[henrymorcs]

New to the forum and tubeless wheels so go easy…

Originally bought a pair of mavic cosmic exalith clinchers but they were damaged so ended up with a pair of their newer cosmic UST wheels and am having trouble with a rim that just won’t seem to seal and it’s doing my head in as I can’t figure out what the cause is.

Background:
Wheels came taped and with tyres already seated to the rim. Set them up as instructed, no apparent issues sealing at the time but front tyre keeps losing pressure – a couple of times overnight and more recently on a ride, although not all the way flat. Weirdly, they have been fine on several 100+km rides. Pressure loss appeared to be coming from the valve area as sealant was bubbling there, suggesting valve or tape issues. After the pressure loss on the ride I unseated the tyre to check the tape which looked a bit messy (sealant on the underside of tape, tape peeling up in places) so I took the whole thing off and retaped the rim (2x round) with stans tape, pumped up with tube and left for a few hours after which time I was pretty happy with how the tape was looking.

Current situation
Decided to test without sealant, allowing me to check for any issues with the seal without worrying about the mess of sealant if I had to take the tyre off. However, I’ve had no luck getting the tyre to stay up. There’s no issue with the bead or inflating the tyre, the Mavic UST system clearly works well here as I can get the trye on and off without levers, and inflate it easily with a standard track pump. I pump the tyre up successfully to its stated max of 87psi and can just about hear air escaping near the valve. Have tried the following to get it to stop:

– dipped valve plug in sealant before seating
– put grease around valve plug
– put an extra o ring between the valve plug and rim tape
– put old bit of inner tube between valve plug and rim tape
– changed valve core
– retaped and re-cut tape over valve area

but nothing has stopped the tyre losing air over the course of about 20 mins. It looks as though there’s a tiny 1mm or so tear in the rim tape on the edge of the valve hole (not helped by inserting and removing the valve several times) but it would be fully covered when the valve is inserted. Elsewhere the tape still looks perfectly in place right across the rim bed and there’s no signs of holes at any of the spoke areas. When faced with the weigh up between adding sealant and hoping for the best or putting an inner tube in so I can keep riding guaranteed, I went for the latter option. I would love to get this working tubeless as the feel on the road and puncture repair is great, and the system clearly can work as the rear has kept pressure for a couple of weeks without issue.

So my questions to anyone with experience in this area are:

– What is the likelihood that this will sort itself out if i put sealant in and shake in order to cover the leaking valve area
– Am I missing something with the valve seal or otherwise with the tape (I know any leak from the tape will show up through the valve hole in the inside of the rim, and this may have been what was happening with the old tape, but I’m pretty sure air is now getting out through the valve area itself as it’s faintly audible)
– Is retaping the whole rim and getting a cleaner valve hole in the tape the only real solution?

Thanks for your help. And fair enough if you’re just commenting to tell me that road tubeless is a waste of time, I suppose it’s deserved but you’re still an ass…

Henry

Topic

[henrymorcs]

Thanks all for your helpful

Thanks all for your helpful advice. The tyre has stayed up now for about a week without any issues. Overall a really big fan of these wheels and I like the way the tyres run, definitely feels smoother on the road than what I was previously used to and the sealing of punctures is really satisfying. I bought some extra tape and some muc off valves, which helpfully have various interchangeable shaped rubber bungs, in case of any issues further down the line.

So the fix seemed to be retaping the rim which I did with some unbranded yellow tape (maybe stans?) provided by a local bike shop – shout out to Spokes Cycles in Welwyn. As some people advised below, the tape was slightly wider than the rim bed – the tape roll was wide enough that it wouldn’t fit within the rim – rim bed is 19mm and tape must have been 23m or so. This meant that when fully applied and flush along the rim bed it sat almost perfectly within the rim walls without riding up. I also put a bit of inner tube around the valve as a plug so perhaps this helped too but I think tape was the main problem. With no sealant air escaped through the valve area with this set up but this was fixed with the addition of the sealant.

Cheers,

Henry

 

[Chris Hayes]

You’d think so, but it is an

You’d think so, but it is an interesting time to find a buyer: bike sales are up and will probably continue to rise, but a significant drop-off in advertising revenues for them – this year, at least.  

The rise in bike sales makes you question companies like Cycle Surgery’s exit from the market though… 

[Hirsute]

Looks as clear as mud as to
Looks as clear as mud as to what is happening there.
Surely someone will take the brand on?

[Anonymous]

A couple of things that might
A couple of things that might help. I’ve had issues in the past with the Mavic ‘shaped’ valves. Replaced them with a Stan’s valve and all sorted. I’ve also had problems with rim tape, namely Gorilla, which tends to come off when removing the bead of the tyre – the bead tending to stick to the edge of the tape. A rule of thumb is to buy tape that is 3-4mm wider than the internal width of your rim (to account for the well in the rim). I’ve had great success with Muc Off tape (28mm on a 25mm internal rim width). Mainly, though the valve replacement is what fixed my issues with Mavic rims.

[Chris Hayes]

Wow…just read that Mavic

Wow…just read that Mavic has been placed into receivership …. The Cyclist. 

[Chris Hayes]

Yes – it was gorilla tape

Yes – it was gorilla tape that I cut to shape (badly) and rode up the rim.  I’d like to think it was seated properly at least, but any misplaced confidence I may have had in my ability to tackle one of these f******s has now deserted me. 

It’s going to be 18 degrees or so in Norfolk, but hopefully less windy than it has been.  My bike is prepped…

[hawkinspeter]

If the tape’s a bit too wide,
If the tape’s a bit too wide, it can still be made to work, but you just need to make sure that it’s applied tightly and very central. The main problem with the tape covering part of the walls is that you’re more likely to damage it when installing/removing tyres (or at least I’m quite prone to that).

I’d recommend getting plenty of rim tape in a couple of different sizes so that you can apply and re-apply if necessary and hopefully return the unused size.

[henrymorcs]

I fear that might be the

I fear that might be the solution, feels like admitting defeat though!

I don’t understand your tape being too wide – was it so wide that it was riding up the side walls and so allowing air underneath? My stans tape is a bit wider than the tape that came on the rims so I wonder if it could be a similar problem. It seems to sit nicely on the rim bed though.

It was lovely and sunny today so hopefully the same for the long weekend. Hope it’s the same for you. I think the sun has got to my head and i’m going to see whether i can get this rim to seal overnight… if not i’ll just be using a sealant-y inner tube come tomorrow. 

[Chris Hayes]

Just had similar issues with

Just had similar issues with some Contis on asymetric Kinlins – but note with some dismay that my Open Pro USTs have also gone down.  

After 6hrs working on the Contis, I gave up and took it to a bike shop.  They fixed it – it was the tape that was too wide – and now it works perfectly.   So…bike shop.  Life really is too short.  Tubes for the Bank Holiday if they can’t do it in time :-)….Hope it’s sunny where you live! 

[henrymorcs]

Thanks Dr Infinity, Peter &

Thanks Dr Infinity, Peter & Joe, 

Other than this annoying issue i’ve been really impressed with the mavic system -i’ve experienced none of the pains people seem to often encounter with getting tyres on/off/seated on the rim. Provided I can find a resolution to this problem I’ll be a tubeless convert. FYI HawkinsPete the tyre goes up fine and doesn’t go flat instantly, it’s more of a slow puncture kind of thing, just gradually leaking air, although going flat in sub-half an hour isn’t much better practically speaking.

I’ve made sure to push the valve into the bed through the tyre and tightened up the o-ring each time before pumping them up so I don’t think i can achieve a better seal this way. I was concerned about doing it up too tight and damaging the valve/rim somehow so haven’t been forcing it beyond what seems reasonable with my hands.

It sounds like it’s worth taking the gamble and adding sealant and hoping it stops the leak, I had just hoped for something more reassuring when I set it up without any sealant… After all, Mavic claims that these UST rims and tyres should run fine without sealant although the sealant is recommended for puncture repair. 

Worst case scenario if it doesn’t seal with sealant in is that i’ll have to remove the sealant and re-tape the whole rim which isn’t the end of the world. I’ll probably try a different valve first in case that helps – this mavic one is shaped to fit flat on the rim bed so i will try one of the standard conical ones which logically should hold fairly well.

For the next couple of days i’ll go ahead with tubes on as I want to get out over the bank holiday but as soon as the weather turns or i’m happy to risk a couple of days off i’ll go ahead and try your suggestions. I’ll make sure to report back in case it is of interest or could help anyone else in the future – i’ve come across so many forum posts without any closure as to what actually solved an issue!

Cheers,

Henry

[hawkinspeter]

I’ve had a minor air leak
I’ve had a minor air leak from around the valve (similar to yours by the sound of it) and I did just leave it for the sealant to fix. However, that ended up with lots of little balls of latex rolling around inside the rims which was a bit annoying. I did manage to get rid of most of the latex by lots of shaking of the front wheel (not on the bike) with the valve removed and the hole at the bottom.

I ended up re-taping the rim when I next changed the tyre and I was careful to ensure the tape was applied nice and smoothly (I’ve never bothered using an inner tube to fix the rim tape – sounds a bit unnecessary).

With rim tape, you need to be careful when you make the hole for valve – don’t use a knife, but instead something that can make a round hole (I think I used a barbecue skewer). When you fit the valve, it can help if you push the valve snugly against the rim (maybe take a little rubber mallet to it as well). Don’t bother with additional o-rings on the inside as they’re unlikely to help. As Joe Totale says, you don’t need to go more than finger tight for the valve collar/o-ring – too tight and the o-ring will be damaged.

So, I forsee some new rim tape in your future. Before applying it, give the rim bed a good clean (isopropyl alcohol is good for that) and just concentrate on getting it smooth and tight with no air bubbles.

My experience is that when the rim tape is applied correctly, you should be able to inflate the tyre without using sealant and it should ‘ping’ into place, though that will also depend on the tyre and using enough lubricant/washing-up liquid to allow the tyre bead to move easily.

[Drinfinity]

Agreed, put some sealant in. 

Agreed, put some sealant in. 

[Joe Totale]

I’ve had this issue before

I’ve had this issue before with other tubeless wheels although I must say my personal experience of the Mavic UST system was very user friendly.
I’d put sealant in and then go for a short ride around the block to make sure it coats everywhere properly. 

Following this I’d leave the bike overnight with the valves at the 6 o’clock position so that the sealant will run down to them and plug any holes. 

If there are any 1mm holes about then they’re small enough for the sealant to plug up. I’ve always lost more air in tubeless tyres without sealant then with sealant, it’s basically impossible to have an airtight seal between tyre and rim without the sealant in my experience. 

I’m sure you’ve already done this but make sure the valve collars are done up tightly, well as tight as you can by your hands, don’t use pliers.

There will be some air loss but hopefully not all of the air will be gone overnight. I find that it takes a couple of proper rides before the air loss stops. Now I find with my tubeless wheels is that they lose air about as my wheels with butyl tubes. 

[Author]

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