Tubless issues with Cushcore

[grantini]

We have been seeing a higher than expected rate of loss of seal with tubeless tires that have cushcores installed. We suspect that perhaps the goop isn't getting between the cushcore and the rim in sufficient volume to seal as effectively as it should. Does anyone have any experience with this or suggestions on how to alleviate the issue?

 

[Hamina]

We suspect that perhaps the goop isn't getting between the cushcore and the rim in sufficient volume to seal as effectively as it should. Does anyone have any experience with this or suggestions on how to alleviate the issue?

Just installed new tires for DT Swiss wheels with Cushcores. The "goop" or the sealant shouldn't have any task to seal the rim. The rimtape is the one that's sealing the rim I guess?

Just thinking: As the tire spins when riding, the radial accelerations pushes sealant to the outer perimeter(?) against the tire. There should be enough space for the liquid to seal potential leaks.¨

Would be interesting if you could specify the problem more precisely

 

[Limy78]

Used Cushcore in various tyres / wheels for just over 2 years. Whenever have found a tyre to be loosing air it was down to the rim tape being damaged during installation.

 

[grantini]

We are actually thinking about the edge of the rim, where the bead is...

 

[Hamina]

The cushcore material is so soft that somehow it sounds impossible that it could overcame the force that air pressure presses tire beading to the rim.

In theory I can only think that when running relatively low tire pressure and making very sharp turns while riding the cushcore could somehow make its way between the rim and beading. Though in these cases the tire would be empty even without cushcore?

 

[Al-Rider]

I've been having the same issue. My rear tire was loosing air fast, so I placed it underwater just to discover that the sidewalls were leaking like crazy (that's a Maxxis Agressor Double down). I bought a new tire, installed it with the cushcore and sealant and found that the tire was loosing all the air in a few hours. I placed it underwater again to find that now the leakage came from the spokes. I uninstalled the tire, removed the rim tape, cleaned the rim with isopropyl alcohol, checked the rim for any damage or holes, re-taped it again and carefully installed the tire with the cushcore, trying my best not to damage the tape with the levers and the tire bead. Well, the tire keeps loosing air by the spokes, but at least I can now manage to ride hard for 2 hours loosing about 6 psi in that time.

I've now decided to buy a different brand of rim tape (I was using Stan's which I've heard is not that great) and I will again mount everything again, being as careful as I can be when forcing the bead inside the well of the rim.

This is getting pretty frustrating and I wonder if Cushcore or someone else could come up with some tips to solve this issue.

 

[FSEngineer]

I've had Rimpact inserts in my wheels (DT Swiss H1700) for around a year with Michelin tyres and Muc Off sealant, absolutely no issues in this respect and the inserts make the tyres all but impossible to de-bead. I did add the sealant via the valve stem though, so there is plenty kicking around between the insert and rim (as well as between the tyre and insert).

 

[grantini]

I think the reality of cushcore is that it's harder for the sealant to get everywhere. I use double the sealant I used before and I reapply more often.

 

[jerry]

The "goop" or the sealant shouldn't have any task to seal the rim. The rimtape is the one that's sealing the rim I guess?

Rimtape by itself creating an airight seal? OF COURSE the sealant does the sealing...
- on the edge of the rim and the rimtape
- on the tire bead

 

[jerry]

I think the reality of cushcore is that it's harder for the sealant to get everywhere. I use double the sealant I used before and I reapply more often.

Jup - the sealant is attempting to seal any "leak" between the tire wall and the cushcore (but such leak would be required for the sealant to reach the rim area). Adding some sealant through the valve should do the job. Or, you could release the air from the tire, and push the tire side walls while sloshing (pushing the cushcore away from the tire wall), this will also allow sealant to reach the space between cushcore and rim.

 

[Al-Rider]

Jup - Or, you could release the air from the tire, and push the tire side walls while sloshing (pushing the cushcore away from the tire wall), this will also allow sealant to reach the space between cushcore and rim.

I always add the sealant through the valve, but that's a good suggestion. I'll add a bit more sealant and slosh the wheel with the tire deflated to try and get the sealant between the cushcore and the rim and tire sidewalls.

 

[Downhillr]

Rimtape by itself creating an airight seal? OF COURSE the sealant does the sealing...
- on the edge of the rim and the rimtape
- on the tire bead

I’ve found that some rims (especially if being converted to tubeless) don’t match up well with tire bead to seal air and have better luck with rims intended for tubeless setup. The tire bead and rim design are important for air seal, goop mostly helps seal porous sidewalls and seal thorn punctures.
Think of your car tires… how many of you are running tubes or goop in them?… yet they seal just fine at bead with little air loss.