4

Today I had a complete loss of pressure while parked. This is what I came back to long distance medium distance

I haven't been able to find a hole in the tyre with a visual inspection or by feeling around the inside of the tyre. One thing that stood out to me was the tape around the rim has a puncture at one spoke point. I don't know enough about tubeless setups to say that this would be the cause or not. enter image description here

The rest of the spoke holes look fine, this is the only punctured area of tape.

On a tube setup I'd normally re-inflate the inner tube with some soapy water on the exterior to find the source of the leak before replacing the inner tube. With the tubeless tire I'm having trouble getting it on the bead the whole way around and I only have a floor pump.

How can I find the cause of the original pressure loss and begin to make repairs without access to shop air supply? Is the tape puncture the cause? Can I use methylated spirits to remove the remaining dried sealant?

Thanks in advance!

update 1: LBS who retailed the bike recommend following the specs on the tyre. The tyre was running right in the middle of the rated range.

update 2: Giant recommended running within 5 PSI to the centre from each of the upper & lower limits specified on the tire, with a few caveats. Backpack, panniers, would push the recommended PSI up a bit. Rider weight & personal preference would also have some bearing on the running PSI.   100 PSI (dead centre of the recommended range) shouldn't be a problem for the tape at my weight at all but If I desired a softer ride I could drop the pressure a bit.

|improve this question
  • 1
    That does look a bit thin to be proper tubeless tape. Do you know what tape was used? – Weiwen Ng Dec 15 '19 at 19:39
  • 1
    @WeiwenNg that looks like the Giant branded tape, which I believe is a rebadged 3M tape. Is very sticky, and has a cellophane type of feel with a little give. It sets up quite nice, and tends to survive tire changes well, but leaves a lot of residue if changed. Typically it does surprisingly well at higher pressure setups, but I have had a similar failure with factory installed tape. The 100 psi may have been too much for a single ply setup that came from the factory. – Rider_X Dec 15 '19 at 19:52
  • 1
    @Criggie good question. It seems to be a liquid latex + solvent mix based on what dry parts there are. I'm guessing it didn't have a lot of time for the solvent to dry out and provide a solid latex form with the rapid decompression from a hole of the size shown in the photo. – Scottmeup Dec 16 '19 at 8:55
  • 2
    @Criggie there's no chance of it sealing a spoke hole leak if the bike is stationary, as all the sealant will be pooled at the bottom of the tyre. – Andy P Dec 16 '19 at 11:31
  • 1
    Also, given the size of the hole, I don't think any sealant would do. Given that the OP specified road tires, I'm not 100% sure the pressure alone is the issue, but I don't think that running 100 PSI is desirable. @VladimirF said elsewhere to use a double layer of tape. I'd second that. If the bike came with only a single layer of tape, I don't think that's good practice. The OP hasn't confirmed that it did. – Weiwen Ng Dec 16 '19 at 19:02
5

If the tape has a hole in it, that's definitely the problem. I'm not sure why the tape would suddenly fail as there is nothing rubbing in it, although the spoke hole in the rim looks strange to me. Is there a sharp edge there that punctured the tape?

If the tire had a large leak you be able to see sealant coming out of it, same if there were a problem with the bead seating on the rim. If you have not seen this your tire is probably OK.

You'll need to replace the tape, perhaps with a heavier duty type. If you can't seat the tire bead yourself enlist the help of a bike repair shop - that's what they're for: backup when you don't have the tools or knowledge to do it yourself.

Methylated spirits or isopropyl alcohol works for removing dried sealant.

|improve this answer
  • Thanks! It feels smooth around the tape - nothing sharp. I had the bike in for a little work which should have had the back wheel taken off but not the tyre. I got it back a few days ago but haven't had a chance to ride it since. I pumped it up to 100psi today, went for a 15 minute ride and parked it outside. Really I've got no idea why the tape would have gone either. I've been keeping it right in the centre of the recommended PSI range & I don't do anything stupid like launching the bike. I'm pretty tempted to go back to tubes, seems a lot simpler to take care of :| – Scottmeup Dec 15 '19 at 13:25
  • 3
    @Scottmeup High pressure could also be the culprit. High pressure tubeless is relatively new (low pressure tubeless is a well tested/refined setup) and there are still some “teething issues.” I have had Giant branded tubeless tape fail as well at the spoke hole at higher pressures. I typically never inflate above 75-80 psi. – Rider_X Dec 15 '19 at 19:46
  • 1
    @Scottmeup The recommended pressure range is typically valid when used with tubes - even for tubeless ready tyres. Tubeless setups typically use lower pressures. On my gravel tyre the pressure range is 45-70 PSI and the usual pressure I run is 40, sometimes even less. I never inflate over 60 without a tube even when seating the tyre and I never run it over 50. – Vladimir F Dec 16 '19 at 10:23
  • Thanks @VladimirF . Do you know where I could find the manufacturer recommended PSI range for the Giant Gavia AC2? I'm unable to find it in either the bicycle owner's manual or the tubeless tyre owner's manuaL . The tubeless tire manual recommends inflating to the maximum pressure as labelled on the tire (9) and then to reinflate (11) after ensuring a proper seal (10) dstqaa92re5c4.cloudfront.net/Manuals/Gear/Bike%20Gear/Tires/… giant-bicycles.com/global/manuals . I haven't been able to find any additional information. – Scottmeup Dec 16 '19 at 11:20
  • 2
    @Scottmeup The J step (inflate to maximum pressure) seems unnecessary to me, but I have no experience with these tyres. But then you are not supposed to use this pressure for riding. It is possible that the high pressure just ruptured your rim tape and all you need is a stronger one. It looks pretty thin in your photograph. You can use two layers. The actual riding pressure is a matter of personal choice and can be lower than the normal minimum because punctures are less likely. If I wanted to be safe, I would use the minimum written on the tyre. – Vladimir F Dec 16 '19 at 13:31
0

Definitely too much psi for that tape. Also way too much psi to actually ride it without it feeling like riding on tires made of stone!

|improve this answer
  • 2
    100 psi is not so uncommon for road tires, could be too much pressure though for the installed rim tape thickness as hinted at in the comments on the original post. 80-100psi appears to be the tire pressure range for road bikes – Maarten -Monica for president Dec 16 '19 at 20:31
  • Agreed- it’s not uncommon for road standard narrow clinchers. however, I think it is uncommon for many, or most road riders that have specifically gone for tubeless with 23c and 25c tires. Regales of the pressure, it shouldn’t leak THAT much with 100psi. The tape probably needs to be redone or doubled up in this instance. – Velobuck Dec 17 '19 at 0:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.