravity Schwalbe to not burp.

Posted by: jamesoz

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Some Rim/Tyre combos just don’t work, especially once the tyre slackens off a bit unfortunately. I’ve got a set of wheels that either need an insert or something like a Super Gravity Schwalbe to not burp.

Yeah at this rate I'm ready just to fill an innertube with sealant and be bloody done with it! 😂

Ordered some Caffelatex strips, worth a try, at least rule out dodgy rim taping...

This thread is reminding me why I gave up on tubeless.

Posted by: johnhe

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This thread is reminding me why I gave up on tubeless.

I tried that last week, new tyres so before I gunked them up I figured I'd run them with tubes until I got a puncture. Lasted 50km before the Hawthorne struck 😭

A lot of it is just bad luck I guess, I could fix it and maybe get away with several months more on tubes without issues. In fact, I'll probably get to test that theory next weekend at this rate unless I get my new rim strips on time...

Run some electrical tape around the rim first. Should be stretchy enough to get into the deep well.

If you have the same tyre on the rear and it's fine then that would make me think the bead on the front is overstretched.

Posted by: Lee

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If you have the same tyre on the rear and it's fine then that would make me think the bead on the front is overstretched.

I mistyped, it's the rear that's losing air, but yes, take your point. 

It was very easy to remove the rear tyre so clearly that's what I need to experiment with, don't know why it is so much baggier than the front given that usually it's the rear rim that's the tighter fit. And how do you over-stretch a kevlar bead??

I've got some Effeto Caffelatex rim strips coming which will at least guarantee an airtight seal without relying on the tape, and if I need to pad out the rim bed with insulating tape then I'll do that also (in fact will have to wrap with insulating tape anyway as I'll probably be using tubes again this weekend...).

Another option might be:

https://fattystripper.com/

I'd caveat that they're not the most durable product in the world. They're fragile to install, degrade with any chemicals or UV (like any latex product, don't get oil anywhere near it).

But it'll glue itself to the tyre after a few rides making a sort of pseudo-tubular tyre with bead hooks that won't burp.

Or just lots of electrical tape untill the rim is tight.

Apologies if this is what you have been describing, but it sounds like you are losing pressure from the tyre over the course of a ride & at some point it gets low enough that the tyre burps when cornering, which is when it becomes noticeable.

I had this once while riding in Spain when I was new to tubeless. The tyre had multiple thorns in it, which the sealant had sealed but each time there had been a loss of pressure, which I hadn't noticed or checked. 
Eventually riding across a large slab of off-camber rock the tyre bead/sidewall decided it wasn't going to stay in contact with the rim anymore which resulted in a sudden deflation of the tyre and put me on my arse. Once pumped back up to adequate pressure, tyre resealed and a glob more sealant chucked in, it was fine for the rest of the week.

I think you probably have a small leak which is going unnoticed until the 'catastrophic' leak from the tyre deformation once the tyre pressure dips too low.
It would be a pain to do, but you could test this by checking tyre pressure every 15mins or so on a ride & seeing if it's losing air.

Another option might be:

https://fattystripper.com/

I'd caveat that they're not the most durable product in the world. They're fragile to install, degrade with any chemicals or UV (like any latex product, don't get oil anywhere near it).

But it'll glue itself to the tyre after a few rides making a sort of pseudo-tubular tyre with bead hooks that won't burp.

Or just lots of electrical tape untill the rim is tight.